Gas Sensors for Monitoring Environmental Changes

A special issue of Chemosensors (ISSN 2227-9040). This special issue belongs to the section "Applied Chemical Sensors".

Deadline for manuscript submissions: closed (30 August 2023) | Viewed by 19581

Special Issue Editors

School of Engineering, RMIT University, Melbourne, VIC 3000, Australia
Interests: low-dimensional materials; gas sensing; optoelectronic devices; micro–nano fabrications
Special Issues, Collections and Topics in MDPI journals
Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China
Interests: nanomaterials; 2D materials and heterostructures; functional materials; gas sensor; microwave absorption
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Global warming and climate change have become serious environmental threats in the last decade. Air pollution due to the rapid development of modernization and urbanization is the major cause of environmental deterioration. The emission of sulfur dioxide (SO2) and nitrogen oxides (NOx), for instance, can be directly linked to the evolution of acid rain. Greenhouse gases, including carbon dioxide (CO2), methane (CH4), and NOx, are the main driver of global warming. Thus, the continuous monitoring and control of such pollutants are imperative to prevent environmental disasters.

This fact has prompted efforts to find new and user-friendly techniques for the detection of gases hazardous to the environment and human health, which has led to the development of key technologies for the rapid, selective, sensitive, and efficient detection of gases, chemical vapors, and explosives. Given the boom of the Internet of Things (IoT), the next generation of gas sensors is expected to be massively deployed into dense network systems with low cost, low power consumption, and long-term stability. In addition, to achieve continuous monitoring, gas sensors may also need to demonstrate a high tolerance to environmental variables such as temperature, humidity, and pressure.

This Special Issue aims to provide a comprehensive collection of the latest advances in gas sensors based on various materials and outlook for the gas sensors in environmental monitoring. We cordially invite you to submit an article to this Special Issue. We welcome short communications, full research articles, and timely reviews focusing on advanced gas sensing techniques. 

Dr. Kai Xu
Dr. Zhong Li
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Chemosensors is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • gas sensors
  • environmental monitoring
  • nanomaterial
  • metal oxides
  • metal sulfides
  • pollutants
  • semiconductor

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Published Papers (12 papers)

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12 pages, 5032 KiB  
Article
Preparation and Hydrogen-Sensitive Property of WO3/Graphene/Pd Ternary Composite
by Lin Wang, Fei An, Xinmei Liu, Dongzhi Zhang and Zhe Yang
Chemosensors 2023, 11(7), 410; https://doi.org/10.3390/chemosensors11070410 - 21 Jul 2023
Cited by 1 | Viewed by 989
Abstract
Hydrogen (H2) is a renewable energy source that has the potential to reduce greenhouse gas emissions. However, H2 is also highly flammable and explosive, requiring sensitive and safe sensors for its detection. This work presents the synthesis and characterization of [...] Read more.
Hydrogen (H2) is a renewable energy source that has the potential to reduce greenhouse gas emissions. However, H2 is also highly flammable and explosive, requiring sensitive and safe sensors for its detection. This work presents the synthesis and characterization of WO3/graphene binary and WO3/graphene/Pd (WG-Pd) ternary nanocomposites with varying graphene and Pd contents using the microwave-assisted hydrothermal method. The excellent catalytic efficacy of Pd nanoparticles facilitated the disintegration of hydrogen molecules into hydrogen atoms with heightened activity, consequently improving the gas-sensing properties of the material. Furthermore, the incorporation of graphene, possessing high conductivity, serves to augment the mobility of charge carriers within the ternary materials, thereby expediting the response/recovery rates of gas sensors. Both graphene and Pd nanoparticles, with work functions distinct from WO3, engender the formation of a heterojunction at the interface of these diverse materials. This enhances the efficacy of electron–hole pair separation and further amplifies the gas-sensing performance of the ternary materials. Consequently, the WG-Pd based sensors exhibited the best gas-sensing performance when compared to anther materials, such as a wide range of hydrogen concentrations (0.05–4 vol.%), a short response time and a good selectivity below 100 °C, even at room temperature. This result indicates that WG-Pd ternary materials are a promising room-temperature hydrogen-sensing materials for H2 detection. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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15 pages, 2209 KiB  
Article
The Human Nose as a Chemical Sensor in the Perception of Coffee Aroma: Individual Variability
by Roberto Crnjar, Paolo Solari and Giorgia Sollai
Chemosensors 2023, 11(4), 248; https://doi.org/10.3390/chemosensors11040248 - 17 Apr 2023
Cited by 2 | Viewed by 1450
Abstract
The flavor of foods and beverages is generally composed of a mixture of volatile compounds, however not all the molecules that form an aroma are sensorially relevant. The odor-active compounds present in a mixture are different for each subject, both in quantitative and [...] Read more.
