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Artemesia tridentata is a foundational plant taxon in western North America and an important medicinal plant threatened by climate change. Low-cost fabrication of sensors is critical for developing large-area sensor networks for understanding and monitoring a range of environmental conditions. However, the availability of materials and manufacturing processes is still in the early stages, limiting the capacity to develop cost-effective sensors at a large scale. In this study, we demonstrate the fabrication of low-cost flexible sensors using laser-induced graphene (LIG); a graphitic material synthesized using a 450-nm wavelength bench top laser patterned onto polyimide substrates. We demonstrate the effect of the intensity and focus of the incident beam on the morphology and electrical properties of the synthesized material. Raman analyses of the synthesized LIG show a defect-rich graphene with a crystallite size in the tens of nanometers. This shows that the high level of disorder within the LIG structure, along with the porous nature of the material provide a good surface for gas adsorption. The initial characterization of the material has shown an analyte response represented by a change in resistance of up to 5% in the presence of volatile organic compounds (VOCs) that are emitted and detected by Artemisia species. Bend testing up to 100 cycles provides evidence that these sensors will remain resilient when deployed across the landscapes to assess VOC signaling in plant communities. The versatile low-cost laser writing technique highlights the promise of low-cost and scalable fabrication of LIG sensors for gas sensor monitoring. [ABSTRACT FROM AUTHOR]

H2S gas sensors with facile preparation, low detection limits, and high selectivity are crucial for environmental and human health monitoring. However, it is difficult to maintain a high response of H2S gas sensors under high humidity in practical applications. To face this dilemma, a layer‐by‐layer growth method is applied to in situ prepare a nanostructured Co(CO3)0.5(OH)·0.11H2O/WO3 coated by a hydrophobic hierarchical ZIF‐67 as the H2S sensor. This novel composite exhibits excellent humidity immunity without sacrificing the excellent sensitivity and selectivity of H2S. At a low operating temperature of 90 °C, a remarkable response value of 1052.3 to 100 ppm H2S has been achieved, which is 779 and 9.36 times higher than that of pure WO3 and Co(CO3)0.5(OH)·0.11H2O/WO3, respectively. More importantly, an 82.2% relative response value remains at a high humidity of 75%RH. The sensing mechanisms are investigated using gas chromatography‐mass spectrometry (GC‐MS), which revealed that the reaction products are H2O and SO2. The high humidity immunity and fast response of the Co(CO3)0.5(OH)·0.11H2O@ZIF‐67/WO3 demonstrate the layer‐by‐layer in situ synthesis method holds the potential application for the development of high‐performance WO3‐based H2S sensors. [ABSTRACT FROM AUTHOR]

In this study, in situ prepared multiple semiconducting TiO 2 in a metallic Ti 3 C 2 T x channel were investigated, which were derived from the Ti 3 AlC 2 MAX phase by oxidation treatments. Several tiny TiO 2 particles were in situ formed on the Ti 3 C 2 T x MXene surface when it was heated to 150 °C at ambient conditions. The phase transformation of pristine Ti 3 C 2 T x MXene to oxidized TiO 2 was accelerated when the gas-sensing channel was heated to higher temperatures up to 200 °C, yielding a TiO 2 /Ti 3 C 2 T x composite. The experimental results revealed that the heat-treatment temperature played an important role in the gradual development of the morphology and gas-sensing activity of the TiO 2 /Ti 3 C 2 T x sensing channel. In particular, the optimal heating temperature of the composite resulted in a good response and recovery time for NO 2 molecules. Furthermore, first-principles calculations indicated the good sensing ability of the TiO 2 /Ti 3 C 2 T x composite for NO 2 than for other gases. These results suggest a new strategy for developing gas-sensing ability by forming a Schottky barrier through a simple process. [ABSTRACT FROM AUTHOR]

Artemesia tridentata is a foundational plant taxon in western North America and an important medicinal plant threatened by climate change. Low-cost fabrication of sensors is critical for developing large-area sensor networks for understanding and monitoring a range of environmental conditions. However, the availability of materials and manufacturing processes is still in the early stages, limiting the capacity to develop cost-effective sensors at a large scale. In this study, we demonstrate the fabrication of low-cost flexible sensors using laser-induced graphene (LIG); a graphitic material synthesized using a 450-nm wavelength bench top laser patterned onto polyimide substrates. We demonstrate the effect of the intensity and focus of the incident beam on the morphology and electrical properties of the synthesized material. Raman analyses of the synthesized LIG show a defect-rich graphene with a crystallite size in the tens of nanometers. This shows that the high level of disorder within the LIG structure, along with the porous nature of the material provide a good surface for gas adsorption. The initial characterization of the material has shown an analyte response represented by a change in resistance of up to 5% in the presence of volatile organic compounds (VOCs) that are emitted and detected by Artemisia species. Bend testing up to 100 cycles provides evidence that these sensors will remain resilient when deployed across the landscapes to assess VOC signaling in plant communities. The versatile low-cost laser writing technique highlights the promise of low-cost and scalable fabrication of LIG sensors for gas sensor monitoring.

Abstract H2S gas sensors with facile preparation, low detection limits, and high selectivity are crucial for environmental and human health monitoring. However, it is difficult to maintain a high response of H2S gas sensors under high humidity in practical applications. To face this dilemma, a layer‐by‐layer growth method is applied to in situ prepare a nanostructured Co(CO3)0.5(OH)·0.11H2O/WO3 coated by a hydrophobic hierarchical ZIF‐67 as the H2S sensor. This novel composite exhibits excellent humidity immunity without sacrificing the excellent sensitivity and selectivity of H2S. At a low operating temperature of 90 °C, a remarkable response value of 1052.3 to 100 ppm H2S has been achieved, which is 779 and 9.36 times higher than that of pure WO3 and Co(CO3)0.5(OH)·0.11H2O/WO3, respectively. More importantly, an 82.2% relative response value remains at a high humidity of 75%RH. The sensing mechanisms are investigated using gas chromatography‐mass spectrometry (GC‐MS), which revealed that the reaction products are H2O and SO2. The high humidity immunity and fast response of the Co(CO3)0.5(OH)·0.11H2O@ZIF‐67/WO3 demonstrate the layer‐by‐layer in situ synthesis method holds the potential application for the development of high‐performance WO3‐based H2S sensors.

