Search

Two‐dimensional materials exhibit significant potential and wide‐ranging application prospects owing to their remarkable tunability, pronounced quantum confinement effects, and notable surface sensitivity. The switching, optoelectronics, and gas‐sensitive properties of the new carbon material poly‐cyclooctatetraene framework (PCF)‐graphene were systematically studied using density functional theory combined with the nonequilibrium Green's function method. First, the diode device based on PCF‐graphene monolayer exhibited an impressive switching ratio of 106, demonstrating excellent diode characteristics. Moreover, in the investigation of the pin junction utilizing monolayer PCF‐graphene, it is noteworthy that significant photocurrent responses were observed in both the zigzag and armchair directions, specifically within the visible and ultraviolet regions. Finally, gas sensors employing monolayer and bilayer PCF‐graphene demonstrate significant chemical adsorption capabilities for NO and NO2. Notably, the maximum gas sensitivity for NO is achieved in monolayer PCF‐graphene, reaching 322% at a bias voltage of 1.0 V. Meanwhile, for bilayer PCF‐graphene‐based gas sensor, the maximum gas sensitivity reaches 52% at a bias voltage of 0.4 V. In addition, the study also examined the influence of various environmental conditions, specifically H2O, O, and OH, on the system under investigation. The obtained results emphasize the multifunctional properties of PCF‐graphene, exhibiting significant potential for various applications, including switching devices, optoelectronic devices, and gas sensors. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Remote Sensing is the property of Editorial Office of Journal of Remote Sensing & Science Publishing Co. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The ZnO−SnO2 nanocomposite has been synthesized using the simple and low‐cost co‐precipitation method. The physicochemical characterization of the prepared nanocomposites was carried out by using X‐ray diffraction (XRD), Field Emission Scanning Electron Microscope (FE‐SEM), High‐resolution Transmission Electron Microscopy (HR‐TEM), Energy Dispersive X‐ray analysis (EDAX) and UV‐visible spectroscopy techniques. In XRD confirmed that, hexagonal wurtzite phase of ZnO with the tetragonal rutile phase of SnO2 was found to be in the pure form. The particle size of the ZnO−SnO2 nanocomposite was fund to be ~23 nm in size. The nano cubes like surface morphology of the ZnO−SnO2 nanocomposite has been investigated using FESEM. Based on this various characterization, the ZnO−SnO2 nanocomposite has been used for the development of the chemiresistive gas sensor application. The gas sensitivity is found to be 29.30 % for 100 ppm NO2 gas at 200 °C operating temperature. This work has been used for the development of gas sensor devices for practical application. [ABSTRACT FROM AUTHOR]

The gas sensitivity of platinum doped TiO2 (101) to two kinds on polyvinyl chloride decomposition production, CO and HCl, were explored based on density functional theory. The binding energy, adsorption distance, charge transfer, and density of states distribution were simulated and discussed. The results suggest that the O oriented mode is probably the best mode for the CO gas molecules adsorption on the Pt-TiO2 and H oriented mode for the HCl adsorption system. HCl and CO molecules obtain electrons from Pt doped TiO2 surface. At room temperature, the recovery time of CO and HCl is 1.9743 × 10-10, 1.2094 × 10-10 respectively. HCl is easier to dissociate from Pt doped TiO2 surface with a little lower energy barrier compared to CO. This work provides theoretical adsorption information of Pt-TiO2 as gas sensor material for HCl and CO detection in the application of online condition monitoring and defect diagnosis in the power cables.

Two-phase thin-film composites consisting of CdxPb1 –xS (0.007 ≤ x ≤ 0.068) substitutional solid solutions with a B1 cubic structure (sp. gr. ) and amorphous cadmium sulfide (CdS) have been produced by chemical deposition. The surface topography of the films has been studied by atomic force microscopy, and the results have been used to calculate surface microtopography parameters. A correlation has been found between the composition and functional properties of thin CdS–PbS films. The sensitivity of CdxPb1 –xS/CdS two-phase films to ammonia (NH3) in air has been assessed for the first time. The room-temperature detection limit for ammonia has been determined to be 10 ppm (6.22 mg/m3). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Porous nanocomposites using two (tin dioxide–silica dioxide) and three (tin dioxide–indium oxide-silica dioxide)-component systems for gas sensors were created with the sol–gel method. To understand some of the physical–chemical processes that occurred during the adsorption of gas molecules on the surface of the produced nanostructures, two models—the Langmuir model and the Brunauer–Emmett–Teller theory—were used to carry out calculations. The results of the phase analysis concerning the interaction between the components during the formation of the nanostructures were obtained through the use of X-ray diffraction, thermogravimetric analysis, the Brunauer–Emmett–Teller technique (to determine the surface areas), the method of partial pressure diagrams in a wide range of temperatures and pressures and the results of the measurement of the nanocomposites' sensitivity. The analysis allowed us to find the optimal temperature for annealing nanocomposites. The introduction of a semiconductor additive into a two-component system based on tin and silica dioxides significantly increased the sensitivity of the nanostructured layers to reductional reagent gases. [ABSTRACT FROM AUTHOR]

