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A dumbbell-like Al doped ZnO(AZO) microstructure was successfully synthesized via a facile, controllable and one-pot hydrothermal method. The samples were characterized by XRD, SEM, EDS and TEM. It showed that all the samples present dumbbell-like structure composed of highly crystalline hexagonal wurtzite ZnO. The dumbbell-like structure is formed through the self-assembly of Al-dopled ZnO nanodisks. Gas sensing tests reveal that the Al-doped dumbbell-like ZnO microstructure (3 at %) shows excellent gas sensing response (5.37 for ethanol with 1 ppm) for ethanol with shorter response-recovery time (53 s/21 s). The notable sensing performance could be mainly attributed to the increased content of oxygen vacancy in ZnO due to the Al doping. Thus, the Al-doped dumbbell-like ZnO microstructures could provide an inspiration for the design and preparation of the highly sensitive ethanol gas sensor with the controllable electronic structure. [ABSTRACT FROM AUTHOR]

In this work, the mechanism of the effect of the surface state of tin oxide on its reductive gas sensitivity was investigated. A simple strategy was used to synthesize tin oxide samples with various structures. The strategy involved a hydrothermal reaction and calcination to transform the triclinic Sn 3 O 4 structure to the tetragonal SnO 2 structure. A combination of experimental and theoretical results, was used to investigate the reasons for the good reductive gas sensitivity of SnO 2 compared with those of other tin oxides. The results show that the origin of the gas sensitivity is surface bonding states that arise because of unoccupied electron orbitals. In contrast, for Sn 3 O 4 , there are surface antibonding states of the terminal Sn atoms with lone pairs and gas adsorption is difficult. The effect of the surface state on the gas sensitivity is also related to the electronegativity of the atoms on the adsorptive surface, and the electronic interactions between a gas molecule and the adsorptive surface. The results provide a feasible strategy for enhancing the gas sensitivity of metallic oxides by modulation of the surface states of the metal oxide. [ABSTRACT FROM AUTHOR]

In this paper, ZnO/NiO composites rich in oxygen vacancies are prepared by the solvothermal method and reduction method. In the test, through the use of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and electron paramagnetic resonance (EPR), we effectively prove the existence of phase, morphology and oxygen vacancies in the material. Through the photocatalysis test and gas sensitivity test, it is found that 10% Ni doped OZN-10 has the best photocatalytic activity and gas sensitivity characteristics. The degradation rate of methylene blue (MB) was 98%. The gas sensitivity test shows that OZN-10 has good selectivity, good response performance (3000 ppm, 27,887%) and excellent response recovery time (response time: 50 s, recovery time: 5–7 s) for saturated NH3 gas at standard atmospheric pressure (101.325 KPa) and room temperature (25 °C). The synergistic effect of oxygen vacancy as the center of a trap and p–n heterojunction forming an electric potential field at the interface is explained, and the mechanism of improving photocatalysis and gas sensitivity is analyzed. This work will provide an innovative vision for dual-performance oxygen vacancy modification of heterojunctions through photocatalysis.

The effect of a pulsed ion beam of nanosecond duration on the morphology, chemical composition, and electronic structure of porous silicon is studied. The gas sensitivity of the initial and irradiated samples is studied under exposure to NO2 and degassing in air. Its degradation is assessed over time. It is established that both the initial and irradiated samples have a sensitivity to NO2 . In the case of the initial porous silicon, it disappears after 6 months, and in irradiated silicon it decreases after 3 months and then remains practically at the same level. This is a consequence of the formation of a passivating film, which prevents the degradation of the composition and properties of porous silicon when it comes into contact with the environment. The presence of such a film, represented by a SiO2 , is confirmed by X-ray photoelectron spectroscopy (XPS) data.

Using the methods of scanning force microscopy, the gas sensitivity properties of individual composite nanostructures based on CNTs, functionalized by argon ions and coated with tin and titanium oxides are investigated. The Fermi level shift and the change in longitudinal conductivity upon absorption ammonia and nitrogen dioxide are determined. It is shown that the change in conductivity of the composite nanostructures to the correlates with the Fermi level shift under gases exposure as a result of charge carriers concentration changing in the metal oxide surface layers upon adsorption of gas molecules.