Nitrogen dioxide (NO2) gas sensors are pivotal in upholding environmental integrity and human health, necessitating heightened sensitivity and exceptional selectivity. Despite the prevalent use of metal oxide semiconductors (MOSs) for NO2 detection, extant solutions exhibit shortcomings in meeting practical application criteria, specifically in response, selectivity, and operational temperatures. Here, we successfully employed a facile microwave-solvothermal method to synthesize a mesoporous CeO2/CNCs nanocomposite. This methodology entails the rapid and comprehensive dispersion of CeO2 nanoparticles onto helical carbon nanocoils (CNCs), resulting in augmented electronic conductivity and an abundance of active sites within the composite. Consequently, the gas-sensing sensitivity of the nanocomposite at room temperature experienced a notable enhancement. Moreover, the presence of cerium oxide and the conversion of Ce3+ and Ce4+ ions facilitated the generation of oxygen vacancies in the composites, thereby further amplifying the sensing performance. Experimental outcomes demonstrate that the nanocomposite exhibited an approximate 9-fold increase in response to 50 ppm NO2 in comparison to pure CNCs at room temperature. Additionally, the CeO2/CNCs sensor displayed remarkable selectivity towards NO2 when exposed to gases such as NH3, CO, SO2, CO2, and C2H5OH. This straightforward microwave-solvothermal method presents an appealing strategy for the research and development of intelligent sensors based on CNCs nanomaterials. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) gas is a dual menace since it is not only hazardous to human health and the environment, but it is also flammable. Given these crucial considerations, the need for competent gas sensors for H 2 S detection becomes apparent. In this endeavor, an investigation of the gas-sensing prowess inherent in sensors made from assembled nanosheets of ZnO–NiO arranged into intricate flower-like structures. The sensing materials were prepared using a straightforward solvothermal process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to thoroughly examine the sensor's chemical properties and structural composition. The gas-sensing abilities of the sensing materials were rigorously assessed, which included a close examination of their electrical response to varied concentrations of H 2 S. The efficacy of the sensors may be due to the synergistic interactions between their distinct flower-like design, endowing them with an expansive surface area for optimum gas adsorption, and the significant catalytic impact supplied by the composition of ZnO–NiO. The results show that the ZnO–NiO flower-like sensors have high sensitivity, selectivity, and stability to H 2 S gas. Within the studied range, the response and recovery times were 51.43 s and 38.11 s respectively at 250 °C in 100 ppm H 2 S. This amalgamation of attributes manifests as an enhancement in the sensors' gas-sensing capabilities, highlighting their suitability for such an application. This research complements the explanation offered by first-principles calculations based on Density Functional Theory (DFT) to dive into the fundamentals of this gas-sensing mechanism. [ABSTRACT FROM AUTHOR]

Zeolite additional layers coating on metal oxide surfaces to improve the selectivity and response values of the sensors are effective and widely used. The specific adsorption and diffusion of gas molecules in the zeolite are recognised to play an important role in gas sensing improvement. In this work, the adsorption and diffusion behaviours of formaldehyde and acetone in H-Y and H-A zeolites were calculated by Monte Carlo and molecular dynamics simulations. The loading of acetone is greater than formaldehyde in these two kinds of zeolites under the same temperature and pressure, and the water load is lower. The simulation results show that the effects of the nature of the guest molecule and steric hindrance of the diffusing molecule on diffusivity are significant. The diffusivity in H-A zeolite decreases by several orders of magnitude than that in H-Y zeolite However, in H-A zeolite, the internal diffusion dominates, and only the smaller diameter formaldehyde can diffuse between the pores, which is beneficial to improving the sensing properties of formaldehyde. In addition, in the competition diffusion with water molecules, formaldehyde dominates than acetone. The H-Y/SnO2 and H-A/SnO2 sensors were prepared to verify the reliability of the molecular simulations. Research highlights The adsorption and diffusion behaviour of formaldehyde and acetone in H-Y and H-A zeolites were investigated using molecular simulation. Molecular diameter mainly influences the kinetic behaviour. The sensitisation mechanism of H-Y/SnO2 sensor to acetone and H-A/SnO2 sensor to formaldehyde was proved. Focuses on the relationship between gas-sensing the performance of zeolite-covered SnO2 sensors and the adsorption. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide (NO2) gas sensors are pivotal in upholding environmental integrity and human health, necessitating heightened sensitivity and exceptional selectivity. Despite the prevalent use of metal oxide semiconductors (MOSs) for NO2 detection, extant solutions exhibit shortcomings in meeting practical application criteria, specifically in response, selectivity, and operational temperatures. Here, we successfully employed a facile microwave-solvothermal method to synthesize a mesoporous CeO2/CNCs nanocomposite. This methodology entails the rapid and comprehensive dispersion of CeO2 nanoparticles onto helical carbon nanocoils (CNCs), resulting in augmented electronic conductivity and an abundance of active sites within the composite. Consequently, the gas-sensing sensitivity of the nanocomposite at room temperature experienced a notable enhancement. Moreover, the presence of cerium oxide and the conversion of Ce3+ and Ce4+ ions facilitated the generation of oxygen vacancies in the composites, thereby further amplifying the sensing performance. Experimental outcomes demonstrate that the nanocomposite exhibited an approximate 9-fold increase in response to 50 ppm NO2 in comparison to pure CNCs at room temperature. Additionally, the CeO2/CNCs sensor displayed remarkable selectivity towards NO2 when exposed to gases such as NH3, CO, SO2, CO2, and C2H5OH. This straightforward microwave-solvothermal method presents an appealing strategy for the research and development of intelligent sensors based on CNCs nanomaterials.

Among nanocomposite materials, multifunctional polymer nanocomposites have prompted important innovations in the field of sensing technology. Polymer-based nanocomposites have been successfully utilized to design high-tech sensors. Thus, conductive, thermoplast, or elastomeric, as well as natural polymers have been applied. Carbon nanoparticles as well as inorganic nanoparticles, such as metal nanoparticles or metal oxides, have reinforced polymer matrices for sensor fabrication. The sensing features and performances rely on the interactions between the nanocomposites and analytes like gases, ions, chemicals, biological species, and others. The multifunctional nanocomposite-derived sensors possess superior durability, electrical conductivity, sensitivity, selectivity, and responsiveness, compared with neat polymers and other nanomaterials. Due to the importance of polymeric nanocomposite for sensors, this novel overview has been expanded, focusing on nanocomposites based on conductive/non-conductive polymers filled with the nanocarbon/inorganic nanofillers. To the best of our knowledge, this article is innovative in its framework and the literature covered regarding the design, features, physical properties, and the sensing potential of multifunctional nanomaterials. Explicitly, the nanocomposites have been assessed for their strain-sensing, gas-sensing, bio-sensing, and chemical-sensing applications. Here, analyte recognition by nanocomposite sensors have been found to rely on factors such as nanocomposite design, polymer type, nanofiller type, nanofiller content, matrix–nanofiller interactions, interface effects, and processing method used. In addition, the interactions between a nanocomposite and analyte molecules are defined by high sensitivity, selectivity, and response time, as well as the sensing mechanism of the sensors. All these factors have led to the high-tech sensing applications of advanced nanocomposite-based sensors. In the future, comprehensive attempts regarding the innovative design, sensing mechanism, and the performance of progressive multifunctional nanocomposites may lead to better the strain-sensing, gas/ion-sensing, and chemical-sensing of analyte species for technical purposes. [ABSTRACT FROM AUTHOR]