In order to improve the response characteristics of the surface acoustic wave (SAW) sensor to trace gases, a SAW CO gas sensor based on a Pd–Pt/SnO2/Al2O3 film with a high-frequency response performance is proposed in this paper. The gas sensitivity and humidity sensitivity of trace CO gas are tested and analyzed under normal temperatures and pressures. The research results show that, compared with the frequency response of the Pd–Pt/SnO2 film, the CO gas sensor based on a Pd–Pt/SnO2/Al2O3 film has a higher frequency response performance, and the sensor has high-frequency response characteristics to CO gas with a concentration in the range of 10–100 ppm. The average response recovery time of 90% ranges from 33.4 s to 37.2 s, respectively. When the CO gas with a concentration of 30 ppm is tested repeatedly, its frequency fluctuation is less than 5%, indicating that the sensor has good stability. In the range of relative humidity (RH) from 25% to 75%, it also has high-frequency response characteristics for CO gas with a 20 ppm concentration. [ABSTRACT FROM AUTHOR]

In this study, SnO2-Pd nanoparticles(NPs) were made with an in situ synthesis-loading method. The in situ method is to simultaneously load a catalytic element during the procedure to synthesize SnO2 NPs. SnO2-Pd NPs were synthesized by using the in situ method and were heat-treated at 300 °C. As a result, tetragonal structured SnO2-Pd NPs, having an ultrafine size of less than 10 nm and a uniformly distributed Pd catalyst in the SnO2 lattice, were well made and a gas sensitive thick film with a thickness of c.a. 40 μm was well fabricated by using the NPs. Gas sensing characterization for CH4 gas indicated that the gas sensitivity, R3500/R1000, of the thick film consistent with SnO2-Pd NPs synthesized with the in situ synthesis-loading method, followed by heat-treatment at 500 °C, was enhanced to 0.59. Therefore, the in situ synthesis-loading method is available for synthesis of SnO2-Pd NPs for gas sensitive thick film. [ABSTRACT FROM AUTHOR]

In this study, a BaTiO3/Ag/WO3 nanocomposite was chemically synthesized for its gas sensing properties towards LPG. The formation of the novel BaTiO3/Ag/WO3 nanocomposite was confirmed by XRD, TEM and FTIR analyses using the peak positions, observed planes, and existing vibrational bands, respectively with, Ag NPs of ~ 24 nm. The direct band gap 3.1 eV and absorption edge (411 nm) of the BaTiO3/Ag/WO3 nanocomposite were determined using UV–Vis spectroscopy. The vibrational bands at 471, 504, 804, and 1636 cm−1 are attributed to the interaction of silver with O–W–O and W–O–W in WO3, Ti–O in BTO, and C–O, respectively in the BTO/Ag/WO3 nanocomposite. The higher dielectric constant and activation energy were estimated to be 2342 and 9.7 meV respectively. The sensitivity towards LPG at high temperature was ~ 99% with ~ 88 µA Ia.c., while a.c. conductivity was very small at high temperatures. Long-time stability (30 days) with lower response time (10-4 s) and recovery time (17–21 s) were achieved. The limit of detection for LPG was found 205 ppm. [ABSTRACT FROM AUTHOR]

The prime objective of the current research was to analyze and utilize the coexistence of basic and acidic metal oxide semiconductors (MOS) for sensing pollutant gases. In the current work, 1 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, and 9 wt.% NiO (basic MOS) was added to MoO3 (acidic MOS), and thick films were prepared using the screen printing technique. Structural characterization was performed by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray analysis (EDAX). The crystallite size was about 50 nm, with intermediate voids. EDAX analysis confirmed the non-stoichiometric composition of the films. The films were oxygen-deficient as per EDAX data. An electrical analysis involving resistivity, temperature coefficient of resistance (TCR), and activation energy was also performed. NiO3 samples showed maximum resistivity of 103.13 × 104 Ω·m and minimum activation energy of 0.3953 eV. The electrical analysis predicted the distinct behavior of the NiO3 sample. A negative TCR value indicated the semiconductor-like behavior of the samples. The pollutant gas response of the samples was analyzed using a static gas sensing apparatus. NiO3 samples showed gas sensitivity of 87% towards the ethanol vapors, with good selectivity, as compared with the responses towards CO, liquid petroleum gas (LPG), NH3, and NO2 gases. The oxygen vacancy-based gas sensing mechanism was the probable reason for the improved ethanol vapor sensing. The response time of the sample was 28 s, while the recovery time was 38 s. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Semiconductor metal oxide films on the surface of gallium arsenide are obtained by chemostimulated oxidation under the influence of a Sb2O3 + Y2O3 composition. The chemical composition of the obtained films and the surface morphology are determined by EPXMA, IR spectroscopy, and AFM. The main components of the films are gallium and arsenic, which are in the oxidized state. The content of the chemical stimulator (Sb2O3) does not exceed 2%. Films obtained under the influence of composites 60% Sb2O3 + 40% Y2O3 and 80% Sb2O3 + 20% Y2O3 are characterized by the maximum surface roughness. The samples obtained in this work demonstrate n-type semiconductor properties in the temperature range of 20–400 °C. It is established that the obtained samples have a gas-sensitive response to NH3 and CO. The maximum value of the sensory signal appears for the samples obtained under the influence of compositions 80% Sb2O3 + 20% Y2O3, which are characterized by the most developed surfaces. The resulting films are selective to the studied gases—the difference in temperature for the maximum signal is 60 °C (200 °C for CO and 260 °C for NH3). [ABSTRACT FROM AUTHOR]

