Sensing Materials: Advances in Synthesis, Functionalities, and Applications

A topical collection in Chemosensors (ISSN 2227-9040). This collection belongs to the section "Materials for Chemical Sensing".

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Collection Editor
Department of Information Engineering, University of Brescia, Via Valotti 9, 25133 Brescia, Italy
Interests: metal oxide nanostructures; carbon-containing nanomaterials; organic–inorganic composites; surface chemistry and surface physics; gas- and biosensors; flexible functional devices; cyber chemical systems for health; food and environmental monitoring
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Topical Collection Information

Dear colleagues,

The pollutant emissions from industrial activities and transport vehicles demonstrate the need for increased public health protection. These are in addition to global warming and climate change, which of course have potentially devastating effects on the environment, including weather patterns, farmlands, animal habitats, plants, and food production. Therefore, the preparation of functional materials and the development of high-performance sensing systems to provide environmental and safety monitoring have become important issues. In this regard, the continuous evolution of nanotechnology has led to the improvement of synthesis methods of low-dimensional materials with a variety of morphologies such as nanotubes, nanowires, nanobelts, nanorods, hierarchical structures, etc. Moreover, the synthesis of doped, functionalized, and more complex materials has become an increasingly important and perspective research subject to improve the functional properties of sensing structures.

The objective of this Topical Collection is to provide recent achievements in the synthesis methods, functionalities, and applications of low-dimensional materials for the development of high-performance sensing systems. Original research works and critical reviews are welcome.

Topics of interest include but are not limited to:

  • Developments in synthesis techniques;
  • Modifications of structure and morphology;
  • Doping and functionalization;
  • Composites;
  • Developments in characterization methods;
  • Improvements of analytical methods;
  • Improvement of sensing response;
  • Solutions for high selectivity;
  • Wireless sensor networks;
  • New concepts and new strategies.

Dr. Vardan Galstyan
Collection Editor

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Keywords

  • Synthesis
  • Low-dimensional structures
  • Nanomaterials
  • Sensing materials
  • Analytical methods
  • Gas sensor
  • Biosensor
  • Environmental monitoring
  • Health diagnostics
  • Process control
  • lab-on-chip sensing structures
  • Small size and mobile devices

Published Papers (17 papers)

2023

Jump to: 2022, 2021, 2020

17 pages, 3047 KiB  
Article
Self-Adaptation of Oxygen Adsorption and Sub-Surface Junction Formation in Thin Nanometric Sheets of Metal Oxides
by Gerhard Müller and Giorgio Sberveglieri
Chemosensors 2023, 11(6), 352; https://doi.org/10.3390/chemosensors11060352 - 20 Jun 2023
Viewed by 1240
Abstract
Oxygen adsorption at metal oxide (MOX) surfaces and the formation of sub-surface depletion zones in thin nanometric sheets of MOX materials are theoretically investigated. It is shown that—under conditions of sufficient oxygen mobility—the bulk thermal generation of oxygen vacancy donors and the adsorption [...] Read more.
Oxygen adsorption at metal oxide (MOX) surfaces and the formation of sub-surface depletion zones in thin nanometric sheets of MOX materials are theoretically investigated. It is shown that—under conditions of sufficient oxygen mobility—the bulk thermal generation of oxygen vacancy donors and the adsorption of surface oxygen ions cooperate in a self-organizing manner to form narrow sub-surface depletion zones which optimally fit into the limited spaces of MOX layers with nanometric cross sections. With this self-organization process in place, both the oxygen adsorption at free surfaces and the bulk generation of oxygen vacancy donors continuously increases as the MOX sheet thickness L is reduced, maintaining at the same time overall electro-neutrality and a state of perfect volume depletion of free carriers in bulk. This process comes to an end when MOX sheet thicknesses of L ≈ 1 nm are approached and when 3d-volumes of about 1 nm3 contain only one single double-donor and two surface oxygen ions on average. It is argued that at this limit of miniaturization, different interpretations of MOX gas sensing phenomena might be required than on larger length scales. Full article
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20 pages, 2657 KiB  
Review
Biosensing Strategies Based on Particle Behavior
by Akihisa Miyagawa and Tetsuo Okada
Chemosensors 2023, 11(3), 172; https://doi.org/10.3390/chemosensors11030172 - 03 Mar 2023
Cited by 2 | Viewed by 2170
Abstract
Micro/nanoparticles are widely used as useful biosensing platforms. Molecular recognition efficiently occurs on their surface, where ligand molecules are accumulated and, in some cases, well organized. The interactions that occur on or in the micro/nanoparticle significantly alter its physicochemical properties. Therefore, highly sensitive [...] Read more.
Micro/nanoparticles are widely used as useful biosensing platforms. Molecular recognition efficiently occurs on their surface, where ligand molecules are accumulated and, in some cases, well organized. The interactions that occur on or in the micro/nanoparticle significantly alter its physicochemical properties. Therefore, highly sensitive detection is possible based on such changes. Usual biosensors convert molecular or biological responses into optical or electrochemical signals. Particle-based biosensing can utilize a variety of other transducing mechanisms, including the changes in the levitation position of particles in physical fields, diffusion behavior, aggregation or dissociation, changes in the surface charge, and changes in size. We review the recent developments in biosensing based on various aspects of particle behavior. Full article
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2022

