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Review

Recent Progress in Spinel Ferrite (MFe2O4) Chemiresistive Based Gas Sensors

by
Run Zhang
1,
Cong Qin
2,
Hari Bala
1,
Yan Wang
3,4,* and
Jianliang Cao
2,4,*
1
School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China
2
College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo 454000, China
3
College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China
4
State Collaborative Innovation Center of Coal Work Safety and Clean-Efficiency Utilization, Henan Polytechnic University, Jiaozuo 454003, China
*
Authors to whom correspondence should be addressed.
Nanomaterials 2023, 13(15), 2188; https://doi.org/10.3390/nano13152188
Submission received: 28 June 2023 / Revised: 17 July 2023 / Accepted: 25 July 2023 / Published: 27 July 2023
(This article belongs to the Special Issue Advanced Gas Sensors Developed by Nanocomposites)

Abstract

:
Gas-sensing technology has gained significant attention in recent years due to the increasing concern for environmental safety and human health caused by reactive gases. In particular, spinel ferrite (MFe2O4), a metal oxide semiconductor with a spinel structure, has emerged as a promising material for gas-sensing applications. This review article aims to provide an overview of the latest developments in spinel-ferrite-based gas sensors. It begins by discussing the gas-sensing mechanism of spinel ferrite sensors, which involves the interaction between the target gas molecules and the surface of the sensor material. The unique properties of spinel ferrite, such as its high surface area, tunable bandgap, and excellent stability, contribute to its gas-sensing capabilities. The article then delves into recent advancements in gas sensors based on spinel ferrite, focusing on various aspects such as microstructures, element doping, and heterostructure materials. The microstructure of spinel ferrite can be tailored to enhance the gas-sensing performance by controlling factors such as the grain size, porosity, and surface area. Element doping, such as incorporating transition metal ions, can further enhance the gas-sensing properties by modifying the electronic structure and surface chemistry of the sensor material. Additionally, the integration of spinel ferrite with other semiconductors in heterostructure configurations has shown potential for improving the selectivity and overall sensing performance. Furthermore, the article suggests that the combination of spinel ferrite and semiconductors can enhance the selectivity, stability, and sensing performance of gas sensors at room or low temperatures. This is particularly important for practical applications where real-time and accurate gas detection is crucial. In conclusion, this review highlights the potential of spinel-ferrite-based gas sensors and provides insights into the latest advancements in this field. The combination of spinel ferrite with other materials and the optimization of sensor parameters offer opportunities for the development of highly efficient and reliable gas-sensing devices for early detection and warning systems.

1. Introduction

Metal oxide semiconductor (MOS) gas sensors operate by detecting alterations in the electrical conductivity of a semiconducting metal oxide when exposed to a gas [1]. When the MOS sensor comes into contact with the target gas, the gas molecules adhere to the sensor material’s surface, resulting in a modification of the sensor’s electrical resistance [2]. The extent and direction of the resistance alteration correlate with the gas concentration and its chemical properties. Numerous metal oxide semiconducting materials, such as tin oxide (SnO2) [3], zinc oxide (ZnO) [4], titanium dioxide (TiO2) [5], and tungsten oxide (WO3) [6], have been widely utilized in the production of MOS sensors. These materials exhibit diverse sensing characteristics towards various gases, and their sensitivity, selectivity, and stability can be adjusted via material doping, surface modification, and operating conditions. To enhance the performance of MOS gas sensors, novel sensing structures such as nanowires [7], nanotubes [8], and nanostructured thin films [9] have been developed, offering larger surface-to-volume ratios and improved gas adsorption capabilities. Additionally, advanced fabrication techniques such as atomic layer deposition (ALD) [10], chemical vapor deposition (CVD) [11], and spray pyrolysis [12] have been employed to achieve precise control over the sensor’s morphology, composition, and functionality. In conclusion, MOS gas sensors have become indispensable tools for monitoring environmental pollution, ensuring industrial safety, and safeguarding public health [13,14]. The ongoing progress in sensor technology and its integration with information and communication systems will create novel opportunities for real-time, reliable, and intelligent gas-sensing solutions.
MOS-gas-sensitive materials can be classified into two categories based on the number of metal ions present in the single-phase metal oxide material: single metal oxides and composite metal oxides. The gas sensors based on single metal oxides exhibit excellent attributes, including easy integration, good repeatability, and effective detection of various gases [15,16,17]. Nonetheless, there is still room for improvement in terms of the selectivity and recovery performance of single-phase gas-sensitive materials. Researchers have explored strategies to enhance the sensing performance by incorporating precious metal catalysts or combining them with other materials to modify the morphology of single metal oxides, aiming to provide activation energy for reactions or form p–n heterojunctions.
In recent times, the distinctive magnetic properties [18], electrical properties [19], microwave absorption [20], and photocatalytic properties [21] of composite metal oxides, specifically spinel ferrites, have garnered significant attention. The primary preparation techniques for MFe2O4-based gas-sensitive materials include the co-precipitation method [22,23,24,25], sol–gel method [26,27,28], and template synthesis method [29]. These methods enable the production of spinel ferrite nanomaterials with diverse morphologies such as nanorods, nanotubes, nanofilms, and core–shell microspheres. The combination of novel synthesis approaches and the integration of new functional materials has led to the development of spinel ferrite and spinel ferrite composite materials with controllable structures and morphologies, thereby expanding their application potential. For instance, the controlled synthesis of spinel ferrite nanoparticles has exhibited promising outcomes in biomedical applications such as drug delivery and cancer therapy [30]. Furthermore, the combination of spinel ferrite with graphene oxide enhances its magnetic and electrical properties, positioning it as a potential candidate for spintronics [31] and electromagnetic shielding applications [32]. Additionally, the incorporation of metal ions or other functional materials into spinel ferrite has shown improved catalytic and photocatalytic properties, thereby finding application in areas such as wastewater treatment [33] and hydrogen production [34]. Overall, the advancement of novel synthesis methods and the integration of functional materials have broadened the scope of zinc ferrite materials and opened up avenues for future research.
As a semiconducting, magnetic oxide material, spinel ferrite has excellent chemical stability, enabling the effective adsorption of various gases [35]. Its inherent catalytic properties stimulate chemisorption processes that result in changes in its electrical resistance when exposed to different gases [36]. This allows for accurate gas detection and measurement. Additionally, spinel ferrite can operate at lower temperatures compared with other gas sensors, which leads to increased energy efficiency [37]. Its high sensitivity [38] and selectivity [39] towards particular gases, coupled with its capacity for miniaturization, make spinel ferrite an optimal material for building reliable, efficient, and compact gas sensors.
This review article is organized as follows: Section 2 presents an introduction to the gas-sensing mechanism of spinel ferrite. Section 3, Section 4 and Section 5 present a detailed review of the recent advancements in spinel-ferrite-based gas-sensing materials for the detection of reducing gases, categorized based on the types of gas-sensing enhancement mechanisms. Finally, in Section 6, a summary and outlook for this review are provided, emphasizing the potential future directions for spinel-ferrite-based gas-sensing materials and their applications.

2. Gas-Sensing Mechanism

With its spinel crystal structure, spinel ferrite emerges as a promising sensing material possessing exceptional properties. Figure 1 illustrates the crystal structure of zinc ferrite, where the face-centered cube of O2− accumulates within its crystal lattice, while the metal ions M2+ and Fe3+ are embedded in the tetrahedral and octahedral gaps formed by O2−. This structure readily facilitates the formation of defects, including oxygen vacancies, both internally and on the surface, making it highly advantageous for gas-sensitive materials. The unique crystal structure, specifically the insertion of the transition metal cation Zn2+ into the Fe2+Fe3+O4 structure, plays a crucial role in the effective detection of reducing gases.
The gas-sensing response of spinel ferrite is determined by the complex interaction that occurs at the interface between the gas and solid material. However, a unified definition of gas sensor mechanisms is lacking. A commonly proposed sensing mechanism for spinel ferrite sensors is as follows: when a spinel-ferrite-based sensor is exposed to air, oxygen molecules adsorb onto its surface, capturing free electrons from the conduction band and forming oxygen anions. The specific form of these oxygen anions depends on the operating temperature. The loss of electrons generates an electron depletion layer (n-type) on the semiconductor surface, resulting in an increase in resistance. In a reducing gas atmosphere, Equation (6) occurs, leading to a reduction in the resistance of the electron depletion region and sensor. It is worth noting that the reaction described in Equation (6) may vary depending on the operating temperature or target gas.
O 2 gas O 2 ads
O 2 ads + e O 2 ads   T < 150   C
O 2 ads + e O 2 ads 150 C < T < 400   C
O ads + e O 2 ads   T > 400   C
G gas G ads
G ads + O GO + e 150 C < T < 400   C
The unique microstructure and high specific surface area of pure MFe2O4 nanomaterials offer numerous adsorption sites, leading to an enhancement in gas-sensing performance. The addition of metal ions through doping reduces the barrier height of grain boundaries, facilitating improved carrier diffusion and transfer rates; heterostructures [40], on the other hand, allow for the modulation of the electron depletion region and potential barrier at the interface by leveraging the interaction between Fermi energy levels and energy bands [41]. These mechanisms collectively contribute to the enhancement of gas sensitivity in the respective materials. More detailed explanations of the gas-sensitive mechanisms specific to these new materials can be found in Section 3 (Nanostructures), Section 4 (Doping), and Section 5 (Heterostructures).

3. Nanostructure

The gas-sensing application has significantly benefited from the use of nanostructured materials, primarily due to their high surface-to-volume ratio, which allows for better interaction with the gas molecules. In particular, zinc ferrite, a type of spinel ferrite, has been widely used due to its specific surface area, contact area, porosity, grain size, and grain stacking order. These factors all contribute to its gas-sensing properties. The operating temperature, humidity, and gas concentration are several external factors that can influence the performance of zinc ferrite-based gas sensors. For instance, at higher operating temperatures, the sensor’s sensitivity can increase due to the enhanced surface reaction rates [42]. On the other hand, excessive humidity may cause the surface of the sensor to become water-saturated, which could inhibit its response to target gases [35]. Apart from these external factors, the morphology-related characteristics of spinel ferrite also play a significant role in its gas-sensing properties. The development of unique morphologies and structures in spinel ferrite is considered a promising approach to enhance its gas-sensing performance. For example, porous spinel ferrite with large specific surface areas can provide more active sites for gas molecule adsorption, facilitating improved surface effects, electronic transfer efficiency, and ultimately a better gas-sensing performance. Various synthesis methods can be employed to create spinel ferrite materials with different morphologies. These include sol–gel, hydrothermal, and co-precipitation methods, among others. Each method offers unique advantages in terms of controlling the size, shape, and distribution of the nanoparticles, thereby allowing for the optimization of the sensor’s performance. In the subsequent sections, we will delve deeper into these topics, providing a comprehensive review of the latest research findings on ferrite sensors with diverse nanostructures. We will also discuss the special properties of these sensors as documented in existing literature (Table 1, Table 2, Table 3 and Table 4). We believe that this review will provide valuable insights into the ongoing advancements in the field of spinel-ferrite-based gas sensors and highlight potential avenues for future research.

3.1. Nanoparticles

The preparation method for spinel ferrite nanoparticles can be achieved through the following steps: First, an appropriate synthesis method, such as sol–gel [109], hydrothermal [101], or co-precipitation [90], is used to mix suitable metal salts with basic precipitants, forming a precipitate. Next, through appropriate washing, centrifugation, and drying processes, the precipitate is transformed into nanoparticle form. Finally, through heat treatment or other surface modification methods, the morphology and properties of the nanoparticles can be controlled [111]. The size of nanoparticles and nanocrystals is not primarily dependent on the synthesis method employed, but rather, it is mainly influenced by the preparation and control of the salt solution.
By dispersing pure CdSO4·8/3H2O and Fe(NO3)3·9H2O in ultra-pure water, Liu et al. [43] prepared mixed salt solutions with different Cd/Fe molar ratios, combined with co-precipitation and calcination at different temperatures to prepare CdO-Fe2O3 composite oxide particles. According to XRD verification, the sample with a Cd/Fe ratio of 1/2 was identified as a spinel phase CdFe2O4, which exhibited the highest sensitivity (48) towards ethanol at 300 °C (Figure 2a). The study conducted by Rao et al. [51] focused on the utilization of the spray pyrolysis deposition technique to fabricate nanocrystalline (Co, Cu, Ni, and Zn) ferrite thin film sensors. The XRD patterns (Figure 2c) show the single cubic spinel phase of the (Co, Cu, Ni, and Zn) ferrite. From Figure 2d, the sensing characteristics of these sensors indicate that the ZnFe2O4 nanocrystalline is more suitable as a sensor at lower temperatures and concentrations. On the other hand, the NiFe2O4 nanocrystalline demonstrates an outstanding LPG sensing ability at higher temperatures.
As discussed earlier, optimizing the grain size and specific surface area of spinel ferrite can significantly enhance the performance of gas sensors. Wei et al. [35] prepared CoFe2O4 nanoparticles via a hydrothermal method. The CFO-400 sensor, which is calcined at 400 °C, shows promising results with its response value of 110 to 100 ppm ethanol gas at 200 °C (Figure 2b). This not only indicates its high sensitivity, but also showcases its good repeatability and stability, which are crucial characteristics for sensor materials. Rathore et al. [52] prepared CoFe2O4 nanoparticles with varying particle sizes through the uniaxial press method. The objective of the research was to examine how the sensing performance of the nanoparticles is influenced by factors such as particle size, temperature, and gas flow. The results of the study demonstrated that CoFe2O4 nanoparticles have good gas sensitivity, and the maximum response value increases with the decrease in particle size. Among them, the response value of 5.8 nm CoFe2O4 nanoparticles to 5 ppm LPG at 250 °C is the highest, reaching 0.72 (Figure 2e), and its response time and recovery time are 3 s and 48 s, respectively. Halvaee et al. [54] employed a hydrothermal synthesis technique to fabricate three distinct nanostructures of CoFe2O4, namely nanoparticles, nanorods, and porous nanoparticles. The structures and properties of these nanostructures were analyzed. A cost-effective gas sensor, constructed using a printed circuit board, was utilized to measure methanol gas and assess its performance at different temperatures (Figure 2f). The optimal operating temperatures for the three sensors were found to be 90 °C and room temperature, respectively. At 90 °C, the CoFe2O4 nanoparticles exhibited a maximum response value of 42.4%, while the CoFe2O4 porous nanoparticles demonstrated a maximum response value of 20.26% at room temperature. The CoFe2O4 nanorods, on the other hand, displayed a maximum response value of 13.3% at 90 °C. In the porous nanoparticle sensor, the optimal temperature was reduced to room temperature due to the high surface volume ratio of the structure.
Sumangala et al. [69] synthesized the MgFe2O4 nanoparticles employing both the co-precipitation and sol–gel methods. The XRD patterns presented in Figure 3a demonstrate the similarity in the structural characteristics of both samples. The co-precipitation sample exhibited a smaller particle size and twice the BET surface area compared with the sol–gel combustion sample. The electrical properties and CO2 sensing capabilities of these two MgFe2O4 nanoparticles were investigated (Figure 3b). Notably, the co-precipitated sample demonstrated a higher sensing response of 36%, whereas the sol–gel combusted sample achieved a sensing response of 24%. Ghosh et al. [78] reported nanocrystalline NiFe2O4 (Figure 3c) through the sol–gel auto-combustion method. Ball milling was performed at room temperature and particle size was controlled to optimize the sensitivity of H2 and H2S. The experimental results show that there was a notable enhancement in the gas response when the particle size was reduced or the specific surface area was increased (Figure 3d). Compared with the other test gases, NiFe2O4 nanocrystals with a particle size of ~5.35 nm had a response value of ~58% to 200 ppm H2 at 100 °C and ~75% to 200 ppm H2S at 150 °C.
In a study conducted by Karpova et al. [88], ZnO, Fe2O3, and zinc ferrite ZnFe2O4 nanopowders were prepared using the co-precipitation method. The gas-sensitive results proved that the sensitivity of ZnFe2O4 towards ethanol and acetone was significantly higher compared with the simple oxides, with values ranging from one to two orders of magnitude greater, respectively. This enhanced gas sensitivity of ZnFe2O4 can be attributed to the presence of a high concentration of acidic Bronsted centers that contain active protons. These centers facilitate participation in REDOX reactions and selectively adsorb ethanol based on the acid−base mechanism. Using the hydrothermal method, Zhang et al. [92] successfully synthesized ZnFe2O4 nanoparticles (about 10 nm) (Figure 3f). The phase and morphology of the prepared products were strongly influenced by the reaction conditions, including the reaction time, temperature, and the molar ratio of raw materials. The experimental findings (Figure 3e) revealed that the prepared ZnFe2O4 nanoparticles exhibited a significantly higher response value of 39.5 to 200 ppm acetone compared with the precursor ZnO, which only had a response value of 4.2, at 200 °C.
Cao et al. [93] employed a solid-state chemical reaction to synthesize various MFe2O4 (M = Fe, Co, Ni, Mg, Cd, and Zn) ferrite materials with distinct morphologies. Compared with traditional semiconductor oxides, these prepared ferrites exhibited enhanced gas sensitivity at lower operating temperatures and demonstrated rapid response and recovery characteristics. At 260 °C, ZnFe2O4 displayed a response value of 37.3 towards 100 ppm methanol (Figure 4a), which was the highest gas response among the different ferrites. It exhibited a response value of 29.1 towards 100 ppm ethanol (Figure 4b) withfast r esponse and recovery times of 5 s and 26 s, respectively. Li et al. [99] successfully synthesized ultra-small ZnFe2O4 nanoparticles (Figure 4c) using the hydrothermal synthesis method. These nanoparticles exhibited excellent selectivity towards NO2 molecules. The ZnFe2O4-based sensor showed an impressive response with a gas-to-air ratio (Rgas/Rair) of 247.7 toward 10 ppm NO2 at 125 °C (Figure 4d), which is a relative low temperature. It also demonstrated a fast response and recovery characteristic (6.5 s/11 s). Li et al. [94] further investigated the mechanism behind the superior selectivity and sensing performance of ZnFe2O4 towards NO2 compared with other gases. Through non-in situ photoluminescence (PL) characterization and density functional theory (DFT) calculations, they found that the gas-sensitive mechanism of ZnFe2O4 towards NO2 is based on surface charge transfer. The presence of oxygen vacancies in the material also enhanced the adsorption energy and charge transfer between ZnFe2O4 and NO2 molecules on the surface.
Zhang et al. [110] synthesized ZnFe2O4 nanoparticles using a solvothermal method with zinc acetylacetone and iron acetylacetone as the precursors. By carrying out the synthesis at 150 °C, ZnFe2O4 nanoparticles (Figure 4e) with a diameter of approximately 20 nm were obtained. These ZnFe2O4 nanoparticles exhibited excellent gas-sensing capabilities, particularly for H2S gas. The sensor was able to detect H2S gas as low as 1 ppm at a temperature of 135 °C, with a sensor response reaching 15.1 for 5 ppm H2S gas at the same temperature (Figure 4f). These results suggest that nano-ZnFe2O4 holds great promise for the development of H2S gas sensors. The group of Jha et al. [102] conducted a study on a selective hydrogen H2S gas sensor based on a zinc ferrite film (Figure 4g). The film was prepared using microwave-assisted solvent-thermal deposition. The sensor exhibited an excellent performance at an operating temperature of 250 °C. The response range of the sensor was found to be 1872–90% for H2S gas concentrations ranging from 5.6 ppm to 0.3 ppm. Through density functional theory calculations, the researchers concluded that the rapid rise and fall times of H2S (approximately 40 s and 70 s, respectively) and the complete recovery of the device were attributed to the physical adsorption of H2S molecules on the partially reversed ZnFe2O4 surface. Figure 4h shows the total density of states (TDOS) of the ZnFe2O4. In the experiment, a double-difference subtraction automatic balance interface circuit was utilized to drive the sensor, and the noise signal was accurately processed and compensated through the differential output.

3.2. Nanorods/Nanotubes

The synthesis methods for spinel ferrite nanorods, nanotubes, and nanowires primarily include hydrothermal [113] and electrospinning [123] techniques. Nanofibers constructed via electrospinning exhibit uniformity and smoothness, thus making the technique widely utilized in the preparation of one-dimensional materials.
In the field of gas sensing, there is a growing interest in one-dimensional (1D) nanostructures such as nanorods, nanotubes, and nanowires, as they are gaining more attention compared with nanoparticles. The reasons for this are manifold. (1) One-dimensional nanostructures often have more active sites compared with nanoparticles. These active sites are the locations where the gas molecules can interact with the material, thereby inducing a detectable change (such as a change in resistance). Therefore, having more active sites means the material can interact with more gas molecules simultaneously, enhancing the sensitivity of the sensor [111]. (2) One-dimensional nanostructures such as nanotubes have unique gas diffusion characteristics. Their channel-like structure allows gas molecules to easily diffuse and permeate through the material. This not only increases the interaction between the gas and the material, but also improves the speed of detection, making the sensor more responsive [119]. (3) Nanotubes and similar structures typically have a relatively high specific surface area [114]. A higher surface area means more space for gas molecules to interact with the material, which further improves the sensitivity of the sensor. One-dimensional nanostructures are known for their favorable electron characteristics. For instance, nanowires can efficiently transport carriers, which is crucial in transducing the interaction between the gas and the material into a detectable electrical signal. In summary, because of their unique structural and electronic properties, materials with 1D nanostructures such as nanorods, nanotubes, and nanowires offer significant advantages in gas sensing and are being actively explored as potential gas-sensing materials.
To investigate the impact of structure on the gas-sensing performance of a sensor, Zhang et al. [113] utilized a high-efficiency anodic alumina template method and a hydrothermal method to prepare NiFe2O4 hollow nanotubes with a length of 1 μm and a diameter of 100 nm, as well as NiFe2O4 nanoparticles, respectively. In comparison with the NiFe2O4 nanoparticles sensor, the NiFe2O4 nanotube sensor possessed a porous structure with overlapping nanotubes, which facilitated improved gas sensitivity. During testing with different NH3 gas concentrations, the NiFe2O4 nanotubes sensor exhibited a higher response compared with the NiFe2O4 nanoparticles sensor, albeit with a slower recovery speed. The high specific surface area of the nanotubes played a crucial role in the ability of the NiFe2O4 nanotubes sensor to detect NH3 gas. Wang et al. [115] developed a novel gas-sensing material, NiFe2O4 porous nanorods (Figure 5a,b), which exhibited improved sensitivity and selectivity for detecting the harmful gas n-propanol. These porous javelin-such as nanorods were synthesized using Ni/Fe bimetallic metal–organic frameworks as templates. As a gas-sensing material, ferrite demonstrated n-type gas-sensing behavior with reduced resistance in a reducing gas atmosphere. The NiFe2O4 nanorods exhibited an outstanding sensing performance for n-propanol (Figure 5c), with an extremely low detection limit of 0.41 ppm at 120 °C. At the same time, the sensor had a good selectivity to n-propanol, good cycle stability, and long-term stability. The exceptional performance of NiFe2O4 nanorods can be attributed to their distinctive morphology and porous structure. The large number of reaction sites offered by the porous structure facilitated the accelerated diffusion of n-propanol gas, allowing the sensor to quickly and accurately detect the presence of the gas. Chu et al. [116] conducted a study where they prepared NiFe2O4 nanorods (Figure 5d) and nanocubes using the hydrothermal method. The nanorods had a length of approximately 1 μm and a diameter of about 30 nm, while the nanocubes had a side length of around 60–100 nm. The results of the study showed that the sensor based on NiFe2O4 nanorods exhibited high sensitivity and selectivity towards triethylamine. Specifically, it achieved a sensitivity of 7 when detecting 1 ppm of triethylamine at 175 °C. However, the NiFe2O4 nanocube-based sensor demonstrated a unique conductivity response in the NH3 environment, showing a significant increase. Specifically, when exposed to 500 ppm triethylamine, the sensor exhibited a response of 0.033. In contrast, the sensors based on NiFe2O4 nanocubes exhibited a different behavior. In a reducing gas atmosphere, the conductivity of the sensor increased. The shape of the crystal, whether nanorods or nanocubes, significantly influenced not only the response value of the gas, but also the type of semiconductor behavior observed.
Nguyen et al. [123] demonstrated the sensitivity of ZnFe2O4 nanofiber (Figure 5e) sensors to H2S, achieving a response of 102 to 1 ppm H2S, along with excellent resistance to humidity and a short response time of 12 s. Zhu et al. [119] synthesized porous ZnFe2O4 nanorods using a microemulsion system with calcination at 500 °C. The resulting ZnFe2O4 nanorods had a diameter of approximately 50 nm, composed of ZnFe2O4 nanocrystals (with a diameter of 5–10 nm) arranged linearly. Compared with ZnFe2O4 nanoparticles, porous ZnFe2O4 nanorods exhibited superior gas-sensing properties to ethanol at room temperature. The enhanced sensing performance can be ascribed to the random arrangement of the porous nanorods and the existence of interconnected porous channels. These factors significantly augmented the specific surface area of the nanorods, facilitating effective diffusion of the target gas for detection. Additionally, the smaller grain size of ZnFe2O4 offered a greater number of active sites, matching the thickness of the electron-depleted region, thereby amplifying the response. Li et al. [122] conducted a study where ZnFe2O4 nanorods (Figure 5f) with a porous structure were synthesized using the hydrothermal method, with ZnFe2(C2O4)3 serving as the template. These nanorods were composed of small nanoparticles and exhibited a significant number of surface pores. The porous ZnFe2O4 nanorods sensor demonstrated a rapid response to acetone, with a response of 52.8 and response/recovery times of 1/11 s at 260 °C for 100 ppm acetone. The exceptional response observed in the porous ZnFe2O4 nanorods sensor can be attributed to several factors, including the fine nanoparticle size, suitable pore size, and reticular pore structure. These characteristics contribute to enhanced gas adsorption and diffusion, allowing for a rapid response to acetone. However, it is important to note that when the concentration of acetone exceeded 100 ppm, the desorption capacity of the sensing material became insufficient compared with its adsorption capacity. As a result, the sensor exhibited a stable response instead of a further increase in signal intensity.

3.3. Nanosheets

The preparation methods for spinel ferrite nanosheets primarily include template hydrothermal [129], sol–gel [127], and spray pyrolysis techniques [128]. The template hydrothermal method can prepare nanosheets with specific pore structures and morphologies, but the demolding step may limit the sample’s morphology and structure [129]. The sol–gel method can prepare spinel ferrite nanosheets with specific compositions and structures, but it tends to introduce impurities [127]. Spray pyrolysis can produce thinner nanosheet films with good lattice matching and crystallinity, but the equipment cost is high and the operation is relatively complex [128].
Nanosheets are a type of two-dimensional nanomaterial characterized by their flat, sheet-like structure. Due to their unique morphology, nanosheets possess a large surface area-to-volume ratio, providing an abundance of reaction sites and diffusion paths for gases to interact with. This increased surface area and availability of reaction sites contribute to improved gas-sensing properties, such as enhanced sensitivity and selectivity. The highly exposed surface of nanosheets allows for efficient gas adsorption and interaction, making them promising candidates for gas-sensing applications.
Singh et al. [126] prepared high-porous CuFe2O4 cascade nanostructures by sol–gel method. It has a porous structure CuFe2O4 with pore size between 10–15 nm. The results of the sensing experiments demonstrate that the porous CuFe2O4 layered structure exhibits a high sensing response of 96% when exposed to LPG at a temperature of 25 °C. Moreover, it demonstrates excellent repeatability and rapid response recovery characteristics. Gao et al. [129] successfully synthesized porous ZnFe2O4 nanosheets (Figure 5g) by utilizing graphene sheets as a rigid template. The resulting ZnFe2O4 nanosheets had pores with a size range of 5–50 nm and were composed of nanoparticles with a diameter of approximately 10–20 nm. In comparison to Fe2O3 nanoparticles, ZnO nanoparticles, and ZnFe2O4 nanoparticles, the sensor based on ZnFe2O4 nanosheets exhibited faster response and recovery times (39 s/43 s), higher response (Ra/Rg = 123) and excellent selectivity. The sensor also demonstrated good repeatability and stability. Moreover, the unique mesoporous ZnFe2O4 nanosheets enabled the detection of H2S gases as low as 500 ppb at 85 °C (Figure 5h). The enhanced performance of the ZnFe2O4 nanosheets can be ascribed to their high specific surface area and porous characteristics. The increased specific surface area provides more active sites for gas molecule adsorption and reaction, enhancing the gas-sensing response. The porous structure of the nanosheets allows for the diffusion of target gas molecules, facilitating their interaction with the sensing material. Additionally, the two-dimensional structure of the nanosheets prevents the aggregation of nanoparticles, ensuring a larger effective surface area for gas sensing and maintaining the structural integrity of the material. Overall, the combination of high specific surface area, porous features, and two-dimensional structure contributes to the enhanced gas-sensing performance of ZnFe2O4.