The development of highly sensitive, selective, and reusable gas sensing devices is crucial for the detection of toxic gases in the environment. Here, we using density-functional theory and the nonequilibrium Green function method to investigate the electronic properties of two-dimensional (2D) Dirac cone Borophosphene (BP) monolayer and its application in gas sensors. Our results reveal that the pristine BP nanodevice exhibits significant anisotropic transport properties at low bias voltage, with the maximum anisotropy ratio reaching on the order of 105, which far exceeding that of BC 5 monolayer and biphenylene network monolayer. Moreover, C 2 H 2 , C 2 H 4 , and HCHO exhibit chemical adsorption on BP monolayer, while CH 3 OH and CH 4 demonstrate physical adsorption. The transport characteristics of BP monolayer nanodevices are highly influenced by the adsorption of C 2 H 2 , C 2 H 4 , and HCHO, indicating the potential of BP monolayer in constructing gas sensors for detecting these gas molecules. In addition, the BP-based gas sensor displays enhanced sensitivity towards HCHO and C 2 H 4 , with gas sensitivities along the zigzag and armchair directions reaching 61 % and 215 %, respectively. Furthermore, the study also examined the influence of various environmental conditions, specifically O 2 and H 2 O on the system under investigation. Finally, by analyzing the local density of states in the zigzag and armchair directions of the BP-based gas sensors after HCHO and C 2 H 4 adsorption, the microscopic mechanism of the BP monolayer with high sensitivity to HCHO and C 2 H 4 gas molecules is systematically revealed. These findings offer promising avenues for the utilization of novel 2D nanomaterials in the design of next-generation gas sensing devices. [ABSTRACT FROM AUTHOR]

ZnO is widely used in semiconductor oxide gas sensors due to its remarkable physical and chemical properties. However, ZnO-based gas sensors face several challenges in practical applications, including limited selectivity, reduced sensitivity, and the requirement for high operating temperatures. In this study, a three-dimensional hollow porous flower-like Co 3 O 4 /ZnO material was synthesized by single-step hydrothermal method, exhibiting an average diameter ranging from 4 to 5 μm. The presence of Co 3 O 4 within ZnO was confirmed through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Through the detection of different gases, the results indicate that the ZnO-based gas sensor, doped with 0.5 at% Co 3 O 4 , exhibits exceptional sensitivity towards toluene gas, with the limit of detection (LOD) (1 ppb). The sensor's response values Ra/Rg to 0.1–200 ppm toluene at 260 °C range from 2 to 225, respectively. In the presence of toluene gas at a concentration of 100 ppm, the sensor demonstrated a high response value of 130, with response and recovery times of 30 s and 50 s, respectively. Furthermore, the response value of this sensor type was tested over a period of 15 days, confirming the device's excellent long-term stability. [ABSTRACT FROM AUTHOR]

The traditional mine gas sensor is vulnerable to the influence of temperature and ambient humidity and other factors, resulting in low stability. In order to solve the above problem, based on the principle of local surface plasmon resonance (LSPR) and the phase change characteristics of vanadium dioxide (VO2), a kind of metasurface dual-gas sensor based on VO2 is designed. The sensor structure is composed of three layers, and the surface is composed of multi-layer metal-dielectric-metal (MDM) structure. According to the phase change characteristics of VO2, the metal plate is heated in the form of resistance heating by changing the applied bias voltage. The temperature of VO2 is carefully controlled, and the different states of VO2 are simulated by changing the conductivity of VO2. When VO2 is in a high-temperature metal state, the upper three layers form MDM structure. VO2 shows metal properties and excites local surface plasmon resonance (LSPR) at 1721.3 nm to realize methane detection. The sensor's absorptance reaches 94.3%, and the methane sensitivity reaches 4.21 nm/%. When VO2 is in a low-temperature insulation state, the lower three layers form MDM structure. LSPR is excited at 2694.6 nm to realize hydrogen detection. The sensor's absorptance reaches 95.9%, and the hydrogen sensitivity reaches 2.10 nm/%. When the environmental refractive index changes, the absorption peaks of VO2 in both states are red-shifted and linear,which can be used to detect the change of the environmental refractive index. In order to verify the feasibility of the sensor, six different concentrations of methane, hydrogen and four different environmental refractive indexes are simulated and analyzed. The results show that the metasurface dual-gas sensor based on VO2 can effectively detect methane and hydrogen with lower concentration. The sensitivity is greatly improved compared with the existing gas sensors. The error between the calculated and theoretical values of the resonant peak shift and the environmental refractive index change and the methane volume fraction change is very small. This indicates that the sensor has high accuracy. By analyzing the relationship between the environmental refractive index and the resonant wavelength, it is concluded that the sensor also has high detection sensitivity when the environmental refractive index changes.