Jump to: 2023, 2021, 2020

11 pages, 3050 KiB  
Article
New Dinitrophenyl Hydrazones as Colorimetric Probes for Anions
by Rui P. C. L. Sousa, Susana P. G. Costa, Rita B. Figueira and M. Manuela M. Raposo
Chemosensors 2022, 10(10), 384; https://doi.org/10.3390/chemosensors10100384 - 23 Sep 2022
Cited by 2 | Viewed by 1299
Abstract
Anion sensing is a dynamic research field due to the biological and environmental importance of some organic or inorganic anions. Hydrazones show promising properties in the design of anion chemosensors due to the presence of proton donor and acceptor sites in their structure. [...] Read more.
Anion sensing is a dynamic research field due to the biological and environmental importance of some organic or inorganic anions. Hydrazones show promising properties in the design of anion chemosensors due to the presence of proton donor and acceptor sites in their structure. In this work, two novel dinitrophenyl hydrazones, functionalized with a quinoline moiety, were synthesized and characterized by spectroscopic and spectrometric techniques. The interaction between the new compounds 3ab with different organic and inorganic anions was assessed. The two compounds showed a change in color from light yellow to magenta in the presence of H2PO4, CH3COO, BzO, CN, and F. The interactions were analyzed by spectrophotometric titrations and the stoichiometry of the interaction was assessed by the method of continuous variation. Compound 3b showed a remarkable sensitivity to CN, with a limit of detection of 0.35 µM. The interaction of compound 3b with CN and F was also analyzed by 1H NMR titrations, showing that an increasing concentration of anions induce a deprotonation of the NH and OH groups. Full article
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12 pages, 4930 KiB  
Article
Thermal, Physical, and Optical Properties of the Solution and Melt Synthesized Single Crystal CsPbBr3 Halide Perovskite
by Kirti Agrawal, Syed Mohammad Abid Hasan, Joanna Blawat, Nishir Mehta, Yuming Wang, Rafael Cueto, Miriam Siebenbuerger, Orhan Kizilkaya, Narasimha S. Prasad, James Dorman, Rongying Jin and Manas Ranjan Gartia
Chemosensors 2022, 10(9), 369; https://doi.org/10.3390/chemosensors10090369 - 16 Sep 2022
Cited by 4 | Viewed by 2463
Abstract
Inorganic lead-halide perovskite, cesium lead bromide (CsPbBr3), shows outstanding optoelectronic properties. Both solution- and melt-based methods have been proposed for CsPbBr3 crystal growth. The solution-based growth was done at low-temperature, whereas the melt-based growth was done at high-temperature. However, the [...] Read more.
Inorganic lead-halide perovskite, cesium lead bromide (CsPbBr3), shows outstanding optoelectronic properties. Both solution- and melt-based methods have been proposed for CsPbBr3 crystal growth. The solution-based growth was done at low-temperature, whereas the melt-based growth was done at high-temperature. However, the comparison of optical, physical, and defect states using these two different growth conditions has been scarcely studied. Here, we have compared the thermal and optical properties of solution-grown and melt-grown single crystals of CsPbBr3. Positron Annihilation Lifetime Spectroscopy (PALS) analysis showed that melt-grown crystal has a relatively smaller number of defects than the chemical synthesis method. In addition, crystals grown using the chemical method showed a higher fluorescence lifetime than melt-grown CsPbBr3. Full article
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15 pages, 1467 KiB  