The flavor of foods and beverages is generally composed of a mixture of volatile compounds, however not all the molecules that form an aroma are sensorially relevant. The odor-active compounds present in a mixture are different for each subject, both in quantitative and qualitative terms. This means that the ability of the human nose to act as a chemical sensor varies among individuals. In this study, we used the headspace of roasted coffee beans as a complex olfactory stimulus and, by means of the coupled Gas Chromatography-Olfactometry (GC-O) technique, the single components of coffee flavor were separated. Each subject, previously classified for his/her olfactory status (normosmic, hyposmic or anosmic) by means of the Sniffin’ Sticks battery (composed of Threshold, Discrimination and Identification subtests), had to identify and evaluate each smelled molecule. The results show that the individual ability to detect individual compounds during the GC-O experiments and the odor intensity reported during the sniffing of pen #10 (the pen of the identification test) containing coffee aroma were related to TDI olfactory status (based on the score obtained from the sum composed of Threshold, Discrimination and Identification scores). We also found that the number of total molecules and of molecules smelling of coffee is linearly related to the TDI olfactory score. Finally, the odor intensity reported when sniffing pen #10 containing coffee aroma is positively correlated with the number of molecules detected and the average intensity reported. In conclusion, our findings show that the human perception of both individual compounds and complex odors is strongly conditioned by the olfactory function of subjects. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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15 pages, 5615 KiB  
Article
Chemoresistive Properties of V2CTx MXene and the V2CTx/V3O7 Nanocomposite Based on It
by Artem S. Mokrushin, Ilya A. Nagornov, Aleksey A. Averin, Tatiana L. Simonenko, Nikolay P. Simonenko, Elizaveta P. Simonenko and Nikolay T. Kuznetsov
Chemosensors 2023, 11(2), 142; https://doi.org/10.3390/chemosensors11020142 - 15 Feb 2023
Cited by 8 | Viewed by 1886 | Correction
Abstract
The in-situ Raman spectroscopy oxidation of the accordion-like V2CTx MXene has been studied. It was found that a nanocomposite of V2CTx/V3O7 composition was formed as a result. The elemental and phase composition, the [...] Read more.
The in-situ Raman spectroscopy oxidation of the accordion-like V2CTx MXene has been studied. It was found that a nanocomposite of V2CTx/V3O7 composition was formed as a result. The elemental and phase composition, the microstructure of the synthesized V2CTx powder and MXene film as well as the V2CTx/V3O7 nanocomposite obtained at a minimum oxidation temperature of 250 °C were studied using a variety of physical and chemical analysis methods. It was found that the obtained V2CTx and V2CTx/V3O7 films have an increased sensitivity to ammonia and nitrogen dioxide, respectively, at room temperature and zero humidity. It was shown that the V2CTx/V3O7 composite material is characterized by an increase in the response value for a number of analytes (including humidity) by more than one order of magnitude, as well as a change in their detection mechanisms compared to the individual V2CTx MXene. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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20 pages, 8504 KiB  
Article
Humidity and Temperature Sensing of Mixed Nickel–Magnesium Spinel Ferrites
by Milena P. Dojcinovic, Zorka Z. Vasiljevic, Lazar Rakocevic, Vera P. Pavlovic, Souad Ammar-Merah, Jelena D. Vujancevic and Maria Vesna Nikolic
Chemosensors 2023, 11(1), 34; https://doi.org/10.3390/chemosensors11010034 - 02 Jan 2023
Cited by 3 | Viewed by 1559
Abstract
Temperature- and humidity-sensing properties were evaluated of NixMg1-x spinel ferrites (0 ≤ x ≤ 1) synthesized by a sol-gel combustion method using citric acid as fuel and nitrate ions as oxidizing agents. After the exothermic reaction, amorphous powders were calcined [...] Read more.