It was shown the possibility of increasing the sensitivity of a gas sensor based on nanocrystalline SiC films by using a scheme of a two-component sensing element, one of which is an n-nc-SiC film with electronic conductivity, and the second is an p-nc-SiC film with hole conductivity. It is shown that due to the opposite polarity of changes in resistance in the films under the simultaneous action of gases, the difference in relative resistance changes Δ in the n-nc-SiC and p-nc-SiC films will always be greater than in each film separately. The expediency of using a two-component sensing element of a gas sensor based on nc-SiC films with electron and hole conduction is shown.

Tin dioxide nanowhiskers were grown by physical vapor deposition and transferred to the contact system by the frozen drop method. The sensors demonstrate gas-sensitivity. Exposing sensors to the atmosphere contained vapors of reducing-gases leads to an increasing of their conductivity. A long-term drift of the sensor conductivity during reducing-gas exposition was shown. A sensitivity response vs concentration for ethanol, acetone, and propanol-2 vapors at temperature 300°C was investigated. Desorption energies of the particles and the positions of the donor levels induced by adsorption of reducing gases particles were calculated by analysis of the conductivity vs concentration dependence. The calculated parameters had a significantly smaller time drift in comparison with the conductivity. Using of these parameters makes possible to recognize gas-air mixtures: classify the each of three studied samples to one of classes.

A new method for rapid and facile fabrication of homoporous films with high volatile amine sensitivity was developed. First, red cabbage anthocyanin was encapsulated in ethyl cellulose to form water-in-organic (W/O) emulsion. Afterward, the W/O emulsion was rapidly dried using the supporting matrix Magnolia Grandiflora Linn leaf vein at 60% relative humidity and 50 °C to form a colorimetric film with regular hexagonal pores with an average side length of about 23 μm. The films exhibited good sensitivity to ammonia (NH 3 ), dimethylamine, and trimethylamine, with limit of detection of 0.26, 0.24, and 0.38 μM, respectively, and high stability when stored in high humid environments. An obvious color change of the films from pink to green was clearly observed during the freshness monitoring of pork, chicken, salmon, and shrimp. Thus, this work offered a novel and reliable method for the development of porous films for food freshness monitoring.

Constructing van der Waals (vdW) heterostructures is a prospective approach that is essential for developing a new generation of functional two-dimensional (2D) materials and designing new conceptual nanodevices. Using density-functional theory combined with a nonequilibrium Green's function approach allows for the theoretical and systematic exploration of the electronic structure, transport properties, and sensitivity of organic small molecules adsorbed on 2D C 3 B/graphene (Gra) and C 3 N/Gra vdW heterojunctions. Calculations show the metallic properties of C 3 B/Gra and C 3 N/Gra after the formation of heterojunctions. Interestingly, the heterojunctions C 3 B/Gra (C 3 N/Gra) for the adsorption of small organic molecules (C 2 H 2 , C 2 H 4 , CH 3 OH, CH 4 , and HCHO) at the C 3 B (C 3 N) side are sensitive to the chemisorption of C 2 H 2 and C 2 H 4 . Similarly, the Gra/C 3 B is chemisorbed for both C 2 H 2 and C 2 H 4 when adsorbed on Gra side, while it is only chemisorbed for C 2 H 2 in Gra/C 3 N. Interestingly, all heterojunctions on different sides are physisorbed for CH 3 OH, CH 4 , and HCHO. Furthermore, the calculated I-V curves demonstrate that the devices based on the adsorption of C 2 H 2 and C 2 H 4 at each side of the heterojunction have remarkable anisotropy, in with the current being considerably greater in the zigzag direction than in the armchair direction. More specifically, with C 2 H 2 adsorbed on the Gra side, the sensitivity along the armchair direction is up to 85.0% for Gra/C 3 B and close to 100% for Gra/C 3 N. This study reveals that C 3 B/Gra (C 3 N/Gra) heterojunctions with high selectivity, high anisotropy, and excellent sensitivity are highly prospective 2D materials for applications, which further contributes new insights into the development of future electronic nanodevices.

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.

In order to lessen the effect of La-doped on the gas-sensing response of SnO2 powders, different La-doped SnO2 powders were prepared by sol-gel method, and the prepared SnO2 and La-doped SnO2 powders were characterized and analyzed by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscope (SEM), specific surface area and pore size tester (BET) and X-ray diffractometer (XRD). The gas-sensing response of the samples were tested. The results show that La doping reduces the grain size of SnO2. With the increase of La doping, the gas-sensing response of La-doped SnO2 powders to ethanol increases first and then decreases. When the molar ratio of La/Sn is 0.25, the gas-sensing response of La-doped SnO2 powder to ethanol is the highest, 43.5% higher than that of pure SnO2 to ethanol.

A novel nanoflower/rod-like hierarchical SnO2 was prepared one step on FTO conductive glass which has SnO2 seed crystal under hydrothermal condition at 200 ℃ with SnCl4 and NaOH as raw materials. The morphology, crystal phase composition and gas-sensing performance of the product were tested by SEM, XRD, N2 adsorption-desorption and gas-sensing tester. The results indicate that the product is tetragonal phase, and "nano carpet" is formed by nanorod arrays which are perpendicular to the base in the hierarchical SnO2 and with spherical nanoflowers growing on it, and the nanorods and petals are all assembled by fuzzy fibers; its specific surface area is 109.8 m2·g-1 which is 13 times than that of the ordinary precipitated SnO2 powder. The product has high gas sensitivity which is 36.1 to 1000×10-6 acetone, 7.9 times of the ordinary precipitated SnO2 powder.