3.4. Nanospheres

Spinel ferrite nanospheres can be classified into solid spheres [147], hollow spheres [149], core−shell spheres [139], and double-shell (or triple-shell) spheres [153]. They are mainly prepared using solvent thermal methods or metal–organic framework (MOF) [142] methods. In recent years, the template-free solvent thermal method has become the mainstream approach for synthesizing three-dimensional spinel ferrite materials.
Nanospheres typically consist of solid spheres or hollow spheres that can evolve from the core–shell structure. They are characterized by their low density, high specific surface area, pronounced surface activity, and notable stability [148]. Previous research suggests that to achieve a larger specific surface area, it is essential to decrease the size of the nanoparticles. Assembling nanoparticles into nanospheres allows for better control over the size, resulting in larger specific surface areas and higher sensitivity. The enhanced reactivity and gas-sensing performance of nanospheres can be attributed to their increased surface area-to-volume ratio.
Zhai et al. [142] conducted a study where they synthesized NiFe2O4 polyhedron structures (Figure 6a) derived from metal–organic frameworks (MOF) using solvothermal synthesis. By altering the solvent composition, they were able to synthesize large NiFe2O4 polyhedra with a more stable morphology and structure. These large polyhedra exhibited excellent gas-sensing properties for TEA. Notably, they demonstrated a fast response time of 6 s to 50 ppm TEA, an enhanced response value of 18.9 to 50 ppm TEA (Figure 6b), and showed good selectivity and repeatability at relatively low operating temperatures of 190 °C. The fast response rate of the sample can be attributed to its unique dense hollow structure. The hollow structure enables the REDOX reaction between TEA molecules and the material to occur predominantly at the surface/interface, while the interior of the material remains inactive. This reduces the electron conduction path, leading to the observed fast response time. Qu et al. [153] conducted research on the synthesis of ZnFe2O4 double-shell microspheres using a hydrothermal method and thermal treatment. Figure 6e is the XRD pattern of the yolk–shell, double-shell hollow spheres, and solid microspheres. Compared with the yolk–shell and solid microspheres, the ZnFe2O4 double-shell hollow spheres not only reduced the operating temperature of the sensor, but also enhanced its acetone sensitivity because of the improved crystallinity and larger specific surface area. The sensor displayed a response of 2.6 to 5 ppm acetone at 206 °C (Figure 6f), with a response time of 6 s and a recovery time of 10 s. Furthermore, it is noteworthy that the detection limit for acetone achieved by the sensor was reported to be 0.13 ppm. This value is significantly below the established risk level for life and health, which is 20,000 ppm. Additionally, it is well below the diagnostic threshold for diabetes, which is set at 0.8 ppm. This indicates the high sensitivity and potential of the sensor in accurately detecting and monitoring acetone levels in various applications.
Zhou et al. [147] successfully synthesized porous ZnFe2O4 nanospheres (Figure 6c) using a template-free solvothermal method, followed by annealing at 400 °C. These nanospheres consisted of numerous nanoparticles and possessed a pore size ranging from 10 to 20 nm. The distinctive porous spherical structure greatly improved the sensor’s acetone sensing performance. The response value for 30 ppm acetone reached 11.8, which is 2.5 times higher compared with that for the ZnFe2O4 nanoparticles (Figure 6d). A swift response time of 9 s showcased its ability to promptly detect and react to variations in the target gas. However, the recovery time was relatively longer, taking 272 s. Subsequently, zhou et al. [149] employed a template-free solvent-heat treatment followed by heat treatment at 400 °C for 2 h to fabricate ZnFe2O4 hollow microspheres assembled with nanosheets (Figure 6g). The nanosheets within the microspheres had an average thickness of 20 nm, while the hollow microspheres themselves had diameters ranging from 0.9 to 1.1 μm. The hollow flower-like structure offered multitudes of adsorption/reaction sites, and the presence of diffusion channels, primarily distributed in the aperture range of 2 to 50 nm, facilitated the diffusion of target gases. At an operating temperature of 215 °C, the sensor exhibited a response value of 37.3 to 100 ppm acetone (Figure 6h) and demonstrated good long-term stability. However, under the same conditions, the response to ethanol was also high, measuring at 27.0. The presence of layered hollow structures in semiconductor oxides can enhance the diffusion of target gases, making them advantageous for gas-sensor applications.

4. Doping

Element doping is indeed a powerful strategy to enhance the structure and performance of spinel ferrite materials, and there has been a growing interest in this research area recently. While earlier studies on spinel ferrite doping mostly concentrated on applications such as electrodes and magnetism, recent advancements have shed light on the importance of doping for optimizing gas-sensing properties. However, not all metallic elements are suitable for doping in spinel ferrite materials. Preferably, elements with donor characteristics (high valence elements that can donate electrons) or acceptor characteristics (low valence elements that can accept electrons) are used for modification. Doping in spinel ferrite materials can occur in two forms. The first form of doping involves displacement, where the M2+ (A site) and Fe3+ (B site) ions in the spinel ferrite are replaced by the doping elements. This changes the composition of the spinel ferrite and can affect its properties, such as A-site doping [155], B-site doping [156], and AB-site doping [157]. The second involves the incorporation of doping elements into the tetrahedral and octahedral interstices of MFe2O4 crystals. This results in a solid solution structure, where the doping elements are homogeneously dispersed within the host material [158]. Doping can significantly alter the composition and microstructure of spinel ferrite materials, influencing characteristics such as crystallinity [159]. These changes can, in turn, affect the reference resistance [160] and gas-sensing performance [161] of the ferrite-based gas sensors. For instance, doping can enhance the sensitivity [162], selectivity [163], response speed [28], and stability [164] of the sensors. In this section, we will review the latest research progress on element doping in spinel ferrite materials and its influence on their gas-sensing properties (Table 5, Table 6, Table 7, Table 8 and Table 9). The focus will be on how different doping elements can affect the sensor’s performance, the optimal doping concentrations, and the underlying mechanisms behind these effects. This review will provide valuable insights for the design and fabrication of high-performance ferrite-based gas sensors.

4.1. A Site Doping

Compounds of the MFe2O4 type, where M represents elements such as Mg, Cu, Zn, Ni, and Co, are widely utilized in the field of sensors due to their favorable surface activity. The study conducted by Mukherjee et al. [155] presents an interesting perspective on how the morphology and structure of ferrite-based materials can influence their gas-sensing properties. In their research, they synthesized one-dimensional Mg0.5Zn0.5Fe2O4 hollow tubes using a wet chemical process assisted by an alumina template. They evaluated the gas-sensitive properties of two versions of these nanotubes: one version was embedded in a porous alumina template (Figure 7a) and the other was isolated and coated on a quartz substrate (Figure 7e). The nanotubes exhibited good responsiveness to H2, CO, and N2O gases in both configurations. Interestingly, they observed a difference in the behavior of the nanotubes based on their configuration. Regardless of the type of test gas, the concentration of the test gas, or the operating temperature, the embedded nanotubes consistently behaved as N-type semiconductors. N-type semiconductors are characterized by an excess of electrons (Figure 7b,c). On the other hand, the isolated nanotubes behaved as P-type semiconductors (Figure 7f,g), which are characterized by a deficiency of electrons or an excess of “holes” for the electrons. This inversion from N-type to P-type dominance of carriers, when going from embedded to isolated nanotubes, is a significant finding. It suggests that the electronic properties of ferrites can be customized by changing their surface-to-volume ratio. In other words, by altering the physical configuration of the ferrites (from embedded to isolated), it is possible to control their semiconductor behavior. This finding opens up new possibilities for the design and fabrication of ferrite-based gas sensors, as it introduces an additional degree of tunability in their properties.
Dalawai et al. [90] prepared NixZn1−xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) using the oxalic acid co-precipitation method. With the increase in nickel content in Ni-Zn ferrite, the bond length (A-O) and ionic radius (rA) at site A decreased (Figure 7d), while the bond length (B-O) and ionic radius (rB) at site B remained unchanged. Infrared spectroscopy revealed two major absorption bands near 400 and 600 cm−1, corresponding to tetrahedral and octahedral locations, respectively. Compared with LPG and Cl2, ZnFe2O4 thick films showed a higher sensitivity to ethanol (82%) (Figure 7h), better response time (30 s), and better recovery time (90 s). NiFe2O4 thick film has a good sensitivity (63%), good response (30 s) and good recovery time (70 s) to LPG. Compared with LPG, Ni0.6Zn0.4Fe2O4 displayed a higher sensitivity towards Cl2 and ethanol gases. Zhang et al. [187] conducted a study where they synthesized Cu-doped ZnFe2O4 nanoparticles (Cu-ZFNPs) using a hydrothermal method. Interestingly, the addition of copper did not significantly alter the size of the nanoparticles, which remained around 50 nm for both the pure and Cu-doped ZFNPs. Figure 7j shows the XRD patterns of the pure ZFNPs and Cu-ZFNPs with different Cu concentrations However, the gas-sensing performance of the nanoparticles was notably affected by copper doping. The Cu-ZFNPs exhibited a superior performance in detecting H2S gas compared with the pure ZFNPs, particularly at lower temperatures. This proves that the introduction of copper into the ZnFe2O4 nanoparticles improved their sensitivity to H2S gas, highlighting the effectiveness of element doping in optimizing the properties of spinel ferrite materials. The best gas-sensing performance was achieved with Cu-ZFNPs containing an appropriate concentration of copper. These nanoparticles demonstrated a maximum response of 37.9 to 5 ppm H2S at room temperature (Figure 7k). The sensor also exhibited rapid response and recovery times, taking only 10 s to respond to the presence of H2S and 210 s to recover after the gas was removed.
Using the co-precipitation method, Mondal et al. [201] conducted a study where they synthesized Cu0.5Ni0.25Zn0.25Fe2O4 nanoparticles and Cu0.25Ni0.5Zn0.25Fe2O4 nanoparticles. At ambient room temperature, both sensors demonstrated exceptional responsiveness to acetone and ethanol. The inclusion of Cu in Cu0.5Ni0.25Zn0.25Fe2O4 resulted in a noteworthy enhancement in sensitivity to acetone, reaching an impressive 77%, while the introduction of Ni in Cu0.25Ni0.5Zn0.25Fe2O4 improved the sensitivity to ethanol to 75%. These findings suggest that the addition of specific transition metal elements, such as copper and nickel, enhances the gas-sensing properties of the ferrite nanoparticles, making them promising materials for the detection of acetone and ethanol gases. Gauns et al. [199] fabricated a thick film of Ni0.4Mn0.3Zn0.3Fe2O4 (Figure 7i) on a glass substrate for the detection of Cl2. The thick ferrite film composed of x = 0.3 showed a high selective response to Cl2 gas at 100 °C. For 300 ppm of Cl2 gas, the response was 212% (Figure 7l). The reaction time was less than 10 s and the recovery time was less than 15 s.
Table 6. Summary of the reported spinel ferrite B-site doping-based gas sensors.
Table 6. Summary of the reported spinel ferrite B-site doping-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
MgFe1.98Mo0.02O4Auto-combustionNanoparticles
(310 nm)
Acetone3805000.65 c180 s/-[165]
Li0.5Fe2.45Sm0.05O4Sol–gel self-combustionNanoparticles
(200 nm)
Methanol3402000.86 c--[202]
CuCe0.04Fe1.96O4Molten-saltNanoparticles
(10 nm)
LPG27520000.86 c5 s/68 s-[203]
CoFe1.96Ce0.04O4Molten-saltNanoparticles
(20 nm)
Acetone2251001.77 b45 s/70 s-[204]
NiLaFe2O4Co-precipitationNanoparticles (9.26 nm)NH33550786 a163/64 s-[205]
Bi-Co ferriteSol–gelNanoparticles (6.5–89 nm)NO22302000.34 c31/29 s-[186]
MgFe1.88Ce0.12O4Glycine combustionThick filmAcetone32510000.94 c--[156]
CoSm0.1Fe1.9O4SolvothermalNanoparticlesLPG22510,000846 c--[206]
MgCe0.2Fe1.8O4Glycol-thermalNanoparticlesAcetone225100500 a--[207]
1.5% Sn-BiFe2O4Sol–gelNanoparticlesHCHO28013.05 b2.7 s/25 s100 ppb[208]
1 wt.% La-CoFe2O4Spray-depositedThin filmsNH3RT2000.99 c44/53 s-[209]
a Response is defined as Ra/Rg; b Response is defined as Rg/Ra; c Response is defined as ∆R/Ra.

4.2. B Site Doping

Spinel ferrite, represented by the formula (M2+)(Fe3+)2O4, adopts a face-centered cubic crystal structure. It can be classified into three types: normal spinel, inverse spinel, and mixed spinel. The arrangement of divalent and trivalent metal ions in tetrahedral and octahedral sites within the crystal lattice determines the spinel classification [210]. The introduction of rare earth ions (RE) as substitutions for a small portion of iron can have significant effects on the electrical and magnetic properties of spinel ferrite. For example, the introduction of Ce, which involves the coupling of 3d–4f interactions, leads to changes in the electrical and magnetic behaviors. Furthermore, Ce substitution can also impact the distribution of cations within the spinel lattice, resulting in alterations to its structural, magnetic, physicochemical, and electrical properties [211]. Other rare earth elements, when substituted into the spinel structure, can similarly induce changes in structural, magnetic, and electrical properties, although the specific effects may differ from those observed with Ce3+ [212]. Mkwae et al. [207] conducted a study where they prepared MgCexFe2−xO4 (0 < x < 0.2) nanoparticles (Figure 8a). X-ray diffraction (Figure 8b) analysis confirmed that the sample containing a lower concentration of Ce formed a pure cubic spinel phase. However, with higher Ce doping (x > 0.2), the formation of a secondary phase was observed. The grain size of the compounds ranged from 2.2 nm to 15.3 nm. As the Ce concentration increased, the spin state of 57Fe Mossbauer transitioned from an ordered state to a paramagnetic state. The MgCexFe2−xO4 nano-ferrite exhibited a high sensitivity and selectivity towards the 100 ppm acetone vapors, with a response concentration exceeding 500 at 225 °C (Figure 8c). The sensor also demonstrated excellent repeatability, reversibility, and stability over a period of 120 days.
Table 7. Summary of the reported spinel ferrite AB site doping-based gas sensors.
Table 7. Summary of the reported spinel ferrite AB site doping-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
Mg0.9Sn0.1Mo0.02
Fe1.98O4
Auto-combustionNanoparticlesethanol3805000.64 c--[165]
Ni0.99Co0.01Mn0.02Fe1.98O4Self-combustionNanoparticlesacetone2155004.5 c--[213]
Co0.7Zn0.3Fe1.975
Gd0.025O4
Sol–gelNanoparticlesH2SRT500.4 d11 s/5 s-[157]
Co0.7Zn0.3La0.1
Fe1.9O4
Sol–gelNanoparticles (20 nm)NH3RT2000.87 c116 s/45 s-[214]
Zn0.7Mn0.3Gd0.025Fe1.975O4Co-precipitationNanoparticles (20–30 nm)acetoneRTsaturated0.53 c36 s/56 s-[215]
c Response is defined as ∆R/Ra; d Response is defined as ∆R/Rg.
Table 8. Summary of the reported noble metal-decorated spinel-ferrite-based gas sensors.
Table 8. Summary of the reported noble metal-decorated spinel-ferrite-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
Au/NiFe2O4Solid-state reactionNanoparticlesH2S300535.8 b--[216]
Au/NiFe2O4Co-precipitationNanoparticlesC6H5CH3350100015.8 b--[217]
Au/ZnFe2O4SolvothermalYolk–shell
Microspheres
H2SRT20065.9 a46/629 s-[218]
ZnO/ZnFe2O4/AuElectrospinning, atomic layer deposition and solution reactionHollow meshesAcetone22510030.3 a1/59 s-[219]
Au/ZnFe2O4Solution-phase
deposition
Yolk–shell
Spheres
C6H5Cl1501090.9 a-100 ppb[220]
Au/ZnFe2O4HydrothermalNanoparticlesAcetone1204026 a4/69 s-[221]
ZnO/ZnFe2O4/AuHydrothermal and Co-precipitationYolk–shell microspheres assembled from nanosheetsAcetone20610018.18 a4/23 s0.7 ppm[222]
Ag/NiFe2O4Solid-state reactionNanoparticlesAcetone-100043 a1/10 s-[223]
Ag/ZnFe2O4HydrothermalHollow sphereAcetone17510033.8 a17/148 s-[224]
Pd/Co0.8Ni0.2Fe2O4Sol–gelNanoparticlesNH32102000.91 c20 s/--[225]
Pd/MgFe2O4Molten saltNanoparticles
(15–20 nm)
LPG200200432 a--[226]
Pd/NiFe2O4Spray pyrolysisNanoparticlesEthanol325154.15 c3/13 s-[158]
Pd/NiFe2O4Spray pyrolysisThin filmsCl237556.9 d--[227]
Pd/Co0.55Zn0.45Fe2O4HydrothermalNanoparticlesH227550000.99 c25/3 s [228]
Pt/CuFe2O4ElectrospinningNanotubesAcetone30010016.5 a--[229]
Ru/NiFe2O4Co-precipitationNanoparticles
(0.48 nm)
H2S100501.39 b--[230]
a Response is defined as Ra/Rg; b Response is defined as Rg/Ra; c Response is defined as ∆R/Ra; d Response is defined as ∆R/Rg.

4.3. AB Site Doping

Rezlescu et al. [165] conducted a study where they prepared Mg1−xSnxMoyFe2−yO4 (x = 0, 0.1, and y = 0, 0.02) ferrites using metal nitrate as the raw materials using the self-combustion method. The introduction of Sn and Mo ions induced structural changes in terms of grain size and porosity. Specifically, the sample containing tin exhibited the highest porosity, with particle sizes around 100 nm. When Sn ions partially replaced Mg in MgFe2O4 ferrite, the resistivity of the material improved by approximately two orders of magnitude. The samples were subjected to testing to evaluate their sensing capabilities towards reducing gases, specifically ethanol and acetone. The gas sensitivity was found to depend largely on the type of substituted ion and the specific gas being detected. Overall, all ferrites exhibited a higher sensitivity to acetone compared with ethanol. Among all of the ferrites tested, Mg0.9Sn0.1Fe2O4 demonstrated the highest sensitivity to acetone. These findings highlight the potential of Mg0.9Sn0.1Fe2O4 ferrite as a highly sensitive material for the detection of acetone gas. Mugutkar et al. [214] synthesized Co0.7Zn0.3LaxFe2−2xO4 (x = 0–0.1) nanoparticles (Figure 8d) using the sol–gel method. The XRD pattern (Figure 8e) of ferrite powder was refined using the Rietveld technique, and it was found that a single-phase spinel structure was formed. Through the analysis of the gas-sensitive properties, the response of the Co0.7Zn0.3LaxFe2−2xO4 sensor was 0.87 towards 200 ppm NH3 at RT, with a short response and recovery time of 116 and 45 s (Figure 8f), respectively.

4.4. Noble Metal Doping

Currently, the noble metals widely utilized in gas-sensing applications encompass Pt, Pd, Au, Ag, and Ru, as well as their bimetallic composites. The enhancement of gas-sensing performance can be attributed to two key mechanisms: the electronic sensitization effect achieved by constructin metal−semiconductor contact [231] and the chemical sensitization effect stemming from the spillover phenomenon [232]. These mechanisms work in tandem, facilitating rapid interaction between noble-metal-decorated semiconductor spinel ferrite and target gases, while also effectively lowering the work temperatures by reducing the activation energy required for gas sensing.
Table 9. Summary of the reported other element doping spinel-ferrite-based gas sensors.
Table 9. Summary of the reported other element doping spinel-ferrite-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
V-ZnFe2O4Citrate pyrolysisNanoparticlesAcetone30010023 a--[233]
Zr-CaFe2O4Solid-state reactionNanoparticlesCO235050003.3 a--[234]
In-CuFe2O4Co-precipitationThin filmLPG255 vol%0.3715 c229 s/--[184]
Sb-ZnFe2O4Spray pyrolysisMicroporous spheresn-butanol25010033.5 a4 s/250 s-[235]
V-NiFe2O4Co-precipitationNanoparticlesNORT20043 a5 s/--[236]
W-CoFe2O4Sol–gelNanoparticlesAcetone35020001.45 c- [237]
a Response is defined as Ra/Rg; c Response is defined as ∆R/Ra.
Li et al. [220] conducted a study wherein they utilized the liquid phase deposition precipitation method to prepare a ZnFe2O4 egg yolk–shell ball structure consisting of ultra-thin nanosheets and ultra-small nanoparticles. The surface of this structure was adorned with nanoscale gold particles, each with a diameter ranging from 1 to 2 nm. The experimental results revealed a significant four-fold increase in response (Rair/Rgas = 90.9) for the Au/ZnFe2O4 sensor when exposed to 10 ppm chlorobenzene at 150 °C (Figure 9b), compared with the original ZFO sensor. Furthermore, the Au/ZnFe2O4 sensor demonstrated excellent selectivity and exhibited the potential for application in chlorobenzene monitoring. The introduction of nanoscale gold particles onto the surface of the ZFO yolk–shell balls (Figure 9a) resulted in electronic and chemical sensitization effects, thereby enhancing the chlorobenzene sensing performance of the ZnFe2O4 yolk–shell balls. Additionally, density functional theory (DFT) calculations were employed to corroborate the findings, confirming that the presence of gold nanoparticles on the surface of ZnFe2O4 increased electron density, exhibited a higher adsorption energy, and facilitated net charge transfer. These factors collectively contributed to the heightened sensing response of the sensor towards chlorobenzene. Zhang et al. [224] employed a hydrothermal method to introduce Ag into ZnFe2O4 hollow structures (Figure 9c) composed of stacked nanosheets. The addition of Ag altered the surface structure, but did not significantly affect the size of the hollow structures. At a temperature of 175 °C, the sensor based on 0.25 wt.% Ag-doped ZnFe2O4 (Ag/ZnFe2O4) exhibited a superior sensing performance compared with the pure ZnFe2O4 sensor (Figure 9d). This improvement in performance can be attributed to the suitable hollow structure and the activation effect of Ag. Ag/ZnFe2O4 sensors show promising potential for detecting low concentrations of acetone in the parts per million range. Additionally, these sensors demonstrate good gas selectivity to acetone and minimal influence from humidity. However, further research and improvement are needed to address the long-term stability of Ag/ZnFe2O4 sensors.
Li et al. [219] successfully synthesized ZnO/ZnFe2O4/Au heterostructures (Figure 9e,f) with a porous mesh structure using a three-step method (a combination of electrospinning, atomic layer deposition, and solution reaction). The resulting ZnO/ZnFe2O4/Au structures exhibited a porous mesh-like morphology. The composite structure comprised of a uniform ZnO nanotube skeleton measuring 50 nm, ultra-thin ZnFe2O4 nanosheets with a thickness of 10 nm, and well-dispersed Au nanoparticles. It had the characteristics of a large specific surface area, porous structure, ultra-thin thickness and high catalytic activity. The gas-sensing results show that the sensor based on the ZnO/ZnFe2O4/Au nanonet had the highest sensing response (30.3), a significantly enhanced selectivity, and a faster response/recovery speed (1 s/59 s). The response of ZnO/ZnFe2O4/Au to acetone was about three times higher than that of ZnO/ZnFe2O4 composites and 5.5 times higher than that of the original ZnO (Figure 9g). The enhanced sensing performance was mainly due to the increase in the surface active sites of AuNPs, the obvious resistance modulation effect, and the excellent sensitization ability.

4.5. Other Element Doping

Doping refers to the process of introducing impurity atoms into a material, which can have various effects on the lattice and structure of the host material. One effect of doping is the alteration of the lattice constant, which is the spacing between the atoms in the crystal lattice. The presence of dopant atoms can disrupt the regular arrangement of atoms in the lattice, leading to changes in the lattice constant. Furthermore, doping can also introduce structural defects into the matrix material. These defects can include vacancies, where atoms are missing from lattice sites, or interstitials, where dopant atoms occupy spaces between lattice sites [238]. These defects can affect the overall structure and properties of the material, such as its electrical conductivity or optical properties. In addition to changing the lattice constant and introducing structural defects, doping can also regulate the charge exchange behavior of the material [239]. Doped ions often have multiple valence states, meaning they can exist in different charge states depending on the electron configuration [184]. When doped ions occupy equivalent lattice locations, they can undergo charge exchange with neighboring ions, leading to changes in the electronic properties of the material. This charge exchange behavior can influence the material’s conductivity, magnetism, or other electronic properties [236,237]. Overall, doping is a versatile technique that can be used to modify the lattice, introduce defects, and regulate the charge exchange behavior in materials, thereby tailoring their properties for specific applications. Jiang et al. [233] conducted a study where they prepared ZnFe2O4 nanoparticles and vanadium (V)-doped ZnFe2O4 nanoparticles using citrate pyrolysis. Interestingly, the particle size of the spherical particles remained unaffected by the V content added. However, as the V content increased, the resistance of the thick film based on ZnFe2O4 decreased. The study also revealed that the addition of V had varying effects on the sensitivity to different VOCs (Figure 9h). The sensitivity to ethanol and acetone was significantly reduced due to the addition of V. However, at higher temperatures, the addition of V notably improved the sensitivity to benzene, toluene, and xylene. These findings suggest that V doping in ZnFe2O4 nanoparticles can have a selective impact on the sensitivity to different VOCs. While the sensitivity to ethanol and acetone decreased, the sensitivity to benzene, toluene, and xylene improved, particularly at elevated temperatures.

5. Heterostructure

In Section 3 and Section 4, it has been discussed how the gas-sensitive performance of spinel ferrite sensors can be enhanced through the manipulation of their morphology or the introduction of doping elements. However, to achieve the desired properties, researchers have explored the development of spinel ferrite composites, which find more extensive applications in the fields of photocatalysis and sensing. Consequently, the objective of this section is to provide a review of the latest research on spinel ferrite composites and to present the impact of these two types of composites on the gas-sensitive properties (Table 10, Table 11 and Table 12). The development of spinel ferrite composites has gained significant attention due to their potential to synergistically enhance the gas-sensitive performance. These composites often involve combining spinel ferrite with other materials such as metal oxides, carbon-based materials, or polymers. The unique properties of these composite materials can be leveraged to improve the gas-sensing properties of spinel ferrite sensors. For example, metal-oxide-based spinel ferrite composites have demonstrated an improved gas-sensing performance due to the enhanced specific surface area and increased active sites provided by the metal oxide component. The combination of spinel ferrite with carbon-based materials, such as graphene or carbon nanotubes, can enhance the electrical conductivity and provide additional adsorption sites, leading to enhanced gas-sensing capabilities. In summary, the development of spinel ferrite composites has opened up new avenues for enhancing the gas-sensitive properties of spinel ferrite sensors. These composites, whether metal-oxide-based, carbon-based, or incorporating polymers, offer unique advantages that can be leveraged to achieve an improved gas-sensing performance.