Triacetone triperoxide (TATP) is widely used in terrorist attacks because of its simple synthesis but hard to be directly detected. Herein, polyphenylene vinylene (PPV) derivative with the vinyl group on the side chain is cross‐linked by Au nanoclusters (Au NCs) to construct flexible Schottky sensors to arrange the uncontactless detection of TATP vapor. Experiments and simulations show that Au NCs generate a strong electromagnetic field with collective coupling which can effectively promote the photoinduced electron‐hole separation of the PPV and detection sensitivity to TATP. The simple fingerprint patterns can discriminate TATP from 2,4,6‐trinitrotoluene (TNT), 2,4‐dinitrotoluene (DNT), p‐nitrotoluene (PNT), picric acid (PA), Hexogen (RDX), and tetryl by pattern to recognize inherent kinetics and thermodynamics of interaction between the sensors and specimen. The electron transfers from Au NCs to PPV after the adsorption of TATP molecules as the electronegativity of TATP is smaller than that of Au NCs and which is obvious in electron donating effect. Therefore, Au acts as a hole trap and reduces the hole concentration as well as restricting the carrier transport. However, the oscillator strength of the charge transferred from Au NCs to PPV simulation indicates that the role of Au NCs change from the hole trap to electron trap after adsorption of other explosives. Furthermore, the flexibility and stability of the sensor films are also demonstrated in this paper which is of great significance for the practical application of flexible electronic devices with high performance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Al-Doped ZnO (AZO) nanocrystals with a novel cactus morphology have been successfully synthesized by a facile and efficient hydrothermal method. The crystal structure, surface morphology and chemical composition of the samples were determined by X-ray diffraction and scanning electron microscopy with an energy-dispersive X-ray analyzer, indicating that the presence of a small quantity of Al ions can greatly affect the morphology of the ZnO nanostructures. Further, the heater gas sensors were fabricated and an investigation of gas sensing properties has been carried out. The sensors based AZO powders exhibited distinctive selectivity, good response repeatability, and preferable long-term stability to ethanol. This confirms that AZO has potential applications in high-performance gas sensing materials. [ABSTRACT FROM AUTHOR]

The current work concern a surface potential based approach to study the bias voltage dependent sensitivity of 1-D metal oxide gas sensors. Bias dependent sensitivity for granular metal oxide gas sensors has already been reported. Considering the wide applicability of 1-D nanomaterials in gas sensing application, the bias dependent sensitivity has been studied in present work by theoretical route which was supported by experimental findings. The concept was established based on the surface potential ($\Psi _{{\mathbf {S}}}$) effect due to the carrier concentration gradient by surface adsorption of gases on the metal oxide. Considering the effect of both the potentials i.e. $\Psi _{{\mathbf {S}}}$ and bias voltage, the exact bias point was found to get the peak response of 1-D metal oxide gas sensor. TiO2 nanotubes array was considered as the test sensing material. In the first phase of the article, the theoretical approach has been reported to estimate the sensor response of 1-D nanotubes and in the second phase of the study, the theoretical concept has been justified with experimental results. Highly oriented TiO2 nanotube array was synthesized, characterized and used to fabricate Au/TiO2 nanotubes/Ti type vertical structured sensor device. Simulation results exhibited the highest response of the TiO2 nanotube sensor in-between 0.1-0.4 V of bias voltage which was then authenticated with the experimental ethanol sensing behavior of the sensor in the concentration range of 90 to 630 ppm at 300 K. [ABSTRACT FROM AUTHOR]

Layered black phosphorus (BP), as a well-known type of two-dimensional (2D) material, has exhibited many fascinating properties in the fields of electronics, photonics, and chemical applications. However, the instability of 2D phosphorus is the primary obstruction toward practical applications, and the properties of one-dimensional (1D) black phosphorus remain unexplored. Here, we have first successfully synthesized 1D single crystalline BP nanowires, which represent the characteristics of good stability, narrow width (∼100 nm), wafer-scale arrays, and high surface to volume ratio. The used melting–injection–transformation method at high pressure with red phosphorus being the starting material is inexpensive, controllable, and productive. The unique superiorities of BP nanowires thus enable a one-step fabrication of BP gas sensors with fast response, long operating life, and strong robustness. This work opens a dimension to explore the properties of BP and also provides a 1D structure engineering strategy toward an efficient large-scale fabrication, endowing traditional materials with fresh attributes for practical applications. [ABSTRACT FROM AUTHOR]

In this paper, a new diffusion-reaction equation was formulated to research the influences of grain radius on the transients of gas transport and gas sensitivity for porous thin film medium semiconducting metal oxide gas sensor, based on the phenomenon that a target gas diffuses in the sensing film via Knudsen diffusion and reacts with adsorbed oxygen on the pore surfaces following Langmuir adsorption. In order to describe gas transport inside the sensing film, the equation has been solved numerically under unsteady-state conditions. When the gas concentration reached a steady state, the relationship between gas concentration and film depth was formulated using data fitting method to investigate the influences of grain radius on gas sensitivity, according to the linear relation between the sheet conductance of the sensing film and the gas concentration at the corresponding depth, and the reality that the conductance of the entire film is an integration of sheet conductance over the whole range of the film from the surface to the substrate. [ABSTRACT FROM AUTHOR]