First, the device based on Janus ZrBrCl monolayer exhibits a high switching ratio of 1011 at a biaxial strain of −14%. Furthermore, the pin junction photodiode based on Janus ZrBrCl monolayer exhibits significant photocurrent response in the visible region. The photocurrent density peak undergoes interesting red and blue shifts phenomena in the biaxial strain range of −4% to +4%. Finally, the gas sensor based on Janus ZrBrCl monolayer exhibits high gas sensitivity, strain selectivity and strain sensitivity. These findings indicate promising candidate materials for high-performance switching and optoelectronic devices, and also provide a strategy for improved gas sensors. The gas sensors based on ZrBrCl monolayer exhibits high gas sensitivity, strain selectivity and sensitivity. [Display omitted] • The device based on Janus ZrBrCl monolayer exhibits a switching ratio of 1011 at a biaxial compressive strain of −14 %. • The biaxial strain and electric field can modulate the visible light absorption and photocurrent of ZrBrCl monolayer. Janus monolayers materials exhibit extraordinary physical and chemical properties because of crystal field changes caused by their asymmetric structures. Here, we investigate the electronic, switching, optoelectronic, and strain-sensitive gas-sensing properties of a Janus ZrBrCl monolayer via density-functional theory and the nonequilibrium Green's function methods. The electronic properties can be tuned by applying biaxial strain and electric fields. In particular, the band gap can be changed from indirect to direct via applied a + 8 % biaxial tensile strain. It can be transformed from a semiconductor to a metal with an applied −14 % biaxial compressive strain, with a 1011 switching ratio. In addition, a biaxial strain and an electric field can modulate visible light absorption and photocurrents. Under a −12 % biaxial compressive strain, the absorption coefficient increased to 5.26 × 105 cm−1 from the intrinsic 4.08 × 105 cm−1. Across biaxial strains from −4% to + 4 %, the photocurrent density peak displayed red and blue shifts, respectively, with increasing tensile and compressive strains. NH 3 , NO 2 , and NO physically adsorb on the Br side of the ZrBrCl monolayer. Maximum gas sensitivity values of a ZrBrCl sensor are 52 % in the zigzag direction and 21 % in the armchair direction. After application of the −14 % biaxial strain, the maximum values respectively increased to 76 % and 179 %. The biaxial compressive strain-sensitive gas-sensing properties are driven by changes in the electrostatic potential difference between the Br and Cl surfaces. These findings indicate promising candidate materials for high-performance switching and optoelectronic devices, and also provide a strategy for improved gas sensors. [ABSTRACT FROM AUTHOR]

The gas-sensitive properties of Ga 2 O 3 films, first synthesized by plasma-enhanced chemical vapor deposition (PECVD), with respect to gaseous species of environmental and industrial interest were investigated in detail. The addition of some N 2 during the PECVD process made it possible to reduce the inherent high resistance of Ga 2 O 3 material and increase its gas sensitivity. The PECVD-Ga 2 O 3 films demonstrated high responses to H 2 , O 2 and NH 3 with maximum response temperatures of 600 °C, 700 °C and 350 °C, correspondingly. The responses of Ga 2 O 3 films to 1 vol % of H 2 , 40 vol % of O 2 and 1 vol % of NH 3 at these temperatures were 400.73 %, 480.22 % and 335.35 %, correspondingly. The short response and recovery times of 7.6 s and 31.0 s have been achieved under H 2 exposure. A plausible mechanism of the sensory effect of the PECVD-Ga 2 O 3 films was suggested. Thus, the PECVD synthesized Ga 2 O 3 films demonstrate a large potential for the development of high-speed performance H 2 and O 2 sensors working at high temperatures. • Gas-sensitivity of PECVD deposited Ga 2 O 3 films were investigated for first time. • Addition of N 2 at PECVD reduces resistance and increase gas-sensitivity of Ga 2 O 3. • PECVD β-Ga 2 O 3 with small fraction of GaN is characterized by large active surface. • PECVD β-Ga 2 O 3 are of interest for high temperature sensors of H 2 , O 2 and NH 3. [ABSTRACT FROM AUTHOR]

Porous nanocomposites using two (tin dioxide–silica dioxide) and three (tin dioxide–indium oxide-silica dioxide)-component systems for gas sensors were created with the sol–gel method. To understand some of the physical–chemical processes that occurred during the adsorption of gas molecules on the surface of the produced nanostructures, two models—the Langmuir model and the Brunauer–Emmett–Teller theory—were used to carry out calculations. The results of the phase analysis concerning the interaction between the components during the formation of the nanostructures were obtained through the use of X-ray diffraction, thermogravimetric analysis, the Brunauer–Emmett–Teller technique (to determine the surface areas), the method of partial pressure diagrams in a wide range of temperatures and pressures and the results of the measurement of the nanocomposites’ sensitivity. The analysis allowed us to find the optimal temperature for annealing nanocomposites. The introduction of a semiconductor additive into a two-component system based on tin and silica dioxides significantly increased the sensitivity of the nanostructured layers to reductional reagent gases.