Article
Broadband Dielectric Spectroscopic Detection of Ethanol: A Side-by-Side Comparison of ZnO and HKUST-1 MOFs as Sensing Media
by Papa K. Amoah, Zeinab Mohammed Hassan, Pengtao Lin, Engelbert Redel, Helmut Baumgart and Yaw S. Obeng
Chemosensors 2022, 10(7), 241; https://doi.org/10.3390/chemosensors10070241 - 25 Jun 2022
Cited by 4 | Viewed by 1855
Abstract
The most common gas sensors are based on chemically induced changes in electrical resistivity and necessarily involve making imperfect electrical contacts to the sensing materials, which introduce errors into the measurements. We leverage thermal- and chemical-induced changes in microwave propagation characteristics (i.e., S-parameters) [...] Read more.
The most common gas sensors are based on chemically induced changes in electrical resistivity and necessarily involve making imperfect electrical contacts to the sensing materials, which introduce errors into the measurements. We leverage thermal- and chemical-induced changes in microwave propagation characteristics (i.e., S-parameters) to compare ZnO and surface-anchored metal–organic-framework (HKUST-1 MOF) thin films as sensing materials for detecting ethanol vapor, a typical volatile organic compound (VOC), at low temperatures. We show that the microwave propagation technique can detect ethanol at relatively low temperatures (<100 °C), and afford new mechanistic insights that are inaccessible with the traditional dc-resistance-based measurements. In addition, the metrological technique avoids the inimical measurand distortions due to parasitic electrical effects inherent in the conductometric volatile organic compound detection. Full article
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19 pages, 4866 KiB  
Article
Origin of Baseline Drift in Metal Oxide Gas Sensors: Effects of Bulk Equilibration
by Gerhard Müller and Giorgio Sberveglieri
Chemosensors 2022, 10(5), 171; https://doi.org/10.3390/chemosensors10050171 - 02 May 2022
Cited by 14 | Viewed by 5183
Abstract
Metal oxide (MOX) gas sensors and gas sensor arrays are widely used to detect toxic, combustible, and corrosive gases and gas mixtures inside ambient air. Important but poorly researched effects counteracting reliable detection are the phenomena of sensor baseline drift and changes in [...] Read more.
Metal oxide (MOX) gas sensors and gas sensor arrays are widely used to detect toxic, combustible, and corrosive gases and gas mixtures inside ambient air. Important but poorly researched effects counteracting reliable detection are the phenomena of sensor baseline drift and changes in gas response upon long-term operation of MOX gas sensors. In this paper, it is shown that baseline drift is not limited to materials with poor crystallinity, but that this phenomenon principally also occurs in materials with almost perfect crystalline order. Building on this result, a theoretical framework for the analysis of such phenomena is developed. This analysis indicates that sensor drift is caused by the slow annealing of quenched-in non-equilibrium oxygen-vacancy donors as MOX gas sensors are operated at moderate temperatures for prolonged periods of time. Most interestingly, our analysis predicts that sensor drift in n-type MOX materials can potentially be mitigated or even suppressed by doping with metal impurities with chemical valences higher than those of the core metal constituents of the host crystals. Full article
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2021