Temperature- and humidity-sensing properties were evaluated of NixMg1-x spinel ferrites (0 ≤ x ≤ 1) synthesized by a sol-gel combustion method using citric acid as fuel and nitrate ions as oxidizing agents. After the exothermic reaction, amorphous powders were calcined at 700 °C followed by characterization with XRD, FTIR, XPS, EDS and Raman spectroscopy and FESEM microscopy. Synthesized powders were tested as humidity- and temperature-sensing materials in the form of thick films on interdigitated electrodes on alumina substrate in a climatic chamber. The physicochemical investigation of synthesized materials revealed a cubic spinel Fd3¯m phase, nanosized but agglomerated particles with a partially to completely inverse spinel structure with increasing Ni content. Ni0.1Mg0.9Fe2O4 showed the highest material constant (B30,90) value of 3747 K and temperature sensitivity (α) of −4.08%/K compared to pure magnesium ferrite (B30,90 value of 3426 K and α of −3.73%/K) and the highest average sensitivity towards humidity of 922 kΩ/%RH in the relative humidity (RH) range of 40–90% at the working temperature of 25 °C. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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12 pages, 2423 KiB  
Article
Hydrogen Sensors Based on In2O3 Thin Films with Bimetallic Pt/Pd Catalysts on the Surface and Tin and Dysprosium Impurities in the Bulk
by Nadezhda Maksimova, Tatyana Malinovskaya, Valentina Zhek, Nadezhda Sergeychenko, Evgenii Chernikov, Ivan Lapin and Valery Svetlichnyi
Chemosensors 2023, 11(1), 23; https://doi.org/10.3390/chemosensors11010023 - 27 Dec 2022
Cited by 1 | Viewed by 1244
Abstract
This paper presents the results of studying the characteristics of hydrogen sensors based on thin In2O3 films modified with tin and dysprosium with dispersed double Pt/Pd catalysts deposited on the surface. To control the content of Sn and Dy in [...] Read more.
This paper presents the results of studying the characteristics of hydrogen sensors based on thin In2O3 films modified with tin and dysprosium with dispersed double Pt/Pd catalysts deposited on the surface. To control the content of Sn and Dy in the films, an original technology was developed, and ceramic targets were fabricated from powders of the In–Dy–O, Dy–Sn–O, and In–Dy–Sn–O systems synthesized by the sol–gel method. Films of complex composition were obtained by RF magnetron sputtering of the corresponding targets. Structural features of the obtained thin films were studied by Raman spectroscopy. It is shown that various combinations of tin and dysprosium concentrations, as well as the presence of Pt/Pd catalysts on the surface, have a significant effect on the defectiveness of the films and the density of oxygen adsorption centers. As a result, the resistance of sensors in pure air (R0), the activation energies of the temperature dependences of R0, the bending of the energy bands at the grain boundaries of the semiconductor, and the responses to the action of hydrogen in the concentration range of 20–25,000 ppm change. A unique feature of Pt/Pd/ In2O3: Sn (0.5 at%), Dy (4.95 at%) films is their high sensitivity at 20–100 ppm and the absence of signal saturation in the region of high hydrogen concentrations of 5000–25,000 ppm, allowing them to be used to detect H2 in a wide range of concentrations. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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17 pages, 5684 KiB  
Article
Effect of Ti2CTx MXene Oxidation on Its Gas-Sensitive Properties
by Artem S. Mokrushin, Ilya A. Nagornov, Philipp Yu. Gorobtsov, Aleksey A. Averin, Tatiana L. Simonenko, Nikolay P. Simonenko, Elizaveta P. Simonenko and Nikolay T. Kuznetsov
Chemosensors 2023, 11(1), 13; https://doi.org/10.3390/chemosensors11010013 - 22 Dec 2022
Cited by 8 | Viewed by 2064
Abstract
The oxidation process was studied for the synthesized low-layer Ti2CTx MXene deposited on a special Al2O3/Pt sensor substrate using in situ Raman spectroscopy. It is noted that on the ceramic parts of the substrate (Al2 [...] Read more.