In this study, we employed electrospinning technology and in situ polymerization to prepare wearable and highly sensitive PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors. PEDOT, PEDOT:PSS, and TiO2 were prepared via in situ polymerization and tested for characteristic peaks using energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR), then characterized using a scanning electron microscope (SEM), a four-point probe resistance measurement, and a gas sensor test system. The gas sensitivity was 3.46–12.06% when ethanol with a concentration between 12.5 ppm and 6250 ppm was measured; 625 ppm of ethanol was used in the gas sensitivity measurements for the PEDOT/composite conductive woven fabrics, PVP/PEDOT:PSS nanofiber membranes, and PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors. The latter exhibited the highest gas sensitivity, which was 5.52% and 2.35% greater than that of the PEDOT/composite conductive woven fabrics and PVP/PEDOT:PSS nanofiber membranes, respectively. In addition, the influence of relative humidity on the performance of the PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors was examined. The electrical sensitivity decreased with a decrease in ethanol concentration. The gas sensitivity exhibited a linear relationship with relative humidity lower than 75%; however, when the relative humidity was higher than 75%, the gas sensitivity showed a highly non-linear correlation. The test results indicated that the PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors were flexible and highly sensitive to gas, qualifying them for use as a wearable gas sensor platform at room temperature. The proposed gas sensors demonstrated vital functions and an innovative design for the development of a smart wearable device. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai University / Shanghai Daxue Xuebao is the property of Journal of Shanghai University (Natural Sciences) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tin dioxide nanowhiskers were grown by the vapor deposition. The effect of technological parameters on the morphology of the grown nanostructures was investigated. It is shown that an increase in the partial pressure of oxygen in the range from 0,06 mbar to 9,3 mbar and the temperature of the deposition zone in the range from 940°C to 995°C leads to an increase in the diameter of the formed nanocrystals. Experimentally it was shown that the average diameter of nanowhiskers varied from 80 nm to 250 nm. A gas sensor was formed with an active layer, based on the nanocrystals, sensitive to acetone vapor. The value of the gas sensitivity and the characteristic times of the sensor are sufficient for practical use in gas analyzers and systems for recognizing gas mixtures and odors.

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The time characteristics of resistance change of individual nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs), initial and irradiated with electrons, protons and argon ions has been measured upon exposure to ammonia and nitrogen dioxide. It is found that the initial N-MWCNTs have n-type conductivity, N-MWCNTs irradiated with protons and argon ions have p-type conductivity, and those irradiated with electrons have n-type conductivity. The relative gas sensitivity of individual N-MWCNTs, initial and irradiated with ions and electrons, has been determined.

For the first time, the morphology of the surface layers of porous silicon, as well as composites based on them formed using highpower pulsed ion beams of nanosecond duration (PIB) with different exposure ratios are analyzed. The results showed that a single radiation exposure is the most rational regime for both porous silicon and composites. With this modification, surface structures are characterized by higher por-Si and SnOx crystallinity and uniformity. The gas sensitivity of the structures formed using PIB to nitrogen dioxide as well as the process of its degradation over time is studied. It is found that the most promising of all structures is a por-Si/SnOx composite irradiated with a single PIB pulse. It has the best gas sensitivity after creation and, with time, is less susceptible to aging, thus, being the most stable.

Abstract A detailed analysis of the electrical response of In0.3Ga0.7As surface quantum dots (SQDs) coupled to 5-layer buried quantum dots (BQDs) is carried out as a function of ethanol and acetone concentration while temperature-dependent photoluminescence (PL) spectra are also analyzed. The coupling structure is grown by solid source molecular beam epitaxy. Carrier transport from BQDs to SQDs is confirmed by the temperature-dependent PL spectra. The importance of the surface states for the sensing application is once more highlighted. The results show that not only the exposure to the target gas but also the illumination affect the electrical response of the coupling sample strongly. In the ethanol atmosphere and under the illumination, the sheet resistance of the coupling structure decays by 50% while it remains nearly constant for the reference structure with only the 5-layer BQDs but not the SQDs. The strong dependence of the electrical response on the gas concentration makes SQDs very suitable for the development of integrated micrometer-sized gas sensor devices.

In this study, SnO2-Pd nanoparticles(NPs) were made with an in situ synthesis-loading method. The in situ method is to simultaneously load a catalytic element during the procedure to synthesize SnO2 NPs. SnO2-Pd NPs were synthesized by using the in situ method and were heat-treated at 300 °C. As a result, tetragonal structured SnO2-Pd NPs, having an ultrafine size of less than 10 nm and a uniformly distributed Pd catalyst in the SnO2 lattice, were well made and a gas sensitive thick film with a thickness of c.a. 40 μm was well fabricated by using the NPs. Gas sensing characterization for CH4 gas indicated that the gas sensitivity, R3500/R1000, of the thick film consistent with SnO2-Pd NPs synthesized with the in situ synthesis-loading method, followed by heat-treatment at 500 °C, was enhanced to 0.59. Therefore, the in situ synthesis-loading method is available for synthesis of SnO2-Pd NPs for gas sensitive thick film.