5.1. Other MOSs/Ferrite

There are primarily two methods for synthesizing heterostructures between other metal oxides and spinel ferrite: the one-step method [283] and the multi-step method [258]. The one-step method can yield highly uniform heterostructures, forming microscopic heterojunctions, but it is challenging to control the ratio of the two phases [271]. The multi-step method allows for more precise control in different synthesis stages, including the reaction conditions, proportions, and reaction time, to obtain the desired product properties and structures. However, it increases the duration and cost of the synthesis process [273].
Xu et al. [258] conducted a study in which they prepared NiO/NiFe2O4 nanocomposites using a straightforward two-step hydrothermal method. The nanocomposites consisted of NiO nano-tetrahedrons with numerous NiFe2O4 nanoparticles dispersed on their outer surface (Figure 10a,b), forming p–p type heterojunctions. By adjusting the amount of Fe added during the synthesis process, the Fe to Ni ratio was optimized. The nanocomposite designated as NiFe-0.008 exhibited a remarkable gas-sensing performance (Figure 10c), with a high response of 19.1 towards 50 ppm formaldehyde smoke at 240 °C. Additionally, it displayed a low detection limit of 200 ppb and demonstrated good long-term stability. Comparatively, the optimized NiFe-0.008 nanocomposite outperformed individual NiO nano-tetrahedrons (with a response of 11.6 at 250 °C) and NiFe2O4 nanoparticles (with a response of 6.8 at 300 °C) in terms of the gas-sensing performance. These findings highlight the improved response performance achieved by the optimized NiFe-0.008 nanocomposite. Hu et al. [248] conducted a study where they modified CuO microspheres by incorporating CuFe2O4 nanoparticles (Figure 10f), resulting in CuFe2O4/CuO heterostructures. These heterostructures exhibited a high sensitivity to hydrogen H2S. The researchers investigated the relationship between the mass ratio of CuFe2O4 to CuO and the operating temperature to optimize the sensor’s response to H2S.The results of the study demonstrate that the optimized CuFe2O4/CuO heterostructures exhibited a significantly enhanced response to 10 ppm H2S at 240 °C (Figure 10g), reaching approximately 20 times that of the initial CuO microspheres. Moreover, the optimized heterostructures showed excellent fast response and recovery abilities. These findings suggest that the incorporation of CuFe2O4 nanoparticles into CuO microspheres can effectively enhance the gas-sensing performance of the sensor towards H2S. The optimized CuFe2O4/CuO heterostructures demonstrated a substantial improvement in sensitivity compared with the preliminary CuO microspheres, making them promising candidates for the detection of H2S gas. Balaji et al. [263] conducted a study in which they synthesized SnO2 composite Mn1−xCuFe2O4 (x = 0, 0.5, and 1.0) nanocomposites with an equal mass percentage using the chemical coprecipitation method. The addition of SnO2 to copper-substituted manganese ferrite resulted in an increase in grain size and a decrease in strain value. The morphological analysis revealed that the average particle size of the ferritic materials decreased linearly with the decrease in Mn2+ concentration. The presence of SnO2 on the surface of Cu-Mn ferrite led to an increase in particle size and a weakening of the magnetic properties. Furthermore, the addition of SnO2 to MnFe2O4 and Mn1−xCuxFe2O4 enhanced the sensitivity of the gas sensor. MnFe2O4 exhibited resistance to oxygen and carbon dioxide, while SnO2-CuFe2O4 showed a weak sensitivity. This indicates that the adsorption/chemisorption of oxygen or surface lattice oxygen atoms plays a dominant role in the complete oxidation of molecules. These findings highlight the impact of SnO2 addition on the structural and gas-sensing properties of Mn1−xCuFe2O4 nanocomposites. The changes in grain size, strain value, particle size, and gas sensitivity provide valuable insights into the design and optimization of gas-sensing materials for specific applications.
Wei et al. [254] successfully synthesized MOF-based Fe2O3/ZnFe2O4 porous nanocomposites using a solvothermal method. The nanocomposites consist of spindles-like Fe2O3 with a length of about 2 μm and a width of about 400 nm (Figure 10d), which are uniformly adhered to ZnFe2O4 nanoparticles. Through the analysis of the TEA (triethylamine) gas-sensing mechanism, it was observed that the heterojunction between the spindles-like Fe2O3 and ZnFe2O4 nanoparticles played a crucial role in improving the gas-sensing performance. Compared with pure MOF-derived Fe2O3 spindles, the gas-sensitive properties of Fe2O3/ZnFe2O4 nanocomposites were enhanced and exhibited a remarkable response value of up to 69.24 when exposed to 100 ppm TEA (Figure 10e). This indicates a significant improvement in the gas-sensing performance of the nanocomposites compared with the pure Fe2O3 spindles derived from MOF. Using Cu@carbon as a sacrificial template, Li et al. [29] successfully synthesized CuFe2O4/α-Fe2O3 hollow spheres with a diameter of ~210 nm with porous non-thin shells (Figure 10h) by thermal oxidation and solid phase reaction. The gas-sensitive properties of CuFe2O4/α-Fe2O3 composites were compared with those of pure α-Fe2O3 hollow spheres. As anticipated, the sensor based on the CuFe2O4/α-Fe2O3 composite exhibited a higher sensitivity (Ra/Rg = 14), faster response and recovery times (6 s/100 s), and lower detection limits (100 ppb) compared with the original α-Fe2O3 hollow spheres (Figure 10i). The enhanced sensing performance of the CuFe2O4/α-Fe2O3 composites can be attributed to several factors. Firstly, the hollow porous structure of the composites provides a larger surface area, which increases the number of active sites for gas adsorption and improves sensitivity. Additionally, the presence of the heterojunction between CuFe2O4 and α-Fe2O3 allows for modulation of the resistance and facilitates charge transfer, further enhancing the gas-sensing performance. Lastly, the catalytic performance of CuFe2O4 in the composites contributes to the improved sensing properties.
Li et al. [287] utilized a metal–organic skeleton to prepare a precursor similar to Prussian blue, and then employed direct pyrolysis to fabricate hollow ZnO/ZnFe2O4 microspheres with a heterogeneous structure (Figure 11a). These microspheres had a diameter of approximately 1.5 μm. As a gas-sensitive material, the hollow ZnO/ZnFe2O4 microspheres exhibited a temperature-dependent n–p–n-type abnormal conductive transition (Figure 11b) when detecting low concentrations of volatile organic compounds (VOCs) such as ethanol, acetone, toluene, and benzene. This phenomenon can be primarily attributed to the interplay of highly separated electron–hole pairs caused by the staggered band arrangement at the heterogeneous interface of the ZnO-ZnFe2O4 shell. This interplay is influenced by the heat-dependent ionization reaction of the surface-absorbed oxygen molecules and the additional electron injection resulting from the reducing VOCs’ surface reaction during the gas-sensitive process. The abnormal conductive transition observed in the hollow ZnO/ZnFe2O4 microspheres when exposed to low concentrations of VOCs is a result of the complex interplay between the different processes occurring at the heterogeneous interface. This understanding of the underlying mechanism contributes to the understanding and optimization of gas-sensing properties for applications in VOC detection. Wang et al. [278] devised a design and synthesis method to create ZnO/ZnFe2O4 hollow nanocages with a diameter of around 100 nm using a metal–organic framework (MOF) technique. The synthesis process involved two steps: the preparation of Fe(III)MOF-5 nanocages as a precursor, followed by the conversion into ZnO/ZnFe2O4 hollow nanocages through hot annealing in air. Based on the BET analysis, it is observed that the ZnO/ZnFe2O4 nanocages, in their as-prepared state, possessed a BET specific surface area of 48.4 m2·g−1 and an average pore size of 9.1 nm, as determined using the BJH method (Figure 11c). Gas-sensing experiments revealed that the ZnO/ZnFe2O4 hollow nanocages exhibited a superior response value of 25.8 to 100 ppm acetone (Figure 11g), with a detection limit of 1 ppm at the optimized temperature of 290 °C. This response value surpassed that of ZnO hollow nanocages (7.9) and ZnFe2O4 nanospheres (8.1). Furthermore, the gas-sensing response of the ZnO/ZnFe2O4 nanocages outperformed that of the other structures, with the response order being as follows: hollow nanocages > double shell > hollow microsphere; hybrid hollow spheres > nanoparticles with rods. Yang et al. [41] conducted a study in which they synthesized coral-like ZnFe2O4-ZnO heterostructures with mesoporous structures (Figure 11d,e) and evaluated their gas-sensing performance towards the volatile organic compound TEA. The prepared sensor was subjected to thorough gas-sensing tests, and the results demonstrated several advantages, including a high response value (Ra/Rg = 21.3 at 240 °C), fast response and recovery times (0.9 s/23 s), and good repeatability (Figure 11f). The combination of the unique coral-like mesoporous morphology, the formation of n–n heterojunctions, and the synergistic effect of ZnFe2O4′s Bronsted centers contributed to the improved TEA sensing properties of the coral-like ZnFe2O4-ZnO. These findings provide valuable insights for the design and optimization of gas-sensing materials for the detection of volatile organic compounds.

5.2. Nanostructure Materials/Ferrite

In order to maintain the structural stability of nanostructured materials during heterojunction formation, a two-step method is typically employed [300]. This approach not only maintains the stability of the structural materials, but also suppresses the aggregation of the perovskite iron oxides during synthesis [304].
Nanostructured materials, such as two-dimensional (2D), one-dimensional (1D), and zero-dimensional (0D) structures, possess unique dimensional characteristics that contribute to their attractive physicochemical properties. These structures exhibit small volume, high electron mobility, and large specific surface areas, making them highly advantageous in various applications. In the field of gas sensing, nanostructures with a large surface area and high porosity have been found to significantly enhance the performance of gas sensors. The increased surface area and porosity provide more reaction sites, enabling more efficient interaction between the sensing material and the target gas molecules. This enhanced interaction leads to improved sensitivity and selectivity in gas-sensing applications. A notable strategy to achieve synergistic effects is the integration of metal oxide semiconductor (MOS) materials with nanostructured materials possessing large specific surface areas.
Zhang et al. [290] achieved the successful synthesis of porous microsphere composites by incorporating g-C3N4 into MgFe2O4 (Figure 12a,b) using a solvothermal method. In the study, the content of g-C3N4 was varied, and it was found that the sensor based on the MgFe2O4/g-C3N4 composite material exhibited excellent gas-sensing performance. Specifically, when the g-C3N4 content was 10 wt.%, the sensor showed several desirable characteristics, including high sensitivity and selectivity, fast response and recovery times. Notably, the maximum response to acetone increased by approximately 145 times compared with the sensors without g-C3N4. Moreover, the optimal temperature for sensing was reduced by 60 °C. Chu et al. [291] conducted a study in which they prepared ZnFe2O4/graphene quantum dot (GQD) nanocomposites (Figure 12c) using a hydrothermal method. The researchers aimed to investigate the influence of GQD content on the gas-sensitive response and selectivity of the ZnFe2O4/GQD nanocomposites. The results demonstrated that the sensor based on the ZnFe2O4/GQD nanocomposites exhibited a response of 13.3 to 1000 ppm acetone and a response of 1.2 to 5 ppm acetone at room temperature (Figure 12d). The response time and recovery time for the detection of acetone r were both less than 12 s. However, it should be noted that the long-term gas-sensitive stability of the ZnFe2O4/GQD nanocomposites was not satisfactory. This indicates that further research and improvement are needed to address the stability issue and enhance the long-term performance of the nanocomposites in gas-sensing applications. Bai et al. [298] synthesized rGO/WO3/ZnFe2O4 composites (Figure 12e,f) with varying proportions using hydrothermal, chemical water bath, and chemical reduction methods. The gas sensitivity of the synthesized composites was tested, yielding noteworthy results. Among the different compositions tested, the 0.8 wt.% rGO-9WO3-ZnFe2O4 terpolymer exhibited a superior gas-sensing performance. It demonstrated a significantly higher response value of 26.92, which is six times higher than that of pure WO3 and thirteen times higher than that of ZnFe2O4 (Figure 12i). Furthermore, the synthesized gas-sensitive material displayed excellent selectivity, a shorter response time of 51 s, and a lower detection limit of 0.02 ppm. These characteristics indicate the enhanced performance of the composite material in terms of sensitivity, selectivity, and response speed compared with the individual components. The successful synthesis of the rGO/WO3/ZnFe2O4 composites and their improved gas-sensing performance suggest their potential for applications in gas-sensing devices. Further optimization and exploration of the composite composition and structure can enable the development of highly efficient gas sensors for various target gases.

5.3. Conducting Polymer/Ferrite

In recent years, the synthesis of conductive polymer magnetic nanocomposites has received much attention from researchers because of its lightweight, low-cost preparation methods, and enhanced magnetoelectric properties. Among conductive polymers, polyaniline (PANI) has emerged as a P-type semiconductor material with an excellent sensing ability. While polyaniline-based ammonia sensors have been widely reported, developing faster, highly sensitive, and fully recyclable greenhouse gas sensors remain a major challenge. In this regard, Wang et al. [307] prepared polyaniline/CuFe2O4 heterostructures (Figure 12j) through in situ polymerization. In contrast with the polyaniline-based sensor, the polyaniline/CoFe2O4 composite showed a higher response, with a response of up to 27.37% at 5 ppm NH3, surpassing the performance of the original PANI and CuFe2O4 films by a significant margin. This finding suggests that by combining CuFe2O4 with polyaniline to form a p–n heterojunction, the gas-sensing performance could be enhanced (Figure 12j,k). The p–n heterojunction formed between CuFe2O4 and polyaniline is expected to improve the gas-sensing performance of polyaniline-based sensors. The synergies between the two materials allows for increased sensitivity, faster response times, and better recoverability.

6. Summary and Prospect

This paper provides an exhaustive review of the advancements in spinel-ferrite-based gas sensors, emphasizing three critical areas: nanostructure, elemental doping, and heterostructure. Spinel ferrite gas sensors have garnered interest due to their broad sensitivity and excellent selectivity to various flammable, explosive, toxic, and harmful gases. The gas-sensing mechanism of these sensors depends on intricate interactions and electron transfer at the gas−solid interface. Consequently, alterations in the microstructure of spinel ferrite nanomaterials, such as grain size, specific surface area, and porosity, can substantially influence the sensor’s gas-sensing performance. Metal element doping in spinel ferrite enhances the specific surface area and provides activation energy, while maintaining the original crystal structure. Moreover, the creation of heterojunctions at the interface between different gas-sensitive materials is pivotal in modulating the sensor response by forming an electron depletion layer. A detailed comparison reveals that refining the microstructure, suitable metal element doping, or employing material composites can lead to a certain level of enhancement in the sensing capabilities of gas sensors based on spinel ferrite. Nonetheless, practical applications face challenges, including high power consumption due to thermal excitation effects and extended recovery times due to slow gas desorption. Therefore, innovative research directions are required to achieve swift sensor recuperation and consistent detection at low temperatures, potentially even at ambient room temperature. To overcome these challenges, we suggest a blend of the aforementioned strategies, which may encompass refining the microstructure of spinel ferrites or controlling the iron stoichiometry, designing composite materials composed of spinel ferrite multi-layer porous shells or hollow spheres integrated with nanostructured materials such as reduced graphene oxide and molybdenum disulfide, and developing multi-component hybrid materials. These strategies aim to boost the performance of spinel ferrite gas sensors, with a primary emphasis on achieving a high response and low operating temperatures.

Author Contributions

Conceptualization, Y.W. and J.C.; validation, C.Q., Y.W. and H.B.; formal analysis, J.C.; investigation, R.Z.; data curation, R.Z.; writing—original draft preparation, R.Z.; writing—review and editing, C.Q.; visualization, Y.W.; supervision, J.C. All authors have read and agreed to the published version of the manuscript.

Funding

This work was funded by the National Natural Science Foundation of China (62273134 and 62173129), Program for Science and Technology Innovative Research Team at the University of Henan Province (21IRTSTHN006), the Natural Science Foundation of Henan Province (212300410042), Key Science and Technology Program of Henan Province (232102220009), the Fundamental Research Funds for the Universities of Henan Province (NSFRF220101 and NSFRF230432), and the Key Scientific Research Projects of Colleges and Universities in Henan Province (23A150012).