The oxidation process was studied for the synthesized low-layer Ti2CTx MXene deposited on a special Al2O3/Pt sensor substrate using in situ Raman spectroscopy. It is noted that on the ceramic parts of the substrate (Al2O3), the beginning of oxidation (appearance of anatase mod phase) is observed already at 316 °C, in comparison with platinum, for which the appearance of anatase is noted only at 372 °C. At the temperature 447 °C, the initial MXene film is completely oxidized to TiO2. Using scanning electron microscopy and atomic force microscopy, the microstructure and dispersity of the obtained MXene film were studied. It was found that the obtained films exhibit chemoresistive responses to the detection of a wide group of gases, H2, CO, NH3, C6H6, C3H6O, CH4, C2H5OH and O2, at room temperature and RH = 50%. The highest sensitivity is observed for NH3. The partial oxidation of the Ti2CTx MXene was shown to favorably affect the gas-sensitive properties. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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20 pages, 4582 KiB  
Article
Tetrafluorosubstituted Metal Phthalocyanines: Study of the Effect of the Position of Fluorine Substituents on the Chemiresistive Sensor Response to Ammonia
by Darya Klyamer, Dmitry Bonegardt, Pavel Krasnov, Alexander Sukhikh, Pavel Popovetskiy and Tamara Basova
Chemosensors 2022, 10(12), 515; https://doi.org/10.3390/chemosensors10120515 - 04 Dec 2022
Cited by 5 | Viewed by 1357
Abstract
A comparative analysis of the chemiresistive sensor response of thin films of a series of tetrasubstituted phthalocyanines of various metals with F-substituent in peripheral (MPcF4-p, M = Cu, Co, Zn, Pb, VO) and non-peripheral (MPcF4-np) positions in macroring to [...] Read more.
A comparative analysis of the chemiresistive sensor response of thin films of a series of tetrasubstituted phthalocyanines of various metals with F-substituent in peripheral (MPcF4-p, M = Cu, Co, Zn, Pb, VO) and non-peripheral (MPcF4-np) positions in macroring to low concentrations of ammonia (1–50 ppm) was carried out. It was found that MPcF4-p films exhibit a higher sensor response than MPcF4-np ones. A CoPcF4-p film demonstrated a calculated LOD of 0.01 ppm with a recovery time of 215 s, while a VOPcF4-p film had LOD of 0.04 ppm and the recovery time of 270 s. The selectivity test showed that CO2, ethanol, acetone, benzene, and formaldehyde did not interfere with the determination of ammonia, while H2S at a concentration of more than 10 ppm could act as an interfering gas. It was shown that, as a result of quantum-chemical calculations, the observed regularities are best described by the interaction of NH3 with phthalocyanines through the formation of hydrogen bonds between NH3 and side atoms of the macroring. In the case of MPcF4-p, the NH3 molecule approaches the macrocycle more closely and binds more strongly than in the case of MPcF4-np. The stronger binding leads to a stronger effect of the ammonia molecule on the electronic structure of phthalocyanine and, as a consequence, on the chemiresistive sensor response of the films to ammonia. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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11 pages, 3017 KiB  
Article
Prediction of Diamene-Based Chemosensors
by Danil W. Boukhvalov and Vladimir Yu. Osipov
Chemosensors 2022, 10(11), 480; https://doi.org/10.3390/chemosensors10110480 - 15 Nov 2022
Cited by 4 | Viewed by 1494
Abstract
This paper presents the results of systematic studies of the atomic structure of the layered bulk, bilayer, and monolayer of diamene (a two-dimensional diamond monolayer recently synthesized by various methods) functionalized with fluorine and hydroxyl groups with the chemical formulas C2F [...] Read more.