In order to improve the response characteristics of the surface acoustic wave (SAW) sensor to trace gases, a SAW CO gas sensor based on a Pd–Pt/SnO2/Al2O3 film with a high-frequency response performance is proposed in this paper. The gas sensitivity and humidity sensitivity of trace CO gas are tested and analyzed under normal temperatures and pressures. The research results show that, compared with the frequency response of the Pd–Pt/SnO2 film, the CO gas sensor based on a Pd–Pt/SnO2/Al2O3 film has a higher frequency response performance, and the sensor has high-frequency response characteristics to CO gas with a concentration in the range of 10–100 ppm. The average response recovery time of 90% ranges from 33.4 s to 37.2 s, respectively. When the CO gas with a concentration of 30 ppm is tested repeatedly, its frequency fluctuation is less than 5%, indicating that the sensor has good stability. In the range of relative humidity (RH) from 25% to 75%, it also has high-frequency response characteristics for CO gas with a 20 ppm concentration.

Dimethylformamide (DMF) vapor is a toxic compound that has many industrial applications. In this article, a DMF gas sensor was developed using cadmium-doped nickel manganese ferrite/cadmium oxide nanoparticles based on the co-precipitation method. A study of response/recovery characteristics in a temperature range of 50 °C–300 °C revealed that the best operating temperature is 250 °C. At this temperature, a fast response/recovery time and a high response magnitude were achieved. The sensor was highly selective at this temperature for DMF among other toxic gases. The sensor also showed a very low drift of less than 2% in its response magnitude over 15 days. [ABSTRACT FROM AUTHOR]

Thin-film objects with a reproducible temperature dependence of the resistance, thermally stable, and easy to obtain can be used as the sensitive elements in semiconductor gas sensors. The aim of this study was to create thin films on the InP surface under the influence of an oxide chemostimulator + inert component (PbO + Y2O3, respectively) compositions and to determine their gas-sensitive properties and their dependence on the formula of the composition. Thin films were synthesised on the InP surface by the method of chemically stimulated thermal oxidation under the influence of various PbO + Y2O3 compositions. The thickness of the formed films, their elemental and chemical composition were determined (by laser ellipsometry, X-ray phase analysis, and infra-red spectroscopy). A number of experiments were carried out to establish the gas-sensitive properties of the obtained films with respect to ammonia with concentrations of 120, 100, and 80 ppm. By chemically stimulated thermal oxidation, we obtained thin films with semiconductor properties on the InP surface. It was determined that the samples had n-type conductivity. A gas-sensitive response was detected in the presence of ammonia in the atmosphere. The ability to create thin films with a predetermined value of sensory response was demonstrated

The development of gas sensor technology has a positive effect on the development of human society. Recent studies have shown that,atomic-level dispersed materials have ultra-high activity, unique electronic structure and quantum size effect, etc. Therefore, loading certain single atoms on certain gas-sensing mate rials will significantly improve the gas-sensing properties. This article reviews the preparation and characterization techniques of single atom materials in recent years and their research progress in gas sensors, and analyzes the performance advantages of single atom materials, single-,atom loading strategies, analysis methods, gas sensitivity and mechanisms, etc. The existing problems and the future development trend of single atom material based gas sensors are discussed, and finally some relevant opinions on the application and development of single atom materials in gas sensors are put forward. [ABSTRACT FROM AUTHOR]

In order to lessen the effect of La-doped on the gas-sensing response of SnO2 powders, different La-doped SnO2 powders were prepared by sol-gel method, and the prepared SnO2 and La-doped SnO2 powders were characterized and analyzed by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscope (SEM), specific surface area and pore size tester ( BET) and X-ray diffractometer (XRD). The gas-sensing response of the samples were tested. The results show that La doping reduces the grain size of SnO2. With the increase of La doping, the gas-sensing response of La-doped SnO2 powders to ethanol increases first and then decreases. When the molar ratio of La/Sn is 0.25, the gas-sensing response of La-doped SnO2 powder to ethanol is the highest, 43. 5 % higher than that of pure SnO2 to ethanol. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the Mn 2 O 3 @In 2 O 3 core-shell structures were prepared by a two-step hydrothermal method for TEA detection. Characterization of the morphological composition reveals that Mn 2 O 3 @In 2 O 3 is a microsphere structure with Mn 2 O 3 as the core and In 2 O 3 as the shell. The results of the gas-sensitive performance tests showed that the response of Mn 2 O 3 @In 2 O 3 to 100 ppm TEA was 47 at 180 °C, which was a significant improvement over the original In 2 O 3 , and it had excellent long-term stability and reproducibility. The improved gas-sensitive properties are due to the special structure of the core-shell material and the successful construction of p-n heterojunctions between the interfaces. • Mn 2 O 3 @In 2 O 3 core-shell microspheres were prepared by a two-step thermal method. • The special structure of core-shell effectively enhances the gas sensitive property of TEA. • Mn 2 O 3 @In 2 O 3 core-shell has excellent response and long-term stability to TEA. [ABSTRACT FROM AUTHOR]