Jump to: 2023, 2022, 2020

13 pages, 2923 KiB  
Communication
pH-Dependent Selective Colorimetric Detection of Proline and Hydroxyproline with Meldrum’s Acid-Furfural Conjugate
by Lisa Zeußel, Carlos Aziz, Andreas Schober and Sukhdeep Singh
Chemosensors 2021, 9(12), 343; https://doi.org/10.3390/chemosensors9120343 - 04 Dec 2021
Cited by 4 | Viewed by 4356
Abstract
Activated 2-furfural gives intense color formation when reacted with amines, due to a ring opening reaction cascade that furnishes a conjugated molecular system. Unique colorimetric characteristic of this reaction makes it an interesting candidate for developing chemosensors operating in visible range. Among many [...] Read more.
Activated 2-furfural gives intense color formation when reacted with amines, due to a ring opening reaction cascade that furnishes a conjugated molecular system. Unique colorimetric characteristic of this reaction makes it an interesting candidate for developing chemosensors operating in visible range. Among many activated 2-furfural derivatives, Meldrum’s acid furfural conjugate (MAFC) recently gained significant interest as colorimetric chemosensor. MAFC has been explored as selective chemosensor for detecting amines in solution, secondary amines on polymer surfaces and even nitrogen rich amino acids (AA) in aqueous solution. In this work, the pH dependency of MAFC-AA reaction is explored. It was found that proline gives an exceptionally fast colored reaction at pH 11, whereas at other pHs, no naked eye color product formation was observed. The reaction sequence including ring opening reaction upon nucleophilic addition of cyclic amine of proline resulting in a conjugated triene was confirmed by NMR titrations. The highly pH dependent reaction can e.g., potentially be used to detect proline presence in biological samples. An even more intense color formation takes place in the reaction of natural proline derivative 4-hydroxyproline. The detection limit of proline and 4-hydroxyproline with MAFC solution was found to be 11 µM and 6 µM respectively. Full article
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40 pages, 2198 KiB  
Review
Sensing Methods for Hazardous Phenolic Compounds Based on Graphene and Conducting Polymers-Based Materials
by Hazwani Suhaila Hashim, Yap Wing Fen, Nur Alia Sheh Omar and Nurul Illya Muhamad Fauzi
Chemosensors 2021, 9(10), 291; https://doi.org/10.3390/chemosensors9100291 - 14 Oct 2021
Cited by 13 | Viewed by 2683
Abstract
It has been known for years that the phenolic compounds are able to exert harmful effects toward living organisms including humans due to their high toxicity. Living organisms were exposed to these phenolic compounds as they were released into the environment as waste [...] Read more.
It has been known for years that the phenolic compounds are able to exert harmful effects toward living organisms including humans due to their high toxicity. Living organisms were exposed to these phenolic compounds as they were released into the environment as waste products from several fast-growing industries. In this regard, tremendous efforts have been made by researchers to develop sensing methods for the detection of these phenolic compounds. Graphene and conducting polymers-based materials have arisen as a high potential sensing layer to improve the performance of the developed sensors. Henceforth, this paper reviews the existing investigations on graphene and conducting polymer-based materials incorporated with various sensors that aimed to detect hazardous phenolic compounds, i.e., phenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4-dimethylphenol. The whole picture and up-to-date information on the graphene and conducting polymers-based sensors are arranged in systematic chronological order to provide a clearer insight in this research area. The future perspectives of this study are also included, and the development of sensing methods for hazardous phenolic compounds using graphene and conducting polymers-based materials is expected to grow more in the future. Full article
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20 pages, 6242 KiB  
Article
Additive Manufacturing as a Means of Gas Sensor Development for Battery Health Monitoring
by Oleg Lupan, Helge Krüger, Leonard Siebert, Nicolai Ababii, Niklas Kohlmann, Artur Buzdugan, Mani Teja Bodduluri, Nicolae Magariu, Maik-Ivo Terasa, Thomas Strunskus, Lorenz Kienle, Rainer Adelung and Sandra Hansen
Chemosensors 2021, 9(9), 252; https://doi.org/10.3390/chemosensors9090252 - 06 Sep 2021