In this study, a kind of novel porous 3D multi-edges cube SnO2/ZnO composite with n-n heterojunctions was prepared through a facile hydrothermal route. A kind of ordered mesoporous ZnO must be used as precursor in the hydrothermal reaction which was fabricated by soft-template method. The surfaces of the 3D multi-edges cube SnO2/ZnO composite were distributed with ordered mesoporous of 10.2 nm. The grain refinement effect was happen by SnO2, it led to the specific surface area of the material reached to 135.641 $\text{m}^{\textsf {2}}\cdot \text{g}^{\textsf {-1}}$ , which was nearly 3.9 times of ZnO matrix. At room temperature (25°), the 3D multi-edges cube SnO2/ZnO nanomaterial showed excellent gas response to NOx, whose response to 100 ppm NOx reached 60.41±0.5%, the response time was only 2 s, and the detection limit was 0.2 ppm. It broke the tradition that SnO2/ZnO composite showed gas response to NOx only in relatively high temperatures. [ABSTRACT FROM AUTHOR]

Thin (SnO2)х(In2O3)1 –х (x = 0–1) films on the order of 500 nm in thickness have been produced on hot (400°C) substrates by RF magnetron sputtering of ceramic targets with various compositions. The phase composition of the films has been determined by X-ray diffraction, and the formation of the In4Sn3O12 phase has been demonstrated at x = 0.3. The solubility limit of In in SnO2 and Sn in In2O3 has been estimated at about 10 wt %. All of the grown films have been shown to be transparent in the visible spectral region. We have determined the transmittance, absorption coefficient, and band gap of the films. The results demonstrate that the formation of the In4Sn3O12 phase is accompanied by a decrease in band gap to 3.3 eV. Infrared transmission measurements have shown that the (SnO2)х(In2O3)1 –х films with x = 0.1 do not transmit infrared radiation and can be used as thermal mirrors. Carrier concentration and mobility in the (SnO2)х(In2O3)1 –х films have been determined over the entire range of x values using Hall effect measurements. These parameters are largest in the x = 0.1 (ITO) films: n = 9.1 × 1021 cm–3 and μ = 81.3 cm2/(V s). The x = 0.9 films have the highest sheet resistance and can be effectively used as gas sensors. The sensitivity of the films to ethanol vapor in air has been assessed. [ABSTRACT FROM AUTHOR]

Thin nanofilms have been grown on the surface of single-crystal InP wafers using PbO + V2O5 mixtures in the gas phase. The oxide mixtures used as chemical stimulators have been shown to accelerate the thermal oxidation of InP. The resultant films exhibit gas-sensing properties for ammonia (concentration of 140 ppm) and carbon monoxide (95 ppm). The highest gas sensitivity is near 1.2 arb. units, at temperatures in the range 200–240°C. [ABSTRACT FROM AUTHOR]

The investigation of the gas sensitive properties of an array of nanorods of zinc oxide obtained by hydrothermal synthesis is carried out. Their morphology and crystal structure as well as electrophysical and gas sensitive properties are studied. A thermodynamic analysis of the process of interaction of carbon monoxide (CO) with the surface of the nanorods of zinc oxide is performed based on the experimentally determined activation energy of conductivity and gas sensitivity coefficient. It is shown that the process under study includes an interaction between a CO molecule and a charged adsorption site of the surface of zinc oxide. [ABSTRACT FROM AUTHOR]