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Nadargi, D.Y.; Umar, A.; Nadargi, J.D.; Lokare, S.A.; Akbar, S.; Mulla, I.S.; Suryavanshi, S.S.; Bhandari, N.L.; Chaskar, M.G. Gas sensors and factors influencing sensing mechanism with a special focus on MOS sensors. J. Mater. Sci. 2023, 58, 559–582. [Google Scholar]
  2. Yang, X.; Deng, Y.; Yang, H.; Liao, Y.; Cheng, X.; Zou, Y.; Wu, L.; Deng, Y. Functionalization of Mesoporous Semiconductor Metal Oxides for Gas Sensing: Recent Advances and Emerging Challenges. Adv. Sci. 2023, 10, 2204810. [Google Scholar] [CrossRef] [PubMed]
  3. Das, S.; Jayaraman, V. SnO2: A comprehensive review on structures and gas sensors. Prog. Mater. Sci. 2014, 66, 112–255. [Google Scholar]
  4. Kurugundla, G.K.; Godavarti, U.; Saidireddy, P.; Pothukanuri, N. Zinc oxide based gas sensors and their derivatives: A critical review. J. Mater. Chem. C 2023, 11, 3906–3925. [Google Scholar]
  5. Tian, X.; Cui, X.; Lai, T.; Ren, J.; Yang, Z.; Xiao, M.; Wang, B.; Xiao, X.; Wang, Y. Gas sensors based on TiO2 nanostructured materials for the detection of hazardous gases: A review. Nano Mater. Sci. 2021, 3, 390–403. [Google Scholar] [CrossRef]
  6. Kukkola, J.; Mäklin, J.; Halonen, N.; Kyllönen, T.; Tóth, G.; Szabó, M.; Shchukarev, A.; Mikkola, J.-P.; Jantunen, H.; Kordás, K. Gas sensors based on anodic tungsten oxide. Sens. Actuators B 2011, 153, 293–300. [Google Scholar]
  7. Cho, S.-Y.; Yoo, H.-W.; Kim, J.Y.; Jung, W.-B.; Jin, M.L.; Kim, J.-S.; Jeon, H.-J.; Jung, H.-T. High-resolution p-type metal oxide semiconductor nanowire array as an ultrasensitive sensor for volatile organic compounds. Nano Lett. 2016, 16, 4508–4515. [Google Scholar] [CrossRef]
  8. Kauffman, D.R.; Star, A. Carbon nanotube gas and vapor sensors. Angew. Chem. Int. Ed. 2008, 47, 6550–6570. [Google Scholar] [CrossRef]
  9. Beckers, N.; Taschuk, M.; Brett, M. Selective room temperature nanostructured thin film alcohol sensor as a virtual sensor array. Sens. Actuators B 2013, 176, 1096–1102. [Google Scholar] [CrossRef]
  10. Pan, H.; Zhou, L.; Zheng, W.; Liu, X.; Zhang, J.; Pinna, N. Atomic layer deposition to heterostructures for application in gas sensors. Int. J. Extreme Manuf. 2023, 5, 22008. [Google Scholar] [CrossRef]
  11. Srivastava, S.; Pal, P.; Sharma, D.K.; Kumar, S.; Senguttuvan, T.; Gupta, B.K. Ultrasensitive Boron–Nitrogen-Codoped CVD Graphene-Derived NO2 Gas Sensor. ACS Mater. Au 2022, 2, 356–366. [Google Scholar] [CrossRef] [PubMed]
  12. Sriram, S.R.; Parne, S.R.; Pothukanuri, N.; Edla, D.R. Prospects of spray pyrolysis technique for gas sensor applications-A comprehensive review. J. Anal. Appl. Pyrolysis 2022, 164, 105527. [Google Scholar]
  13. Zhang, D.; Yang, Z.; Yu, S.; Mi, Q.; Pan, Q. Diversiform metal oxide-based hybrid nanostructures for gas sensing with versatile prospects. Coord. Chem. Rev. 2020, 413, 213272. [Google Scholar]
  14. Majhi, S.M.; Mirzaei, A.; Kim, H.W.; Kim, S.S.; Kim, T.W. Recent advances in energy-saving chemiresistive gas sensors: A review. Nano Energy 2021, 79, 105369. [Google Scholar]
  15. Selvakumar, D.; Sonu, K.; Ramadoss, G.; Sivaramakrishnan, R.; Jayavel, R.; Eswaramoorthy, M.; Rao, K.V.; Pugazhendhi, A. Heterostructures of polyaniline and Ce-ZnO nanomaterial coated flexible PET thin films for LPG gas sensing at standard environment. Chemosphere 2023, 314, 137492. [Google Scholar] [CrossRef]
  16. Souri, M.; Yamini, Y.; Amoli, H.S. The synergistic effect of Ce dopant/Cotton bio-template on the performance of the SnO2 gas sensor for the detection of Ethanol. Mater. Sci. Eng. 2023, 294, 116501. [Google Scholar]
  17. Qu, Z.; Li, Y.; Xu, R.; Li, C.; Wang, H.; Wang, H.; Zhang, Y.; Wei, Q. Candy-like heterojunction nanocomposite of WO3/Fe2O3-based semiconductor gas sensor for the detection of triethylamine. Microchim. Acta 2023, 190, 139. [Google Scholar] [CrossRef] [PubMed]
  18. Zhou, J.; Lin, Y.; Yang, H.; Ren, Y.; Xu, F. Structural, morphological and magnetic properties of low temperature sintered LiZnTiBi ferrites. J. Alloys Compd. 2023, 932, 167616. [Google Scholar]
  19. Vinod, G.; Rajashekhar, K.; Naik, J.L. Dysprosium doped Cu0.8Cd0.2DyxFe2-xO4 nano ferrites: A combined impact of Dy3+ on enhanced physical, optical, magnetic, and DC-electrical properties. Ceram. Int. 2023, 49, 2829–2851. [Google Scholar]
  20. Wang, X.; Lv, X.; Liu, Z.; Zhang, H.; Liu, M.; Xu, C.; Zhou, X.; Yuan, M.; Yang, L.; You, W. Multi-interfacial 1D magnetic ferrite@ C fibers for Broadband microwave absorption. Mater. Today Phys. 2023, 35, 101140. [Google Scholar] [CrossRef]
  21. Kumari, S.; Dhanda, N.; Thakur, A.; Gupta, V.; Singh, S.; Kumar, R.; Hameed, S.; Thakur, P. Nano Ca-Mg-Zn ferrites as tuneable photocatalyst for UV light-induced degradation of rhodamine B dye and antimicrobial behavior for water purification. Ceram. Int. 2023, 49, 12469–12480. [Google Scholar] [CrossRef]
  22. Singh, S.; Singh, A.; Yadav, B.C.; Tandon, P. Synthesis, characterization, magnetic measurements and liquefied petroleum gas sensing properties of nanostructured cobalt ferrite and ferric oxide. Mater. Sci. Semicond. Process. 2014, 23, 122–135. [Google Scholar] [CrossRef]
  23. Srivastava, R.; Yadav, B.C.; Singh, M.; Yadav, T.P. Synthesis, Characterization of Nickel Ferrite and Its Uses as Humidity and LPG Sensors. J. Inorg. Organomet. Polym. Mater. 2016, 26, 1404–1412. [Google Scholar] [CrossRef]
  24. Rathore, D.; Kurchania, R.; Pandey, R.K. Fabrication of Ni1xZnxFe2O4 (x = 0, 0.5 and 1) nanoparticles gas sensor for some reducing gases. Sens. Actuators A 2013, 199, 236–240. [Google Scholar] [CrossRef]
  25. Abu-Hani, A.F.S.; Mahmoud, S.T.; Awwad, F.; Ayesh, A.I. Design, fabrication, and characterization of portable gas sensors based on spinel ferrite nanoparticles embedded in organic membranes. Sens. Actuators B 2017, 241, 1179–1187. [Google Scholar] [CrossRef]
  26. Maharajan, M.; Mursalin, M.D.; Narjinary, M.; Rana, P.; Sen, S.; Sen, A. Synthesis, Characterization and Vapour Sensing Properties of Nanosized ZnFe2O4. Trans. Indian Ceram. Soc. 2014, 73, 102–104. [Google Scholar] [CrossRef]
  27. De Oliveira, R.C.; Pontes Ribeiro, R.A.; Cruvinel, G.H.; Ciola Amoresi, R.A.; Carvalho, M.H.; Aparecido de Oliveira, A.J.; de Oliveira, M.C.; de Lazaro, S.R.; da Silva, L.F.; Catto, A.C.; et al. Role of Surfaces in the Magnetic and Ozone Gas-Sensing Properties of ZnFe2O4 Nanoparticles: Theoretical and Experimental Insights. ACS Appl. Mater. Interfaces 2021, 13, 4605–4617. [Google Scholar] [CrossRef] [PubMed]
  28. Chethan, B.; Ravikiran, Y.T.; Vijayakumari, S.C.; Rajprakash, H.G.; Thomas, S. Nickel substituted cadmium ferrite as room temperature operable humidity sensor. Sens. Actuators A 2018, 280, 466–474. [Google Scholar] [CrossRef]
  29. Li, X.; Lu, D.; Shao, C.; Lu, G.; Li, X.; Liu, Y. Hollow CuFe2O4/α-Fe2O3 composite with ultrathin porous shell for acetone detection at ppb levels. Sens. Actuators B 2018, 258, 436–446. [Google Scholar] [CrossRef]
  30. Gavilán, H.; Rizzo, G.M.; Silvestri, N.; Mai, B.T.; Pellegrino, T. Scale-up approach for the preparation of magnetic ferrite nanocubes and other shapes with benchmark performance for magnetic hyperthermia applications. Nat. Protoc. 2023, 18, 783–809. [Google Scholar] [CrossRef] [PubMed]
  31. Shen, L.; Lan, G.; Lu, L.; Ma, C.; Cao, C.; Jiang, C.; Fu, H.; You, C.; Lu, X.; Yang, Y. A strategy to modulate the bending coupled microwave magnetism in nanoscale epitaxial lithium ferrite for flexible spintronic devices. Adv. Sci. 2018, 5, 1800855. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  32. Wang, W.; Gumfekar, S.P.; Jiao, Q.; Zhao, B. Ferrite-grafted polyaniline nanofibers as electromagnetic shielding materials. J. Mater. Chem. C 2013, 1, 2851–2859. [Google Scholar] [CrossRef]
  33. Kefeni, K.K.; Mamba, B.B.; Msagati, T.A. Application of spinel ferrite nanoparticles in water and wastewater treatment: A review. Sep. Purif. Technol. 2017, 188, 399–422. [Google Scholar]
  34. Scheffe, J.R.; Allendorf, M.D.; Coker, E.N.; Jacobs, B.W.; McDaniel, A.H.; Weimer, A.W. Hydrogen production via chemical looping redox cycles using atomic layer deposition-synthesized iron oxide and cobalt ferrites. Chem. Mater. 2011, 23, 2030–2038. [Google Scholar] [CrossRef]
  35. Wei, K.; Huai, H.-X.; Zhao, B.; Zheng, J.; Gao, G.-Q.; Zheng, X.-Y.; Wang, C.-C. Facile synthesis of CoFe2O4 nanoparticles and their gas sensing properties. Sens. Actuators B 2022, 369, 132279. [Google Scholar] [CrossRef]
  36. Nemufulwi, M.I.; Swart, H.C.; Shingange, K.; Mhlongo, G.H. ZnO/ZnFe2O4 heterostructure for conductometric acetone gas sensors. Sens. Actuators B 2023, 377, 133027. [Google Scholar] [CrossRef]
  37. Rathore, D.; Mitra, S.; Kurchania, R.; Pandey, R.K. Physicochemical properties of CuFe2O4 nanoparticles as a gas sensor. J. Mater. Sci. Mater. Electron. 2018, 29, 1925–1932. [Google Scholar] [CrossRef]
  38. Zhang, J.; Chen, D.; Chen, L. Preparation of ultrafine ZnFe2O4 and its gas-sensing properties for Cl2. Sens. Mater. 2006, 18, 277–282. [Google Scholar]
  39. Zhang, Y.; Zhou, Y.; Li, Z.; Chen, G.; Mao, Y.; Guan, H.; Dong, C. MOFs-derived NiFe2O4 fusiformis with highly selective response to xylene. J. Alloys Compd. 2019, 784, 102–110. [Google Scholar] [CrossRef]
  40. Wu, K.; Lu, Y.; Liu, Y.; Liu, Y.; Shen, M.; Debliquy, M.; Zhang, C. Synthesis and acetone sensing properties of copper (Cu2+) substituted zinc ferrite hollow micro-nanospheres. Ceram. Int. 2020, 46, 28835–28843. [Google Scholar] [CrossRef]
  41. Yang, T.; Yang, X.; Zhu, M.; Zhao, H.; Zhang, M. Coral-like ZnFe2O4-ZnO mesoporous heterojunction architectures: Synthesis and enhanced sensing properties for triethylamine. Inorg. Chem. Front. 2020, 7, 1918–1926. [Google Scholar] [CrossRef]
  42. Afzal, A.; Mujahid, A.; Iqbal, N.; Javaid, R.; Qazi, U.Y. Enhanced High-Temperature (600 degrees C) NO2 Response of ZnFe2O4 Nanoparticle-Based Exhaust Gas Sensors. Nanomaterials 2020, 10, 2133. [Google Scholar] [CrossRef] [PubMed]
  43. Liu, X.; Xu, Z.; Liu, Y.; Shen, Y. A novel high performance ethanol gas sensor based on CdO-Fe2O3 semiconducting materials. Sens. Actuators B 1998, 52, 270–273. [Google Scholar] [CrossRef]
  44. Chu, X.; Zheng, C. Sulfide-sensing characteristics of MFe2O4 (M = Zn, Cd, Mg and Cu) thick film prepared by co-precipitation method. Sens. Actuators B 2003, 96, 504–508. [Google Scholar] [CrossRef]
  45. Gopal Reddu, C.V.; Manorama, S.V.; Rao, V.J. Preparation and characterization of ferrites as gas sensor materials. J. Mater. Sci. Lett. 2000, 19, 775–778. [Google Scholar] [CrossRef]
  46. Chu, X.; Jiang, D.; Yu, G.; Zheng, C. Ethanol gas sensor based on CoFe2O4 nano-crystallines prepared by hydrothermal method. Sens. Actuators B 2006, 120, 177–181. [Google Scholar] [CrossRef]
  47. Raut, S.D.; Awasarmol, V.V.; Ghule, B.G.; Shaikh, S.F.; Gore, S.K.; Sharma, R.P.; Pawar, P.P.; Mane, R.S. Enhancement in room-temperature ammonia sensor activity of size-reduced cobalt ferrite nanoparticles on gamma-irradiation. Mater. Res. Express 2018, 5, 65035. [Google Scholar] [CrossRef]
  48. Montahaei, R.; Emamian, H.R. The impact of microwave-assisted sintering on fabrication of cobalt ferrite nanostructure foams for gas-sensing. Ceram. Int. 2022, 48, 26629–26637. [Google Scholar] [CrossRef]
  49. Umesh, S.; Usha, A.; Bailey, K.; Sujatha, K.; Varadharajaperumal, S.; Shivashankar, S.A.; Raghavan, M.S. Nanocrystalline Spinel CoFe2O4 Thin Films Deposited via Microwave-Assisted Synthesis for Sensing Application. J. Electron. Mater. 2022, 51, 5395–5404. [Google Scholar] [CrossRef]
  50. Luby, S.; Chitu, L.; Jergel, M.; Majkova, E.; Siffalovic, P.; Caricato, A.P.; Luches, A.; Martino, M.; Rella, R.; Manera, M.G. Oxide nanoparticle arrays for sensors of CO and NO2 gases. Vacuum 2012, 86, 590–593. [Google Scholar] [CrossRef]
  51. Rao, P.; Godbole, R.V.; Phase, D.M.; Chikate, R.C.; Bhagwat, S. Ferrite thin films: Synthesis, characterization and gas sensing properties towards LPG. Mater. Chem. Phys. 2015, 149, 333–338. [Google Scholar] [CrossRef]
  52. Rathore, D.; Kurchania, R.; Pandey, R.K. Gas Sensing Properties of Size Varying CoFe2O4 Nanoparticles. IEEE Sens. J. 2015, 15, 4961–4966. [Google Scholar] [CrossRef]
  53. Zhang, H.-J.; Liu, L.-Z.; Zhang, X.-R.; Zhang, S.; Meng, F.-N. Microwave-assisted solvothermal synthesis of shape-controlled CoFe2O4 nanoparticles for acetone sensor. J. Alloys Compd. 2019, 788, 1103–1112. [Google Scholar] [CrossRef]
  54. Halvaee, P.; Dehghani, S.; Hoghoghifard, S. Low Temperature Methanol Sensors Based on Cobalt Ferrite Nanoparticles, Nanorods, and Porous Nanoparticles. IEEE Sens. J. 2020, 20, 4056–4062. [Google Scholar] [CrossRef]
  55. Sun, Z.; Liu, L.; Ha, D.Z.; Pan, W. Simple synthesis of CuFe2O4 nanoparticles as gas-sensing materials. Sens. Actuators B 2007, 125, 144–148. [Google Scholar] [CrossRef]
  56. Tudorache, F.; Rezlescu, E.; Popa, P.D.; Rezlescu, N. Study of some simple ferrites as reducing gas sensors. J. Optoelectron. Adv. Mater. 2008, 10, 1889–1893. [Google Scholar]
  57. Singh, S.; Yadav, B.C.; Gupta, V.D.; Dwivedi, P.K. Investigation on effects of surface morphologies on response of LPG sensor based on nanostructured copper ferrite system. Mater. Res. Bull. 2012, 47, 3538–3547. [Google Scholar] [CrossRef]
  58. Abu Haija, M.; Abu-Hani, A.F.S.; Hamdan, N.; Stephen, S.; Ayesh, A.I. Characterization of H2S gas sensor based on CuFe2O4 nanoparticles. J. Alloys Compd. 2017, 690, 461–468. [Google Scholar] [CrossRef]
  59. Abu Haija, M.; Ayesh, A.I.; Ahmed, S.; Katsiotis, M.S. Selective hydrogen gas sensor using CuFe2O4 nanoparticle based thin film. Appl. Surf. Sci. 2016, 369, 443–447. [Google Scholar] [CrossRef]
  60. Ayesh, A.I.; Abu Haija, M.; Shaheen, A.; Banat, F. Spinel ferrite nanoparticles for H2S gas sensor. Appl. Phys. A Mater. Sci. Process. 2017, 123, 1–8. [Google Scholar] [CrossRef]
  61. Liu, Y.-L.; Liu, Z.-M.; Yang, Y.; Yang, H.-F.; Shen, G.-L.; Yu, R.-Q. Simple synthesis of MgFe2O4 nanoparticles as gas sensing materials. Sens. Actuators B 2005, 107, 600–604. [Google Scholar] [CrossRef]
  62. Hankare, P.P.; Jadhav, S.D.; Sankpal, U.B.; Patil, R.P.; Sasikala, R.; Mulla, I.S. Gas sensing properties of magnesium ferrite prepared by co-precipitation method. J. Alloys Compd. 2009, 488, 270–272. [Google Scholar] [CrossRef]
  63. Mukherjee, K.; Bharti, D.C.; Majumder, S.B. Combustible Gas Sensing Characteristics of Chemical Solution Synthesized Nanocrystalline Magnesium Ferrite Spinel Particles. Trans. Indian Ceram. Soc. 2010, 69, 187–192. [Google Scholar] [CrossRef]
  64. Mukherjee, K.; Bharti, D.C.; Majumder, S.B. Solution synthesis and kinetic analyses of the gas sensing characteristics of magnesium ferrite particles. Sens. Actuators B 2010, 146, 91–97. [Google Scholar] [CrossRef]
  65. Patil, J.Y.; Khandekar, M.S.; Mulla, I.S.; Suryavanshi, S.S. Combustion synthesis of magnesium ferrite as liquid petroleum gas (LPG) sensor: Effect of sintering temperature. Curr. Appl. Phys. 2012, 12, 319–324. [Google Scholar] [CrossRef]
  66. Patil, J.Y.; Mulla, I.S.; Suryavanshi, S.S. Gas response properties of citrate gel synthesized nanocrystalline MgFe2O4: Effect of sintering temperature. Mater. Res. Bull. 2013, 48, 778–784. [Google Scholar] [CrossRef]
  67. Godbole, R.; Rao, P.; Bhagwat, S. Magnesium ferrite nanoparticles: A rapid gas sensor for alcohol. Mater. Res. Express 2017, 4, 25032. [Google Scholar] [CrossRef]
  68. Nagarajan, V.; Thayumanavan, A. MgFe2O4 thin films for detection of ethanol and acetone vapours. Surf. Eng. 2018, 34, 711–720. [Google Scholar] [CrossRef]
  69. Sumangala, T.P.; Pasquet, I.; Presmanes, L.; Thimont, Y.; Bonningue, C.; Venkataramani, N.; Prasad, S.; Baco-Carles, V.; Tailhades, P.; Barnabe, A. Effect of synthesis method and morphology on the enhanced CO2 sensing properties of magnesium ferrite MgFe2O4. Ceram. Int. 2018, 44, 18578–18584. [Google Scholar] [CrossRef] [Green Version]
  70. Jaiswal, A.K.; Sikarwar, S.; Singh, S.; Dey, K.K.; Yadav, B.C.; Yadav, R.R. Fabrication of nanostructured magnesium ferrite polyhedrons and their applications in heat transfer management and gas/humidity sensors. J. Mater. Sci. Mater. Electron. 2020, 31, 80–89. [Google Scholar] [CrossRef]
  71. Aono, H.; Hirazawa, H.; Naohara, T.; Maehara, T. Surface study of fine MgFe2O4 ferrite powder prepared by chemical methods. Appl. Surf. Sci. 2008, 254, 2319–2324. [Google Scholar] [CrossRef]
  72. Godbole, R.V.; Rao, P.; Alegaonkar, P.S.; Bhagwat, S. Influence of fuel to oxidizer ratio on LPG sensing performance of MgFe2O4 nanoparticles. Mater. Chem. Phys. 2015, 161, 135–141. [Google Scholar] [CrossRef]
  73. Reddy, K.M.; Satyanarayana, L.; Manorama, S.V.; Misra, R.D.K. A comparative study of the gas sensing behavior of nanostructured nickel ferrite synthesized by hydrothermal and reverse micelle techniques. Mater. Res. Bull. 2004, 39, 1491–1498. [Google Scholar] [CrossRef]
  74. Lee, P.Y.; Ishizaka, K.; Suematsu, H.; Jiang, W.; Yatsui, K. Magnetic and gas sensing property of nanosized NiFe2O4 powders synthesized by pulsed wire discharge. J. Nanopart. Res. 2006, 8, 29–35. [Google Scholar] [CrossRef]
  75. Busurin, S.M.; Tsygankov, P.A.; Busurina, M.L.; Kovalev, I.D.; Boyarchenko, O.D.; Sachkova, N.V.; Sychev, A.E. Production, electrical conductivity, and gas-sensing properties of thin nickel ferrite films. Dokl. Phys. Chem. 2012, 444, 83–87. [Google Scholar] [CrossRef]
  76. Sutka, A.; Stingaciu, M.; Mezinskis, G.; Lusis, A. An alternative method to modify the sensitivity of p-type NiFe2O4 gas sensor. J. Mater. Sci. 2012, 47, 2856–2863. [Google Scholar] [CrossRef]
  77. Patil, J.Y.; Nadargi, D.Y.; Gurav, J.L.; Mulla, I.S.; Suryavanshi, S.S. Synthesis of glycine combusted NiFe2O4 spinel ferrite: A highly versatile gas sensor. Mater. Lett. 2014, 124, 144–147. [Google Scholar] [CrossRef]
  78. Ghosh, P.; Mukherjee, A.; Fu, M.; Chattopadhyay, S.; Mitra, P. Influence of particle size on H2 and H2S sensing characteristics of nanocrystalline nickel ferrite. Phys. E 2015, 74, 570–575. [Google Scholar] [CrossRef]
  79. Singh, A.; Singh, A.; Singh, S.; Tandon, P.; Yadav, B.C. Preparation and characterization of nanocrystalline nickel ferrite thin films for development of a gas sensor at room temperature. J. Mater. Sci. Mater. Electron. 2016, 27, 8047–8054. [Google Scholar] [CrossRef]
  80. Kashyap, R.; Kumar, R.; Devi, S.; Kumar, M.; Tyagi, S.; Kumar, D. Ammonia gas sensing performance of nickel ferrite nanoparticles. Mater. Res. Express 2019, 6, 1150d3. [Google Scholar] [CrossRef]
  81. Jia, C.; Zhang, Y.; Kong, Q.; Wang, Q.; Chen, G.; Guam, H.; Dong, C. Soft-template synthesis of mesoporous NiFe2O4 for highly sensitive acetone detection. J. Mater. Sci. Mater. Electron. 2020, 31, 6000–6007. [Google Scholar] [CrossRef]
  82. Chaudhari, P.R.; Gaikwad, V.M.; Acharya, S.A. Rapid microwave-assisted combustion route for production of MFe2O4 (M = Zn, Ni, Co) nanoferrites for gas sensors view point. Ferroelectrics 2022, 587, 76–83. [Google Scholar] [CrossRef]
  83. Kumar, A.; Kashyap, R.; Kumar, R.; Singh, R.; Prasad, B.; Kumar, M.; Kumar, D. Experimental and Numerical Modelling of a Nanostructured Nickel Ferrite-Based Ammonia Gas Sensor. J. Electron. Mater. 2022, 51, 4040–4053. [Google Scholar] [CrossRef]
  84. Rezaeipour, A.; Dehghani, S.; Hoghoghifard, S. VOC Sensors Based on Nanoparticles and Nanorods of Nickel Ferrite. IEEE Sens. J. 2022, 22, 16464–16471. [Google Scholar] [CrossRef]
  85. Niu, X.; Du, W.; Du, W. Preparation and gas sensing properties of ZnM2O4 (M = Fe, Co, Cr). Sens. Actuators B 2004, 99, 405–409. [Google Scholar] [CrossRef]
  86. Chu, X.; Jiang, D.; Zheng, C. The gas-sensing properties of thick film sensors based on nano-ZnFe2O4 prepared by hydrothermal method. Mater. Sci. Eng. B 2006, 129, 150–153. [Google Scholar] [CrossRef]
  87. Darshane, S.L.; Deshmukh, R.G.; Suryavanshi, S.S.; Mulla, I.S. Gas-sensing properties of zinc ferrite nanoparticles synthesized by the molten-salt route. J. Am. Ceram. Soc. 2008, 91, 2724–2726. [Google Scholar] [CrossRef]
  88. Karpova, S.S.; Moshnikov, V.A.; Mjakin, S.V.; Kolovangina, E.S. Surface functional composition and sensor properties of ZnO, Fe2O3, and ZnFe2O4. Semiconductors 2013, 47, 392–395. [Google Scholar] [CrossRef]
  89. Patil, J.Y.; Nadargi, D.Y.; Gurav, J.L.; Mulla, I.S.; Suryavanshi, S.S. Glycine combusted ZnFe2O4 gas sensor: Evaluation of structural, morphological and gas response properties. Ceram. Int. 2014, 40, 10607–10613. [Google Scholar] [CrossRef]
  90. Dalawai, S.P.; Shinde, T.J.; Gadkari, A.B.; Vasambekar, P.N. Ni-Zn ferrite thick film gas sensors. J. Mater. Sci. Mater. Electron. 2015, 26, 9016–9025. [Google Scholar] [CrossRef]
  91. Tyagi, S.; Batra, N.; Paul, A.K. Influence of Temperature on Reducing Gas Sensing Performance of Nanocrystalline Zinc Ferrite. Trans. Indian Inst. Met. 2015, 68, 707–713. [Google Scholar] [CrossRef]
  92. Zhang, J.; Song, J.-M.; Niu, H.-L.; Mao, C.-J.; Zhang, S.-Y.; Shen, Y.-H. ZnFe2O4 nanoparticles: Synthesis, characterization, and enhanced gas sensing property for acetone. Sens. Actuators B 2015, 221, 55–62. [Google Scholar] [CrossRef] [Green Version]
  93. Cao, Y.; Qin, H.; Niu, X.; Jia, D. Simple solid-state chemical synthesis and gas-sensing properties of spinel ferrite materials with different morphologies. Ceram. Int. 2016, 42, 10697–10703. [Google Scholar] [CrossRef]
  94. Ghosh, P.; Das, M.R.; Mitra, P. Influence of particle size on H2 and H2S sensing characteristics of nanocrystalline zinc ferrite. Indian J. Phys. 2016, 90, 1367–1373. [Google Scholar] [CrossRef]
  95. Wu, J.; Gao, D.; Sun, T.; Bi, J.; Zhao, Y.; Ning, Z.; Fan, G.; Xie, Z. Highly selective gas sensing properties of partially inversed spinel zinc ferrite towards H2S. Sens. Actuators B 2016, 235, 258–262. [Google Scholar] [CrossRef]
  96. You, J.; Chen, X.; Zheng, B.; Geng, X.; Zhang, C. Suspension Plasma-Sprayed ZnFe2O4 Nanostructured Coatings for ppm-Level Acetone Detection. J. Therm. Spray Technol. 2017, 26, 728–734. [Google Scholar] [CrossRef]
  97. Hernandez, P.T.; Kuznetsov, M.V.; Morozov, I.G.; Parkin, I.P. Application of levitation jet synthesized nickel-based nanoparticles for gas sensing. Mater. Sci. Eng. B 2019, 244, 81–92. [Google Scholar] [CrossRef]
  98. Khurshid, R.; Ali, F.; Afzal, A.; Ali, Z.; Qureshi, M.T. Polyol-Mediated Coprecipitation and Aminosilane Grafting of Superparamagnetic, Spinel ZnFe2O4 Nanoparticles for Room-Temperature Ethanol Sensors. J. Electrochem. Soc. 2019, 166, B258–B265. [Google Scholar] [CrossRef]
  99. Li, K.; Luo, Y.; Liu, B.; Gao, L.; Duan, G. High-performance NO2-gas sensing of ultrasmall ZnFe2O4 nanoparticles based on surface charge transfer. J. Mater. Chem. A 2019, 7, 5539–5551. [Google Scholar] [CrossRef]
  100. Peng, S.; Wang, Z.; Liu, R.; Bi, J.; Wu, J. Controlled oxygen vacancies of ZnFe2O4 with superior gas sensing properties prepared via a facile one-step self-catalyzed treatment. Sens. Actuators B 2019, 288, 649–655. [Google Scholar] [CrossRef]
  101. Nemufulwi, M.I.; Swart, H.C.; Mdlalose, W.B.; Mhlongo, G.H. Size-tunable ferromagnetic ZnFe2O4 nanoparticles and their ethanol detection capabilities. Appl. Surf. Sci. 2020, 508, 144863. [Google Scholar] [CrossRef]
  102. Jha, R.K.; Nanda, A.; Sai, R.; Kishore, K.; Yadav, A.; Kahmei, R.D.R.; Bhat, N. Development of a Ferrite Film Based Solid State Sensor System for Ultra Low Concentration Hydrogen Sulfide Gas Detection. IEEE Sens. J. 2022, 22, 8402–8409. [Google Scholar] [CrossRef]