Chlorine (Cl2), ammonia (NH3), and sulphur dioxide (SO2) are three typical toxic gases of tank-vehicle transportation. it is necessary to conduct online detection of these gases to ensure transportation safety and exhaust emission monitoring. In this study, tin dioxide (SnO2)n (n = 1–3) modified molybdenum (IV) telluride (MoTe2) monolayer were selected to explore its adsorption characteristics towards Cl2, NH3, and SO2 gases. All calculations are based on density function theory, geometric structure, charge transfer, adsorption energy, the density of states, and molecular orbitals were taken into account to compare and analyze the adsorption performance of the gas-sensing material before and after surface modification. The results show that these three gases are physically adsorbed on the intrinsic material. The modified (SnO2)n (n = 1–3) are all stably bound to the MoTe2 surface. For both Cl2 and NH3, the adsorption energies are in order of SnO2-MoTe2 > (SnO2)2-MoTe2 > (SnO2)3-MoTe2. And the adsorption energies for SO2 can be ranked as (SnO2)3-MoTe2 > SnO2-MoTe2 > (SnO2)2-MoTe2. The significant changes in electrical conductivity indicate the modified MoTe2 system consistently showed excellent sensitivity to the three gases. Therefore, the (SnO2)n-modified MoTe2 system is expected to be a candidate gas-sensing material for Cl2, NH3, and SO2, opening up a new perspective on MoTe2 in the field of gas detection.

TiOx films were prepared by gas impulse magnetron sputtering under oxygen-deficient (ODC) and oxygen-rich conditions (ORC) and annealing at 100–800 °C was used. The O2 content had an effect on their transparency level (Tλ). The films from the ORC mode had ca. Tλ = 60%, which decreased slightly in the VIS range after annealing. The film from the ODC mode had lower transmission (ca. <10%), which increased in the NIR range after annealing by up to ca. 60%. Differences in optical band gap (Egopt) and Urbach energy (Eu) were also observed. The deposition parameters had an influence on the microstructure of TiOx coatings. The ORC and ODC modes resulted in columnar and grainy structures, respectively. Directly after deposition, both coatings were amorphous according to the GIXRD results. In the case of TiOxORC films, this state was retained even after annealing, while for TiOxODC, the crystalline forms of Ti and TiO2-anatase were revealed with increasing temperature. Sensor studies have shown that the response to H2 in the coating deposited under oxygen-rich conditions was characteristic of n-type conductivity, while oxygen-deficient conditions led to a p-type response. The highest sensor responses were achieved for TiOxODC annealed at 300 °C and 400 °C. [ABSTRACT FROM AUTHOR]

In this study, a two-layered thin-film structure consisting of a dispersed nanoscaled Ag2O phase and SnO2 layer (SA) and a mono-composite film layer (CSA) consisting of a nanoscale Ag2O phase in the SnO2 matrix are designed and fabricated for NO2 gas sensor applications. Two-layered and mono-layered SnO2–Ag2O composite thin films were synthesized using two-step SnO2 and Ag2O sputtering processes and Ag2O/SnO2 co-sputtering approach, respectively. In NO2 gas-sensing measurement results, both SA and CSA thin films that functionalized with an appropriate Ag2O content exhibit enhanced gas-sensing responses toward low-concentration NO2 gas in comparison with that of pristine SnO2 thin film. In particular, a gas sensor made from the mono-composite SnO2–Ag2O layer demonstrates apparently higher NO2 gas-sensing performance than that of double-layered SnO2–Ag2O thin-film sensor. This is attributed to substantially numerous p–n junctions of Ag2O/SnO2 formed in the top region of the SnO2 matrix. The gas-sensing response of the optimal sample (CSA270) toward 10 ppm NO2 gas is 5.91, and the response/recovery speeds in a single cycle dynamic response plot are 28 s/168 s toward 10 ppm NO2, respectively. Such a p–n thin-film configuration is beneficial to induce large electric resistance variation before and after the introduction of NO2 target gas during gas-sensing tests. The experimental results herein demonstrate that the gas-sensing performance of p–n oxide composite thin films can be tuned via the appropriate design of composite thin-film configuration.

With the progression of society and the rise in human activities, the detrimental effects of atmospheric ammonia on humans and the environment have grown more severe. Given that ammonia is widely utilized in numerous industrial sectors as a gas and is also a highly toxic and corrosive substance posing threats to human health and the environment, there is an immediate requirement for highly sensitive, selective, and precise sensing techniques to enable effective detection of ammonia. In this study, a V 2 CT x @PANI composite was prepared and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and EDS mapping to confirm the successful combination of the two materials. The composite's sensing performance for ammonia gas at different concentrations (5–100 ppm) and room temperature was also evaluated. The results demonstrated that the V 2 CT x @PANI composite sensors exhibited significantly improved response to ammonia gas and faster response/recovery times compared to both the pristine V 2 CT x -based and pure PANI sensors. Additionally, the composite displayed good long-term stability and selectivity in sensing ammonia. The study also provides a systematic discussion of the sensing mechanism, attributing the enhanced performance to the formation of heterojunctions and an abundance of active sites. Furthermore, first-principles calculations of adsorption energy and density of states were used to demonstrate the high selectivity of V 2 CT x @PANI for ammonia. • V 2 CT x @PANI composite material synthesized by ultrasonic mixing method. • The sensor can be used for rapid detection of ammonia at room temperature. • The sensor has good reproducibility, stability and selectivity. • Heterojunction formation improves the ammonia response of the sensor. • High selectivity of the sensor for ammonia verified by DFT calculation. [ABSTRACT FROM AUTHOR]

H 2 S gas sensors with facile preparation, low detection limits, and high selectivity are crucial for environmental and human health monitoring. However, it is difficult to maintain a high response of H 2 S gas sensors under high humidity in practical applications. To face this dilemma, a layer-by-layer growth method is applied to in situ prepare a nanostructured Co(CO 3 ) 0.5 (OH)·0.11H 2 O/WO 3 coated by a hydrophobic hierarchical ZIF-67 as the H 2 S sensor. This novel composite exhibits excellent humidity immunity without sacrificing the excellent sensitivity and selectivity of H 2 S. At a low operating temperature of 90 °C, a remarkable response value of 1052.3 to 100 ppm H 2 S has been achieved, which is 779 and 9.36 times higher than that of pure WO 3 and Co(CO 3 ) 0.5 (OH)·0.11H 2 O/WO 3 , respectively. More importantly, an 82.2% relative response value remains at a high humidity of 75%RH. The sensing mechanisms are investigated using gas chromatography-mass spectrometry (GC-MS), which revealed that the reaction products are H 2 O and SO 2 . The high humidity immunity and fast response of the Co(CO 3 ) 0.5 (OH)·0.11H 2 O@ZIF-67/WO 3 demonstrate the layer-by-layer in situ synthesis method holds the potential application for the development of high-performance WO 3 -based H 2 S sensors., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

In the domain of gas sensing, metal oxide nanostructures have been demonstrated to have very attractive properties due to their large surface-over-volume ratio, combined with the possibility to use multiple materials and multi-functional properties. Here, we review the basic physical principles underlying the transducer function of metal oxide nanostructures, from single nanostructures to nanostructure networks. These principles have been adapted to describe the response of more complex nanostructures, such as heterostructures, combining two different metal oxide materials, or a metal with a metal oxide, in order to further enhance the sensitivity and selectivity of such devices. We finally present the activation of nanostructures by light exposure as a promising alternative to the standard method based on high temperature activation, which is earning increasing consensus in the perspective of low-power Internet of Things applications.