In this paper, the first-principle calculations of the lateral heterojunction model synthesized by hBN-Graphene were carried out, and it was found that the bandgap of graphene varied with the change in the proportion of hBN, and the bandgap was best regulated with a bandgap of 1.177 eV when the proportion of hBN was 66.67 %. At this time, the adsorption structures of HCN, CO, NH3, and Cl 2 were established and energy band calculations were performed on the hBN and Graphene portions of the hBN-Graphene lateral heterojunctions, respectively, and it was found that the adsorption of Cl 2 resulted in a significant change in the band gap, which showed a very high electrical sensitivity. To further investigate the adsorption mechanism of Cl 2 on the surface of hBN-Graphene lateral heterojunction, the energy band structure, PDOS, charge transfer, adsorption energy, and recovery time of each stabilized adsorption site of Cl 2 on the surface of hBN-Graphene lateral heterojunction were calculated. The results show that the adsorption of Cl 2 on the surface of hBN-Graphene lateral heterojunction is a stable chemisorption, and the band gap of C-Top1 increases to 1.274 eV, and the band gaps of C-Top3, N-Top1, and N-Top2 decrease to 0.684 eV, 0.376 eV, and 0.398 eV, respectively, and the changes of band gaps are significant and easy to be electrically detection. The recovery time of Cl 2 on the surface of hBN-Graphene lateral heterojunction was 7.36 s–2.59 s in visible light and in the temperature interval of 273 K–283 K. The recovery time of Cl 2 on the surface of hBN-Graphene lateral heterojunction was 7.36 s–2.59 s in visible light and in the temperature interval of 273 K–283 K. These findings have implications for the research and application of graphene-based Cl 2 gas sensors. [Display omitted] • The best electron modulation of hBN-Graphene lateral heterojunction was achieved when the ratio of hBN was 66.67 %. • The effective adsorption sites for Cl 2 by the hBN-Graphene lateral heterojunction amounted to 44.44 %. • HBN-Graphene lateral heterojunctions exhibit high sensitivity to Cl 2 for electrical properties. • Cl 2 recovery time on hBN-Graphene lateral heterojunction is 7.36 s–2.59 s with high reuse efficiency. [ABSTRACT FROM AUTHOR]

The nanocomposites of polythiophene and carboxylated multiwalled carbon nanotubes (MWCNTs) were synthesized by in-situ chemical oxidative polymerization method using anhydrous ferric chloride (FeCl3) as an oxidant. The MWCNTs functionalized and ultrasonicated to obtain uniform dispersion within the polythiophene matrix. Field emission scanning electron microscopy was used to characterize the morphology of the nanocomposite. X-Ray diffraction, Fourier Transform Infrared Spectroscopy, Raman spectroscopy, and thermogravimetric analysis were used to characterize the synthesized MWCNT-polythiophene nanocomposites. It was found that in-situ polymerized polythiophene layer matrix was formed on carboxylated MWCNT and there was uniform dispersion of MWCNTs within the polythiophene matrix with significant interaction between polythiophene and MWCNTs. The sensitivity response of the prepared MWCNT-polythiophene nanocomposite sensors was studied in using Ammonia gas. The synergistic effects of the polythiophene-coated MWCNTs improve the gas sensing properties. Results showed that the sensitivity increased with ammonia concentration and it is also affected by the MWCNT content in polythiophene matrix. Furthermore, the sensor in pellet form reported here is robust, cost effective, and relatively stable at room temperature.

In this paper, Co3O4-ZnO nanomaterials with Co3O4 doping mass fractions of 0%, 2.13%, 4.13%, and 6.13% were prepared by sol-gel method. In order to explain and confirm the influence of the incorporation of Co3O4 on the surface morphology and gas sensitivity of ZnO at a relatively low gas concentration, additional studies such as XRD, XPS, SEM, EDS and UV-vis spectroscopy were performed. And its photoelectric response to 100 ppm acetone at near room temperature and visible light irradiation was studied. Due to the formation of P-N heterojunctions, the Co3O4-ZnO heterostructural nanoparticles has a highe response to low concentrations of acetone gas than undoped ZnO nanoparticles even at operating temperatures as low as 30ºC. The addition of Co3O4 improves the sensitivity and selectivity of ZnO thick films. The sensitivity of the 4.13wt% Co3O4-ZnO sample to 100 ppm acetone at a working temperature of 30ºC was 24.36. The light excitation effect was significantly enhanced. Under visible light irradiation, the sensitivity can reach 37.21. In addition, the Co3O4-ZnO P-N heterojunction model was combined with visible light excitation theory to further explore the mechanism of gas sensing reaction.

A sensor operating at room temperature has low power consumption and is beneficial for the detection of environmental pollutants such as ammonia and benzene vapor. In this study, polyaniline (PANI) is made from aniline under acidic conditions by chemical oxidative polymerization and doped with tin dioxide (SnO2) at a specific percentage. The PANI/SnO2 hybrid material obtained is then ground at room temperature. The results of scanning electron microscopy show that the prepared powder comprises nanoscale particles and has good dispersibility, which is conducive to gas adsorption. The thermal decomposition temperature of the powder and its stability are measured using a differential thermo gravimetric analyzer. At 20 °C, the ammonia gas and benzene vapor gas sensing of the PANI/SnO2 hybrid material was tested at concentrations of between 1 and 7 ppm of ammonia and between 0.4 and 90 ppm of benzene vapor. The tests show that the response sensitivities to ammonia and benzene vapor are essentially linear. The sensing mechanisms of the PANI/SnO2 hybrid material to ammonia and benzene vapors were analyzed. The results demonstrate that doped SnO2 significantly affects the sensitivity, response time, and recovery time of the PANI material.