  103. Ishigami, H.; Kawaguchi, T.; Sakamoto, N.; Che, S.; Koshida, N.; Shinozaki, K.; Suzuki, H.; Wakiya, N. Dynamic Aurora PLD with Si and porous Si to prepare ZnFe2O4 Thin films for liquefied petroleum gas sensing. J. Ceram. Soc. Jpn. 2020, 128, 457–463. [Google Scholar] [CrossRef]
  104. Mukherjee, K.; Majumder, S.B. Analyses of response and recovery kinetics of zinc ferrite as hydrogen gas sensor. J. Appl. Phys. 2009, 106, 064912. [Google Scholar] [CrossRef]
  105. Cao, Y.; Jia, D.; Hu, P.; Wang, R. One-step room-temperature solid-phase synthesis of ZnFe2O4 nanomaterials and its excellent gas-sensing property. Ceram. Int. 2013, 39, 2989–2994. [Google Scholar] [CrossRef]
  106. Jeseentharani, V.; George, M.; Jeyaraj, B.; Dayalan, A.; Nagaraja, K.S. Synthesis of metal ferrite (MFe2O4, M = Co, Cu, Mg, Ni, Zn) nanoparticles as humidity sensor materials. J. Exp. Nanosci. 2013, 8, 358–370. [Google Scholar] [CrossRef] [Green Version]
  107. Sutka, A.; Mezinskis, G.; Zamovskis, M.; Jakovlevs, D.; Pavlovska, I. Monophasic ZnFe2O4 synthesis from a xerogel layer by auto combustion. Ceram. Int. 2013, 39, 8499–8502. [Google Scholar] [CrossRef]
  108. Srivastava, R.; Yadav, B.C. Nanostructured ZnFe2O4 thick film as room temperature liquefied petroleum gas sensor. J. Exp. Nanosci. 2015, 10, 703–717. [Google Scholar] [CrossRef]
  109. Raut, S.D.; Awasarmol, V.V.; Gghule, B.; Shaikh, S.F.; Gore, S.K.; Sharma, R.P.; Pawar, P.P.; Mane, R.S. gamma-irradiation induced zinc ferrites and their enhanced room-temperature ammonia gas sensing properties. Mater. Res. Express 2018, 5, 35702. [Google Scholar] [CrossRef]
  110. Zhang, H.-J.; Meng, F.-N.; Liu, L.-Z.; Chen, Y.-J.; Wang, P.-J. Highly sensitive H2S sensor based on solvothermally prepared spinel ZnFe2O4 nanoparticles. J. Alloys Compd. 2018, 764, 147–154. [Google Scholar] [CrossRef]
  111. Sun, K.-M.; Song, X.-Z.; Wang, X.-F.; Li, X.; Tan, Z. Annealing temperature-dependent porous ZnFe2O4 olives derived from bimetallic organic frameworks for high-performance ethanol gas sensing. Mater. Chem. Phys. 2020, 241, 122379. [Google Scholar] [CrossRef]
  112. Prasad, P.D.; Hemalatha, J. Enhanced magnetic properties of highly crystalline cobalt ferrite fibers and their application as gas sensors. J. Magn. Magn. Mater. 2019, 484, 225–233. [Google Scholar] [CrossRef]
  113. Zhang, L.; Jiao, W. The effect of microstructure on the gas properties of NiFe2O4 sensors: Nanotube and nanoparticle. Sens. Actuators B 2015, 216, 293–297. [Google Scholar] [CrossRef]
  114. Chaudhuri, A.; Mandal, K.; Pati, S.P.; Das, D. High performance gas sensing based on nano rods of nickel ferrite fabricated by a facile solvothermal route. Mater. Res. Express 2018, 5, 36202. [Google Scholar] [CrossRef]
  115. Wang, X.-F.; Sun, K.-M.; Li, S.-J.; Song, X.-Z.; Cheng, L.; Ma, W. Porous Javelin-Like NiFe2O4 Nanorods as n-Propanol Sensor with Ultrahigh-Performance. Chemistryselect 2018, 3, 12871–12877. [Google Scholar] [CrossRef]
  116. Chu, X.; Jiang, D.; Zheng, C. The preparation and gas-sensing properties of NiFe2O4 nanocubes and nanorods. Sens. Actuators B 2007, 123, 793–797. [Google Scholar] [CrossRef]
  117. Zhang, Y.; Jia, C.; Wang, Q.; Kong, Q.; Chen, G.; Guan, H.; Dong, C. Highly Sensitive and Selective Toluene Sensor of Bimetallic Ni/Fe-MOFs Derived Porous NiFe2O4 Nanorods. Ind. Eng. Chem. Res. 2019, 58, 9450–9457. [Google Scholar] [CrossRef]
  118. Zhang, G.; Li, C.; Cheng, F.; Chen, J. ZnFe2O4 tubes: Synthesis and application to gas sensors with high sensitivity and low-energy consumption. Sens. Actuators B 2007, 120, 403–410. [Google Scholar] [CrossRef]
  119. Zhu, H.; Gu, X.; Zuo, D.; Wang, Z.; Wang, N.; Yao, K. Microemulsion-based synthesis of porous zinc ferrite nanorods and its application in a room-temperature ethanol sensor. Nanotechnology 2008, 19, 405503. [Google Scholar] [CrossRef]
  120. Singh, S.; Singh, A.; Yadav, R.R.; Tandon, P. Growth of zinc ferrite aligned nanorods for liquefied petroleum gas sensing. Mater. Lett. 2014, 131, 31–34. [Google Scholar] [CrossRef]
  121. Singh, A.; Singh, A.; Singh, S.; Tandon, P.; Yadav, B.C.; Yadav, R.R. Synthesis, characterization and performance of zinc ferrite nanorods for room temperature sensing applications. J. Alloys Compd. 2015, 618, 475–483. [Google Scholar] [CrossRef]
  122. Li, L.; Tan, J.; Dun, M.; Huang, X. Porous ZnFe2O4 nanorods with net-worked nanostructure for highly sensor response and fast response acetone gas sensor. Sens. Actuators B 2017, 248, 85–91. [Google Scholar] [CrossRef]
  123. Nguyen Van, H.; Chu Manh, H.; Nguyen Duc, H.; Nguyen Van, D.; Nguyen Van, H. Facile on-chip electrospinning of ZnFe2O4 nanofiber sensors with excellent sensing performance to H2S down ppb level. J. Hazard. Mater. 2018, 360, 6–16. [Google Scholar] [CrossRef]
  124. Chu, X.; Gan, Z.; Bai, L.; Dong, Y.; Rumyantseva, M.N. Acetone-sensing Properties of ZnFe2O4 Nanofibers Prepared via Electrospinning Method. Rare Metal Mat. Eng. 2019, 48, 1371–1379. [Google Scholar]
  125. Singh, S.; Yadav, B.C.; Prakash, R.; Bajaj, B.; Lee, J.R. Synthesis of nanorods and mixed shaped copper ferrite and their applications as liquefied petroleum gas sensor. Appl. Surf. Sci. 2011, 257, 10763–10770. [Google Scholar] [CrossRef]
  126. Singh, A.; Singh, A.; Singh, S.; Tandon, P. Fabrication of copper ferrite porous hierarchical nanostructures for an efficient liquefied petroleum gas sensor. Sens. Actuators B 2017, 244, 806–814. [Google Scholar] [CrossRef]
  127. Patil, J.; Nadargi, D.; Mulla, I.S.; Suryavanshi, S.S. Spinel MgFe2O4 thick films: A colloidal approach for developing gas sensors. Mater. Lett. 2018, 213, 27–30. [Google Scholar] [CrossRef]
  128. Sutka, A.; Zavickis, J.; Mezinskis, G.; Jakovlevs, D.; Barloti, J. Ethanol monitoring by ZnFe2O4 thin film obtained by spray pyrolysis. Sens. Actuators B 2013, 176, 330–334. [Google Scholar] [CrossRef]
  129. Gao, X.; Sun, Y.; Zhu, C.; Li, C.; Ouyang, Q.; Chen, Y. Highly sensitive and selective H2S sensor based on porous ZnFe2O4 nanosheets. Sens. Actuators B 2017, 246, 662–672. [Google Scholar] [CrossRef]
  130. Madake, S.B.; Hattali, M.R.; Rajpure, K.Y. Porogen induced formation of mesoporous zinc ferrite thin films and their chemiresistive properties. Mater. Sci. Eng. B 2021, 263, 114867. [Google Scholar] [CrossRef]
  131. Xu, Y.; Sun, D.; Hao, H.; Gao, D.; Sun, Y. Non-stoichiometric Co(II), Ni(II), Zn(II)-ferrite nanospheres: Size controllable synthesis, excellent gas-sensing and magnetic properties. RSC Adv. 2016, 6, 98994–99002. [Google Scholar] [CrossRef]
  132. Wang, L.; Wang, Y.; Tian, H.; Qiao, L.; Zeng, Y. Enhanced ammonia detection using wrinkled porous CoFe2O4 double-shelled spheres prepared by a thermally driven contraction process. Sens. Actuators B 2020, 314, 128085. [Google Scholar] [CrossRef]
  133. Wu, K.-D.; Xu, J.-Y.; Debliquy, M.; Zhang, C. Synthesis and NH3/TMA sensing properties of CuFe2O4 hollow microspheres at low working temperature. Rare Met. 2020, 40, 1768–1777. [Google Scholar] [CrossRef]
  134. Yang, X.; Zhang, S.; Yu, Q.; Sun, P.; Liu, F.; Lu, H.; Yan, X.; Zhou, X.; Liang, X.; Gao, Y.; et al. Solvothermal synthesis of porous CuFe2O4 nanospheres for high performance acetone sensor. Sens. Actuators B 2018, 270, 538–544. [Google Scholar] [CrossRef]
  135. Lai, X.; Cao, K.; Shen, G.; Xue, P.; Wang, D.; Hu, F.; Zhang, J.; Yang, Q.; Wang, X. Ordered mesoporous NiFe2O4 with ultrathin framework for low-ppb toluene sensing. Sci. Bull. 2018, 63, 187–193. [Google Scholar] [CrossRef] [PubMed]
  136. Ma, Y.; Lu, Y.; Gou, H.; Zhang, W.; Yan, S.; Xu, X. Octahedral NiFe2O4 for high-performance gas sensor with low working temperature. Ceram. Int. 2018, 44, 2620–2625. [Google Scholar] [CrossRef]
  137. Song, X.-Z.; Meng, Y.-L.; Chen, X.; Sun, K.-M.; Wang, X.-F. Hollow NiFe2O4 hexagonal biyramids for high-performance n-propanol sensing at low temperature. New J. Chem. 2018, 42, 14071–14074. [Google Scholar] [CrossRef]
  138. Song, X.-Z.; Sun, F.-F.; Dai, S.-T.; Lin, X.; Sun, K.-M.; Wang, X.-F. Hollow NiFe2O4 microspindles derived from Ni/Fe bimetallic MOFs for highly sensitive acetone sensing at low operating temperatures. Inorg. Chem. Front. 2018, 5, 1107–1114. [Google Scholar] [CrossRef]
  139. Zhou, T.; Zhang, T.; Zeng, Y.; Zhang, R.; Lou, Z.; Deng, J.; Wang, L. Structure-driven efficient NiFe2O4 materials for ultra-fast response electronic sensing platform. Sens. Actuators B 2018, 255, 1436–1444. [Google Scholar] [CrossRef]
  140. Zhang, S.; Jiang, W.; Li, Y.; Yang, X.; Sun, P.; Liu, F.; Yan, X.; Gao, Y.; Liang, X.; Ma, J.; et al. Highly-sensitivity acetone sensors based on spinel-type oxide (NiFe2O4) through optimization of porous structure. Sens. Actuators B 2019, 291, 266–274. [Google Scholar] [CrossRef]
  141. Zhang, Y.; Jia, C.; Wang, Q.; Kong, Q.; Chen, G.; Guan, H.; Dong, C. MOFs-Derived Porous NiFe2O4 Nano-Octahedrons with Hollow Interiors for an Excellent Toluene Gas Sensor. Nanomaterials 2019, 9, 1059–1077. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  142. Zhai, C.; Zhang, H.; Du, L.; Wang, D.; Xing, D.; Zhang, M. Nickel/iron-based bimetallic MOF-derived nickel ferrite materials for triethylamine sensing. Crystengcomm 2020, 22, 1286–1293. [Google Scholar] [CrossRef]
  143. Wang, X.F.; Li, X.; Zhang, G.Z.; Wang, Z.H.; Song, X.Z.; Tan, Z.Q. Surface Structure Engineering of Nanosheet-Assembled NiFe2O4 Fluffy Flowers for Gas Sensing. Nanomaterials 2021, 11, 8. [Google Scholar] [CrossRef] [PubMed]
  144. Zhang, Y.-L.; Jia, C.-W.; Tian, R.-N.; Guan, H.-T.; Chen, G.; Dong, C.-J. Hierarchical flower-like NiFe2O4 with core-shell structure for excellent toluene detection. Rare Met. 2020, 40, 1578–1587. [Google Scholar] [CrossRef]
  145. Liu, N.; Wang, X.-F.; Zhang, G.; Liang, H.; Li, T.; Zhao, Y.; Zhang, T.; Tan, Z.; Song, X.-Z. Metal-Organic Framework-Derived Porous NiFe2O4 Nanoboxes for Ethyl Acetate Gas Sensors. ACS Appl. Nano Mater. 2022, 5, 14320–14327. [Google Scholar] [CrossRef]
  146. Li, Z.; Lai, X.; Wang, H.; Mao, D.; Xing, C.; Wang, D. General Synthesis of Homogeneous Hollow Core-Shell Ferrite Microspheres. J. Phys. Chem. C 2009, 113, 2792–2797. [Google Scholar] [CrossRef]
  147. Zhou, X.; Liu, J.; Wang, C.; Sun, P.; Hu, X.; Li, X.; Shimanoe, K.; Yamazoe, N.; Lu, G. Highly sensitive acetone gas sensor based on porous ZnFe2O4 nanospheres. Sens. Actuators B 2015, 206, 577–583. [Google Scholar] [CrossRef]
  148. Zhou, X.; Wang, B.; Sun, H.; Wang, C.; Sun, P.; Li, X.; Hu, X.; Lu, G. Template-free synthesis of hierarchical ZnFe2O4 yolk-shell microspheres for high-sensitivity acetone sensors. Nanoscale 2016, 8, 5446–5453. [Google Scholar] [CrossRef]
  149. Zhou, X.; Li, X.; Sun, H.; Sun, P.; Liang, X.; Liu, F.; Hu, X.; Lu, G. Nanosheet-Assembled ZnFe2O4 Hollow Microspheres for High-Sensitive Acetone Sensor. ACS Appl. Mater. Interfaces 2015, 7, 15414–15421. [Google Scholar] [CrossRef]
  150. Sahoo, R.; Santra, S.; Ray, C.; Pal, A.; Negishi, Y.; Ray, S.K.; Pal, T. Hierarchical growth of ZnFe2O4 for sensing applications. New J. Chem. 2016, 40, 1861–1871. [Google Scholar] [CrossRef]
  151. Dong, C.; Liu, X.; Xiao, X.; Du, S.; Wang, Y. Monodisperse ZnFe2O4 nanospheres synthesized by a nonaqueous route for a highly slective low-ppm-level toluene gas sensor. Sens. Actuators B 2017, 239, 1231–1236. [Google Scholar] [CrossRef]
  152. Liu, T.; Liu, J.; Liu, Q.; Li, R.; Zhang, H.; Jing, X.; Wang, J. Shape-controlled fabrication and enhanced gas sensing properties of uniform sphere-like ZnFe2O4 hierarchical architectures. Sens. Actuators B 2017, 250, 111–120. [Google Scholar] [CrossRef]
  153. Qu, F.; Shang, W.; Thomas, T.; Ruan, S.; Yang, M. Self-template derived ZnFe2O4 double-shell microspheres for chemresistive gas sensing. Sens. Actuators B 2018, 265, 625–631. [Google Scholar] [CrossRef]
  154. Yang, H.; Bai, X.; Hao, P.; Tian, J.; Bo, Y.; Wang, X.; Liu, H. A simple gas sensor based on zinc ferrite hollow spheres: Highly sensitivity, excellent selectivity and long-term stability. Sens. Actuators B 2019, 280, 34–40. [Google Scholar] [CrossRef]
  155. Mukherjee, K.; Majumder, S.B. Synthesis of embedded and isolated Mg0.5Zn0.5Fe2O4 nano-tubes and investigation on their anomalous gas sensing characteristics. Sens. Actuators B 2013, 177, 55–63. [Google Scholar] [CrossRef]
  156. Patil, J.Y.; Nadargi, D.Y.; Mulla, I.S.; Suryavanshi, S.S. Cerium doped MgFe2O4 nanocomposites: Highly sensitive and fast response-recoverable acetone gas sensor. Heliyon 2019, 5, e01489. [Google Scholar] [CrossRef] [Green Version]
  157. Mugutkar, A.B.; Gore, S.K.; Mane, R.S.; Patange, S.M.; Jadhav, S.S.; Shaikh, S.F.; Al-Enizi, A.M.; Nafady, A.; Thamer, B.M.; Ubaidullah, M. Structural modifications in Co-Zn nanoferrites by Gd substitution triggering to dielectric and gas sensing applications. J. Alloys Compd. 2020, 844, 11. [Google Scholar] [CrossRef]
  158. Rao, P.; Godbole, R.V.; Bhagwat, S. Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor. J. Magn. Magn. Mater. 2016, 416, 292–298. [Google Scholar] [CrossRef]
  159. George, J.; Abraham, K.E.; Thomas, K.J. Influence of zinc on the multifunctional properties of ferrites M1-xZnxFe2O4 (M = Cu, Mg, Ni, x = 0, 0.35). J. Magn. Magn. Mater. 2022, 546, 168904. [Google Scholar] [CrossRef]
  160. Sutka, A.; Mezinskis, G.; Lusis, A.; Stingaciu, M. Gas sensing properties of Zn-doped p-type nickel ferrite. Sens. Actuators B 2012, 171, 354–360. [Google Scholar] [CrossRef]
  161. Singh, A.; Singh, S.; Joshi, B.D.; Shukla, A.; Yadav, B.C.; Tandon, P. Synthesis, characterization, magnetic properties and gas sensing applications of ZnxCu1-xFe2O4 (0.0 <= x <= 0.8) nanocomposites. Mater. Sci. Semicond. Process. 2014, 27, 934–949. [Google Scholar] [CrossRef]
  162. Bodade, A.B.; Bodade, A.B.; Wankhade, H.G.; Chaudhari, G.N.; Kothari, D.C. Conduction mechanism and gas sensing properties of CoFe2O4 nanocomposite thick films for H2S gas. Talanta 2012, 89, 183–188. [Google Scholar] [CrossRef]
  163. Srinivas, C.; Ranjith Kumar, E.; Tirupanyam, B.V.; Singh Meena, S.; Bhatt, P.; Prajapat, C.L.; Chandrasekhar Rao, T.V.; Sastry, D.L. Study of magnetic behavior in co-precipitated Ni–Zn ferrite nanoparticles and their potential use for gas sensor applications. J. Magn. Magn. Mater. 2020, 502, 166534. [Google Scholar] [CrossRef]
  164. Wu, S.; Li, X.; Xu, Y.; Wu, J.; Wang, Z.; Han, Y.; Zhang, X. Hierarchical spinel NixCo1-xFe2O4 microcubes derived from Fe-based MOF for high-sensitive acetone sensor. Ceram. Int. 2018, 44, 19390–19396. [Google Scholar] [CrossRef]
  165. Rezlescu, N.; Doroftei, C.; Rezlescu, E.; Popa, P.D. The influence of Sn 4+and/or Mo6+ions on the structure, electrical and gas sensing properties of Mg-ferrite. Phys. Status Solidi A-Appl. Mater. Sci. 2006, 203, 306–316. [Google Scholar] [CrossRef]
  166. Kadu, A.V.; Jagtap, S.V.; Chaudhari, G.N. Studies on the preparation and ethanol gas sensing properties of spinel Zn0.6Mn0.4Fe2O4 nanomaterials. Curr. Appl. Phys. 2009, 9, 1246–1251. [Google Scholar] [CrossRef]
  167. Kapse, V.D.; Ghosh, S.A.; Raghuwanshi, F.C.; Kapse, S.D. Nanocrystalline spinel Ni0.6Zn0.4Fe2O4: A novel material for H2S sensing. Mater. Chem. Phys. 2009, 113, 638–644. [Google Scholar] [CrossRef]
  168. Kazin, A.P.; Rumyantseva, M.N.; Prusakov, V.E.; Suzdalev, I.P.; Gaskov, A.M. Nanocrystalline ferrites NixZn1-xFe2O4: Influence of cation distribution on acidic and gas sensing properties. J. Solid State Chem. 2011, 184, 2799–2805. [Google Scholar] [CrossRef]
  169. Muthurani, S.; Balaji, M.; Gautam, S.; Chae, K.H.; Song, J.H.; Padiyan, D.P.; Asokan, K. Magnetic and Humidity-Sensing Properties of Nanostructured CuxCo1-xFe2O4 Synthesized via Autocombustion. J. Nanosci. Nanotechnol. 2011, 11, 5850–5855. [Google Scholar] [CrossRef] [Green Version]
  170. Tang, Y.; Wang, X.; Zhang, Q.; Li, Y.; Wang, H. Solvothermal synthesis of Co1−xNixFe2O4 nanoparticles and its application in ammonia vapors detection. Prog. Nat. Sci. Mater. Int. 2012, 22, 53–58. [Google Scholar] [CrossRef] [Green Version]
  171. Koseoglu, Y.; Aldemir, I.; Bayansal, F.; Kahraman, S.; Cetinkara, H.A. Synthesis, characterization and humidity sensing properties of Mn0.2Ni0.8Fe2O4 nanoparticles. Mater. Chem. Phys. 2013, 139, 789–793. [Google Scholar] [CrossRef]
  172. Karmakar, M.; Das, P.; Pal, M.; Mondal, B.; Majumder, S.B.; Mukherjee, K. Acetone and ethanol sensing characteristics of magnesium zinc ferrite nano-particulate chemi-resistive sensor. J. Mater. Sci. 2014, 49, 5766–5771. [Google Scholar] [CrossRef]
  173. Kumar, E.R.; Jayaprakash, R.; Devi, G.S.; Reddy, P.S.P. Magnetic, dielectric and sensing properties of manganese substituted copper ferrite nanoparticles. J. Magn. Magn. Mater. 2014, 355, 87–92. [Google Scholar] [CrossRef]
  174. Kumar, E.R.; Jayaprakash, R.; Devi, G.S.; Reddy, P.S.P. Synthesis of Mn substituted CuFe2O4 nanoparticles for liquefied petroleum gas sensor applications. Sens. Actuators B 2014, 191, 186–191. [Google Scholar] [CrossRef]
  175. Zohrabi, Y.; Ghazi, M.E.; Izadifard, M. The Gas-Sensing Properties of Ni-Zn Ferrite (Ni0.6Zn0.4Fe2O4) Nanoparticles Prepared by the Microwave Method. Chin. J. Phys. 2015, 53, 120801. [Google Scholar] [CrossRef]
  176. Joshi, S.; Kamble, V.B.; Kumar, M.; Umarji, A.M.; Srivastava, G. Nickel substitution induced effects on gas sensing properties of cobalt ferrite nanoparticles. J. Alloys Compd. 2016, 654, 460–466. [Google Scholar] [CrossRef]
  177. Kumar, E.R.; Kamzin, A.S.; Janani, K. Effect of annealing on particle size, microstructure and gas sensing properties of Mn substituted CoFe2O4 nanoparticles. J. Magn. Magn. Mater. 2016, 417, 122–129. [Google Scholar] [CrossRef]
  178. Rao, P.; Godbole, R.V.; Bhagwat, S. Copper doped nickel ferrite nano-crystalline thin films: A potential gas sensor towards reducing gases. Mater. Chem. Phys. 2016, 171, 260–266. [Google Scholar] [CrossRef]
  179. Anggraini, S.A.; Fujio, Y.; Ikeda, H.; Miura, N. YSZ-based sensor using Cr-Fe-based spinel-oxide electrodes for selective detection of CO. Anal. Chim. Acta 2017, 982, 176–184. [Google Scholar] [CrossRef] [PubMed]
  180. Kamzin, A.S.; Kumar, E.R.; Ramadevi, P.; Selvakumar, C. The properties of Mn-CuFe2O4 spinel ferrite nanoparticles under various synthesis conditions. Phys. Solid State 2017, 59, 1841–1851. [Google Scholar] [CrossRef]
  181. Kumar, E.R.; Srinivas, C.; Seehra, M.S.; Deepty, M.; Pradeep, I.; Kamzin, A.S.; Mehar, M.V.K.; Mohan, N.K. Particle size dependence of the magnetic, dielectric and gas sensing properties of Co substituted NiFe2O4 nanoparticles. Sens. Actuators Ba-Phys. 2018, 279, 10–16. [Google Scholar] [CrossRef]
  182. Manikandan, V.; Li, X.; Mane, R.S.; Chandrasekaran, J. Room Temperature Gas Sensing Properties of Sn-Substituted Nickel Ferrite (NiFe2O4) Thin Film Sensors Prepared by Chemical Co-Precipitation Method. J. Electron. Mater. 2018, 47, 3403–3408. [Google Scholar] [CrossRef]
  183. Manikandan, V.; Singh, M.; Yadav, B.C.; Denardin, J.C. Fabrication of lithium substituted copper ferrite (Li-CuFe2O4) thin film as an efficient gas sensor at room temperature. J. Sci. Adv. Mater. Devices 2018, 3, 145–150. [Google Scholar] [CrossRef]
  184. Manikandan, V.; Singh, M.; Yadav, B.C.; Vigneselvan, S. Room-Temperature Gas Sensing Properties of Nanocrystalline-Structured Indium-Substituted Copper Ferrite Thin Film. J. Electron. Mater. 2018, 47, 6366–6372. [Google Scholar] [CrossRef]
  185. Koli, P.B.; Kapadnis, K.H.; Deshpande, U.G. Nanocrystalline-modified nickel ferrite films: An effective sensor for industrial and environmental gas pollutant detection. J. Nanostruct. Chem. 2019, 9, 95–110. [Google Scholar] [CrossRef] [Green Version]
  186. Mutkule, S.U.; Tehare, K.K.; Gore, S.K.; Gunturu, K.C.; Mane, R.S. Ambient temperature operable Bi-Co ferrite NO2 sensors with high sensitivity and selectivity. Mater. Res. Bull. 2019, 115, 150–158. [Google Scholar] [CrossRef]
  187. Zhang, W.; Shen, Y.; Zhang, J.; Bi, H.; Zhao, S.; Zhou, P.; Han, C.; Wei, D.; Cheng, N. Low-temperature H2S sensing performance of Cu-doped ZnFe2O4 nanoparticles with spinel structure. Appl. Surf. Sci. 2019, 470, 581–590. [Google Scholar] [CrossRef]
  188. Zou, Y.; Wang, H.; Yang, R.; Lai, X.; Wan, J.; Lin, G.; Liu, D. Controlled synthesis and enhanced toluene-sensing properties of mesoporous NixCo1-xFe2O4 nanostructured microspheres with tunable composite. Sens. Actuators B 2019, 280, 227–234. [Google Scholar] [CrossRef]
  189. Abu Haija, M.; Chamakh, M.; Othman, I.; Banat, F.; Ayesh, A.I. Fabrication of H2S gas sensors using ZnxCu1-xFe2O4 nanoparticles. Appl. Phys. A Mater. Sci. Process. 2020, 126, 489. [Google Scholar] [CrossRef]
  190. Deepty, M.; Srinivas, C.; Kumar, E.R.; Ramesh, P.N.; Mohan, N.K.; Meena, S.S.; Prajapat, C.L.; Vermag, A.; Sastry, D.L. Evaluation of structural and dielectric properties of Mn2+-substituted Zn-spinel ferrite nanoparticles for gas sensor applications. Sens. Actuators B 2020, 316, 128127. [Google Scholar] [CrossRef]
  191. Manikandan, V.; Singh, M.; Yadav, B.C.; Mane, R.S.; Vigneselvan, S.; Mirzaei, A.; Chandrasekaran, J. Room temperature LPG sensing properties of tin substituted copper ferrite (Sn-CuFe2O4) thin film. Mater. Chem. Phys. 2020, 240, 122265. [Google Scholar] [CrossRef]
  192. Pawar, H.; Khan, M.; Mitharwal, C.; Dwivedi, U.K.; Mitra, S.; Rathore, D. Co1-xBaxFe2O4(x=0, 0.25, 0.5, 0.75 and 1) nanoferrites as gas sensor towards NO2 and NH3 gases. RSC Adv. 2020, 10, 35265–35272. [Google Scholar] [CrossRef] [PubMed]
  193. Powar, R.R.; Phadtare, V.D.; Parale, V.G.; Pathak, S.; Sanadi, K.R.; Park, H.-H.; Patil, D.R.; Piste, P.B.; Zambare, D.N. Effect of zinc substitution on magnesium ferrite nanoparticles: Structural, electrical, magnetic, and gas-sensing properties. Mater. Sci. Eng. B 2020, 262, 114776. [Google Scholar] [CrossRef]
  194. Yang, J.; Li, X.L.; Wu, J.B.; Han, Y.D.; Wang, Z.P.; Zhang, X.; Xu, Y. Yolk-shell (Cu,Zn)Fe2O4 ferrite nano-microspheres with highly selective triethylamine gas-sensing properties. Dalton Trans. 2020, 49, 14475–14482. [Google Scholar] [CrossRef]
  195. Yilmaz, O.E.; Erdem, R. Evaluating hydrogen detection performance of an electrospun CuZnFe2O4 nanofiber sensor. Int. J. Hydrog. Energy 2020, 45, 26402–26412. [Google Scholar] [CrossRef]
  196. Deivatamil, D.; Mark, J.A.M.; Raghavan, T.; Jesuraj, J.P. Fabrication of MnFe2O4 and Ni: MnFe2O4 nanoparticles for ammonia gas sensor application. Inorg. Chem. Commun. 2021, 123, 108355. [Google Scholar] [CrossRef]
  197. Madake, S.B.; Hattali, M.R.; Thorat, J.B.; Pedanekar, R.S.; Rajpure, K.Y. Chemiresistive Gas Sensing Properties of Copper Substituted Zinc Ferrite Thin Films Deposited by Spray Pyrolysis. J. Electron. Mater. 2021, 50, 2460–2465. [Google Scholar] [CrossRef]
  198. Sankaran, K.J.; Suman, S.; Sahaw, A.; Balaji, U.; Sakthivel, R. Improved LPG sensing properties of nickel doped cobalt ferrites derived from metallurgical wastes. J. Magn. Magn. Mater. 2021, 537, 168231. [Google Scholar] [CrossRef]
  199. Gauns Dessai, P.P.; Singh, A.K.; Verenkar, V.M.S. Mn doped Ni-Zn ferrite thick film as a highly selective and sensitive gas sensor for Cl2 gas with quick response and recovery time. Mater. Res. Bull. 2022, 149, 111521. [Google Scholar] [CrossRef]