Among nanocomposite materials, multifunctional polymer nanocomposites have prompted important innovations in the field of sensing technology. Polymer-based nanocomposites have been successfully utilized to design high-tech sensors. Thus, conductive, thermoplast, or elastomeric, as well as natural polymers have been applied. Carbon nanoparticles as well as inorganic nanoparticles, such as metal nanoparticles or metal oxides, have reinforced polymer matrices for sensor fabrication. The sensing features and performances rely on the interactions between the nanocomposites and analytes like gases, ions, chemicals, biological species, and others. The multifunctional nanocomposite-derived sensors possess superior durability, electrical conductivity, sensitivity, selectivity, and responsiveness, compared with neat polymers and other nanomaterials. Due to the importance of polymeric nanocomposite for sensors, this novel overview has been expanded, focusing on nanocomposites based on conductive/non-conductive polymers filled with the nanocarbon/inorganic nanofillers. To the best of our knowledge, this article is innovative in its framework and the literature covered regarding the design, features, physical properties, and the sensing potential of multifunctional nanomaterials. Explicitly, the nanocomposites have been assessed for their strain-sensing, gas-sensing, bio-sensing, and chemical-sensing applications. Here, analyte recognition by nanocomposite sensors have been found to rely on factors such as nanocomposite design, polymer type, nanofiller type, nanofiller content, matrix–nanofiller interactions, interface effects, and processing method used. In addition, the interactions between a nanocomposite and analyte molecules are defined by high sensitivity, selectivity, and response time, as well as the sensing mechanism of the sensors. All these factors have led to the high-tech sensing applications of advanced nanocomposite-based sensors. In the future, comprehensive attempts regarding the innovative design, sensing mechanism, and the performance of progressive multifunctional nanocomposites may lead to better the strain-sensing, gas/ion-sensing, and chemical-sensing of analyte species for technical purposes.

The semiconductors based on lanthanum ferrite (LaFeO3) with perovskite structure have received increased attention for gas sensing, due to their stability and high gas-sensing response. However, it remains a challenge to design and fabricate LaFeO3-based gas sensors with high electrical conductivity and low prime working temperature. Based on this consideration, porous LaFeO3 hexagonal nano-sheets were prepared via thermal decomposition of La[Fe(CN)6]·5H2O, which was synthesized by a facile co-precipitation method. The LaFeO3 nano-sheets-based sensor possesses a relatively low resistance, which is 0.5 MΩ under air atmosphere at a low operating temperature of 100 °C, which means a low-power consumption. Moreover, the sensor exhibits an infrequent selectivity to n-propanol. This approach presents an effective way for the control and optimization of the rare earth perovskite nanomaterials for gas sensing. Gas sensor based on the fabricated porous LaFeO3 hexagonal nano-sheets presents a low resistance of 0.5 MΩ and a good sensing performance to n-propanol at a low working temperature of 100 °C. [ABSTRACT FROM AUTHOR]

In gas-insulated switchgear (GIS), partial discharge (PD) can be monitored by detecting sulfur hexafluoride-nitrogen (SF6-N2) decomposition components. In this paper, silver oxide (Ag2O) modification was introduced to improve the gas-sensing properties of graphene-like indium nitride (InN). The adsorption process of NO2, SO2F2, SOF2 and SOF4 on Ag2O-InN was simulated based on the first principles calculation and density functional theory (DFT). The gas sensing mechanism was revealed by density of states theory and molecular orbital theory. It is found that Ag2O doping greatly improves the adsorption properties of InN to NO2 and SOF2 molecules. The adsorption capacity of Ag2O-InN to the four gas molecules is: NO2 > SOF2 > SOF4 > SO2F2. All adsorptions can proceed spontaneously, and the gas molecules are electron donors and Ag2O-InN is an electron acceptor. Through the analysis of recovery time, it is found that NO2 is difficult to desorb from the substrate due to the significant adsorption energy of −2.201 eV, while SOF4, SOF2 and SO2F2 have a moderate adsorption energy of −0.185 eV, −0.754 eV and 0.173 eV and extremely short desorption time. The conductivity of the whole system changed after these four gases were adsorbed on the Ag2O-InN monolayer. In summary, Ag2O-InN can be used as NO2 adsorbent and gas sensors to detect SOF4, SOF2 and SO2F2. This paper provides a method for on-line monitoring of partial discharge in GIS. [ABSTRACT FROM AUTHOR]

A thin platinum oxide film was stacked on a tin oxide film, a well-known gas-sensing semiconductor, to improve its gas sensitivity. The response property to ethanol gas was enhanced by about three times by the stacking annealed at 600 °C. Post-annealing, platinum oxide was reduced to platinum and tin oxide was in a polycrystalline state. The results indicate that applying platinum oxide is effective in improving sensitivity when annealing at a high temperature of 600 °C is required for the fabrication of gas sensors. [ABSTRACT FROM AUTHOR]

The H2S concentration in exhaled breath increases marginally with the progress of periodontal disease, and H2S is considered to be one of the most important gases related to meat and seafood decomposition; however, the concentration of H2S is low and difficult to detect in such scenarios. In this study, Au–PrFeO3 nanocrystalline powders with high specific surface areas and porosities were prepared using an electrospinning method. Our experimental results show that loading Au on the material provides an effective way to increase its gas sensitivity. Au doping can decrease the material’s resistance by adjusting its energy band, allowing more oxygen ions to be adsorbed onto the material’s surface due to a spillover effect. Compared with pure PrFeO3, the response of 3 wt% Au–PrFeO3 is improved by more than 10 times, and the response time is more than 10 s shorter. In addition, the concentration of H2S due to the decomposition of shrimp was detected using the designed gas sensor, where the error was less than 15%, compared with that obtained using a GC-MS method. This study fully demonstrates the potential of Au–PrFeO3 for H2S concentration detection.

A Co2+:ZnS-doped chalcogenide glass with broadband mid-infrared emission was prepared by using a hot uniaxial pressing process. The refractive index difference (Δn) between matrix glass (As 2 S 5) and crystal (Co2+:ZnS) was controlled to be 0.0042 in the emission spectral range of Co2+ to minimize the scattering effect. An ultrabroadband mid-infrared emission of 2–4 μm was observed at room temperature in the samples after excitation by using a commercially available laser diode of 1550 nm. The significant changes in the lifetime and fluorescence intensity of Co2+:ZnS-doped chalcogenide glass were measured in the temperature range of 90–290 K. A resolution of approximately 0.18 K was observed when used as a temperature detector. Furthermore, a gas-sensing device was built by using the strong and broad emissions of the sample, and the detection sensitivity of butane reached 56 ppm. These results show that this glass-ceramics can be used as optical sensing of gas and temperature. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the gas‐sensing properties of copper oxide porous nanosheets in amorphous and highly crystalline states were comparatively investigated on the premise of almost the same specific surface area, morphology and size. Unexpectedly, the results show that amorphous copper oxide porous nanosheets have much better gas sensing properties than highly crystalline copper oxide to a serious of volatile organic compounds, and the lowest detection limit (LOD) of the amorphous copper oxide porous nanosheets to methanal is even up to 10 ppb. By contrast, the LOD of the highly crystalline copper oxide porous nanosheets to methanal is 95 ppb. Experiments prove that the oxygen vacancies contained in the amorphous copper oxide porous nanosheets play a key role in improving gas sensitivity, which greatly improve the chemical activity of the materials, especially for the adsorption of molecules containing oxygen‐groups such as methanal and oxygen.