In the present study, we have deposited hierarchical flower-like microstructured zinc oxide (ZnO) thin films directly on a glass substrate by using the simplistic aqueous chemical route for different concentrations of triethanolamine (TEA) which acted like a complexing agent. The as-synthesized ZnO thin films were subsequently annealed at 300 °C and are characterized with characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL), and electrical resistivity. The hexagonal wurtzite crystal structure of as-synthesized ZnO thin films was confirmed by their XRD patterns and the well-resolved ZnO flowers-like morphology was revealed from the FESEM micrographs. From FESEM images it can be seen that the ZnO flower is composed of dozens of nanorods originating from the same core in a symmetric fashion with an average diameter of around 180-300 nm. The flower-like morphology was obtained at 0.3 M TEA concentration. Due to its hierarchical structure, the deposited ZnO thin films were employed for multiple applications such as gas sensing and anti-microbial activity. The ZnO thin films with micro-flowers like morphology showed the maximum gas sensor sensitivity ∼64.50 at 150 °C for 100 ppm of NO2 gas. Moreover, the bacteria were completely destroyed in the presence of as-deposited ZnO thin films. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xinyang Normal University Natural Science Edition is the property of Journal of Xinyang Normal University 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.)

Zinc oxide nanowire (ZnO NW) gas sensor with single Schottky contact is capable of sensitive detection of gas molecules. In this paper, we investigate the effect of design factors, such as NW defect density, diameter, and length, on the gas sensitivity using the 3-D numerical simulation. The sensor with lower defect density or smaller NW diameter exhibits improved gas sensitivity, while length does not have an impact when not considering the external environment, such as background gases and binding probability. Lower defect density causes low electron density within the NW in air environment, and the change in electron density due to gas adsorption is intensified, thus improving gas sensitivity. As the NW diameter decreases, the change in the electrical conductivity due to gas molecules is greatly increased due to an increase in the ratio of the depletion area to the entire NW area. In contrast, the NW length does not impact the gas sensitivity because the change in the electron density due to the gas molecule adsorption is independent of the length. These results are helpful to understand the sensing mechanism and provide design guidelines to maximize the sensitivity. [ABSTRACT FROM AUTHOR]

Doping and surface engineering of zinc oxide (ZnO) nanostructures are the practical approach in promoting the gas sensing capabilities. However, the mechanism and the factors that affect such improvement are not well understood. We performed the first-principles based on density functional theory (DFT) calculations to investigate palladium (Pd) decoration on the gas sensing properties of ZnO (0001) surface. Various Pd loading contents on the ZnO surface have been simulated for the resulting sensing capabilities towards a series of gas molecules. The simulations indicate that the modified ZnO surfaces actively interact with the CO and NH _3 gas molecules with great adsorption energies ranging from −1.02 eV to −5.56 eV. Moreover, the most stable structure of the decorated ZnO surface by a three-Pd ring cluster has revealed the drastically enhanced selectivity towards NH _3 gas. Hence, surface decoration by Pd atoms could be an effective approach in promoting gas selectivity and sensitivity.

Metal-organic Frameworks (MOFs) have been widely studied due to their high porosity and large surface area. In this paper, Co 3 O 4 -modified SnO 2 hollow spheres with excellent ethanol gas sensitivity were prepared by using ZIF-67 as template by two-step hydrothermal pyrolysis at 300 °C. The elemental composition, morphology, structure and gas sensitivity properties of the materials were characterized by XRD, SEM and gas-sensitive analysis system. The experiment shows that the ZIF-67-derived Co 3 O 4 -SnO 2 composite has a response value of 33.9 to 100 ppm ethanol gas at the optimum operating temperature of 225 °C, which is significantly higher than that of pure SnO 2. According to the characteristics of gas sensitivity and morphology, the enhancement of gas sensitivity is due to the increase of oxygen vacancies, which promotes oxygen adsorption and surface chemical reaction. • SnO 2 hollow spheres were prepared by carbon template hair. • ZIF-67-derived Co 3 O 4 was successfully prepared. • The MOFs-derived Co 3 O 4 -SnO 2 hollow spheres exhibit excellent sensing performance for ethanol. [ABSTRACT FROM AUTHOR]