  200. Gómez Méndez, E.; Posada, C.M.; Jaramillo Ocampo, J.M. Statistical analysis of Sr substituted NiFe2O4 thin films for liquefied petroleum gas sensor applications. Mater. Sci. Eng. 2022, 278, 115614. [Google Scholar] [CrossRef]
  201. Mukherjee, C.; Mondal, R.; Dey, S.; Kumar, S.; Das, J. Nanocrystalline CopperNickelZinc Ferrite: Efficient sensing materials for ethanol and acetone at room temperature. IEEE Sens. J. 2017, 17, 2662–2669. [Google Scholar] [CrossRef]
  202. Rezlescu, N.; Doroftei, C.; Rezlescu, E.; Popa, P.D. Lithium ferrite for gas sensing applications. Sens. Actuators B 2008, 133, 420–425. [Google Scholar] [CrossRef]
  203. Khandekar, M.S.; Tarwal, N.L.; Patil, J.Y.; Shaikh, F.I.; Mulla, I.S.; Suryavanshi, S.S. Liquefied petroleum gas sensing performance of cerium doped copper ferrite. Ceram. Int. 2013, 39, 5901–5907. [Google Scholar] [CrossRef]
  204. Khandekar, M.S.; Tarwal, N.L.; Mulla, I.S.; Suryavanshi, S.S. Nanocrystalline Ce doped CoFe2O4 as an acetone gas sensor. Ceram. Int. 2014, 40, 447–452. [Google Scholar] [CrossRef]
  205. Deepapriya, S.; Devi, S.L.; Vinosha, P.A.; Rodney, J.D.; Raj, C.J.; Jose, J.E.; Das, S.J. Estimating the ionicity of an inverse spinel ferrite and the cation distribution of La-doped NiFe2O4 nanocrystals for gas sensing properties. Appl. Phys. A Mater. Sci. Process. 2019, 125, 1–13. [Google Scholar] [CrossRef]
  206. Gumbi, S.W.; Mkwae, P.S.; Kortidis, I.; Kroon, R.E.; Swart, H.C.; Moyo, T.; Nkosi, S.S. Electronic and Simple Oscillatory Conduction in Ferrite Gas Sensors: Gas-Sensing Mechanisms, Long-Term Gas Monitoring, Heat Transfer, and Other Anomalies. ACS Appl. Mater. Interfaces 2020, 12, 43231–43249. [Google Scholar] [CrossRef]
  207. Mkwae, P.S.; Kortidis, I.; Kroon, R.E.; Leshabane, N.; Jozela, M.; Swart, H.C.; Nkosi, S.S. Insightful acetone gas sensing behaviour of Ce substituted MgFe2O4 spinel nano-ferrites. J. Mater. Res. Technol. 2020, 9, 16252–16269. [Google Scholar] [CrossRef]
  208. Das, T.; Mojumder, S.; Chakraborty, S.; Saha, D.; Pal, M. Beneficial effect of Sn doping on bismuth ferrite nanoparticle-based sensor for enhanced and highly selective detection of trace formaldehyde. Appl. Surf. Sci. 2022, 602, 452–461. [Google Scholar] [CrossRef]
  209. Vadivel, M.; Ramesh Babu, R.; Sridharan, M. Spray-Deposited Rare Earth Metal Ions (La3+ and Sm3+) Substituted CoFe2O4 Thin Films for NH3 Gas-Sensing Applications. J. Supercond. Novel Magn. 2022, 35, 2563–2571. [Google Scholar] [CrossRef]
  210. Šutka, A.; Gross, K.A. Spinel ferrite oxide semiconductor gas sensors. Sens. Actuators B 2016, 222, 95–105. [Google Scholar] [CrossRef]
  211. Almessiere, M.A.; Slimani, Y.; Rehman, S.; Khan, F.A.; Güngüneş, Ç.; Güner, S.; Shirsath, S.E.; Baykal, A. Magnetic properties, anticancer and antibacterial effectiveness of sonochemically produced Ce3+/Dy3+ co-activated Mn-Zn nanospinel ferrites. Arabian J. Chem. 2020, 13, 7403–7417. [Google Scholar] [CrossRef]
  212. Almessiere, M.; Slimani, Y.; Korkmaz, A.D.; Güner, S.; Baykal, A.; Shirsath, S.; Ercan, I.; Kögerler, P. Sonochemical synthesis of Dy3+ substituted Mn0.5Zn0. 5Fe2−xO4 nanoparticles: Structural, magnetic and optical characterizations. Ultrason. Sonochem. 2020, 61, 104836. [Google Scholar] [CrossRef] [PubMed]
  213. Rezlescu, N.; Iftimie, N.; Rezlescu, E.; Doroftei, C.; Popa, P.D. Semiconducting gas sensor for acetone based on the fine grained nickel ferrite. Sens. Actuators B 2006, 114, 427–432. [Google Scholar] [CrossRef]
  214. Mugutkar, A.B.; Gore, S.K.; Patange, S.M.; Mane, R.S.; Raut, S.D.; Shaikh, S.F.; Ubaidullah, M.; Pandit, B.; Jadhav, S.S. Ammonia gas sensing and magnetic permeability of enhanced surface area and high porosity lanthanum substituted Co–Zn nano ferrites. Ceram. Int. 2022, 48, 15043–15055. [Google Scholar] [CrossRef]
  215. Radu, I.; Turcan, I.; Lukacs, A.V.; Roman, T.; Bulai, G.-A.; Olariu, M.A.; Dumitru, I.; Pui, A. Structural, dielectric and gas sensing properties of gadolinium (Gd3+) substituted zinc-manganese nanoferrites. Polyhedron 2022, 221, R713–R715. [Google Scholar] [CrossRef]
  216. Liu, Y.-L.; Wang, H.; Yang, Y.; Liu, Z.-M.; Yang, H.-F.; Shen, G.-L.; Yu, R.-Q. Hydrogen sulfide sensing properties of NiFe2O4 nanopowder doped with noble metals. Sens. Actuators B 2004, 102, 148–154. [Google Scholar] [CrossRef]
  217. Yang, L.; Xie, Y.; Zhao, H.; Wu, X.; Wang, Y. Preparation and gas-sensing properties of NiFe2O4 semiconductor materials. Solid-State Electron. 2005, 49, 1029–1033. [Google Scholar] [CrossRef]
  218. Yan, Y.; Nizamidin, P.; Turdi, G.; Kari, N.; Yimit, A. Room-temperature H2S Gas Sensor Based on Au-doped ZnFe2O4 Yolk-shell Microspheres. Anal. Sci. 2017, 33, 945–951. [Google Scholar] [CrossRef] [Green Version]
  219. Li, X.; Han, C.; Lu, D.; Shao, C.; Li, X.; Liu, Y. Highly electron-depleted ZnO/ZnFe2O4/Au hollow meshes as an advanced material for gas sensing application. Sens. Actuators B 2019, 297, 126769. [Google Scholar] [CrossRef]
  220. Li, K.; Luo, Y.; Gao, L.; Li, T.; Duan, G. Au-Decorated ZnFe2O4 Yolk-Shell Spheres for Trace Sensing of Chlorobenzene. ACS Appl. Mater. Interfaces 2020, 12, 16792–16804. [Google Scholar] [CrossRef]
  221. Nemufulwi, M.I.; Swart, H.C.; Mhlongo, G.H. Evaluation of the effects of Au addition into ZnFe2O4 nanostructures on acetone detection capabilities. Mater. Res. Bull. 2021, 142, 111395. [Google Scholar] [CrossRef]
  222. Qin, Q.; Li, A.; Fan, Y.; Zhang, X. A ZnO/ZnFe2O4 n–n heterojunction and Au loading synergistically improve the sensing performance of acetone. Inorg. Chem. Front. 2022, 9, 5663–5672. [Google Scholar] [CrossRef]
  223. Jiao, W.-l.; Zhang, L. Preparation and gas sensing properties for acetone of amorphous Ag modified NiFe2O4 sensor. Trans. Nonferrous Met. Soc. China 2012, 22, 1127–1132. [Google Scholar] [CrossRef]
  224. Zhang, C.; Wu, Q.; Zheng, B.; You, J.; Luo, Y. Synthesis and acetone gas sensing properties of Ag activated hollow sphere structured ZnFe2O4. Ceram. Int. 2018, 44, 20700–20707. [Google Scholar] [CrossRef]
  225. Gedam, N.N.; Padole, P.R.; Rithe, S.K.; Chaudhari, G.N. Ammonia gas sensor based on a spinel semiconductor, Co0.8Ni0.2Fe2O4 nanomaterial. J. Sol-Gel Sci. Technol. 2009, 50, 296–300. [Google Scholar] [CrossRef]
  226. Darshane, S.; Mulla, I.S. Influence of palladium on gas-sensing performance of magnesium ferrite nanoparticles. Mater. Chem. Phys. 2010, 119, 319–323. [Google Scholar] [CrossRef]
  227. Rao, P.; Godbole, R.V.; Bhagwat, S. Chlorine gas sensing performance of palladium doped nickel ferrite thin films. J. Magn. Magn. Mater. 2016, 405, 219–224. [Google Scholar] [CrossRef]
  228. Miralaei, M.; Salari, S.; Kameli, P.; Goodarzi, M.T.; Ranjbar, M. Electrical and hydrogen gas sensing properties of Co1-xZnxFe2O4 nanoparticles; effect of the sputtered palladium thin layer. Int. J. Hydrog. Energy 2023, 48, 20133–20150. [Google Scholar] [CrossRef]
  229. Zhao, C.; Lan, W.; Gong, H.; Bai, J.; Rarnachandran, R.; Liu, S.; Wang, F. Highly sensitive acetone-sensing properties of Pt-decorated CuFe2O4 nanotubes prepared by electrospinning. Ceram. Int. 2018, 44, 2856–2863. [Google Scholar] [CrossRef]
  230. Manikandan, V.; Mirzael, A.; Vigneselvan, S.; Kavita, S.; Mane, R.S.; Kim, S.S.; Chandrasekaran, J. Role of Ruthenium in the Dielectric, Magnetic Properties of Nickel Ferrite (Ru-NiFe2O4) Nanoparticles and Their Application in Hydrogen Sensors. Acs Omega 2019, 4, 12919–12926. [Google Scholar] [CrossRef] [Green Version]
  231. Lee, J.; Jung, Y.; Sung, S.-H.; Lee, G.; Kim, J.; Seong, J.; Shim, Y.-S.; Jun, S.C.; Jeon, S. High-performance gas sensor array for indoor air quality monitoring: The role of Au nanoparticles on WO3, SnO2, and NiO-based gas sensors. J. Mater. Chem. A 2021, 9, 1159–1167. [Google Scholar] [CrossRef]
  232. Wang, Y.; Meng, X.-n.; Cao, J.-l. Rapid detection of low concentration CO using Pt-loaded ZnO nanosheets. J. Hazard. Mater. 2020, 381, 120944. [Google Scholar] [CrossRef]
  233. Jiang, Y.; Song, W.; Xie, C.; Wang, A.; Zeng, D.; Hu, M. Electrical conductivity and gas sensitivity to VOCs of V-doped ZnFe2O4 nanoparticles. Mater. Lett. 2006, 60, 1374–1378. [Google Scholar] [CrossRef]
  234. Obata, K.; Mizuta, K.; Obukuro, Y.; Sakai, G.; Hagiwara, H.; Ishihara, T.; Matsushima, S. CO2 Sensing Properties of Zr-Added Porous CaFe2O4 Powder. Sens. Mater. 2016, 28, 1157–1164. [Google Scholar]
  235. Lv, L.; Cheng, P.; Wang, Y.; Xu, L.; Zhang, B.; Lv, C.; Ma, J.; Zhang, Y. Sb-doped three-dimensional ZnFe2O4 macroporous spheres for N-butanol chemiresistive gas sensors. Sens. Actuators B 2020, 320, 128384. [Google Scholar] [CrossRef]
  236. Manikandan, V.; Petrila, I.; Kavita, S.; Mane, R.S.; Denardin, J.C.; Lundgaard, S.; Juodkazis, S.; Vigneselvan, S.; Chandrasekaran, J. Effect of Vd-doping on dielectric, magnetic and gas sensing properties of nickel ferrite nanoparticles. J. Mater. Sci. Mater. Electron. 2020, 31, 16728–16736. [Google Scholar] [CrossRef]
  237. Abd-Elkader, O.; Al-Enizi, A.M.; Shaikh, S.F.; Ubaidullah, M.; Abdelkader, M.O.; Mostafa, N.Y. The Structure, Magnetic, and Gas Sensing Characteristics of W-Substituted Co-Ferrite Nanoparticles. Crystals 2022, 12, 393. [Google Scholar] [CrossRef]
  238. Heiba, Z.K.; Mohamed, M.B.; Wahba, A.M.; Almalowi, M. Effect of vanadium doping on structural and magnetic properties of defective nano-nickel ferrite. Appl. Phys. A 2018, 124, 1–9. [Google Scholar] [CrossRef]
  239. Narayan, R.; Tripathi, R.; Das, B.; Jain, G. Pentavalent vanadium ion addition to Ni-Zn ferrites: Part 2 Electrical conductivity. J. Mater. Sci. 1983, 18, 1934–1940. [Google Scholar] [CrossRef]
  240. Sarrami, H.; Ebrahimi, H.R.; Emami, H. Synthesis, Characterization, and Sensing Behavior Study of Cadmium-Doped Nickel Manganese Ferrite/CdO Nanoparticles. IEEE Trans. Magn. 2021, 57, 1–6. [Google Scholar] [CrossRef]
  241. Zhang, N.; Ruan, S.; Qu, F.; Yin, Y.; Li, X.; Wen, S.; Adimi, S.; Yin, J. Metal-organic framework-derived Co3O4/CoFe2O4 double-shelled nanocubes for selective detection of sub-ppm-level formaldehyde. Sens. Actuators B 2019, 298, 126887. [Google Scholar] [CrossRef]
  242. Hu, J.; Xiong, X.; Guan, W.; Chen, Y.; Long, H. Design and construction of core-shelled Co3O4-CoFe2O4 heterojunction for highly sensitive and selective detection of ammonia. Chem. Eng. J. 2023, 452, 139346. [Google Scholar] [CrossRef]
  243. Chapelle, A.; Barnabe, A.; Presmanes, L.; Tailhades, P. Copper and iron based thin film nanocomposites prepared by radio-frequency sputtering. Part II: Elaboration and characterization of oxide/oxide thin film nanocomposites using controlled ex-situ oxidation process. J. Mater. Sci. 2013, 48, 3304–3314. [Google Scholar] [CrossRef] [Green Version]
  244. Boepple, M.; Zhu, Z.; Hu, X.; Weimar, U.; Barsan, N. Impact of heterostructures on hydrogen sulfide sensing: Example of core-shell CuO/CuFe2O4 nanostructures. Sens. Actuators B 2020, 321, 128523. [Google Scholar] [CrossRef]
  245. Chapelle, A.; El Younsi, I.; Vitale, S.; Thimont, Y.; Nelis, T.; Presmanes, L.; Barnabe, A.; Tailhades, P. Improved semiconducting CuO/CuFe2O4 nanostructured thin films for CO2 gas sensing. Sens. Actuators B 2014, 204, 407–413. [Google Scholar] [CrossRef] [Green Version]
  246. Sumangala, T.P.; Thimont, Y.; Baco-Carles, V.; Presmanes, L.; Bonningue, C.; Pasquet, I.; Tailhades, P.; Barnabe, A. Study on the effect of cuprite content on the electrical and CO2 sensing properties of cuprite-copper ferrite nanopowder composites. J. Alloys Compd. 2017, 695, 937–943. [Google Scholar] [CrossRef] [Green Version]
  247. De, S.; Venkataramani, N.; Prasad, S.; Dusane, R.O.; Presmanes, L.; Thimont, Y.; Tailhades, P.; Baco-Carles, V.; Bonningue, C.; Pisharam, S.T.; et al. Ethanol and Hydrogen Gas-Sensing Properties of CuO-CuFe2O4 Nanostructured Thin Films. IEEE Sens. J. 2018, 18, 6937–6945. [Google Scholar] [CrossRef] [Green Version]
  248. Hu, X.; Zhu, Z.; Li, Z.; Xie, L.; Wu, Y.; Zheng, L. Heterostructure of CuO microspheres modified with CuFe2O4 nanoparticles for highly sensitive H2S gas sensor. Sens. Actuators B 2018, 264, 139–149. [Google Scholar] [CrossRef]
  249. Zhang, N.; Ruan, S.; Han, J.; Yin, Y.; Li, X.; Liu, C.; Adimi, S.; Wen, S.; Xu, Y. Oxygen vacancies dominated CuO@ZnFe2O4 yolk-shell microspheres for robust and selective detection of xylene. Sens. Actuators B 2019, 295, 117–126. [Google Scholar] [CrossRef]
  250. Zhang, H.; Gao, S.; Feng, Z.; Sun, Z.; Yan, X.; Li, Z.; Yang, X.; Pan, G.; Yuan, Y.; Guo, L. Room temperature detection of low-concentration H2S based on CuO functionalized ZnFe2O4 porous spheres. Sens. Actuators B 2022, 368, 869–874. [Google Scholar] [CrossRef]
  251. Zhou, T.; Zhang, R.; Wang, Y.; Zhang, T. MOF-Derived 1 D α-Fe2O3/NiFe2O4 heterojunction as efficient sensing materials of acetone vapors. Sens. Actuators B 2019, 281, 885–892. [Google Scholar] [CrossRef]
  252. Li, Y.; Luo, N.; Sun, G.; Zhang, B.; Ma, G.; Jin, H.; Wang, Y.; Cao, J.; Zhang, Z. Facile synthesis of ZnFe2O4/α-Fe2O3 porous microrods with enhanced TEA-sensing performance. J. Alloys Compd. 2018, 737, 255–262. [Google Scholar] [CrossRef]
  253. Ma, Q.; Li, H.; Liu, Y.; Liu, M.; Fu, X.; Chu, S.; Li, H.; Guo, J. Facile synthesis of flower-like α-Fe2O3/ZnFe2O4 architectures with self-assembled core-shell nanorods for superior TEA detection. Curr. Appl. Phys. 2021, 21, 161–169. [Google Scholar] [CrossRef]
  254. Wei, Q.; Sun, J.; Song, P.; Li, J.; Yang, Z.; Wang, Q. Spindle-like Fe2O3/ZnFe2O4 porous nanocomposites derived from metal-organic frameworks with excellent sensing performance towards triethylamine. Sens. Actuators B 2020, 317, R713–R715. [Google Scholar] [CrossRef]
  255. Hashishin, T.; Onoda, H.; Sanada, T.; Fujioka, D.; Kojima, K.; Naka, T. Magnesium Ferrite Sensor for H2S Detection. Sens. Mater. 2016, 28, 1229–1236. [Google Scholar]
  256. Sakaguchi, C.; Nara, Y.; Hashishin, T.; Abe, H.; Matsuda, M.; Tsurekawa, S.; Kubota, H. Direct observation of potential phase at joining interface between p-MgO and n-MgFe2O4. Sci. Rep. 2020, 10, 17055. [Google Scholar] [CrossRef]
  257. Aliah, H.; Iman, R.N.; Sawitri, A.; Syarif, D.G.; Setiawan, A.; Darmalaksana, W.; Malik, A. The optimization of ZnFe2O4/Mn2O3-based nanocomposite ceramic fabrication utilizing local minerals as an ethanol gas detector. Mater. Res. Express 2019, 6, 95908. [Google Scholar] [CrossRef]
  258. Xu, Y.; Tian, X.; Fan, Y.; Sun, Y. A formaldehyde gas sensor with improved gas response and sub-ppm level detection limit based on NiO/NiFe2O4 composite nanotetrahedrons. Sens. Actuators B 2020, 309, 127719. [Google Scholar] [CrossRef]
  259. Xu, Y.; Fan, Y.; Tian, X.; Liang, Q.; Liu, X.; Sun, Y. p-p heterojunction composite of NiFe2O4 nanoparticles-decorated NiO nanosheets for acetone gas detection. Mater. Lett. 2020, 270, 127728. [Google Scholar] [CrossRef]
  260. Lv, L.; Wang, Y.; Cheng, P.; Zhang, B.; Dang, F.; Xu, L. Ultrasonic spray pyrolysis synthesis of three-dimensional ZnFe2O4-based macroporous spheres for excellent sensitive acetone gas sensor. Sens. Actuators B 2019, 297, 129652. [Google Scholar] [CrossRef]
  261. Lin, G.; Wang, H.; Li, X.; Lai, X.; Zou, Y.; Zhou, X.; Liu, D.; Wan, J.; Xin, H. Chestnut-like CoFe2O4@SiO2@In2O3 nanocomposite microspheres with enhanced acetone sensing property. Sens. Actuators B 2018, 255, 3364–3373. [Google Scholar] [CrossRef]
  262. Liu, M.Y.; Wang, C.G.; Yang, M.K.; Tang, L.R.; Wang, Q.; Sun, Y.Q.; Xu, Y.Y. Novel strategy to construct porous Sn-doped ZnO/ZnFe2O4 heterostructures for superior triethylamine detection. Mater. Sci. Semicond. Process. 2021, 125, 10. [Google Scholar] [CrossRef]
  263. Balaji, M.; Jeyaram, R.A.; Matheswaran, P. Enhanced performance of SnO2-Mn1-XCuXFe2O4 gas sensors towards carbon dioxide and oxygen. J. Alloys Compd. 2017, 696, 435–442. [Google Scholar] [CrossRef]
  264. Ni, Q.; Sun, L.; Cao, E.; Hao, W.; Zhang, Y.; Ju, L. Enhanced acetone sensing performance of the ZnFe2O4/SnO2 nanocomposite. Appl. Phys. A Mater. Sci. Process. 2019, 125, 1–8. [Google Scholar] [CrossRef]
  265. He, L.; Hu, J.; Yuan, Q.; Xia, Z.; Jin, L.; Gao, H.; Fan, L.; Chu, X.; Meng, F. Synthesis of porous ZnFe2O4/SnO2 core-shell spheres for high-performance acetone gas sensing. Sens. Actuators B 2023, 378, 133123. [Google Scholar] [CrossRef]
  266. Babu Reddy, L.P.; Megha, R.; Raj Prakash, H.G.; Ravikiran, Y.T.; Ramana, C.H.V.V.; Vijaya Kumari, S.C.; Kim, D. Copper ferrite-yttrium oxide (CFYO) nanocomposite as remarkable humidity sensor. Inorg. Chem. Commun. 2019, 99, 180–188. [Google Scholar] [CrossRef]
  267. Zhang, W.-H.; Zhang, W.-D.; Zhou, J.-F. Solvent thermal synthesis and gas-sensing properties of Fe-doped ZnO. J. Mater. Sci. 2010, 45, 209–215. [Google Scholar] [CrossRef]
  268. Arshak, K.; Gaidan, I. Development of a novel gas sensor based on oxide thick films. Mater. Sci. Eng. B 2005, 118, 44–49. [Google Scholar] [CrossRef]
  269. Arshak, K.; Gaidan, I. Gas sensing properties of ZnFe2O4/ZnO screen-printed thick films. Sens. Actuators B 2005, 111, 58–62. [Google Scholar] [CrossRef]
  270. Arshak, K.; Gaidan, I.; Moore, E.G.; Cunniffe, C. The effect of the addition of carbon black and the increase in film thickness on the sensing layers of ZnO/ZnFe2O4 in polymer thick film gas sensors. Superlattices Microstruct. 2007, 42, 348–356. [Google Scholar] [CrossRef]
  271. Wang, S.; Gao, X.; Yang, J.; Zhu, Z.; Zhang, H.; Wang, Y. Synthesis and gas sensor application of ZnFe2O4-ZnO composite hollow microspheres. RSC Adv. 2014, 4, 57967–57974. [Google Scholar] [CrossRef]
  272. Li, X.; Wang, C.; Guo, H.; Sun, P.; Liu, F.; Liang, X.; Lu, G. Double-Shell Architectures of ZnFe2O4 Nanosheets on ZnO Hollow Spheres for High-Performance Gas Sensors. ACS Appl. Mater. Interfaces 2015, 7, 17811–17818. [Google Scholar] [CrossRef] [PubMed]
  273. Ma, J.; Cai, Y.; Li, X.; Yao, S.; Liu, Y.; Liu, F.; Lu, G. Synthesis of hierarchical ZnO/ZnFe2O4 nanoforests with enhanced gas-sensing performance toward ethanol. Crystengcomm 2015, 17, 8683–8688. [Google Scholar] [CrossRef]
  274. Wang, S.; Zhang, J.; Yang, J.; Gao, X.; Zhang, H.; Wang, Y.; Zhu, Z. Spinel ZnFe2O4 nanoparticle-decorated rod-like ZnO nanoheterostructures for enhanced gas sensing performances. RSC Adv. 2015, 5, 10048–10057. [Google Scholar] [CrossRef]
  275. Liu, S.-R.; Guan, M.-Y.; Li, X.-Z.; Guo, Y. Light irradiation enhanced triethylamine gas sensing materials based on ZnO/ZnFe2O4 composites. Sens. Actuators B 2016, 236, 350–357. [Google Scholar] [CrossRef]
  276. Zhang, R.; Zhang, T.; Zhou, T.; Lou, Z.; Deng, J.; Wang, L. Fast and real-time acetone gas sensor using hybrid ZnFe2O4/ZnO hollow spheres. RSC Adv. 2016, 6, 66738–66744. [Google Scholar] [CrossRef]
  277. Ma, X.; Zhou, X.; Gong, Y.; Han, N.; Liu, H.; Chen, Y. MOF-derived hierarchical ZnO/ZnFe2O4 hollow cubes for enhanced acetone gas-sensing performance. RSC Adv. 2017, 7, 34609–34617. [Google Scholar] [CrossRef] [Green Version]
  278. Wang, X.; Zhang, S.; Shao, M.; Huang, J.; Deng, X.; Hou, P.; Xu, X. Fabrication of ZnO/ZnFe2O4 hollow nanocages through metal organic frameworks route with enhanced gas sensing properties. Sens. Actuators B 2017, 251, 27–33. [Google Scholar] [CrossRef]
  279. Runa, A.; Zhang, X.; Wen, G.; Zhang, B.; Fu, W.; Yang, H. Actinomorphic flower-like n-ZnO/p-ZnFe2O4 composite and its improved NO2 gas-sensing property. Mater. Lett. 2018, 225, 73–76. [Google Scholar] [CrossRef]
  280. Song, X.-Z.; Qiao, L.; Sun, K.-M.; Tan, Z.; Ma, W.; Kang, X.-L.; Sun, F.-F.; Huang, T.; Wang, X.-F. Triple-shelled ZnO/ZnFe2O4 heterojunctional hollow microspheres derived from Prussian Blue analogue as high-performance acetone sensors. Sens. Actuators B 2018, 256, 374–382. [Google Scholar] [CrossRef]
  281. Zhai, C.; Zhao, Q.; Gu, K.; Xing, D.; Zhang, M. Ultra-fast response and recovery of triethylamine gas sensors using a MOF-based ZnO/ZnFe2O4 structures. J. Alloys Compd. 2019, 784, 660–667. [Google Scholar] [CrossRef]
  282. Cao, E.; Guo, Z.; Song, G.; Zhang, Y.; Hao, W.; Sun, L.; Nie, Z. MOF-derived ZnFe2O4/(Fe-ZnO) nanocomposites with enhanced acetone sensing performance. Sens. Actuators B 2020, 325, 128783. [Google Scholar] [CrossRef]
  283. Hu, Y.; Wang, H.; Liu, D.; Lin, G.; Wan, J.; Jiang, H.; Lai, X.; Hao, S.; Liu, X. Lychee-like ZnO/ZnFe2O4 core-shell hollow microsphere for improving acetone gas sensing performance. Ceram. Int. 2020, 46, 5960–5967. [Google Scholar] [CrossRef]
  284. Zheng, C.; Zhang, C.; He, L.; Zhang, K.; Zhang, J.; Jin, L.; Asiri, A.M.; Alamry, K.A.; Chu, X. ZnFe2O4/ZnO nanosheets assembled microspheres for high performance trimethylamine gas sensing. J. Alloys Compd. 2020, 849, 690–701. [Google Scholar] [CrossRef]
  285. Li, D.; Ma, J.; Chen, K. 2-D zinc ferrite “moss” furred on 3-D zinc oxide tetrapods to boost detection sensitivity of hydrogen sulfide. J. Phys. Chem. Solids 2021, 148, 109656. [Google Scholar] [CrossRef]
  286. Li, S.; Zhang, Y.; Han, L.; Li, X.; Xu, Y. Hierarchical kiwifruit-like ZnO/ZnFe2O4 heterostructure for high-sensitive triethylamine gaseous sensor. Sens. Actuators B 2021, 344, 130251. [Google Scholar] [CrossRef]
  287. Li, W.; Wu, X.; Chen, J.; Gong, Y.; Han, N.; Chen, Y. Abnormal n-p-n type conductivity transition of hollow ZnO/ZnFe2O4 nanostructures during gas sensing process: The role of ZnO-ZnFe2O4 hetero-interface. Sens. Actuators B 2017, 253, 144–155. [Google Scholar] [CrossRef]
  288. Liu, C.; Wang, B.; Wang, T.; Liu, J.; Sun, P.; Chuai, X.; Lu, G. Enhanced gas sensing characteristics of the flower-like ZnFe2O4/ZnO microstructures. Sens. Actuators B 2017, 248, 902–909. [Google Scholar] [CrossRef]
  289. Zhang, R.; Wang, Y.; Zhang, Z.; Cao, J. Synthesis of g-C3N4-Decorated Magnesium Ferrite Nanoparticle Composites for Improved Ethanol Sensing. Chem. Sel. 2018, 3, 12269–12273. [Google Scholar] [CrossRef]
  290. Zhang, R.; Wang, Y.; Zhang, Z.; Cao, J. Highly Sensitive Acetone Gas Sensor Based on g-C3N4 Decorated MgFe2O4 Porous Microspheres Composites. Sensors 2018, 18, 2211. [Google Scholar] [CrossRef] [Green Version]
  291. Chu, X.; Dai, P.; Liang, S.; Bhattacharya, A.; Dong, Y.; Epifani, M. The acetone sensing properties of ZnFe2O4-graphene quantum dots (GQDs) nanocomposites at room temperature. Phys. E 2019, 106, 326–333. [Google Scholar] [CrossRef]
  292. Liu, F.; Chu, X.; Dong, Y.; Zhang, W.; Sun, W.; Shen, L. Acetone gas sensors based on graphene-ZnFe2O4 composite prepared by solvothermal method. Sens. Actuators B 2013, 188, 469–474. [Google Scholar] [CrossRef]
  293. Zhang, K.; Ding, C.; She, Y.; Wu, Z.; Zhao, C.; Pan, B.; Zhang, L.; Zhou, W.; Fan, Q. CuFe2O4/MoS2 Mixed-Dimensional Heterostructures with Improved Gas Sensing Response. Nanoscale Res. Lett. 2020, 15, 1–7. [Google Scholar] [CrossRef] [Green Version]
  294. Hajihashemi, R.; Rashidi, A.M.; Alaie, M.; Mohammadzadeh, R.; Izadi, N. The study of structural properties of carbon nanotubes decorated with NiFe2O4 nanoparticles and application of nano-composite thin film as H2S gas sensor. Mater. Sci. Eng. C 2014, 44, 417–421. [Google Scholar] [CrossRef] [PubMed]
  295. Tang, Y.; Zhang, Q.; Li, Y.; Wang, H. Highly selective ammonia sensors based on Co1−xNixFe2O4/multi-walled carbon nanotubes nanocomposites. Sens. Actuators B 2012, 169, 229–234. [Google Scholar] [CrossRef]
  296. Achary, L.S.K.; Kumar, A.; Barik, B.; Nayak, P.S.; Tripathy, N.; Kar, J.P.; Dash, P. Reduced graphene oxide-CuFe2O4 nanocomposite: A highly sensitive room temperature NH3 gas sensor. Sens. Actuators B 2018, 272, 100–109. [Google Scholar] [CrossRef]