TiOx films were prepared by gas impulse magnetron sputtering under oxygen-deficient (ODC) and oxygen-rich conditions (ORC) and annealing at 100–800 °C was used. The O2 content had an effect on their transparency level (Tλ). The films from the ORC mode had ca. Tλ = 60%, which decreased slightly in the VIS range after annealing. The film from the ODC mode had lower transmission (ca. gopt) and Urbach energy (Eu) were also observed. The deposition parameters had an influence on the microstructure of TiOx coatings. The ORC and ODC modes resulted in columnar and grainy structures, respectively. Directly after deposition, both coatings were amorphous according to the GIXRD results. In the case of TiOxORC films, this state was retained even after annealing, while for TiOxODC, the crystalline forms of Ti and TiO2-anatase were revealed with increasing temperature. Sensor studies have shown that the response to H2 in the coating deposited under oxygen-rich conditions was characteristic of n-type conductivity, while oxygen-deficient conditions led to a p-type response. The highest sensor responses were achieved for TiOxODC annealed at 300 °C and 400 °C.

FeVO4 nanoparticles are synthesized by the hydrothermal method. The effect of micromorphology under different pH conditions is investigated. Their microstructure, morphology, and chemical composition are analyzed by X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, and N2 adsorption–desorption. The results showed that an increase in pH leads to agglomeration of the material. The effect of different pH conditions on the gas‐sensitive performance of FeVO4 is subsequently investigated, and the best response performance of the FeVO4 sensor is achieved at a pH of 3. The consequences showed that the FeVO4 sensor has a response of 3.383 to 100 ppm ethanol gas, with the response and recovery time of 1 and 7 s. The response cycle test has proved that FeVO4 has good stability. Analyzed in conjunction with the characterization results, the oxygen vacancies on the surface of the nanoparticles not only improve the electronic conductivity but also provide active sites for the adsorption of gases, which helps to improve the sensitivity of the material to gases. [ABSTRACT FROM AUTHOR]

[Display omitted] • MoO 3 NC film with high-energy (0 6 0) crystal facet was realized using a gas-phase cluster beam deposition system by adding a small amount of helium to argon as a buffer gas into the aggregation chamber to influence the nucleation and growth of Mo NCs. • The increase in the number of dangling bonds and active site density allows high-energy crystal facets to reduce the energy barrier for oxygen adsorption, thus increasing the amount of adsorbed oxygen and improving gas-sensing performance. Adsorbed oxygen species on the surface of metal oxide semiconductors (MOS) play an important role in the field of gas-sensing. However, considering the large number of possible MOS, manipulating surface oxygen species by exposing high-energy crystal facets often requires strict experimental conditions and may not be efficiently repeated for nano MOS. This poses a huge challenge to the rational design of advanced gas-sensing materials. This study explores the fabrication of MoO 3 nanocluster (NC) film by cluster beam deposition. Helium (He) is co-fed with argon (Ar) into the aggregation chamber to influence the nucleation and growth of Mo NCs. This unique process facilitated the exposure of the high-energy (060) crystal facet in MoO 3 during the aging phase. This exposed crystal facet greatly reduces the oxygen adsorption energy barrier and increases the adsorbed oxygen content, resulting in a significant improvement in gas-sensing performance. The study examined the impact of energetic facets on gas sensor sensitivity by using ethanol, ammonia, and toluene as target gases. The results indicate that exposing high-energy crystal facets significantly enhances sensor performance. This approach to creating NCs with high-energy crystal facets has broad potential for advancing MOS nanostructure-based gas sensors. [ABSTRACT FROM AUTHOR]

The amalgamation of high-sensitivity gas sensors with neural electrical stimulation technology stands as a compelling solution for eliciting behavioral responses in the presence of low-level hazardous gases. The utilization of battery-powered or coil-based configurations introduces spatiotemporal limitations, encompassing constrained experimental durations due to battery life or the necessity to confine subjects to specific locales for wireless power transmission. In this study, we present an advanced wireless neural modulator, meticulously engineered for behavioral intervention in unrestricted environments. This device integrates a solar-powered unit, gas sensor, brain stimulation signal management system, and a neurostimulation electrode. The solar energy utilization eliminates the necessity for battery replacements and local range limitations. The surface of the solar cells is treated with a superhydrophobic coating, enhancing performance in outdoor settings by mitigating surface contamination issues inherent in traditional solar cells. This innovation guarantees continuous, long-term, on-demand operational capacity, ensuring uninterrupted power supply to the system. Experimentation revealed shortened locomotor activity in mice, induced by stimulation of the periaqueductal gray (PAG) brain region, for up to thirty minutes. These results underscore the significant potential of our technology for spatially and temporally unrestricted neuromodulatory applications, offering a viable strategy to alleviate the detrimental effects of hazardous gas exposure on physiological functions. [Display omitted] ● Solar Flexibility: Solar energy allows for free movement outdoors, removing the limitations of fixed power sources. ● Durable Panels: Superhydrophobic coatings protect solar panels from dirt, keeping them efficient. ● Sensitive Gas Detection: Advanced sensors in the system detect low levels of harmful gases, helping prevent health risks. [ABSTRACT FROM AUTHOR]

In gas-insulated switchgear (GIS), partial discharge (PD) can be monitored by detecting sulfur hexafluoride-nitrogen (SF6-N2) decomposition components. In this paper, silver oxide (Ag2O) modification was introduced to improve the gas-sensing properties of graphene-like indium nitride (InN). The adsorption process of NO2, SO2F2, SOF2 and SOF4 on Ag2O-InN was simulated based on the first principles calculation and density functional theory (DFT). The gas sensing mechanism was revealed by density of states theory and molecular orbital theory. It is found that Ag2O doping greatly improves the adsorption properties of InN to NO2 and SOF2 molecules. The adsorption capacity of Ag2O-InN to the four gas molecules is: NO2 > SOF2 > SOF4 > SO2F2. All adsorptions can proceed spontaneously, and the gas molecules are electron donors and Ag2O-InN is an electron acceptor. Through the analysis of recovery time, it is found that NO2 is difficult to desorb from the substrate due to the significant adsorption energy of −2.201 eV, while SOF4, SOF2 and SO2F2 have a moderate adsorption energy of −0.185 eV, −0.754 eV and 0.173 eV and extremely short desorption time. The conductivity of the whole system changed after these four gases were adsorbed on the Ag2O-InN monolayer. In summary, Ag2O-InN can be used as NO2 adsorbent and gas sensors to detect SOF4, SOF2 and SO2F2. This paper provides a method for on-line monitoring of partial discharge in GIS.