The fabrication of high-performance gas-sensitive materials with enhanced moisture resistance is an important research topic. In this work, monodisperse Y-type CoO hierarchical nanostructures with a branch length of about 16 nm have been prepared, and then uniformly dispersed on the surface of reduced oxide graphene (rGO) by hot injection method. The composite exhibited a rapid response to NO 2 at room temperature. The optimal response was about 40–100 ppm NO 2 , the response time was 620 s to 10 ppm NO 2 and the detection limit was 0.01 ppm. It was due to the combination of more NO 2 adsorption active sites of Y-type CoO and faster carrier transfer of rGO. Even at high relative humidity (RH) conditions of 80%, the sensor still retained a high response value of about 90% of that measured at the normal RH (25%). The effective wrapping of stearate ligands inhibited the entrance of water vapor molecules, which could effectively improve the hydrophobic properties of the composite and resulted in enhanced moisture resistance. It may provide a new path for improved NO 2 detection with enhanced moisture resistance at room temperature. [Display omitted] • Y-type CoO/reduced graphene oxide was synthesized with a hot injection method. • The composite sensor exhibited a rapid response to NO 2 at room temperature. • The composite sensor also presented an improved moisture resistance. • The enhanced moisture resistance was due to the wrapping of stearate ligands. [ABSTRACT FROM AUTHOR]

In this work, perylene bisimide derivatives (PBI-1 and PBI-2) with tertiary amine groups were designed and synthesized. To control the final morphologies and properties of their aggregates, seven kinds of organic acids were used to alter the self-assembly environment. The influence of organic acids on the morphology of the aggregates was investigated. Photophysical properties of the aggregates were markedly affected by the kind and concentration of the organic acid. The thermal and gas sensitivities of the PBI-1 aggregates were studied with the use of UV–visible spectroscopy and digital imaging. The shift of the UV–visible spectra varied with time, temperature, acid type and acid concentration. Furthermore, PBI-1 aggregates showed a red-to-blue color change after addition of seven organic acids, whereas the color of the PBI-2 aggregates remained red. These changes of morphologies, photophysical properties and their thermal and gas sensitivities make these aggregates potentially useful in the fields of optoelectronics or sensors.

As a graphene-like material, molybdenum disulfide has similar properties to graphene, but due to its excellent properties such as adjustable band gap, molybdenum disulfide has a broader application in many aspects (such as gas sensors). With the deepening of research, molybdenum disulfide cannot fully meet the needs of researchers due to defects and other reasons. Therefore, researches on doping and compounding of molybdenum disulfide have gradually attracted attention. At present, most of the research on gas sensitivity has focused on harmful gases (such as nitrogen dioxide, ammonia and carbon monoxide, etc.). There are few studies on the erosive chemical toxic mustard gas. In this paper, vanadium-doped molybdenum disulfide were prepared based on chemical vapor deposition, and the gas-sensitive response of vanadium-doped molybdenum disulfide to mustard gas was studied.

Sulfur hexafluoride (SF6) is widely utilized in gas-insulated switchgear (GIS). However, part of SF6 decomposes into different components under partial discharge (PD) conditions. Previous research has shown that the gas responses of intrinsic and 4 Å-type molecular sieve-deposited multi-wall carbon nanotubes (MWNTs) to SOF2 and SO2F2, two important decomposition components of SF6, are not obvious. In this study, a K-type molecular sieve-deposited MWNTs sensor was developed. Its gas response characteristics and the influence of the mixture ratios of gases on the gas-sensing properties were studied. The results showed that, for sensors with gas mixture ratios of 5:1, 10:1, and 20:1, the resistance change rate increased by nearly 13.0% after SOF2 adsorption, almost 10 times that of MWNTs sensors, while the sensors’ resistance change rate with a mixture ratio of 10:1 reached 17.3% after SO2F2 adsorption, nearly nine times that of intrinsic MWNT sensors. Besides, a good linear relationship was observed between concentration of decomposition components and the resistance change rate of sensors.

Abstract This study aimed at the preparation of In 2 O 3 sensitized disordered porous SnO 2 aerogel (In 2 O 3 /SnO 2) gas-sensing material by a sol-gel hard template method, and tested its gas-sensing properties to NO x gas at room temperature. The remarkable gas-sensing material was achieved by doped In 2 O 3 into disordered porous SnO 2 aerogel. The SiO 2 could catalyze the SnCl 2 ·2H 2 O to form the sol-gel system when the Sn, In and Si sources were mixed in alcohol and water, the silicon templates were formed during the reaction, and the disordered porous In 2 O 3 /SnO 2 aerogel composite was obtained when the silicon templates were removed. When the doped concentration of In 2 O 3 was 0.1%, the composite exhibited the highest sensitivity and selectivity. For doping 0.1% In 2 O 3 sample, when the NO x concentration was 100 ppm, the response reached 80.3%, the response time was only 2.0 s. The detection limit to NO x gas reached 0.08 ppm. The response of sample to NOx was much higher than the same concentration other gases (NH 3 , H 2 , O 2 and N 2). The gas sensing mechanism was proposed that the addition of In 2 O 3 into SnO 2 enhanced the catalytic activity for the reaction. In addition, the morphology and unique structure were helpful to the gas reaction on the surface of the sensing materials. The prepared In 2 O 3 /SnO 2 composite immensely reduced the dosage of the much expensive In element, and had the much higher response, which would have a great development space in the gas sensor field. Highlights • Disordered porous SnO 2 aerogel gas-sensing material was prepared • In 2 O 3 sensitized disordered porous SnO 2 aerogel gas-sensing material. • In 2 O 3 was doped into disordered porous SnO 2 aerogel. • The In 2 O 3 changed the original morphology, immensely increased the specific surface area and pore size. [ABSTRACT FROM AUTHOR]