  297. Niresh, J.; Archana, N.; Neelakrishna, S.; Sivakumar, V.M.; Dharun, D.S. Optimization of low temperature hydrogen sensor using nano ceramicparticles for use in hybrid electric vehicles. J. Ceram. Process. Res. 2020, 21, 343–350. [Google Scholar] [CrossRef]
  298. Bai, S.; Zuo, Y.; Zhang, K.; Zhao, Y.; Luo, R.; Li, D.; Chen, A. WO3-ZnFe2O4 heterojunction and rGO decoration synergistically improve the sensing performance of triethylamine. Sens. Actuators B 2021, 347, 130619. [Google Scholar] [CrossRef]
  299. Zhou, L.-J.; Zhang, X.-X.; Zhang, W.-Y. Sulfur dioxide sensing properties of MOF-derived ZnFe2O4 functionalized with reduced graphene oxide at room temperature. Rare Met. 2020, 40, 1604–1613. [Google Scholar] [CrossRef]
  300. Wu, K.; Luo, Y.; Li, Y.; Zhang, C. Synthesis and acetone sensing properties of ZnFe2O4/rGO gas sensors. Beilstein J. Nanotechnol. 2019, 10, 2516–2526. [Google Scholar] [CrossRef] [Green Version]
  301. Van Hoang, N.; Hung, C.M.; Hoa, N.D.; Van Duy, N.; Park, I.; Van Hieu, N. Excellent detection of H2S gas at ppb concentrations using ZnFe2O4 nanofibers loaded with reduced graphene oxide. Sens. Actuators B 2019, 282, 876–884. [Google Scholar] [CrossRef]
  302. Zheng, C.; Zhang, C.; Zhang, K.; Zhang, J.; Jin, L.; Asiri, A.M.; Alamry, K.A.; He, L.F.; Chu, X.F. Growth of ZnFe2O4 nanosheets on reduced graphene oxide with enhanced ethanol sensing properties. Sens. Actuators B 2021, 330, 8. [Google Scholar] [CrossRef]
  303. Bag, A.; Kumar, M.; Moon, D.B.; Hanif, A.; Sultan, M.J.; Yoon, D.H.; Lee, N.E. A room-temperature operable and stretchable NO2 gas sensor composed of reduced graphene oxide anchored with MOF-derived ZnFe2O4 hollow octahedron. Sens. Actuators B 2021, 346, 130463. [Google Scholar] [CrossRef]
  304. Achary, L.S.K.; Maji, B.; Kumar, A.; Ghosh, S.P.; Kar, J.P.; Dash, P. Efficient room temperature detection of H2 gas by novel ZnFe2O4-Pd decorated rGO nanocomposite. Int. J. Hydrog. Energy 2020, 45, 5073–5085. [Google Scholar] [CrossRef]
  305. Zhang, L.; Jiao, W. Synthesis and gas sensing properties of high porosity n-type nickel ferrite thin film assisted by altering magnetic field. Curr. Appl. Phys. 2015, 15, 789–793. [Google Scholar] [CrossRef]
  306. Anjitha, T.; Anilkumar, T.; Mathew, G.; Ramesan, M.T. Zinc ferrite @ polyindole nanocomposites: Synthesis, characterization and gas sensing applications. Polym. Compos. 2019, 40, 2802–2811. [Google Scholar] [CrossRef]
  307. Wang, X.; Gong, L.; Zhang, D.; Fan, X.; Jin, Y.; Guo, L. Room temperature ammonia gas sensor based on polyaniline/copper ferrite binary nanocomposites. Sens. Actuators B 2020, 322, 128615. [Google Scholar] [CrossRef]
  308. Sonwane, N.D.; Kondawar, S.B. Electrospun nickel ferrite nanofibers reinforced polyaniline composite for high-performance room temperature ammonia sensing. Synth. Met. 2022, 284, 117004. [Google Scholar] [CrossRef]
Figure 1. The crystal structure of ZnFe2O4, with Zn2+ in the tetrahedron gap and Fe3+ in the octahedron gap.
Figure 1. The crystal structure of ZnFe2O4, with Zn2+ in the tetrahedron gap and Fe3+ in the octahedron gap.
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Figure 2. (a) The effect of operating temperature of the CdFe2O4 sensor on the various gas responses. (b) Response of the sensors to 100 ppm ethanol at different operating temperatures. (c) XRD pattern of (Co, Cu, Ni, and Zn) ferrite thin films. (d) Response value of (Co, Cu, Ni, and Zn) ferrite thin films to 5 ppm LPG at different operating temperatures. (e) Size of CoFe2O4 nanoparticles dependent on response value (%) with varying temperatures for 200 ppm ethanol. (f) The sensitivity of individual CoFe2O4 sensors to 100 ppm methanol across varying temperature conditions. (a) Reproduced with permission [43], copyright 1998, Elsevier B.V. (b) Reproduced with permission [35], copyright 2022, Elsevier B.V. (c,d) Reproduced with permission [51], copyright 2015, Elsevier B.V. (e) Reproduced with permission [52], copyright 2015, IEEE Xplore. (f) Reproduced with permission [54], copyright 2020, IEEE Xplore.
Figure 2. (a) The effect of operating temperature of the CdFe2O4 sensor on the various gas responses. (b) Response of the sensors to 100 ppm ethanol at different operating temperatures. (c) XRD pattern of (Co, Cu, Ni, and Zn) ferrite thin films. (d) Response value of (Co, Cu, Ni, and Zn) ferrite thin films to 5 ppm LPG at different operating temperatures. (e) Size of CoFe2O4 nanoparticles dependent on response value (%) with varying temperatures for 200 ppm ethanol. (f) The sensitivity of individual CoFe2O4 sensors to 100 ppm methanol across varying temperature conditions. (a) Reproduced with permission [43], copyright 1998, Elsevier B.V. (b) Reproduced with permission [35], copyright 2022, Elsevier B.V. (c,d) Reproduced with permission [51], copyright 2015, Elsevier B.V. (e) Reproduced with permission [52], copyright 2015, IEEE Xplore. (f) Reproduced with permission [54], copyright 2020, IEEE Xplore.
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Figure 3. (a) XRD of the synthesized MgFe2O4 samples. (b)Variation in the response of MgFe2O4 samples at 300 °C. (c) HRTEM image showing cubic NiFe2O4. (d) H2S sensitivity of NiFe2O4 with various milled times at operating temperatures. (e) Responses of sensors to 500 ppm acetone at various temperatures. (f) TEM images of the synthesized ZnFe2O4 nanoparticles. (a,b) Reproduced with permission [69], copyright 2018, Elsevier B.V. (c,d) Reproduced with permission [78], copyright 2015, Elsevier B.V. (e,f) Reproduced with permission [92], copyright 2015, Elsevier B.V.
Figure 3. (a) XRD of the synthesized MgFe2O4 samples. (b)Variation in the response of MgFe2O4 samples at 300 °C. (c) HRTEM image showing cubic NiFe2O4. (d) H2S sensitivity of NiFe2O4 with various milled times at operating temperatures. (e) Responses of sensors to 500 ppm acetone at various temperatures. (f) TEM images of the synthesized ZnFe2O4 nanoparticles. (a,b) Reproduced with permission [69], copyright 2018, Elsevier B.V. (c,d) Reproduced with permission [78], copyright 2015, Elsevier B.V. (e,f) Reproduced with permission [92], copyright 2015, Elsevier B.V.
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Figure 4. (a) The sensitivity–temperature characteristics of various MFe2O4 sensors in detecting formaldehyde. (b) The sensitivity-temperature characteristics of various MFe2O4 sensors in detecting formaldehyde ethanol: (a) Fe3O4, (b) CoFe2O4, (c) NiFe2O4, (d) MgFe2O4, (e) CdFe2O4, (f) ZnFe2O4. (c) TEM image of the ZnFe2O4 nanoparticles. (d) Comparative analysis of the NO2 response among sensors based on ZFO-300, ZFO-500, and ZFO-700 materials when exposed to 10 ppm NO2 at varying operating temperatures. (e) The TEM image of ZnFe2O4 nanoparticles at low magnification. (f) The response values of sensors based on ZnFe2O4 nanoparticles to 5 ppm H2S gas at different working temperatures. (g) Cross-sectional FESEM image of the ZnFe2O4 film. (h) Total density of states (TDOS) of the ZnFe2O4. (a,b) Reproduced with permission [93], copyright 2016, Elsevier B.V. (c,d) Reproduced with permission [99], copyright 2019, Royal Society of Chemistry. (e,f) Reproduced with permission [110], copyright 2018, Elsevier B.V. (g,h) Reproduced with permission [102], copyright 2022, IEEE Xplore.
Figure 4. (a) The sensitivity–temperature characteristics of various MFe2O4 sensors in detecting formaldehyde. (b) The sensitivity-temperature characteristics of various MFe2O4 sensors in detecting formaldehyde ethanol: (a) Fe3O4, (b) CoFe2O4, (c) NiFe2O4, (d) MgFe2O4, (e) CdFe2O4, (f) ZnFe2O4. (c) TEM image of the ZnFe2O4 nanoparticles. (d) Comparative analysis of the NO2 response among sensors based on ZFO-300, ZFO-500, and ZFO-700 materials when exposed to 10 ppm NO2 at varying operating temperatures. (e) The TEM image of ZnFe2O4 nanoparticles at low magnification. (f) The response values of sensors based on ZnFe2O4 nanoparticles to 5 ppm H2S gas at different working temperatures. (g) Cross-sectional FESEM image of the ZnFe2O4 film. (h) Total density of states (TDOS) of the ZnFe2O4. (a,b) Reproduced with permission [93], copyright 2016, Elsevier B.V. (c,d) Reproduced with permission [99], copyright 2019, Royal Society of Chemistry. (e,f) Reproduced with permission [110], copyright 2018, Elsevier B.V. (g,h) Reproduced with permission [102], copyright 2022, IEEE Xplore.
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Figure 5. (a) SEM image and (b) TEM image of as-prepared NiFe2O4 nanorods. (c) The dynamic response−recovery characteristics of NiFe2O4 nanorods to n-propanol at different concentrations. Insert: response and recovery curve of the sensor to 100 ppm n-propanol. (d) TEM image of NiFe2O4 nanorods. (e) SEM images of ZnFe2O4 nanofiber. (f) SEM images of porous ZnFe2O4 nanorods. (g) SEM images of ZnFe2O4 nanosheets. (h) The response values of the sensors to 1 ppm H2S at various operating temperatures. (ac) Reproduced with permission [115], copyright 2018, Wiley-VCH. (d) Reproduced with permission [116], copyright 2007, Elsevier B.V. (e) Reproduced with permission [123], copyright 2018, Elsevier B.V. (f) Reproduced with permission [122], copyright 2017, Elsevier B.V. (g,h) Reproduced with permission [129], copyright 2017, Elsevier B.V.
Figure 5. (a) SEM image and (b) TEM image of as-prepared NiFe2O4 nanorods. (c) The dynamic response−recovery characteristics of NiFe2O4 nanorods to n-propanol at different concentrations. Insert: response and recovery curve of the sensor to 100 ppm n-propanol. (d) TEM image of NiFe2O4 nanorods. (e) SEM images of ZnFe2O4 nanofiber. (f) SEM images of porous ZnFe2O4 nanorods. (g) SEM images of ZnFe2O4 nanosheets. (h) The response values of the sensors to 1 ppm H2S at various operating temperatures. (ac) Reproduced with permission [115], copyright 2018, Wiley-VCH. (d) Reproduced with permission [116], copyright 2007, Elsevier B.V. (e) Reproduced with permission [123], copyright 2018, Elsevier B.V. (f) Reproduced with permission [122], copyright 2017, Elsevier B.V. (g,h) Reproduced with permission [129], copyright 2017, Elsevier B.V.
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Figure 6. (a) SEM and TEM images of the NiFe2O4 polyhedron. (b) The response comparison of sensors to 50 ppm TEA at various temperatures. (c) SEM image and TEM image (inset) of the ZnFe2O4 sphere. (d) Comparative analysis of the 30 ppm acetone response of porous ZnFe2O4 nanospheres and the 100 ppm acetone response of ZnFe2O4 nanoparticles at varying operating temperatures. (e) XRD patterns of ZnFe2O4 double-shell, yolk–shell, and solid microspheres. (f) The sensitivity–temperature characteristics of the ZnFe2O4 double-shell, yolk–shell, and solid microsphere-based sensors in detecting 20 ppm acetone. (g) SEM image and TEM image (inset) of the hierarchical ZnFe2O4 microspheres. (h) Dynamic curve of the gas sensor to acetone with different concentrations at 215 °C. (a,b) Reproduced with permission [142], copyright 2020, Royal Society of Chemistry. (c,d) Reproduced with permission [147], copyright 2015, Elsevier B.V. (e,f) Reproduced with permission [153], copyright 2018, Elsevier B.V. (g,h) Reproduced with permission [149], copyright 2015, American Chemical Society.
Figure 6. (a) SEM and TEM images of the NiFe2O4 polyhedron. (b) The response comparison of sensors to 50 ppm TEA at various temperatures. (c) SEM image and TEM image (inset) of the ZnFe2O4 sphere. (d) Comparative analysis of the 30 ppm acetone response of porous ZnFe2O4 nanospheres and the 100 ppm acetone response of ZnFe2O4 nanoparticles at varying operating temperatures. (e) XRD patterns of ZnFe2O4 double-shell, yolk–shell, and solid microspheres. (f) The sensitivity–temperature characteristics of the ZnFe2O4 double-shell, yolk–shell, and solid microsphere-based sensors in detecting 20 ppm acetone. (g) SEM image and TEM image (inset) of the hierarchical ZnFe2O4 microspheres. (h) Dynamic curve of the gas sensor to acetone with different concentrations at 215 °C. (a,b) Reproduced with permission [142], copyright 2020, Royal Society of Chemistry. (c,d) Reproduced with permission [147], copyright 2015, Elsevier B.V. (e,f) Reproduced with permission [153], copyright 2018, Elsevier B.V. (g,h) Reproduced with permission [149], copyright 2015, American Chemical Society.
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Figure 7. (a) FESEM image of embedded Mg0.5Zn0.5Fe2O4 nanotubes. (b) Resistance transients of embedded Mg0.5Zn0.5Fe2O4 nanotubes towards H2 (∼1660 ppm). (c) Dynamic curve of the resistance embedded Mg0.5Zn0.5Fe2O4 nanotube sensors to the 10–1660 ppm range of H2 at ∼350 °C. (d) Variations of the lattice constant with Ni content of NiZnFe2O4 system. (e) SEM image of the isolated Mg0.5Zn0.5Fe2O4 nanotubes. (f) Resistance transient of isolated Mg0.5Zn0.5Fe2O4 nanotubes to 1660 ppm H2. (g) Dynamic curve of the resistance isolated Mg0.5Zn0.5Fe2O4 nanotube sensors to the 10–1660 ppm range of H2 at 350 °C. (h) Response of sensors based on NixZn1−xFe2O4 (x = 0, 0.6, 1.0) to LPG gas at different operating temperatures. (i) The TEM images and SAED pattern of Ni0.7−xMnxZn0.3Fe2O4. (j) Small-range XRD patterns of the pure ZFNPs and Cu-ZFNPs with different Cu concentrations. (k) The variation in sensitivity with operating temperatures of pure ZFNPs and Cu-ZFNPs for 5 ppm H2S. (l) The response−concentration plots of Ni0.4Mn0.3Zn0.3Fe2O4 towards different test gases. (ac,eg) Reproduced with permission [155], copyright 2013, Elsevier B.V. (d,h) Reproduced with permission [90], copyright 2015, Springer Nature. (i,l) Reproduced with permission [199], copyright 2022, Elsevier B.V. (j,k) Reproduced with permission [187], copyright 2019, Elsevier B.V.
Figure 7. (a) FESEM image of embedded Mg0.5Zn0.5Fe2O4 nanotubes. (b) Resistance transients of embedded Mg0.5Zn0.5Fe2O4 nanotubes towards H2 (∼1660 ppm). (c) Dynamic curve of the resistance embedded Mg0.5Zn0.5Fe2O4 nanotube sensors to the 10–1660 ppm range of H2 at ∼350 °C. (d) Variations of the lattice constant with Ni content of NiZnFe2O4 system. (e) SEM image of the isolated Mg0.5Zn0.5Fe2O4 nanotubes. (f) Resistance transient of isolated Mg0.5Zn0.5Fe2O4 nanotubes to 1660 ppm H2. (g) Dynamic curve of the resistance isolated Mg0.5Zn0.5Fe2O4 nanotube sensors to the 10–1660 ppm range of H2 at 350 °C. (h) Response of sensors based on NixZn1−xFe2O4 (x = 0, 0.6, 1.0) to LPG gas at different operating temperatures. (i) The TEM images and SAED pattern of Ni0.7−xMnxZn0.3Fe2O4. (j) Small-range XRD patterns of the pure ZFNPs and Cu-ZFNPs with different Cu concentrations. (k) The variation in sensitivity with operating temperatures of pure ZFNPs and Cu-ZFNPs for 5 ppm H2S. (l) The response−concentration plots of Ni0.4Mn0.3Zn0.3Fe2O4 towards different test gases. (ac,eg) Reproduced with permission [155], copyright 2013, Elsevier B.V. (d,h) Reproduced with permission [90], copyright 2015, Springer Nature. (i,l) Reproduced with permission [199], copyright 2022, Elsevier B.V. (j,k) Reproduced with permission [187], copyright 2019, Elsevier B.V.
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Figure 8. (a) HRTEM images of MgCe0.2Fe1.8O4. (b) The XRD patterns of MgCexFe2−xO4. (c) Responses of MgCexFe2−xO4 nanoferrites (x = 0, 0.05, 0.1, and 0.2) to various gas with 100 ppm. (d) TEM image of CZLF ferrite with x = 0.1. (e) XRD pattern of La3+-CZLF powders. (f) The resistance plot of a sensor based on Co0.7Zn0.3La0.1Fe1.9O4. (ac) Reproduced with permission [207], copyright 2020, Elsevier B.V. (df) Reproduced with permission [214], copyright 2022, Elsevier B.V.
Figure 8. (a) HRTEM images of MgCe0.2Fe1.8O4. (b) The XRD patterns of MgCexFe2−xO4. (c) Responses of MgCexFe2−xO4 nanoferrites (x = 0, 0.05, 0.1, and 0.2) to various gas with 100 ppm. (d) TEM image of CZLF ferrite with x = 0.1. (e) XRD pattern of La3+-CZLF powders. (f) The resistance plot of a sensor based on Co0.7Zn0.3La0.1Fe1.9O4. (ac) Reproduced with permission [207], copyright 2020, Elsevier B.V. (df) Reproduced with permission [214], copyright 2022, Elsevier B.V.
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Figure 9. (a) HRTEM images of the Au nanoparticles/ZFO yolk–shell spheres and the inset is the size distribution of Au nanoparticles (marked with red circle). (b) Dynamic curve of the gas sensor based on the ZFO and Au/ZFO sphere to CB with different concentrations at 150 °C. (c) TEM images of 0.25 wt.% Ag/ZnFe2O4. (d) The effect of operating temperatures of the Ag/ZnFe2O4-sensor on the various gas responses of the sensors to 100 ppm acetone vapor at 125–200 °C. (e) SEM and (f) TEM images of ZnO/ZnFe2O4/Au ternary heterostructure. (g) Responses–temperature characteristics of the ZnO/ZnFe2O4/Au sensors to 100 ppm acetone. (h) The responses of sensors to ZnFe2O4 thick films vs. the content of V doping. (a,b) Reproduced with permission [220], copyright 2019, American Chemical Society. (c,d) Reproduced with permission [224], copyright 2018, Elsevier B.V. (eg) Reproduced with permission [219], copyright 2019, Elsevier B.V. (h) Reproduced with permission [233], copyright 2006, Elsevier B.V.
Figure 9. (a) HRTEM images of the Au nanoparticles/ZFO yolk–shell spheres and the inset is the size distribution of Au nanoparticles (marked with red circle). (b) Dynamic curve of the gas sensor based on the ZFO and Au/ZFO sphere to CB with different concentrations at 150 °C. (c) TEM images of 0.25 wt.% Ag/ZnFe2O4. (d) The effect of operating temperatures of the Ag/ZnFe2O4-sensor on the various gas responses of the sensors to 100 ppm acetone vapor at 125–200 °C. (e) SEM and (f) TEM images of ZnO/ZnFe2O4/Au ternary heterostructure. (g) Responses–temperature characteristics of the ZnO/ZnFe2O4/Au sensors to 100 ppm acetone. (h) The responses of sensors to ZnFe2O4 thick films vs. the content of V doping. (a,b) Reproduced with permission [220], copyright 2019, American Chemical Society. (c,d) Reproduced with permission [224], copyright 2018, Elsevier B.V. (eg) Reproduced with permission [219], copyright 2019, Elsevier B.V. (h) Reproduced with permission [233], copyright 2006, Elsevier B.V.
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Figure 10. (a) SEM and (b) TEM images of NiO/NiFe2O4. (c) Dynamic curve of the NiO/NiFe2O4-sensor to formaldehyde with different concentrations at 240 °C. (d) SEM image of Fe2O3/ZnFe2O4. (e) Comparative analysis of the 100 ppm TEA response among sensors based on Fe2O3 spindles and Fe2O3/ZnFe2O4 at varying operating temperatures. (f) SEM images of CuO/CuFe2O4. (g) Comparative analysis of the 100 ppm TEA response among sensors based on CuO microspheres, CuFe2O4 nanoparticles, and CuO/CuFe2O4 heterostructure at varying operating temperatures. (h) TEM images of Fe2O3/CuFe2O4 composite. (i) Gas-sensing performances of hollow Fe2O3 and CuFe2O4/Fe2O3-2-composite-based sensors under various concentrations of acetone ranging from 5 to 500 ppm. (ac) Reproduced with permission [258], copyright 2020, Elsevier B.V. (d,e) Reproduced with permission [254], copyright 2020, Elsevier B.V. (f,g) Reproduced with permission [248], copyright 2018, Elsevier B.V. (h,i) Reproduced with permission [29], copyright 2018, Elsevier B.V.
Figure 10. (a) SEM and (b) TEM images of NiO/NiFe2O4. (c) Dynamic curve of the NiO/NiFe2O4-sensor to formaldehyde with different concentrations at 240 °C. (d) SEM image of Fe2O3/ZnFe2O4. (e) Comparative analysis of the 100 ppm TEA response among sensors based on Fe2O3 spindles and Fe2O3/ZnFe2O4 at varying operating temperatures. (f) SEM images of CuO/CuFe2O4. (g) Comparative analysis of the 100 ppm TEA response among sensors based on CuO microspheres, CuFe2O4 nanoparticles, and CuO/CuFe2O4 heterostructure at varying operating temperatures. (h) TEM images of Fe2O3/CuFe2O4 composite. (i) Gas-sensing performances of hollow Fe2O3 and CuFe2O4/Fe2O3-2-composite-based sensors under various concentrations of acetone ranging from 5 to 500 ppm. (ac) Reproduced with permission [258], copyright 2020, Elsevier B.V. (d,e) Reproduced with permission [254], copyright 2020, Elsevier B.V. (f,g) Reproduced with permission [248], copyright 2018, Elsevier B.V. (h,i) Reproduced with permission [29], copyright 2018, Elsevier B.V.
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Figure 11. (a) SEM images of hollow ZnO/ZnFe2O4 microspheres. (b) Response value towards acetone with 0.1–5 ppm. (c) N2 adsorption−desorption isotherms for ZnO/ZnFe2O4 nanocages (inset is the pore size distribution). (d,e) SEM images of the coral-like ZnO/ZnFe2O4 with different magnifications. (f) Dynamic response/recover curves of the coral-like ZnO/ZnFe2O4 to different TEA concentrations at 240 °C. (g) Dynamic continuous response of ZnO/ZnFe2O4 hollow nanocages to 100 ppm acetone at 290 °C. (a,b) Reproduced with permission [287], copyright 2017, Elsevier B.V. (c,g) Reproduced with permission [278], copyright 2017, Elsevier B.V. (df) Reproduced with permission [41], copyright 2019, Elsevier B.V.
Figure 11. (a) SEM images of hollow ZnO/ZnFe2O4 microspheres. (b) Response value towards acetone with 0.1–5 ppm. (c) N2 adsorption−desorption isotherms for ZnO/ZnFe2O4 nanocages (inset is the pore size distribution). (d,e) SEM images of the coral-like ZnO/ZnFe2O4 with different magnifications. (f) Dynamic response/recover curves of the coral-like ZnO/ZnFe2O4 to different TEA concentrations at 240 °C. (g) Dynamic continuous response of ZnO/ZnFe2O4 hollow nanocages to 100 ppm acetone at 290 °C. (a,b) Reproduced with permission [287], copyright 2017, Elsevier B.V. (c,g) Reproduced with permission [278], copyright 2017, Elsevier B.V. (df) Reproduced with permission [41], copyright 2019, Elsevier B.V.
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Figure 12. (a) TEM image of g-C3N4. (b) SEM image of MgFe2O4/g-C3N4 composites. (c) TEM images of ZnFe2O4/GQDs. (d) The dynamic response/recover curves of the sensor based on the sample S-15 composite to various concentrations of acetone at RT. (e) SEM image of 9WO3-ZnFe2O4. (f) SEM micrographs of the 0.8 wt.% rGO/9WO3/ZnFe2O4 composite. (g) SEM images of PANI/CuFe2O4. (h) The sensitivity–temperature characteristics of the sensors based on MgFe2O4/g-C3N4 composites to 500 ppm acetone. (i) Dynamic responses curve of the different ratio of rGO/WO3/ZnFe2O4 composites; (j) Response of the sensors toward NH3 at 20 °C. (k) Response and recovery curves of the sensors toward 5 ppm NH3 at 20 °C. (a,b,h) Reproduced with permission [290], copyright 2018, MDPI. (c,d) Reproduced with permission [291], copyright 2019, Elsevier B.V. (e,f,i) Reproduced with permission [298], copyright 2021, Elsevier B.V. (g,j,k) Reproduced with permission [307], copyright 2020, Elsevier B.V.
Figure 12. (a) TEM image of g-C3N4. (b) SEM image of MgFe2O4/g-C3N4 composites. (c) TEM images of ZnFe2O4/GQDs. (d) The dynamic response/recover curves of the sensor based on the sample S-15 composite to various concentrations of acetone at RT. (e) SEM image of 9WO3-ZnFe2O4. (f) SEM micrographs of the 0.8 wt.% rGO/9WO3/ZnFe2O4 composite. (g) SEM images of PANI/CuFe2O4. (h) The sensitivity–temperature characteristics of the sensors based on MgFe2O4/g-C3N4 composites to 500 ppm acetone. (i) Dynamic responses curve of the different ratio of rGO/WO3/ZnFe2O4 composites; (j) Response of the sensors toward NH3 at 20 °C. (k) Response and recovery curves of the sensors toward 5 ppm NH3 at 20 °C. (a,b,h) Reproduced with permission [290], copyright 2018, MDPI. (c,d) Reproduced with permission [291], copyright 2019, Elsevier B.V. (e,f,i) Reproduced with permission [298], copyright 2021, Elsevier B.V. (g,j,k) Reproduced with permission [307], copyright 2020, Elsevier B.V.