Real-time monitoring of SF6 status is of exceptional importance to ensure stable operation of the power system, to promptly diagnose whether an insulation failure has occurred and to assess the severity. Considering the excellent physicochemical properties and insulation defects of hexagonal boron nitride, the strategy of surface modification, namely, hydrogenation, fluorination, and combinations of the two ways, is proposed to improve its chemical activity, and the gas-sensing potential of the most effective one is investigated using density functional theory. The typical adsorption models of SF6 decomposition component gases on the surface of F-BN-H are constructed, and the most stable adsorption structures with their density of states, molecular orbitals, and sensing responses are analyzed. The results show that F-BN-H has good sensitivity to decomposition components of SF6. To be specific, SO2 and SOF2 have good adsorption properties, prominent charge transfer, and distinct change in electronic properties. The response of gas adsorption can be detected timely by the change in conductivity, and, additionally, the adsorbent has fast desorption capacity at room temperature. These results indicate that the F-BN-H-based gas sensor is a qualified potential candidate with dependable application and recoverability for detecting SF6 decomposition in high-voltage insulated equipment. [ABSTRACT FROM AUTHOR]

ZnSnO 3 hollow spheres were successfully synthesized via a mild hydrothermal strategy followed by an annealing process. Their microstructures, morphologies and chemical compositions were characterized by a variety of techniques, including X-ray diffraction, transmission electron microscopy and N 2 adsorption-desorption. Due to rapid co-precipitation and self-assembly, a resultant hollowing process was achieved, and ZnSnO 3 particles were reorganized into hollow structures. Furthermore, the possible formation mechanism was interpreted by means of several experiments under different reaction conditions. The as-fabricated ZnSnO 3 sensors with hollow interiors and permeable surfaces were investigated with six volatile gases, which exhibited fast response and high selectivity to n-butanol at the much-lowered optimal temperature of 200 °C. In particular, the response time of the sensors based on ZnSnO 3 hollow spheres was 3 s, implying that they are a potential candidate for n-butanol gas detection. In addition, the gas-sensing mechanism of the ZnSnO 3 sensor was also investigated. [ABSTRACT FROM AUTHOR]

The suitability of embedding metal atoms (Ca versus Mn) in the pores of C 2 N to be employed as the anode material for metal-ion battery applications is studied using density-functional theory. The effect of single-atom catalyst (SAC) versus dimer-atom catalyst (DAC) on the uptake catalyst capacity is put under focus. Our results show that both metal atoms exhibit very strong interactions with the pyridinic-nitrogen pore and show the ability of the pore to accommodate either a single Ca atom or a dimer of Mn atoms within its membrane-plane. While the theoretical irreducible capacitance in case of SAC Ca catalyst is limited to about 200 mAhg−1, it can exceed this value in case of DAC-Mn catalyst to reach 1110 mAhg−1. Regarding the adsorption, the H 2 molecule exhibits strong physisorption on Ca-catalyst and moderate chemisorption on Mn-catalyst, with an adsorption energy increasing from SAC to DAC cases. The SAC of Mn is found not only concurrent candidate to Ca for energy-storage applications but further promising for platform of reusable hydrogen gas-sensors with very low recovery time (i.e., τ « 1 s). Our findings are in good agreement with the available experimental data and theoretical results. Image 1 • DFT study of hydrogen adsorption on Metal-catalyst embedded (Ca versus Mn) C 2 N at Room Temperature. • Ca has E coh < E bind in C 2 N, thus, is relevant for energy storage but only SAC can be used for irreducible uptake capacity. • Mn SAC & DAC have cohesive energy < binding energy to C 2 N, thus, is concurrent to Ca for MIBs applications. • Mn DAC showed even higher irreversible uptake capacity (1110 mAhg-1) than Ca SAC (200 mAhg−1). • C 2 N:Mn showed potential for reusable magnetic hydrogen gas sensor with high sensor response and low recovery time. [ABSTRACT FROM AUTHOR]

Lithium iron phosphate (LiFePO4) membranes were fabricated by coating LiFePO4 particles dispersed in various dispersants on tin-diffused glass slides and alumina ceramic tubes for xylene gas detection. The influences of dispersants, including polyvinyl alcohol (PVA), sodium dodecylbenzene sulfonate (SDBS), and methyl methacrylate (MMA), on the optical properties and opto-electrical gas-sensing performance of the LiFePO4 particle-based membranes were investigated. The LiFePO4 particle-based membrane, prepared using PVA, exhibited less agglomeration, better transparency, optimum refractive index, and a higher response toward xylene gas at concentrations of 10 ppb to 1000 ppm in a planar optical waveguide sensor. However, in a resistance-type electrochemical sensing system at room temperature, the LiFePO4-PVA membrane exhibited low response even at high xylene concentrations. The membranes sensitivities increased in the order MMA < SDBS < PVA. After dispersing in PVA, the membrane sensitivity toward xylene was increased ~ 100 times, proving the positive effects of PVA on the optical properties and gas-sensing performance of LiFePO4 particles. [ABSTRACT FROM AUTHOR]

Gas-sensing properties of nitrogenated holey graphene (C 2 N), graphdiyne (GDY) and their van der Waals heterostructure (C 2 N...GDY) have been studied towards particular volatile organic compounds (VOCs) by means of spin-polarized, dispersion-corrected DFT calculations. We find that VOCs such as acetone, ethanol, propanal, and toluene interact weakly with the GDY monolayer; however, the bindings are significantly enhanced with the C 2 N monolayer and the hybrid C 2 N...GDY heterostructure in AB stacking. Electron localization function (ELF) analysis shows that all VOCs are van der Waals bound (physical binding) to the 2D materials, which result in significant changes of the charge density of C 2 N and GDY monolayers and the C 2 N...GDY heterostructure. These changes alter the electronic properties of C 2 N and GDY, and the C 2 N...GDY heterostructure, upon VOC adsorption, which are investigated by density-of-states plots. We further apply thermodynamic analysis to study the sensing characteristics of VOCs under varied conditions of pressure and temperature. Our findings clearly indicate that the C 2 N...GDY heterostructure is a promising material for sensing of certain VOCs. Image 1063 [ABSTRACT FROM AUTHOR]