Cited by 5 | Viewed by 3463
Abstract
Lithium-ion batteries (LIBs) still need continuous safety monitoring based on their intrinsic properties, as well as due to the increase in their sizes and device requirements. The main causes of fires and explosions in LIBs are heat leakage and the presence of highly [...] Read more.
Lithium-ion batteries (LIBs) still need continuous safety monitoring based on their intrinsic properties, as well as due to the increase in their sizes and device requirements. The main causes of fires and explosions in LIBs are heat leakage and the presence of highly inflammable components. Therefore, it is necessary to improve the safety of the batteries by preventing the generation of these gases and/or their early detection with sensors. The improvement of such safety sensors requires new approaches in their manufacturing. There is a growing role for research of nanostructured sensor’s durability in the field of ionizing radiation that also can induce structural changes in the LIB’s component materials, thus contributing to the elucidation of fundamental physicochemical processes; catalytic reactions or inhibitions of the chemical reactions on which the work of the sensors is based. A current method widely used in various fields, Direct Ink Writing (DIW), has been used to manufacture heterostructures of Al2O3/CuO and CuO:Fe2O3, followed by an additional ALD and thermal annealing step. The detection properties of these 3D-DIW printed heterostructures showed responses to 1,3-dioxolan (DOL), 1,2-dimethoxyethane (DME) vapors, as well as to typically used LIB electrolytes containing LiTFSI and LiNO3 salts in a mixture of DOL:DME, as well also to LiPF6 salts in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) at operating temperatures of 200 °C–350 °C with relatively high responses. The combination of the possibility to detect electrolyte vapors used in LIBs and size control by the 3D-DIW printing method makes these heterostructures extremely attractive in controlling the safety of batteries. Full article
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10 pages, 4058 KiB  
Article
UV-Light-Driven Enhancement of Peroxidase-Like Activity of Mg-Aminoclay-Based Fe3O4/TiO2 Hybrids for Colorimetric Detection of Phenolic Compounds
by Yoon Jung Jang, Vu Khac Hoang Bui, Phuong Thy Nguyen, Young-Chul Lee and Moon Il Kim
Chemosensors 2021, 9(8), 219; https://doi.org/10.3390/chemosensors9080219 - 11 Aug 2021
Cited by 6 | Viewed by 2322
Abstract
Light-activated nanozymes possess several advantages, such as light-mediated activity regulation, utilization of molecular oxygen as a green oxidant, and highly enhanced activity; however, the types of light-activated nanozymes are still limited. In this study, we found that Mg aminoclay-based Fe3O4 [...] Read more.
Light-activated nanozymes possess several advantages, such as light-mediated activity regulation, utilization of molecular oxygen as a green oxidant, and highly enhanced activity; however, the types of light-activated nanozymes are still limited. In this study, we found that Mg aminoclay-based Fe3O4/TiO2 hybrids (MgAC-Fe3O4/TiO2) exhibited peroxidase-like catalytic activity to catalyze the oxidation of the peroxidase substrate 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) in the presence of H2O2, which was significantly enhanced under ultraviolet (UV)-light irradiation. Compared with MgAC-Fe3O4 and MgAC-TiO2, MgAC-Fe3O4/TiO2 showed around three-fold enhancement in the absorption intensity corresponding to the oxidized ABTS under UV-light irradiation, presumably due to the synergistic effect between Fe3O4 and TiO2, thereby facilitating photocatalytic electron transfer during the catalytic action. In addition, the MgAC-Fe3O4/TiO2 showed vivid stability enhancement in wide range of pH and temperature values compared with natural peroxidase. The UV-light-driven MgAC-Fe3O4/TiO2-based system was successfully applied for the colorimetric detection of phenolic compounds, including pyrocatechol and resorcinol, in a dynamic linear range of 0.15–1.30 mg/mL with a limit of detection as low as 0.1 mg/mL. Further, the system could successfully determine the phenolic compounds in spiked tap water, and thus, it can be used for practical applications. We believe that the UV-light-driven enhancement in the peroxidase-like catalytic performances highlights the potential of MgAC-Fe3O4/TiO2 for detecting phenolic compounds as well as other clinically and environmentally important substances. Full article