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Table 1. Summary of the reported spinel ferrite nanoparticles-based gas sensors.
Table 1. Summary of the reported spinel ferrite nanoparticles-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
CdFe2O4Co-precipitatingNanoparticlesEthanol300100048 a--[43]
CdFe2O4Co-precipitatingNanoparticlesCH3SH3000.012 a600 s/--[44]
CoFe2O4Citrate processNanoparticlesH2S225-0.6 c--[45]
CoFe2O4HydrothermalNanoparticlesTEA190504.5 a100 s/120 s-[46]
CoFe2O4HydrothermalNanoparticlesEthanol150506 a50 s/60 s-[46]
CoFe2O4Co-precipitationNanoparticles
(12 nm)
LPGRT5 vol.%2700 c30 s/60 s-[22]
CoFe2O4Sol–gel
auto-combustion
NanoparticlesNH3RT1000.7 c118 s/145 s-[47]
CoFe2O4Sol–gel methodNanoparticles
(~50 nm)
Ethanol3001500.72 c75 s/110 s-[48]
CoFe2O4Microwave-assistedNanoparticlesSO21203.53.50 d10 s/20 s250 ppb[49]
CoFe2O4HydrothermalNanoparticlesEthanol200100110 a15 s/18 s-[35]
CoFe2O4Solution phase reactionhexagonally
nanoparticle
CO4001003 a--[50]
CoFe2O4Spray pyrolysisNanoparticles
(54 nm)
LPG25050.2 c--[51]
CoFe2O4Uniaxial pressNanoparticles
(5.8 nm)
LPG2502000.72 c3.8 s/43.2 s-[52]
CoFe2O4SolvothermalNanoparticles
(10 nm)
Acetone22010017.3 a27 s/7 s-[53]
CoFe2O4HydrothermalNanoparticlesCH3OH901000.42 c--[54]
CoFe2O4HydrothermalPorous
nanoparticles
CH3OHRT1000.20 c--[54]
CuFe2O4Citrate processNanoparticlesCO200-0.4 c--[45]
CuFe2O4Solid-state reactionNanoparticles
(70–150 nm)
Ethanol33210007.5 a10 s/15 s-[55]
CuFe2O4Sol–gelNanoparticlesLPG3001500.45 c180 s/240 s-[56]
CuFe2O4Co-precipitationNanoparticlesLPGRT1 vol.%2.6 c30 s/200 s-[57]
CuFe2O4Sol–gel techniqueNanoparticles (35.8 ± 5.3 nm)H2S80250.15 c51.5 s/--[58]
CuFe2O4Co-precipitationNanoparticle
(7 ± 2.1 nm)
H2S803000.39 d21.9 s/--[25]
CuFe2O4SputteringNanoparticlesH2501 vol.%0.15 c48 ± 11 s/--[59]
CuFe2O4Co-precipitation and annealedNanoparticles
(22 ± 3 nm)
H2S1403000.3 d32 ± 10 s/--[60]
CuFe2O4Co-precipitationNanoparticles
(6.4 nm)
NH3RT200.6 c8 s/300 s-[37]
MgFe2O4Solid-state reactionNanoparticlesH2S160213 b--[61]
MgFe2O4Solid-state reactionNanoparticles
(15–30 nm)
Ethanol3505013 b--[61]
MgFe2O4Co-precipitation methodParticle (1 µm)LPG25033 a--[62]
MgFe2O4Wet chemicalNanoparticles
(84 nm)
H231510000.53 c--[63]
MgFe2O4Wet chemicalNanoparticlesH225016601.02 c--[64]
MgFe2O4Sol–gelNanoparticles
(38 nm)
LPG32520000.71 c--[65]
MgFe2O4Citrate gel combustionNanoparticles
(37 nm)
LPG4001000.22 c34 s/67 s-[66]
MgFe2O4Auto-combustionSpherical particles (15–20 nm)Ethanol27550.73 c--[67]
MgFe2O4Spray pyrolysisNanoparticles
(25–45 nm)
Acetone323 k75193% c--[68]
MgFe2O4Co-precipitation0.9 ± 0.2 µmCO230050000.36 c120 s/240 s-[69]
MgFe2O4Sol gel combustion0.18 ± 0.06 µmCO230050000.24 c300 s/300 s-[69]
MgFe2O4Sol–gel synthesisNanoparticlesLPGRT4 vol%27.9% c158 s/152 s-[70]
MgFe2O4Polymerization methodNanoparticles
(120 nm)
NO23001039.5 a--[71]
MgFe2O4Reverse coprecipitationNanoparticles
(132 nm)
NO23001015 a--[71]
MgFe2O4Auto-combustionNanoparticles
(41 nm)
LPG25050.3 c--[72]
NiFe2O4Citrate processNanoparticlesCl2300-0.75 c--[45]
NiFe2O4Reverse micelleNanoparticlesLPG3801000.18 c--[73]
NiFe2O4HydrothermalNanoparticlesLPG2001000.4 c--[73]
NiFe2O4Pulsed wire dischargeNanoparticles
(18–45 nm)
Cl23505000.39 c--[74]
NiFe2O4Ion beam sputteringNanoparticles
(35 nm)
CH413020,0001.12 a--[75]
NiFe2O4Sol–gel auto
combustion
NanoparticlesAcetone2755004.65 c170 s/600 s-[76]
NiFe2O4Glycine combustionNanoparticles
(38 nm)
LPG3502000375% a40 s/140 s-[77]
NiFe2O4Sol–gel self-combustionNanoparticles (5.35 nm)H2S1502000.75 c60 s/300 s-[78]
NiFe2O4Sol–gel methodNanoparticles
(23 nm)
LPGRT20002.1 a72 s/183 s-[79]
NiFe2O4Sol–gel methodNanoparticles
(23 nm)
CO2RT20001.3 b100 s/400 s-[79]
NiFe2O4Co-precipitationNanoparticles
(15 nm)
LPGRT4 vol.%62.3 b200 s/250 s-[23]
NiFe2O4Auto-combustionNanoparticles
(17 nm)
NH340025023% c100 s/119 s-[80]
NiFe2O4Ligand-assisted self-assemblyNanoparticles
(20–40 nm)
Acetone21020057 a44 s/24 s-[81]
NiFe2O4CombustionNanoparticles
(16 nm)
LPG300300035.62% c--[82]
NiFe2O4Auto-combustionNanoparticlesNH3410K100065.29% c--[83]
NiFe2O4HydrothermalNanoparticlesAcetone190100120% c70 s/130 s-[84]
ZnFe2O4Citrate processNanoparticlesH2S200-0.65 c--[45]
ZnFe2O4W/O microemulsionNanoparticlesCl22705083.6 a4 s/30 s-[85]
ZnFe2O4HydrothermalNanoparticlesEthanol18010076 a--[86]
ZnFe2O4W/O microemulsionSpherical particles (30 nm)Cl22705085 a4 s/30 s-[38]
ZnFe2O4Solid-state reactionNanoparticles
(15–20 nm)
H2S2502003.25 a20 s/90 s-[87]
ZnFe2O4Co-precipitationNanoparticlesAcetone3001000100,000 a--[88]
ZnFe2O4Wet chemicalNanoparticles
(25–30 nm)
Ethanol3501000.6 c--[26]
ZnFe2O4Glycine combustionNanoparticles
(25–30 nm)
Acetone250200057% c--[89]
ZnFe2O4Co-precipitationNanoparticles
(65 nm)
Ethanol1901000.82 c30 s/90 s-[90]
ZnFe2O4Co-precipitationNanoparticles
(65 nm)
Cl21525000.75 c20 s/50 s-[90]
ZnFe2O4Auto combustionSpherical particles (10 nm)Ethanol2502001.35 a70 s/90 s-[91]
ZnFe2O4HydrothermalNanoparticles
(10 nm)
Acetone20020039.5 a--[92]
ZnFe2O4Solid-stateNanoparticlesHCHO26010037.3 a4 s/17 s-[93]
ZnFe2O4Solid-stateNanoparticlesEthanol30010029.1 a2 s/7 s-[93]
ZnFe2O4Sol–gel self-combustionNanoparticles
(7 nm)
H2S1502000.82 c40 s/210 s-[94]
ZnFe2O4Molten salt routeNanoparticles
(27 nm)
H2S2605022.5 a8 s/20 s-[95]
ZnFe2O4Co-precipitationNanoparticles
(5 ± 1.4 nm)
H2S803000.64 d20.1 s/--[25]
ZnFe2O4Plasma sprayingNanoparticles
(30 nm)
Acetone2001002.7 a--[96]
ZnFe2O4Plasma sprayingNanoparticles
(30 nm)
Acetone2001002.7 a-1.8 ppm[97]
ZnFe2O4Co-precipitationNanoparticles
(4.8 nm)
Ethanol300 k4037.1a50 s/116 s-[98]
ZnFe2O4HydrothermalNanoparticles
(10 nm)
NO212510247.7 b6.5 s/11 s-[99]
ZnFe2O4Self-catalyzed
treatment
Nanoparticles
(20 nm)
Acetone28010027.6 a6 s/4 s-[100]
ZnFe2O4Ball milling and
annealed
Nanoparticles (23.03 nm)NO26003005% d145 s/20 s-[42]
ZnFe2O4HydrothermalNanoparticles
(23 nm)
Ethanol22040202.5 a56 s/46 s-[101]
ZnFe2O4HydrothermalNanoparticlesO32000.033.7 a--[27]
ZnFe2O4SolvothermalNanoparticlesH2S2502498% d48 s/74 s-[102]
ZnFe2O4PLDNanoparticles
(48 nm)
LPG375500093% c110 s/180 s-[103]
ZnFe2O4Sol–gelNanoparticles
(100 nm)
Ethanol3501500.37 c120 s/240 s-[56]
ZnFe2O4Wet chemical-H235010000.47 c33 s/199 s-[104]
ZnFe2O4Solid-phase reactionNanoparticlesEthanol33210021.5 a4 s/14 s-[104]
ZnFe2O4Solid-phaseNanoparticlesH2S24010014.8 a7 s/25 s-[105]
ZnFe2O4Solid-state reactionNanoparticles (37.8 nm)Humidity--2895 a--[106]
ZnFe2O4Sol–gel auto
combustion
Nanoparticles
(20 nm)
Ethanol2751004.1 c10 s/40 s-[107]
ZnFe2O4Spray pyrolysisNanoparticles
(61 nm)
LPG30050.26 c--[51]
ZnFe2O4Screen printingNanoparticles
(4 nm)
LPGRT5 vol.%16 a120 s/150 s-[108]
ZnFe2O4Sol–gel
auto-combustion
NanoparticlesNH3RT1000.81 c381 s/333 s-[109]
ZnFe2O4SolvothermalNanoparticles (21.6 nm)H2S135515.1 a30 s/120 s-[110]
ZnFe2O4MOF and annealing treatmentPorous
olive-shaped
nanoparticles
Ethanol120200223 a10 s/184 s-[111]
O.T. operating temperature; Conc. concentration; tres/trec response time/recovery time; LOD limit of detection. a Response is defined as Ra/Rg; b Response is defined as Rg/Ra; c Response is defined as ∆R/Ra; d Response is defined as ∆R/Rg. Ra: resistance of the sensor in air; Rg: resistance of the sensor exposed to target gas; ∆R: the change in resistance, which equals |Ra–Rg|.
Table 2. Summary of the reported spinel ferrite nanorods/nanotubes-based gas sensors.
Table 2. Summary of the reported spinel ferrite nanorods/nanotubes-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
CoFe2O4ElectrospinningNanofibersNH3RT9000.42 a-25 ppm[112]
CoFe2O4HydrothermalNanorodsCH3OH9010013.3% c--[54]
NiFe2O4HydrothermalNanorodsNH31501005 a--[113]
NiFe2O4SolvothermalNanorodsLPG2002000.687 c114/18 s-[114]
NiFe2O4Annealing treatmentNanorodsn-propanol12010089.2 a19/41 s0.41 ppm[115]
NiFe2O4HydrothermalNanorodAcetone31010070% c45/75 s-[84]
NiFe2O4HydrothermalNanorodsTEA17517 a12 s/--[116]
NiFe2O4HydrothermalNanorodsToluene20050059.64 a-1 ppm[117]
ZnFe2O4Sol–gel templateTubesLPG30050017.56 a--[118]
ZnFe2O4Microemulsion and calcinationPorous nanorodsEthanolRT5014 a--[119]
ZnFe2O4Sol–gelAligned nanorodsLPGRT50004.35 a60/220 s-[120]
ZnFe2O4Sol–gel spin coatingNanorodsLPGRT2000140% c--[121]
ZnFe2O4HydrothermalNanorodsAcetone26010052.8 a1 s/11 s-[122]
ZnFe2O4ElectrospinningNanofiberH2S3501102 a--[123]
ZnFe2O4ElectrospinningNanofibersAcetone1901000 μL/L13.5 a15/17 s1 μL/L[124]
CuFe2O4Co-precipitationNanorodsLPGRT5 vol.%0.57 c150/510 s-[125]
a Response is defined as Ra/Rg; c Response is defined as ∆R/Ra.
Table 3. Summary of the reported spinel ferrite nanosheets -based gas sensors.
Table 3. Summary of the reported spinel ferrite nanosheets -based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
CuFe2O4Sol–gelPorous hierarchicalLPGRT500096% d60 s/--[126]
MgFe2O4Sol–gelThick filmsacetone725 K100080% c13/6 s-[127]
ZnFe2O4Spray pyrolysisThin filmethanol39051.2 c40/120 s1 ppm[128]
ZnFe2O4hydrothermalPorous nanosheetsH2S855123 a39/34 s0.5 ppm[129]
ZnFe2O4Sol gelThin filmsLPG375900,00079% c110/180 s [103]
ZnFe2O4Spray pyrolysisThick filmsSO215010025% c--[130]
a Response is defined as Ra/Rg; c Response is defined as ∆R/Ra; d Response is defined as ∆R/Rg.
Table 4. Summary of the reported spinel ferrite nanosphere-based gas sensors.
Table 4. Summary of the reported spinel ferrite nanosphere-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
CoFe2O4SolvothermalNanospheresn-butanol30010042.3 a--[131]
CoFe2O4Self-templatingDouble-shelled spheresNH3240200.514 c19.6/12.1 s-[132]
CuFe2O4Solvothermal and annealingHollow microspheresTEA105104 b32 s/192 s-[133]
CuFe2O4SolvothermalPorous nanospheresAcetone25010020.1 a3 s/185 s-[134]
NiFe2O4Metal–organic framework (MOF)Ultrathin frameworkToluene230177.3 b-2 ppb[135]
NiFe2O4HydrothermalOctahedralAcetone12010018.8 a6 s/13 s-[136]
NiFe2O4Solvothermal and annealingHollow hexagonal biyramidsn-propanol12020032.19 a--[137]
NiFe2O4Metal–organic frameworkHollow microspindlesAcetone12020052.8 a14.2 s/--[138]
NiFe2O4Hydrothermal and Co-precipitationCore−shell nanosphereAcetone28010010.6 a1 s/7 s-[139]
NiFe2O4SolvothermalPorous microspheresAcetone25010027.4 a2 s/-200 ppb[140]
NiFe2O4Refluxing and
calcination
Hollow Nano-OctahedronsToluene2601006.41 a25 s/40 s1 ppm[141]
NiFe2O4HydrothermalMOFs-derived
fusiformis
Xylene30050031.52 a50.10 s/40.30 s10 ppm[39]
NiFe2O4MOFPolyhedronsTEA1905018.9 a6s/--[142]
NiFe2O4AnnealingNanosheet-Assembled Fluffy FlowersEthanol12010023.2 a--[143]
NiFe2O4HydrothermalCore−shell architectureToluene24010019.95 a-1 ppm[144]
NiFe2O4Metal–organic frameworkNanoboxEthyl
acetate
12020064.27 b23 s/62 s0.26 ppm[145]
ZnFe2O4HydrothermalHollow spheresEthanol225100042.1 a10 s/8 s-[146]
ZnFe2O4SolvothermalPorous nanospheresAcetone2003012.4 a9 s/272 s-[147]
ZnFe2O4SolvothermalYolk–shell
microspheres
Acetone2005028.3 a--[148]
ZnFe2O4SolvothermalHollow microspheresAcetone2152011.3 a10 s/200 s1 ppm[149]
ZnFe2O4HydrothermalNanoflowersAcetone300200036.5 a--[150]
ZnFe2O4NonaqueousNanospheresToluene3001009.98 a18 s/29 s-[151]
ZnFe2O4SolvothermalSphere-like hierarchical architecturesEthanol180106.85 a5.1 s/7.2 s500 ppb[152]
ZnFe2O4Hydrothermal and thermalDouble-shell
microspheres
Acetone2062013.6 a6 s/10 s0.13 ppm[153]
ZnFe2O4Hydrothermal and calcinationHollow spheresEthylene glycol20010035.5 a--[154]
a Response is defined as Ra/Rg; b Response is defined as Rg/Ra; c Response is defined as ∆R/Ra.
Table 5. Summary of the reported spinel ferrite A-site doping-based gas sensors.
Table 5. Summary of the reported spinel ferrite A-site doping-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
Mg0.9Sn0.1Fe2O4Auto-combustionNanoparticle
(100 nm)
acetone380-0.83 c3 min/--[165]
Zn0.6Mn0.4Fe2O4Sol–gel citrateNanoparticle
(30–35 nm)
ethanol3002000.78 c--[166]
Ni0.6Zn0.4Fe2O4Sol–gelNanoparticle
(28–42 nm)
H2S225500.65 c--[167]
Ni0.4Zn0.6Fe2O4Aerosol pyrolysisSpherical shape (250–600 nm)NH335012.50.55 c--[168]
Cu0.5Co0.5Fe2O4Auto-combustionNanoparticle
(23–43 nm)
H2ORT80%11.7--[169]
10 wt% Ni and 0.2 wt% Sm doped CoFe2O4Sol–gel citrateNanoparticle
(40 nm)
H2S20010000.78 c5 s/20 s-[162]
Ni0.3Zn0.7Fe2O4Sol–gel auto combustionNanoparticlesAcetone2755002 c120 s
/300 s
-[160]
Co0.8Ni0.2Fe2O4SolvothermalNanoparticles
(40–90 nm)
NH3-40002.8 a--[170]
Mn0.2Ni0.8Fe2O4HydrothermalNanoparticle
(<100 nm)
H2ORT10000.56 c110 s
/160 s
-[171]
Mg0.5Zn0.5Fe2O4Sol PechiniEmbedded nano-tubesH235016600.9 c--[155]
Mg0.5Zn0.5Fe2O4Sol PechiniIsolated nano-tubeH235016600.66 d--[24]
Ni0.5Zn0.5Fe2O4Co-precipitationNanoparticlesNH33052000.7 c--[24]
Mg0.5Zn0.5Fe2O4Sol–gel auto combustionNanoparticles
(58 nm)
acetone325200.32 c137 s
/247 s
-[172]
Mn-CuFe2O4Auto-combustionNanoparticles
(9–45 nm)
LPG30010000.27 c--[173]
Mn-CuFe2O4EvaporationNanoparticlesLPG25010000.25 c40 s/40 s-[174]
Zn0.8Cu0.2Fe2O4Sol–gelNanoparticles
(10.4 nm)
LPGRT20002.5 b60 s
/300 s
-[161]
Ni0.6Zn0.4Fe2O4Co-precipitationNanoparticles
(55 nm)
Cl21775000.66 c30 s/60 s-[90]
Ni0.6Zn0.4Fe2O4MicrowaveNanoparticles
(25 nm)
Acetone25010000.72 c90 s
/720 s
-[175]
Co0.5Ni0.5Fe2O4Co-precipitationNanoparticlesCO35010000.25 c--[176]
Mn-CoFe2O4Auto combustionNanoparticles
(3 nm)
LPG30010000.19 c40 s/50 s-[177]
1 wt% Cu:NiFe2O4Spray pyrolysis depositionNanoparticles
(40–46 nm)
Ethanol32553.2 c--[178]
BaCa2Fe16O27Sol–gelNanoparticlesEthanol3001000.53 c--[179]
Mn–CuFe2O4Auto-combustionNanoparticles
(9 nm)
LPG30010000.28 c10–20 s/--[180]
Ni-CdFe2O4Sol–gel auto combustionGrain size
(300 nm)
H2ORT-0.99 c30 s/45 s-[28]
Ni0.8Co0.2Fe2O4EvaporationNanoparticles
(10 nm)
LPG25010000.7 d40 s/60 s-[181]
Sn0.2Ni0.8Fe2O4Co-precipitationNanoparticles
(35 nm)
SF6RT800.68 c--[182]
Li-CuFe2O4Co-precipitationNanoparticle
(<100 nm)
LPGRT4 vol%1.82 b--[183]
In-CuFe2O4Co-precipitationNanoparticlesLPGRT4 vol%0.37 c229 s/--[184]
Ni0.1Co0.9Fe2O4Sol–gel auto combustionMicrocubesAcetone2402001.67 b--[164]
CoNiFe2O4Co-precipitationNanoparticles
(28 nm)
LPG505000.66 c--[185]
Bi-CoFe2O4Sol–gelNanoparticles
(5–90 nm)
NO22301000.19 c31 s/29 s25 ppm[186]
Cu-ZnFe2O4HydrothermalSpherical
nanoparticles (50 nm)
H2SRT537.9 a10 s
/210 s
-[187]
Ni0.33Co0.67Fe2O4SolvothermalMesoporous
microspheres
Toluene3001035 a10 s/51 s-[188]
Zn0.5Cu0.5Fe2O4Sol–gel
auto-combustion
Nanoparticles
(30–70 nm)
H2S8010000.71 c170 s/--[189]
Mn0.7Zn0.3Fe2O4Co-precipitationNanoparticles
(5.5–10.5 nm)
LPG25010001.88 a40 s/20 s-[190]
Sn0.2Cu0.8Fe2O4Co-precipitationNanoparticles
(37 nm)
LPGRT2 vol%0.78 c32 s
/111 s
-[191]
Co0.25Ba0.75Fe2O4Co-precipitationNanoparticles
(16.5 nm)
NO2RT2200.79 c--[192]
Zn0.5Mg0.5Fe2O4Co-precipitationNanoparticles
(50–150 nm)
H2S400100.11 d16 s/--[193]
Ni0.7Zn0.3Fe2O4Co-precipitation and sinteringNanoparticlesLPG20010000.75 c40 s/30 s-[163]
Cu0.75Zn0.25Fe2O4SolvothermalHollow
micro-nanospheres
Acetone1250.82.37 a66 s
/138 s
-[40]
(Cu,Zn)Fe2O4SolvothermalNano-microspheresTEA165506.77 a58 s
/136 s
-[194]
CuZnFe2O4ElectrospinningNanofibersH22505005.9 a6 s/75 s-[195]
5 wt% Ni-doped MnFe2O4Co-precipitationNanoparticles
(35 nm)
NH3RT2000.51 c17 s/13 s-[196]
Cu0.1Zn0.9Fe2O4Spray pyrolysisThin FilmsSO21202000.474 c--[197]
Co0.87Ni0.13Fe2O4Co-precipitationNanoparticlesLPG40050000.97 c11 s
/110 s
-[198]
Ni0.4Mn0.3Zn0.3
Fe2O4
Precursor
combustion
Thick filmCl21003002.12 d10 s/15 s-[199]
Sr0.2Ni0.8Fe2O4Sol–gel spin
coating
Nanoparticles
(20–50 nm)
LPG20020000.28 c78 s/66 s-[200]
a Response is defined as Ra/Rg; b Response is defined as Rg/Ra; c Response is defined as ∆R/Ra; d Response is defined as ∆R/Rg.
Table 10. Summary of the reported other MOSs/spinel-ferrite-based gas sensors.
Table 10. Summary of the reported other MOSs/spinel-ferrite-based gas sensors.
MaterialsSyntheisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
CdO/Cd0.1Ni0.45Mn0.45Fe2O4Co-precipitationNanoparticlesDMF2502000.85 d28 s/41 s-[240]
Co3O4/CoFe2O4Metal–organic frameworkDouble-shelled nanotubesHCHO1391012.7 b4 s/9 s300 ppb[241]
Co3O4/CoFe2O4CalcinationCore–shell structureNH322010035 a15 s/21 s-[242]
CuO/CuFe2O4Frequency sputteringThick filmCO225050000.17 4 c--[243]
CuO/CuFe2O4CalcinationCore–shellH2S250210.8 a--[244]
CuO/CuFe2O4Frequency sputteringThick filmCO225050000.40 c--[245]
CuO/CuFe2O4Co-precipitationNanopowderCO235050000.072 c--[246]
CuO/CuFe2O4Radio-frequency sputteringThin filmsH24005000.79 c60 s/--[247]
CuO/CuFe2O4Water bath and
calcination
Microspheres/
nanoparticles
H2S2401022.3 a31 s/40 s-[248]
CuO/ZnFe2O4Thermal treatment and solvothermalYolk–shell
microspheres
Xylene22510024.1 a4 s/6 s-[249]
CuO/ZnFe2O4SolvothermalPorous nanospheresH2SRT100.75 c70 s/475 s0.1 ppm[250]
Fe2O3/CuFe2O4Template-induced methodHollow spheresAcetone25010014 a6 s/100 s100 ppb[29]
Fe2O3/NiFe2O4Metal–organic frameworkNanotubesAcetone20010023 a4 s/--[251]
Fe2O3/ZnFe2O4Template-induced methodPorous microrodsTEA30510042.4 a12 s/26 s-[252]
Fe2O3/ZnFe2O4SolvothermalCore–shell nanorodsTEA280100141 a13 s/30 s-[253]
Fe2O3/ZnFe2O4SolvothermalSpindle-likeTEA30010069.24 a2 s/7 s-[254]
MgO/MgFe2O4Co-precipitationThick filmH2S20031086 a18 s/108 s-[255]
MgO/MgFe2O4/Fe2O3CalcinationCore–shell
microsphere
H2S25031.32 b--[256]
Mn2O3/ZnFe2O4Co-precipitationNanopowderEthanol3253000.76 c--[257]
NiO/NiFe2O4Two-step
hydrothermal
Nanotetrahedrons/
nanoparticles
HCHO24020033.3 a12 s/8 s 200 ppb[258]
NiO/NiFe2O4SolvothermalNanosheets/
Nanoparticles
Acetone2805023 a--[259]
PdO/ZnFe2O4Ultrasonic spray
pyrolysis
Microporous spheresAcetone27510018.9 a5 s/54 s-[260]
SiO2/In2O3/CoFe2O4HydrothermalMicrospheresAcetone26010058 a1 s/59 s-[261]
Sn-doped ZnO/ZnFe2O4Heat treatmentPorous
heterostructures
TEA2701028.1 a9 s/7 s0.2 ppm[262]
SnO2/Mn0.5 Cu0.5Fe2O4Co-precipitationNanoparticlesCO2RTsaturated18 c--[263]
SnO2/ZnFe2O4Sol–gelNanoparticlesAcetone17610014.6 a17 s/23 s-[264]
SnO2/ZnFe2O4SolvothermalNanospheresAcetone210100120 a30 s/197 s0.1 ppm[265]
Y2O3/CuFe2O4Sol–gel
auto-combustion
NanoparticlesHumityRT97%4895 a9 s/23 s-[266]
ZnO/Fe2O3/ZnFe2O4SolvothermalThick filmAcetone19015016.2 a5 s/29 s-[267]
ZnO/ZnFe2O4Screen-printingThick filmPropanolRT80003.54 c40 s/70 s-[268]
ZnO/ZnFe2O4Screen-printingThick filmPropanolRT10005.2 c45 s/90 s-[269]
ZnO/ZnFe2O4Screen-printingThick filmPropanolRT20000.15 c--[270]
ZnO/ZnFe2O4HydrothermalHollow
microspheres
n-butanol-20027.7 a10 s/25 s-[271]
ZnO/ZnFe2O4Solution reactionsHollow spheres/
nanosheets
Acetone25010016.8 a1 s/33 s-[272]
ZnO/ZnFe2O4Two-step sprayedBackbones/
nanosheets
Ethanol27510010.5 a--[273]
ZnO/ZnFe2O4HydrothermalRod-liken-butanol2605013.6 a12 s/11 s-[274]
ZnO/ZnFe2O4CalcinationHexagonalTEA80100012.7 a100 s/--[275]
ZnO/ZnFe2O4HydrothermalHollow spheresAcetone280505.2 b7.1 s/10.1 s-[276]
ZnO/ZnFe2O4PyrolysisHollow cubeAcetone25059.4 a5.6/6 min-[277]
ZnO/ZnFe2O4MOFHollow nanocagesAcetone29010025.8 a8 s/32 s-[278]
ZnO/ZnFe2O4Solution reaction and Co-precipitationActinomorphic flower-likeNO2200158 a7/15 s -[279]
ZnO/ZnFe2O4Annealing treatmentTriple-shelled
hollow microspheres
acetone14020023.5 a5.2 s/12.8 s-[280]
ZnO/ZnFe2O4Co-precipitationPrussian blue
analogue
TEA1701007.6 a1 s/9 s-[281]
ZnO/ZnFe2O4Hydrolyzation of MOF-5NanoparticlesAcetone19010030.8 a4.7 s/10.3 s-[282]
ZnO/ZnFe2O4SolvothermalCore−shell hollow microsphereAcetone28010033.6 a8 s/30 s-[283]
ZnO/ZnFe2O4SolvothermalCoral-like
mesoporous
TEA2405021.3 a0.9 s/23 s-[41]
ZnO/ZnFe2O4Solution reactionNanosheets assembled microspheresTMA24010031.5 a3.1 s/5.7 s-[284]
ZnO/ZnFe2O4CalcinationTetrapods/moss-likeH2S25021.5 a2 s/9 s0.6 ppb[285]
ZnO/ZnFe2O4MOFKiwifruitt-likeTEA20010040.5 a32 s/41 s-[286]
ZnO/ZnFe2O4PyrolysisHollow
microspheres
Acetone20018.7 c--[287]
ZnO/ZnFe2O4Solution and
Calcination
MicroflowersAcetone250508.3 a2 s/--[288]
ZnO/ZnFe2O4HydrothermalNanoparticlesAcetone1209092.9 a7.7 s/27 s [36]
ZnO/ZnFe2O4/AuElectrospinning, Atomic layer
deposition and
Solution reaction
NanomeshesAcetone22510030.3 a1 s/-300 ppb[219]
ZnO/ZnFe2O4/AuHydrothermal and
Co-precipitation
Yolk–shell microspheres assembled from nanosheetsAcetone20610018.18 a4 s/23 s0.7 ppm[222]
a Response is defined as Ra/Rg; b Response is defined as Rg/Ra; c Response is defined as ∆R/Ra; d Response is defined as ∆R/Rg.
Table 11. Summary of the reported 2D materials/spinel-ferrite-based gas sensors.
Table 11. Summary of the reported 2D materials/spinel-ferrite-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
g-C3N4/MgFe2O4SolvothermalNanosheets/
Nanoparticles
Ethanol300500112 a11 s/46 s-[289]
g-C3N4/MgFe2O4SolvothermalNanosheets/
Porous microspheres
Acetone320500270 a49 s/29 s-[290]
Graphene quantum dots/ZnFe2O4HydrothermalNanoparticlesAcetoneRT100013.3 a9 s/4 s-[291]
Graphene/ZnFe2O4SolvothermalNanosheets/
Nanoparticles
Acetone27510009.1 a0.7 s/24.7 s-[292]
MoS2/CuFe2O4ElectrospinningNanosheets/
Nanotubes
AcetoneRT10016.4 a--[293]
MWCNTs/NiFe2O4Sol–gelNanotube/
Nanoparticles
H2S3001002.5 a--[294]
MWCNTs/Co0.8Ni0.2Fe2O4SolvothermalNanotubes/
Nanoparticles
NH3-40006.2 a--[295]
rGO/CuFe2O4CombustionNanosheets/
Nanoparticles
NH3RT500.093 c3 s/6 s-[296]
rGO/NiFe2O4HydrothermalNanosheets/
Nanoparticles
H2802003.85 a32 s/85 s-[297]
rGO/WO3/ZnFe2O4Water bathNanosheets/Massive/NanoparticlesTEA1301026.92 a51 s/144 s-[298]
rGO/ZnFe2O4HydrothermalNanosheet/NanorodsSO2RT1000.183 c46 s/54 s-[299]
rGO/ZnFe2O4CalcinationNanosheets/
Hollow spheres
Acetone200108.18 a23 s/203 s0.8 ppm[300]
rGO/ZnFe2O4Electrospinning and CalcinationNanosheets/
Nanofibers
H2S3501147 a--[301]
rGO/ZnFe2O4SolvothermalNanosheets/
Nanosheets
Ethanol21010041.5 a14 s/37 s-[302]
rGO/ZnFe2O4Chemical
precipitation
Nanosheets/
Hollow octahedron
NO2RT21.123 d50 s/250 s0.14 ppb[303]
rGO/ZnFe2O4/PdMicrowaveNanosheets/
Nanoparticles
H2RT2000.11 c18 s/39 s-[304]
a Response is defined as Ra/Rg; c Response is defined as ∆R/Ra; d Response is defined as ∆R/Rg.
Table 12. Summary of the reported polymer/spinel-ferrite-based gas sensors.
Table 12. Summary of the reported polymer/spinel-ferrite-based gas sensors.
MaterialsSynthesisMorphologyGasO.T.
(°C)
Conc.
(ppm)
Responsetres/trecLODRefs.
Polyacrylic acid/
NiFe2O4
SolvothermalThin filmNH31501004.1 a--[305]
Polyindole/
ZnFe2O4
In situ polymerizationNanosheets/
Nanoparticles
NH3RT1000.9 a--[306]
Polyaniline/
CuFe2O4
PolymerizationNanocapsules/
Nanosphere
NH3RT50.27 c84 s/54 s-[307]
Polyaniline/
NiFe2O4
Electrospinning and polymerizationNanofibersNH3RT10030.8 c15 s/21 s250 ppb[308]
a Response is defined as Ra/Rg; c Response is defined as ∆R/Ra.
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Zhang, R.; Qin, C.; Bala, H.; Wang, Y.; Cao, J. Recent Progress in Spinel Ferrite (MFe2O4) Chemiresistive Based Gas Sensors. Nanomaterials 2023, 13, 2188. https://doi.org/10.3390/nano13152188

AMA Style

Zhang R, Qin C, Bala H, Wang Y, Cao J. Recent Progress in Spinel Ferrite (MFe2O4) Chemiresistive Based Gas Sensors. Nanomaterials. 2023; 13(15):2188. https://doi.org/10.3390/nano13152188

Chicago/Turabian Style

Zhang, Run, Cong Qin, Hari Bala, Yan Wang, and Jianliang Cao. 2023. "Recent Progress in Spinel Ferrite (MFe2O4) Chemiresistive Based Gas Sensors" Nanomaterials 13, no. 15: 2188. https://doi.org/10.3390/nano13152188

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