The fundamental aspects, including geometric structure, adsorption energy, thermodynamic properties, charge transfer, and magnetic properties of carbon nitride C 2 N and double-atom catalyst (Fe 2 @C 2 N) monolayers with the adsorption of CO, NO, HCN, CS 2 , and SO 2 molecules, were investigated using DFT and DFT-D3 correction dispersion methods. Compared to pristine C 2 N, the Fe 2 @C 2 N monolayer is more energetically efficient with high adsorption energies and has apparent charge transfer with these toxic gases. Our results revealed that NO preferred to be adsorbed on the Fe 2 @C 2 N with a superior E ads of −7.006 eV. The electric conductivity, sensitivity, and selectivity of C 2 N are significantly influenced by CO, NO, HCN, CS 2 , and SO 2 molecules. Moreover, the opening of band gaps induced by the adsorption of NO gas molecules at Fe 2 @C 2 N can be used as an electronic signal to detect NO gas. Intriguingly, the partial density of states (PDOS) indicated that the NO adsorption of pristine C 2 N and Fe 2 @C 2 N monolayers exhibited half-metallicity behavior and magnetic properties. Non-covalent interactions (NCI) and the quantum theory of atoms in molecules (QTAIM) descriptors were examined to analyze the interaction process. This study can provide a new avenue for synthesizing and developing highly sensitive candidates and inexpensive green double-atom catalysts to capture and detect CO, NO, HCN, CS 2 , and SO 2 molecules from the atmosphere at ambient temperature. [Display omitted] • Sensing characteristics of Fe 2 @C 2 N to CO, NO, HCN, CS 2, and SO 2 were investigated. • A new avenue to sense and capture toxic gases at ambient temperature was outlined. • NO gas is preferred to be adsorbed on the Fe 2 @C 2 N with superior E ads. • Induced band-gaps can use as an electronic signal to detect NO gas at Fe 2 @C 2 N. • The ON@Fe 2 @C 2 N could provide useful information for designing spintronic devices. [ABSTRACT FROM AUTHOR]

Bi2MoO6 nanosheets were synthesized by a hydrothermal method. Morphology and structure of the Bi2MoO6 nanosheets were analyzed by SEM, XRD, N2 adsorption techniques and XPS. Gas-sensing properties of the as-prepared Bi2MoO6 sensors were also systematically investigated. The results showed the reaction temperature greatly affected the morphology and structure of as-prepared Bi2MoO6 nanosheets. When the reaction temperature reached 170 ºC, the morphology of the Bi2MoO6 nanosheets tended to regular, and pure Bi2MoO6 nanosheets were obtained. The operating temperature determined the gas-sensing properties of the Bi2MoO6 sensor. At this optimal operating temperature of 300 ºC, the sensitivity of the Bi2MoO6 sensor towards 20 ppm nitrogen oxide (NO) reached a maximum of 3.13. With the increase of the nitrogen oxide (NO) concentration, the sensitivity of the Bi2MoO6 sensor also rapidly increased, and displayed an almost linear relationship between them. Additionally, the Bi2MoO6 sensor demonstrated excellent selectivity with respect to several typical interfering gases.

Controlling environmental pollution is a burning problem for all countries more than ever. Currently, due to the increasing industrialization, the number of days when the limits of air pollutants are over the threshold levels exceeds 80–85% of the year. Therefore, cheap and effective sensors are always welcome. One idea is to combine such solutions with cars and provide real-time information about the current pollution level. However, the environmental conditions are demanding, and thus the developed sensors need to be characterized by the high 3S parameters: sensitivity, stability and selectivity. In this paper, we present the results on the heterostructure of CuO/SnOx and SnOx/CuO as a possible approach for selective NO2 detection. The developed gas sensors exhibited lower operating temperature and high response in the wide range of NO2 and in a wide range of relative humidity changes. Material characterizations and impedance spectroscopy measurements were also conducted to analyze the chemical and electrical behavior.

Ultrafine WO 3−x (0 < x < 1) nanowires with aspect ratio greater than 100 were successfully synthesized by two-phase strategy. The crystal structure, morphology evolution and thermal stability of the samples were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectrum (XPS), high resolution transmission electron microscopy (HRTEM), and thermal gravimetric analysis (TGA). The morphology of WO 3−x nanowires is closely related to the pH value and oleamine content of the reaction system. By controlling the reaction conditions, a linear product with a diameter of less than 2 nm can be obtained, and the exposed active lattice plane is 110 crystal face. On this basis, the prepared ultrafine WO 3−x nanowire sensor was tested for a series of harmful gases. The sensitivity of WO 3−x -based gas sensors can reach 57.9 for 10 ppm NO 2 at 100 °C, which is much higher than most reported values. The sensor has the excellent sensing performance of ppm NO 2 at low operating temperature, which is due to its nanowire structure and oxygen vacancies. These results demonstrate that this type of sensor is a competitive candidate for NO 2 -sensing applications. [ABSTRACT FROM AUTHOR]

A new type of multi‐metal oxide gas‐sensing material, CoSnO3 was synthesized by a simple hydrothermal method, in which CoSn(OH)6 was used as a precursor, and it was calcined into amorphous CoSnO3. The CoSnO3 nanoparticles were characterized by means of XRD, FE‐SEM, TEM and N2 adsorption‐desorption analysis. The average size of the CoSnO3 nanoparticles was of 90 nm. The sensor based on the CoSnO3 nanoparticles showed good gas‐sensing performances to n‐butanol. The highest response was about 23 to 100 ppm n‐butanol at 200 °C. Moreover, CoSnO3 nanoparticles exhibits promising candidate material for fast, sensitive and selective detection of n‐butanol. [ABSTRACT FROM AUTHOR]

Three kinds of polyhedral α‐Fe2O3 nanoparticles enclosed by different facets including oblique parallel hexahedrons (op‐hexahedral NPs), cracked oblique parallel hexahedrons (cop‐hexahedral NPs), and octadecahedral nanoparticles (octadecahedral NPs), were successfully prepared by simply changing only one reaction parameter in the hydrothermal process. The structural and morphological of the products were systematically studied using various characterizations including X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), revealing that the three kinds of α‐Fe2O3 nanoparticles were enclosed by {104}, {110}/{104}, and {102}/{012}/{104} crystal planes, respectively. The exposed facets and shape of the nanocrystals were found to be affected by the adding amount of ethylene glycol in the solvent. The gas‐sensing properties and mechanism of the α‐Fe2O3 samples were studied and analyzed, which indicated that the sensitivity of the three samples followed the order of octadecahedral NPs > cop‐hexahedral NPs > op‐hexahedral NPs due to the combined effects of specific surface area and oxygen defects in the nanocrystals. [ABSTRACT FROM AUTHOR]

Highlights • Porous 3D SnO 2 are synthesized via a facile hydrothermal method. • Compared with some previous studies, 3D SnO 2 has improved gas sensitivity to CH 4. • The CH 4 sensor has good linear relationship in a wider range of gas concentration. Abstract Porous three-dimensional (3D) hierarchical flower-like SnO 2 nanomaterials were successfully synthesized via facile hydrothermal method combined with subsequent annealing process. Characterization analysis shows that the porous 3D SnO 2 consists of a number of thin nanosheets with pores. Gas sensing properties indicate that the porous 3D SnO 2 sensor has lower initial response temperature and optimal working temperature, better linearity in a certain range of gas concentration, better stability and selectivity to methane. Implies that porous 3D SnO 2 nanomaterials will be promising candidates for methane sensors. [ABSTRACT FROM AUTHOR]