Co 3 O 4 -ZIF- x (x = 0,1,2,3) composites have been prepared by in-situ growth of ZIF membrane on MOFs-derived hierarchical porous Co 3 O 4 by the solvothermal method with adjusting the ratio of dimethylimidazole. The effects of ZIF membrane on Co 3 O 4 structure and acetone-sensing properties are investigated by the techniques of XRD, Raman, SEM, TEM, BET, XPS and performance testing, and the possible gas-sensing enhancement mechanism is analyzed. The results show that the typical Co 3 O 4 -ZIF-1 sensor has the maximum response of 77.8–50 ppm acetone at 180 °C, the short response/recovery time of 7/35 s, and the low detection limit of 0.1 ppm (3.28). It also has the reliable acetone selectivity against to other interfering gases, as well as good repeatability and high stability. Its enhanced acetone-sensing property may be attributed to the synergistic effect of the improved surface state, high specific surface area, adjustable pore size and rich reaction activation sites, which caused by the hierarchical porous structure of MOFs-derived Co 3 O 4 and the gas adsorption and enrichment effect of ZIF membrane, promoting the further reaction and diffusion of acetone. The "internal construction and external modification" role of MOFs playing in Co 3 O 4 provides a new idea for designing high performance sensing materials. [Display omitted] • Co 3 O 4 -ZIF- x was solvothermally prepared by coating ZIF on MOFs-derived Co 3 O 4. • The Co 3 O 4 -ZIF- x has hierarchical porous structure with high specific surface area. • Typical Co 3 O 4 -ZIF-1 has high response to acetone and short response/recovery time. • Enhanced sensing may due to the synergies of porous structure and ZIF membrane. • The work is on the strategy of internal construction and external modification of MOFs. [ABSTRACT FROM AUTHOR]

Based on the first principles of density functional theory, the adsorption behavior of H2CO on original monolayer MoS2 and Zn doped monolayer MoS2 was studied. The results show that the adsorption of H2CO on the original monolayer MoS2 is very weak, and the electronic structure of the substrate changes little after adsorption. A new kind of surface single cluster catalyst was formed after Zn doped monolayer MoS2, where the ZnMo3 small clusters made the surface have high selectivity. The adsorption behavior of H2CO on Zn doped monolayer MoS2 can be divided into two situations. When the H-end of H2CO molecule in the adsorption structure is downward, the adsorption energy is only 0.11 and 0.15 eV and the electronic structure of adsorbed substrate changes smaller. When the O-end of H2CO molecule is downward, the interaction between H2CO and the doped MoS2 is strong leading to the chemical adsorption with the adsorption energy of 0.80 and 0.98 eV. For the O-end-down structure, the adsorption obviously introduces new impurity states into the band gap or results in the redistribution of the original impurity states. All of these may lead to the change of the chemical properties of the doped MoS2 monolayer, which can be used to detect the adsorbed H2CO molecules. The results show that the introduction of appropriate dopant may be a feasible method to improve the performance of MoS2 gas sensor.

In this study, we employed electrospinning technology and in situ polymerization to prepare wearable and highly sensitive PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors. PEDOT, PEDOT:PSS, and TiO2 were prepared via in situ polymerization and tested for characteristic peaks using energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR), then characterized using a scanning electron microscope (SEM), a four-point probe resistance measurement, and a gas sensor test system. The gas sensitivity was 3.46–12.06% when ethanol with a concentration between 12.5 ppm and 6250 ppm was measured; 625 ppm of ethanol was used in the gas sensitivity measurements for the PEDOT/composite conductive woven fabrics, PVP/PEDOT:PSS nanofiber membranes, and PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors. The latter exhibited the highest gas sensitivity, which was 5.52% and 2.35% greater than that of the PEDOT/composite conductive woven fabrics and PVP/PEDOT:PSS nanofiber membranes, respectively. In addition, the influence of relative humidity on the performance of the PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors was examined. The electrical sensitivity decreased with a decrease in ethanol concentration. The gas sensitivity exhibited a linear relationship with relative humidity lower than 75%; however, when the relative humidity was higher than 75%, the gas sensitivity showed a highly non-linear correlation. The test results indicated that the PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors were flexible and highly sensitive to gas, qualifying them for use as a wearable gas sensor platform at room temperature. The proposed gas sensors demonstrated vital functions and an innovative design for the development of a smart wearable device.

In this work, thin composite films of zeolitic imidazolate frameworks (ZIFs) and colloidal two-dimensional (2D) core-crown CdSe/CdS nanoplatelet (NPL) emitters with minimal scattering are formed by a cycled growth method and yield highly transparent coatings with strong and narrow photoluminescence of the NPLs at 546 nm (FWHM: 25 nm) in a solid-state composite structure. The porous ZIF matrix acts as functional encapsulation for the emitters and enables the adsorption of the guest molecules water and ethanol. The adsorption and desorption of the guest molecules is then characterized by a reversable photoluminescence change of the embedded NPLs. The transmittance of the composite films exceeds the values of uncoated glass at visible wavelengths where the NPL emitters show no absorption (>540 nm) and renders them anti-reflective coatings. At NPL absorption wavelengths (440-540 nm), the transmittance of the thin composite film-coated glass lies close to the transmittance of uncoated glass. The fast formation of innovative, smooth NPL/ZIF composite films without pre-polymerizing the colloidal 2D nanostructures first provides a powerful tool toward application-oriented photoluminescence-based gas sensing., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)