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16 pages, 3207 KiB  
Review
Electrochemical Immunosensors for Quantification of Procalcitonin: Progress and Prospects
by Subramanian Nellaiappan, Pavan Kumar Mandali, Amrish Prabakaran and Uma Maheswari Krishnan
Chemosensors 2021, 9(7), 182; https://doi.org/10.3390/chemosensors9070182 - 14 Jul 2021
Cited by 7 | Viewed by 3193
Abstract
Human procalcitonin (PCT) is a peptide precursor of the calcium-regulating hormone calcitonin. Traditionally, PCT has been used as a biomarker for severe bacterial infections and sepsis. It has also been recently identified as a potential marker for COVID-19. Normally, serum PCT is intracellularly [...] Read more.
Human procalcitonin (PCT) is a peptide precursor of the calcium-regulating hormone calcitonin. Traditionally, PCT has been used as a biomarker for severe bacterial infections and sepsis. It has also been recently identified as a potential marker for COVID-19. Normally, serum PCT is intracellularly cleaved to calcitonin, which lowers the levels of PCT (<0.01 ng/mL). In severe infectious diseases and sepsis, serum PCT levels increase above 100 ng/mL in response to pro-inflammatory stimulation. Development of sensors for specific quantification of PCT has resulted in considerable improvement in the sensitivity, linear range and rapid response. Among the various sensing strategies, electrochemical platforms have been extensively investigated owing to their cost-effectiveness, ease of fabrication and portability. Sandwich-type electrochemical immunoassays based on the specific antigen–antibody interactions with an electrochemical transducer and use of nanointerfaces has augmented the electrochemical response of the sensors towards PCT. Identification of a superior combination of electrode material and nanointerface, and translation of the sensing platform into flexible and disposable substrates are under active investigation towards development of a point-of-care device for PCT detection. This review provides an overview of the existing detection strategies and limitations of PCT electrochemical immunosensors, and the emerging directions to address these lacunae. Full article
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15 pages, 4753 KiB  
Article
Optical Sensing of Molecular Oxygen (O2) via Metal Oxide Photoluminescence: A Comparative Study of TiO2, SnO2 and ZnO
by Ambra Fioravanti, Pietro Marani, Sara Morandi, Laura Giordano, Pasqualino Maddalena, Maria Cristina Carotta and Stefano Lettieri
Chemosensors 2021, 9(7), 163; https://doi.org/10.3390/chemosensors9070163 - 28 Jun 2021
Cited by 2 | Viewed by 2449
Abstract
A comparative study is presented on the photoluminescence (PL) response toward molecular oxygen (O2) in tin dioxide (SnO2), zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles. The findings show that both PL enhancement and PL quenching can [...] Read more.
A comparative study is presented on the photoluminescence (PL) response toward molecular oxygen (O2) in tin dioxide (SnO2), zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles. The findings show that both PL enhancement and PL quenching can be observed on different materials, arguably depending on the spatial localization of the defects responsible for the PL emission in each different oxide. No significant results are evidenced for SnO2 nanoparticles. ZnO with red/orange emission shown an O2-induced PL enhancement, suggesting that the radiative emission involves holes trapped in surface vacancy oxygen centers. While the ZnO results are scientifically interesting, its performances are inferior to the ones shown by TiO2, which exhibits the most interesting response in terms of sensitivity and versatility of the response. In particular, O2 concentrations in the range of few percent and in the range of a few tenths of a part per million are both detectable through the same mixed-phase TiO2 sample, whose rutile phase gives a reversible and fast response to larger (0.4–2%) O2 concentration while its anatase phase is usable for detection in the 25–75 ppm range. The data for rutile TiO2 suggest that its surfaces host deeply trapped electrons at large densities, allowing good sensitivities and, more notably, a relatively unsaturated response at large concentrations. Future work is expected to improve the understanding and modeling of the photophysical framework that lies behind the observations. Full article
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19 pages, 45009 KiB  
Review