In this study, we investigated the feasibility of using a D-Li7 neutron generator to replace a deuterium-tritium (D-T) neutron generator in gas saturation logging. The logging response and gas sensitivity of gas saturation logging based on the inelastic gamma spectrum were simulated with the Monte Carlo method, and the factors that influenced the gas sensitivity and inelastic gamma counts were analyzed based on the spatial response distribution. The results showed that the logging response based on the D-Li7 source was similar to that based on the D-T neutron generator after calibration, which validated the feasibility of this method. Using the D-Li7 neutron generator, the sensitivity of gas saturation was higher when the scattering cross section of formation was not high. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Jilin University (Science Edition) / Jilin Daxue Xuebao (Lixue Ban) is the property of Zhongguo Xue shu qi Kan (Guang Pan Ban) Dian zi Za zhi She 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.)

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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.)

Copyright of Journal of College of Education is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) 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 composite of a nanocrystalline SnO2 thick film deposited on an Al-doped ZnO ceramic substrate was firstly proposed. This study also provided a simple, fast and cost effective method to prepare SnO2 thick film and Al-doped ZnO ceramic as well as the final composite. The crystal structure, morphology, composition, pore size distribution and gas sensitivity of the composite were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Barrett-Joyner-Halenda analysis and gas sensitive measurement system. Results indicated that the composite was fully porous consisted of SnO2, ZnO and ZnAl2O4 crystal phases. The macrosized pores generated in the composite could enhance the gas infiltration into the sensing layers effectively. In this way, combining a high gas-transporting-capability and a nanocrystalline SnO2 thick film, the composite showed very impressive performance. The gas sensitivity of the composite was high enough for ethanol vapor with different concentrations, which was comparable to other kinds of reported SnO2 gas sensors, while showing two straight lines with a turning point at 1000ppm. Finally, the gas sensitive mechanism was proposed based on the microstructure and composition of the composite. [ABSTRACT FROM AUTHOR]

Abstract: A kind of novel n–n combined ordered mesoporous WO3/ZnO (OM‐WO3/ZnO) sensor are successfully fabricated in this study. A soft‐template method is used to synthesize the ordered mesoporous ZnO matrix. Surfaces of the ZnO matrix are innovatively modified using silane coupling agent (mark as: OM‐ZnO‐Si), and then a layer of WO3 film is assembled on the surfaces of the OM‐ZnO‐Si by chemical plating method for the first time, and the OM‐WO3/ZnO material is obtained. The prepared OM‐WO3/ZnO sample shows a kind of regular hexagon‐sheet structure. The prepared OM‐WO3/ZnO sensor shows the much better response, much shorter response time, much lower detection limit, and the more excellent selectivity toward NOx gas. When oxynitride (NOx) gas concentration is 100 ppm, the response reaches to 82.64%, the response time is only 6 s at room temperature. The detection limit is only 0.01 ppm. The unique loose porous structure and the synergistic effect of the n–n heterojunction structure endow the prepared OM‐WO3/ZnO material with the superior gas sensing properties. The n–n combined OM‐WO3/ZnO material shows the vast development potential in gas sensor field. [ABSTRACT FROM AUTHOR]

Here, we report, for the first time, the solution growth of n-type MgFe 2 O 4 spinel ferrite nanoparticles on nano-textured p-type silicon (100) substrate. Water soluble MgFe 2 O 4 spinel ferrite nanoparticles are prepared by polyol technique. The MgFe 2 O 4 spinel ferrite nanoparticles were characterized by transmission electron microscopy both at low and high resolution, selected area electron diffraction, energy dispersive spectroscopy, and Raman spectroscopy. The texturing of the surface of the Si(100) substrate to create well-organized nanopillar-like shapes was carried out by a nanosecond laser lithography technique. The water soluble MgFe 2 O 4 spinel ferrite nanoparticles were deposited on the textured Si(100) substrate. The sample was characterized by scanning electron microscopy and X-ray diffraction. The charge carriers transport mechanism was discussed in terms of the variation of the barrier height under the exposure to various gases. A comparison between the MgFe 2 O 4 spinel ferrite nanoparticles grown on planar and textured p-type Si(100) surfaces showed that the latter demonstrated an improvement of gas sensitivity and accelerated response time. These two characteristics, combined with high performance stability, make these sensors promising for practical applications. [ABSTRACT FROM AUTHOR]