This paper presents the results of systematic studies of the atomic structure of the layered bulk, bilayer, and monolayer of diamene (a two-dimensional diamond monolayer recently synthesized by various methods) functionalized with fluorine and hydroxyl groups with the chemical formulas C2F and C2OH. The results of our calculations show that both types of diamene under discussion have a wide optical gap corresponding to the absorption of light in the UV spectral range. The formation of a boundary between these two types of diamene layers leads to a significant decrease in the band gap. Therefore, this layered material, with an interface between fluorinated and hydroxylated diamenes (C2F/C2OH structures), can be considered a suitable material for converting UV radiation into visible light in the orange-yellow part of the spectrum. The adsorption of acetone or water on the C2F/C2OH structures results in visible changes in the band gap. The effect on photoemission is different for different detected analytes. The presence of formaldehyde in water ensures the appearance of distinct peaks in the absorption spectra of structures based on C2F/C2OH. Our simulation results suggest that the simulated C2F/C2OH structures can be used as chemically stable, lightweight materials composed of common elements for a highly selective chemical sensor in liquid and air. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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16 pages, 2965 KiB  
Article
Energy-Efficient Chemiresistive Sensor Array Based on SWCNT Networks, WO3 Nanochannels and SWCNT-Pt Heterojunctions for NH3 Detection against the Background Humidity
by Alexey V. Romashkin, Andrey V. Lashkov, Victor V. Sysoev, Nikolay S. Struchkov, Evgeny V. Alexandrov and Denis D. Levin
Chemosensors 2022, 10(11), 476; https://doi.org/10.3390/chemosensors10110476 - 12 Nov 2022
Viewed by 1323
Abstract
Recently, promising results have been achieved in improving the sensitivity to ammonia in gas sensors through the use of structures composed of heterojunctions or nanochannels. However, their sensitivity is highly dependent on the background humidity under air conditions. The sensor structures which could [...] Read more.
Recently, promising results have been achieved in improving the sensitivity to ammonia in gas sensors through the use of structures composed of heterojunctions or nanochannels. However, their sensitivity is highly dependent on the background humidity under air conditions. The sensor structures which could ensure selective ammonia detection with a low detection limit, despite interference from changing background humidity, remain highly demanded. In this work, we consider sensing units containing (i) nanochannels formed by a continuous tungsten oxide nanolayer to appear in contact between single-walled carbon nanotubes (SWCNTs) and a Pt sublayer and (ii) SWCNT-Pt junctions in frames of mass-scale microelectronic technologies. SWCNTs were deposited by spray-coating on a thin WO3/Pt/W sublayer formed by a photolithographic pattern to be accompanied by satellite samples with just SWCNTs for reference purposes. We elucidate the specific differences that appeared in the response of sensors based on SWCNT-Pt junctions and WO3 nanochannels relative to satellite SWCNT samples with a similar SWCNT network density. Particularly, while a similar response to NH3 vapors mixed with dry air is observed for each sensor type, the response to NH3 is reduced significantly in the presence of background humidity, of 45 rel.%, especially in the case of WO3 nanochannel structures even at room temperature. A multisensor array based on the four various sensing structures involving SWCNT-Pt junctions, WO3 nanochannels, and their satellite-only-SWCNT ones allowed us to determine a correct ammonia concentration via utilizing the linear discriminant analysis despite the presence of background air humidity. Thus, such an energy-efficient multisensor system can be used for environmental monitoring of ammonia content, health monitoring, and other applications. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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13 pages, 7323 KiB  
Article
Gas Sensors Based on Exfoliated g-C3N4 for CO2 Detection
by Ahmed Kotbi, Manal Benyoussef, El Mostafa Ressami, Michael Lejeune, Brahim Lakssir and Mustapha Jouiad
Chemosensors 2022, 10(11), 470; https://doi.org/10.3390/chemosensors10110470 - 10 Nov 2022
Cited by 7 | Viewed by 1817
Abstract
We report on the investigation of graphitic carbon nitride (g-C3N4) for carbon dioxide (CO2) sensor applications. g-C3N4 is prepared by the thermal polycondensation of thiourea and sprayed onto a substrate with interdigitated electrodes. The [...] Read more.