Nanocomposite Materials Based on Electrochemically Synthesized Graphene Polymers: Molecular Architecture Strategies for Sensor Applications
by André Olean-Oliveira, Gilberto A. Oliveira Brito, Celso Xavier Cardoso and Marcos F. S. Teixeira
Chemosensors 2021, 9(6), 149; https://doi.org/10.3390/chemosensors9060149 - 18 Jun 2021
Cited by 8 | Viewed by 3955
Abstract
The use of graphene and its derivatives in the development of electrochemical sensors has been growing in recent decades. Part of this success is due to the excellent characteristics of such materials, such as good electrical and mechanical properties and a large specific [...] Read more.
The use of graphene and its derivatives in the development of electrochemical sensors has been growing in recent decades. Part of this success is due to the excellent characteristics of such materials, such as good electrical and mechanical properties and a large specific surface area. The formation of composites and nanocomposites with these two materials leads to better sensing performance compared to pure graphene and conductive polymers. The increased large specific surface area of the nanocomposites and the synergistic effect between graphene and conducting polymers is responsible for this interesting result. The most widely used methodologies for the synthesis of these materials are still based on chemical routes. However, electrochemical routes have emerged and are gaining space, affording advantages such as low cost and the promising possibility of modulation of the structural characteristics of composites. As a result, application in sensor devices can lead to increased sensitivity and decreased analysis cost. Thus, this review presents the main aspects for the construction of nanomaterials based on graphene oxide and conducting polymers, as well as the recent efforts made to apply this methodology in the development of sensors and biosensors. Full article
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19 pages, 5582 KiB  
Article
Fluorination vs. Chlorination: Effect on the Sensor Response of Tetrasubstituted Zinc Phthalocyanine Films to Ammonia
by Dmitry Bonegardt, Darya Klyamer, Aleksandr Sukhikh, Pavel Krasnov, Pavel Popovetskiy and Tamara Basova
Chemosensors 2021, 9(6), 137; https://doi.org/10.3390/chemosensors9060137 - 11 Jun 2021
Cited by 16 | Viewed by 3022
Abstract
In this work, the effect of fluorine and chlorine substituents in tetrasubstituted zinc phthalocyanines, introduced into the non-peripheral (ZnPcR4-np, R = F, Cl) and peripheral (ZnPcR4-p, R = F, Cl) positions of macrocycle, on their structure and chemiresistive sensor [...] Read more.
In this work, the effect of fluorine and chlorine substituents in tetrasubstituted zinc phthalocyanines, introduced into the non-peripheral (ZnPcR4-np, R = F, Cl) and peripheral (ZnPcR4-p, R = F, Cl) positions of macrocycle, on their structure and chemiresistive sensor response to low concentration of ammonia is studied. The structure and morphology of the zinc phthalocyanines films (ZnPcR4) were investigated by X-ray diffraction and atomic force microscopy methods. To understand different effects of chlorine and fluorine substituents, the strength and nature of the bonding of ammonia and ZnPcHal4 molecules were studied by quantum chemical simulation. It was shown on the basis of comparative analysis that the sensor response to ammonia was found to increase in the order ZnPcCl4-np < ZnPcF4-np < ZnPcF4-p < ZnPcCl4-p, which is in good agreement with the values of bonding energy between hydrogen atoms of NH3 and halogen substituents in the phthalocyanine rings. ZnPcCl4-p films demonstrate the maximal sensor response to ammonia with the calculated detection limit of 0.01 ppm; however, they are more sensitive to humidity than ZnPcF4-p films. It was shown that both ZnPcF4-p and ZnPcCl4-p and can be used for the selective detection of NH3 in the presence of carbon dioxide, dichloromethane, acetone, toluene, and ethanol. Full article
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10 pages, 3560 KiB  
Communication
Terbium(III) as a Fluorescent Probe for Molecular Detection of Ascorbic Acid
by Natalia Selivanova and Yuriy Galyametdinov
Chemosensors 2021, 9(6), 134; https://doi.org/10.3390/chemosensors9060134 - 09 Jun 2021
Cited by 10 | Viewed by 3506
Abstract
Fluorescence analysis is a simple and a highly sensitive method for detection of small amounts of biologically active substances. In this study, a complexation of terbium(III) chelates with 1,10-phenanthroline and ascorbic acid (AA) and luminescent properties of complexes were investigated. The influence of [...] Read more.