This work reports a facile glycerol-assisted solvothermal method for synthesizing hierarchical three-dimensional (3D) wool-ball-like zinc oxide (ZnO) nanostructures and their subsequent modifications with multi-walled carbon nanotubes (MWCNTs) as modifiers for achieving sensitive and selective detection of toxic sulfur dioxide (SO 2 ) gas. Structurally, the as-synthesized 3D wool-ball-like ZnO is assembled of two-dimensional (2D) plate-like structures, which themselves are arranged by numerous small nanoparticles. Furthermore, in this work we observed an interesting new phenomenon in which when a high concentration of MWCNTs is introduced, many small nanorods grew on the surface of the plate-like structures which assemble the 3D wool-ball-like ZnO nanostructures. When evaluated for SO 2 detection, the ZnO/MWCNTs (10:1) composite (ZnO:MWCNTs = 10:1) shows a high response of 220.8 to 70 ppm of SO 2 gas (approximately three times higher than the response of pure wool-ball-like ZnO) at an optimum operating temperature of 300 °C. Additionally, the composite also displays good stability and selectivity to SO 2 with the response to 50 ppm of SO 2 being 7–14 times higher than the responses to other tested gases at a similar concentration. The excellent sensing performance of the wool-ball-like ZnO/MWCNTs (10:1) composite is mainly attributed to: (i) the formation of p - n heterojunctions at the ZnO/MWCNTs interfaces, which greatly enhance the resistance changes upon exposure to SO 2 gas and (ii) the increased amount of adsorption sites for O 2 and SO 2 gas molecules owing to the larger surface area of the composite and defects sites generated by the functionalization process of MWCNTs. [ABSTRACT FROM AUTHOR]

Hierarchical porous and non-porous ZnO microflowers have been successfully fabricated by hydrothermal method. Their crystal structure, morphology and gas-sensing properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical gas sensing intelligent analysis system (CGS). Compared with hierarchical non-porous ZnO microflowers, hierarchical porous ZnO microflowers exhibited ultra-high sensitivity with 50 ppm ethanol at 260 °C and the response is 110, which is 1.8 times higher than that of non-porous ZnO microflowers. Moreover, the lowest concentration limit of hierarchical porous ZnO microflowers (non-porous ZnO microflowers) to ethanol is 0.1 (1) ppm, the response value is 1.6 (1). [ABSTRACT FROM AUTHOR]

Using density functional theory (DFT), we investigated and discussed the adsorption characteristics, gas-sensing response and gas-sensing mechanism of NO molecule on α-Fe 2 O 3 (0 0 1) surface with and without oxygen defect (V O ). The pure and oxygen-defective α-Fe 2 O 3 (0 0 1) surface exhibited opposite electron transfer. The theoretical results proved that the NO molecule acted as a donor for pure α-Fe 2 O 3 (0 0 1) surface. However, it failed to explain the increasing resistance of n-type metal oxide materials. For oxygen-defective α-Fe 2 O 3 (0 0 1) surface, NO molecule acted as an acceptor. The results leaded to a decreasing electron-carrier concentration, and then resulted in an increasing resistance of oxygen-defective α-Fe 2 O 3 (0 0 1) surface after NO molecule was introduced into. The direction of electron transfer was reversed by oxygen defect. In addition, the V O -NO adsorption configuration induced more stable adsorption structure and more significant electron transfer effects between NO molecule and oxygen-defective α-Fe 2 O 3 (0 0 1) surface. The V O -NO adsorption configuration would have better gas-sensing performance for α-Fe 2 O 3 (0 0 1) surface. [ABSTRACT FROM AUTHOR]

Loading of noble metal nanoparticles (NPs) on the surfaces of semiconductor oxides to form a hybrid nanostructure is an effective strategy to improve gas-sensing performance. In this study, WO 3 nanoplatelets decorated with Au NPs were prepared by laser ablation in liquids (LAL) with subsequent aging and annealing treatments. Results indicated that Au NPs with an average size of 7.8 ± 2.5 nm were highly dispersed on the surface of WO 3 nanoplatelets. As gas-sensing materials, the obtained Au-decorated WO 3 nanoplatelets showed lower operating temperature of 320 °C and higher response value of 3.5-fold in detecting ethanol molecules compared with pure WO 3 nanoplatelets. Moreover, Au-decorated WO 3 nanoplatelets displayed good selectivity toward ethanol compared with other tested vapors and excellent stability within several cycled measurements. These results can be ascribed to the supported Au NPs, which promote the adsorption and dissociation of oxygen species, eventually resulting in accelerated electron depletion on the surface of Au–WO 3 hybrids. [ABSTRACT FROM AUTHOR]

Ultrafine nanoparticles conglomerated α-Fe 2 O 3 nanospheres were synthesized by laser irradiation of Fe(CO) 5 in acetone. As-prepared products were characterized by transmission electron microscopy, scanning electron microscopy and X-ray diffraction analysis techniques. Such obtained α-Fe 2 O 3 nanospheres were used as gas-sensing materials, which exhibit good selectivity, fast response and excellent cycle performance to ethanol molecules. [ABSTRACT FROM AUTHOR]

Facile synthesis of 3D flower-like Fe 2 (MoO 4 ) 3 with dominant exposed (100) facets has been achieved by adjusting pH and hydrothermal time. The 3D Fe 2 (MoO 4 ) 3 was characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, and nitrogen adsorption–desorption technique. Results demonstrated the 3D Fe 2 (MoO 4 ) 3 was mesoporous structures composed by nanosheets. As compared with the routine Fe 2 (MoO 4 ) 3 nanosheets, the synthesized Fe 2 (MoO 4 ) 3 with dominant exposed (100) facets shows excellent gas-sensing performance due to the high chemical activity of the exposed (100) facets. The enhancement in the gas-sensing performance suggests that the effect of exposed facet is dominant rather than the size effect, specific surface area. In addition, the 3D flower-like Fe 2 (MoO 4 ) 3 exhibits gas sensing selectivity to xylene, the selectivity should be originated from the surface structure of Fe 2 (MoO 4 ) 3 at the atomic level. Fe 2 (MoO 4 ) 3 has many Mo 6+ active sites from Mo-O tetrahedrons on the surface, which act as catalyst for xylene absorbing and reacting with absorbed oxygen ion. The sensor based on the 3D flower-like Fe 2 (MoO 4 ) 3 is a promising candidate for fast, sensitive and selective detection of xylene. [ABSTRACT FROM AUTHOR]

We carried out first-principle calculations with density functional theory to discuss adsorption properties, gas-sensing performance and mechanism of CO on pure and oxygen-defective α-Fe 2 O 3 (1 1 0) surface. For pure and oxygen-defective α-Fe 2 O 3 (1 1 0) surfaces, new formed CO 2 acted as donors. The electron-transfer effects leaded to an increasing electron-carrier concentration, and resulted in a decreasing resistance of α-Fe 2 O 3 (1 1 0) surface. The results successfully explained the decreasing resistance of gas sensors based on n-type α-Fe 2 O 3 materials. However, our theoretical results demonstrated the oxygen defect in α-Fe 2 O 3 (1 1 0) surface failed to induce more stable adsorption structure and more electron-transfer effects. [ABSTRACT FROM AUTHOR]