We report on the investigation of graphitic carbon nitride (g-C3N4) for carbon dioxide (CO2) sensor applications. g-C3N4 is prepared by the thermal polycondensation of thiourea and sprayed onto a substrate with interdigitated electrodes. The resulting sensor device exhibited a high sensitivity to CO2 molecules of ~200 ppm, a high responsivity of ~730 ms at 40 °C and a full recovery time of 36 s. Furthermore, a set of various characterization measurements demonstrated the excellent stability of both the g-C3N4 nanosheets and the fabricated gas sensor device. Meanwhile, density functional theory (DFT) calculations for the bulk and monolayer models, based on tri-s-triazine, revealed the optoelectronic properties of g-C3N4 and the interaction energy with CO2, which is evaluated at −0.59 eV. This value indicates the very good affinity of g-C3N4 nanosheets to CO2 molecules. Our findings shed light on the potential for g-C3N4 to be used for the development of high-performing gas sensor devices. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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12 pages, 2999 KiB  
Article
Photoactivated In2O3-GaN Gas Sensors for Monitoring NO2 with High Sensitivity and Ultralow Operating Power at Room Temperature
by Jafetra Rambeloson, Dimitris E. Ioannou, Parameswari Raju, Xiao Wang, Abhishek Motayed, Hyeong Jin Yun and Qiliang Li
Chemosensors 2022, 10(10), 405; https://doi.org/10.3390/chemosensors10100405 - 09 Oct 2022
Viewed by 1670
Abstract
Photoactivated gallium nitride (GaN) nanowire-based gas sensors, functionalized with either bare In2O3 or In2O3 coated with a nanolayer of evaporated Au (Au/In2O3), were designed and fabricated for high-sensitivity sensing of NO2 and [...] Read more.
Photoactivated gallium nitride (GaN) nanowire-based gas sensors, functionalized with either bare In2O3 or In2O3 coated with a nanolayer of evaporated Au (Au/In2O3), were designed and fabricated for high-sensitivity sensing of NO2 and low-power operation. The sensors were tested at room temperature under 265 nm and 365 nm ultraviolet illumination at several power levels and in relative humidity ranging from over 20% to 80%. Under all conditions, photoconductivity was lower in the Au/In2O3-functionalized sensors compared to that of sensors functionalized with bare In2O3. However, when tested in the presence of NO2, the Au/In2O3 sensors consistently outperformed In2O3 sensors, the measured sensitivity being greater at 265 nm compared to 365 nm. The results show significant power reduction (×12) when photoactivating at (265 nm, 5 mW) compared to (365 nm, 60 mW). Maximum sensitivities of 27% and 42% were demonstrated with the Au/In2O3 sensors under illumination at (265 nm, 5 mW) for 1 ppm and 10 ppm concentration, respectively. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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12 pages, 3910 KiB  
Article
Simultaneous Detection of CO2 and CH4 Using a DFB Diode Laser-Based Absorption Spectrometer
by Xu Wu, Yulong Du, Shijian Shi, Cong Jiang, Xueliang Deng, Song Zhu, Xiaolong Jin and Jingsong Li
Chemosensors 2022, 10(10), 390; https://doi.org/10.3390/chemosensors10100390 - 24 Sep 2022
Viewed by 1809
Abstract
In this paper, an attractive gas sensing technique based on fiber optical sensing ideal was developed for the detection of multi-gas species simultaneously. Calibration-free laser absorption spectroscopy (LAS) was used and combined with a multi-pass optical absorption cell, two fiber-coupled near-infrared (NIR) distributed [...] Read more.
In this paper, an attractive gas sensing technique based on fiber optical sensing ideal was developed for the detection of multi-gas species simultaneously. Calibration-free laser absorption spectroscopy (LAS) was used and combined with a multi-pass optical absorption cell, two fiber-coupled near-infrared (NIR) distributed feedback (DFB) diode lasers are used and coupled into a single optical path for measuring CO2 and CH4 absorption spectra simultaneously. The optimal sampling pressure, laser tuning characteristics, spectral sampling points, and potential optical interference are theoretically and experimentally investigated in detail. The results indicated that the proposed technique has good reliability and has been successfully demonstrated for ambient CO2 and CH4 detection by using a single sample cell and detector. An Allan–Werle deviation analysis shows that detection limits of 0.12 ppm for CH4 and 35.97 ppm for CO2 can be obtained with an integration time of 181 s and 166 s, respectively. The proposed technique can be expanded to measure more molecules simultaneously by combing laser array and may pave a new way for developing a low-cost and ultra-compact multi-gas laser spectroscopy sensing system. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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