Fluorescence analysis is a simple and a highly sensitive method for detection of small amounts of biologically active substances. In this study, a complexation of terbium(III) chelates with 1,10-phenanthroline and ascorbic acid (AA) and luminescent properties of complexes were investigated. The influence of pH and solubilization of complexes by micellar solutions of nonionic, cationic, and anionic surfactants on fluorescence was studied. The quenching effect of terbium ion fluorescence was detected upon an introduction of ascorbic acid. The quenching effect of the complex with mixed ligands Tb(1,10-phenanthroline)-AA allows for the detection of ascorbic acid with the limit of 7.4 × 10−5 mol·L−1. Full article
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17 pages, 4876 KiB  
Article
One-Pot Synthesis of Copper Iodide-Polypyrrole Nanocomposites
by Artem O. Konakov, Nadejda N. Dremova, Igor I. Khodos, Marcus Koch, Ekaterina V. Zolotukhina and Yuliya E. Silina
Chemosensors 2021, 9(3), 56; https://doi.org/10.3390/chemosensors9030056 - 16 Mar 2021
Cited by 4 | Viewed by 3669
Abstract
A novel one-pot chemical synthesis of functional copper iodide-polypyrrole composites, CuI-PPy, has been proposed. The fabrication process allows the formation of nanodimensional metal salt/polymer hybrid structures in a fully controlled time- and concentration-dependent manner. The impact of certain experimental conditions, viz., duration of [...] Read more.
A novel one-pot chemical synthesis of functional copper iodide-polypyrrole composites, CuI-PPy, has been proposed. The fabrication process allows the formation of nanodimensional metal salt/polymer hybrid structures in a fully controlled time- and concentration-dependent manner. The impact of certain experimental conditions, viz., duration of synthesis, sequence of component addition and concentrations of the intact reagents on the structure, dimensionality and yield of the end-product was evaluated in detail. More specifically, the amount of marshite CuI within the hybrid composite can be ranged from 60 to 90 wt.%, depending on synthetic conditions (type and concentration of components, process duration). In addition, the conditions allowing the synthesis of nano-sized CuI distributed inside the polypyrrole matrix were found. A high morphological stability and reproducibility of the synthesized nanodimensional metal-polymer hybrid materials were approved. Finally, the electrochemical activity of the formed composites was verified by cyclic voltammetry studies. The stability of CuI-PPy composite deposited on the electrodes was strongly affected by the applied anodic limit. The proposed one-pot synthesis of the hybrid nanodimensional copper iodide-polypyrrole composites is highly innovative, meets the requirements of Green Chemistry and is potentially useful for future biosensor development. In addition, this study is expected to generally contribute to the knowledge on the hybrid nano-based composites with tailored properties. Full article
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2020

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8 pages, 3363 KiB  
Letter
Sputtered SnO2/ZnO Heterostructures for Improved NO2 Gas Sensing Properties
by Bharat Sharma, Ashutosh Sharma, Monika Joshi and Jae-ha Myung
Chemosensors 2020, 8(3), 67; https://doi.org/10.3390/chemosensors8030067 - 07 Aug 2020
Cited by 35 | Viewed by 4645
Abstract
A highly sensitive and selective NO2 gas sensor dependent on SnO2/ZnO heterostructures was fabricated using a sputtering process. The SnO2/ZnO heterostructure thin film samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Energy-dispersive X-ray [...] Read more.
A highly sensitive and selective NO2 gas sensor dependent on SnO2/ZnO heterostructures was fabricated using a sputtering process. The SnO2/ZnO heterostructure thin film samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Sensors fabricated with heterostructures attained higher gas response (S = 66.9) and quicker response-recovery (20 s, 45 s) characteristics at 100 °C operating temperature towards 100 ppm NO2 gas efficiently in comparison to sensors based on their mono-counterparts. The selectivity and stability of SnO2/ZnO heterostructures were studied. The more desirable sensing mechanism of SnO2/ZnO heterostructures towards NO2 was described in detail. Full article
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