Nanostructured deposits of ammonia (NH3) sensitive ZnO and ZnO-CuO composites were fabricated on a graphite electrode via electrophoretic deposition (EPD). Deposition was done by holding the applied voltage and deposition time constant at room temperature. Testing of sensing properties of the deposits was conducted using Wheatstone bridge circuit. SEM micrographs show a more open structure and more exposed surface area of the pure ZnO deposit compared to the ZnO-CuO deposit. The average particle size deposited at 500V for ZnO and ZnO-CuO were 241nm and 260nm respectively; whereas at 750V the average particle size is 195nm and 276nm, respectively. Deposits with greater surface area, smaller particle sizes and thicker deposits exhibit high gas sensitivity. On the other hand, addition of CuO resulted to a more compact and dense surface structure and decreased gas sensitivity. Thus, particle size and the surface structure of the deposits dictate the sensitivity of the material.

The article describes the result of the use SnO2-Pd thin films as a gate for structure measured ppb range of NO2 gas by the capacitive method. The technological aspects of fabrication SnO2-Pd gate and one comparison by metrological parameters with the classical Pd gate field effect sensor are discussed. The use of SnO2-Pd material allows improvement in sensitivity of NO2 by an order of magnitude compare the classical Pd based gate field effect sensors.

The homemade explosive, triacetone triperoxide (TATP), is easy to synthesize, sensitive to detonation but hard to detect directly. Vapor sensor arrays composed of a few sensor materials have the potential to discriminate TATP, but the stability of the sensor array is always a tricky problem since each sensor may encounter a device fault. Thus, a sensor array based on a single optoelectronic TiO2/PW11 sensor was first constructed by regulating the excitation wavelength to discriminate TATP from other explosives. By in situ doping of Na3PW12O40, a Keggin structure of PW11 formed on the TiO2 to promote the photoinduced electron-hole separation, thus obviously improving the detection sensitivity of the sensor film and shortening the response time. The response of the TiO2/PW11 sensor film to TATP under 365, 450 and 550 nm illumination is 81%, 42%, and 37%, respectively. The TiO2/PW11 sensor features selectivity to TATP and is able to detect less than 50 ppb. The flexibility and stability of the flexible sensor film is also demonstrated with the extent of bending. Furthermore, the sensing response cannot be affected by ambient air below 60% relative humidity.

Copyright of Romanian Journal of Materials / Revista Romana de Materiale is the property of Foundation for Materials Science & Engineering Serban Solacolu 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 hierarchical ZnO nanostructures with 2-fold symmetrical nanorod arrays on zinc aluminum carbonate (ZnAl-CO) nanosheets have been successfully synthesized through a two-step hydrothermal process. The primary nanosheets, which serve as the lattice-matched substrate for the self-assembly nanorod arrays at the second-step of the hydrothermal route, have been synthesized by using a template of anodic aluminum oxide (AAO). The as-prepared samples were characterized by XRD, FESEM, TEM and SAED. The nanorods have a diameter of about 100 nm and a length of about 2 μm. A growth mechanism was proposed according to the experimental results. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to ethanol at 230°C. In addition, the response mechanism of the sensors has also been discussed according to the transient response of the gas sensors. [ABSTRACT FROM AUTHOR]

Diethyl ether is a common industrial reagent and medical anesthetic. It is necessary to carry out real-time monitoring of this molecule due to its harmful effects on human health. In this paper, a highly sensitive diethyl ether SnO2 gas-sensing material has been prepared by a sol-gel method. The gas sensitivity was tested by a home-made gas-sensing equipment. The surface adsorption and reaction processes between the SnO2 gas-sensing film and the diethyl ether have been studied by in situ diffuse-reflectance Fourier-transform infrared spectroscopy (DRFT-IR) at different temperatures. The results show that the SnO2 gas-sensing material has high sensitivity to diethyl ether, and the lowest detection limit can reach 1 ppm. Furthermore, ethyl (CH3CH2●), oxoethyl (CH3CH2O●), ethanol (CH3CH2OH), formaldehyde (HCHO), acetaldehyde (CH3CHO), ethylene (C2H4), H2O and CO2 surface species are formed during diethyl ether adsorption at different temperatures. A possible mechanism of the reaction process is discussed. [ABSTRACT FROM AUTHOR]