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

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

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

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

The adsorption of ethanol on V 2 O 5 (010) surface was investigated by means of density functional theory (DFT) with a combined generalized gradient approximation (GGA) plus Hubbard U approach to exploit the potential sensing applications. The adsorption configurations were first constructed by considering different orientations of ethanol molecule to V and O sites on the “Hill”- and “Valley”-like regions of corrugated (010) surface. It is found that ethanol molecule can adsorb on whole surface in multiple stable configurations. Nevertheless the molecular adsorption on the “Hill”-like surface is calculated to occur preferentially, and the single coordinated oxygen on “Hill”-like surface (O 1(H) ) acting as the most energetically favorable adsorption site shows the strongest adsorption ability to ethanol molecule. Surface adsorption of ethanol tunes the electronic structure of V 2 O 5 and cause an n-doping effect. As a consequence, the Fermi levels shift toward the conductive bond increasing the charge carrier concentration of electrons in adsorbed V 2 O 5 . The sensitive electronic structure and the multiple stable configurations to ethanol adsorption highlight the high adsorption activity and then the potential of V 2 O 5 (010) surface applied to high sensitive sensor for ethanol vapor detection. Further Mulliken population and Natural bond orbital (NBO) calculations quantify the electron transfer from the adsorbed ethanol to the surface, and correlates the adsorption ability of surface sites with the charge donation and dispersion. [ABSTRACT FROM AUTHOR]

This paper presents an alcohol vapor sensor realized using stretchable optical waveguides doped with commercially available fluorescent dyes. The fabrication technology is based on a cost-efficient replication method, employing polydimethylsiloxane materials mixed with the dye Nile red. Upon introduction of ethanol vapors, the fluorescent emission was found to have a wavelength shift of ~20 nm with a response time of ~10 s. Observing the fluorescence intensity of the shifted emission spectrum in a periodically varying environment inside a gas-sensing setup showed a respective variation with introduction of ethanol vapor. The intensity variation also showed the reversibility of the sensor. The sensing platform is found to hold much promise for further integration and multiplexing. [ABSTRACT FROM PUBLISHER]

A facile approach for synthesis of flower-like p-CuO/n-ZnO heterojunction nanorods was reported. The CuO/ZnO nanorods were prepared by co-precipitation of CuO nanoparticles on the hydrothermally grown ZnO nanorods. The obtained samples were characterized by X-ray diffraction and transmission electron microscopy, which confirms that the heterogeneous nanostructure of the CuO/ZnO nanorods was highly crystalline. The ethanol gas-sensing properties of CuO/ZnO nanorods were evaluated with different ethanol vapor concentrations at the working temperature of 300 °C. The response of 0.25:1 CuO/ZnO nanorod sensor to 100 ppm ethanol was 98.8, which is 2.5 times that of ZnO only sample, with a response and recovery time of 7 s and 9 s, respectively. Good selectivity and long-term stability can also be achieved and the response of low concentration as 1 ppm ethanol can reach the value of 9.68 using the flower-like p-CuO/n-ZnO heterojunction nanorods as sensing material. The enhanced ethanol response is mainly attributed to a wider depletion layer on the CuO/ZnO surface resulted from the formation of p-n heterojunctions between p-CuO nanoparticles and n-type ZnO nanorods. [ABSTRACT FROM AUTHOR]

Abstract: SnO2 precursor inks with appropriate viscosity and surface tension were prepared using the sol–gel technique with anhydrous ethanol as the primary solvent. The inks were printed on both alumina ceramic and silicon substrates using an ink printing apparatus produced by modifying a commercial printer. SnO2 based gas-sensing films with different thicknesses and additives were formed, and the morphologies and electrical properties of these films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and an instrument designed to measure the gas sensing abilities of the films. A linear relationship was observed between the natural logarithm of the electrical resistance of the SnO2 films and the reciprocal of the films’ absolute working temperature in the range between 20°C and 265°C. The electrical and gas-sensing properties of the films changed significantly with the thickness of the films. The film thickness can be easily adjusted by modifying the number of printing events. The SnO2 films selectivity for various gases could be modified by utilizing different additives. This work also showed that ink-jet printing was a convenient and low-cost method to prepare gas-sensing films with controlled film thickness and additive level. [Copyright &y& Elsevier]

Abstract: Monodispersed TiO2 spherical colloids with diameters of about 250nm were prepared by a sol–gel method. Heterostructural Ag–TiO2 spheres were manipulated by surface engineering, in which the Ag nanoparticles with an average size of 10nm were uniformly distributed on the surface of the TiO2 nanospheres by in situ reduction and growth. The gas-sensing properties of the TiO2 nanospheres and heterostructural Ag–TiO2 nanospheres to ethanol and acetone were measured at 350°C. The results indicated that Ag nanoparticles greatly enhanced the response, stability and response characteristic of TiO2 nanospheres to the tested gases. Response times of Ag–TiO2 sensor to 30ppm acetone and 50ppm ethanol were <5s. [Copyright &y& Elsevier]

Macroporous SnO 2 (M − SnO 2) materials with high specific surface area were synthesized by template method. In order to further improve the gas sensing performance of the sensor, Ag modified macroporous SnO 2 (M-Ag/SnO 2) gas sensing materials were finally prepared. The morphology, valence state and crystal structure of the samples were characterized by SEM, XRD, TEM, UV–Vis and XPS. The characterization results indicated that the macroporous gas sensing materials were successfully synthesized, and there were Ag nanoparticles in the samples. The gas sensing test showed that, compared with pure SnO 2 (180), the gas sensitive response value of M − SnO 2 with high specific surface area is 600, which is about 3.33 times than that of pure SnO 2. Moreover, M-Ag/SnO 2 sensor exhibits higher response value (830) to 10000 ppm ethanol gas at 260 °C, which was 4.61 times higher than that of pure SnO 2 nanoparticles. This outstanding gas sensing properties are derived from the high specific surface area and catalytic activity of the M-Ag/SnO 2 materials. More importantly, the great reversibility and repeatability of the material makes it have a broad application prospect in designing high performance ethanol sensors. [ABSTRACT FROM AUTHOR]

Heterostructures with great modulation of electron transfer afford a great opportunity for gas-sensing applications. Herein, a hollow porous ZnO@ZnS core-shell structure with high gas-sensing performance has been successfully hydrothermally synthesized. The phase composition and the morphology of the as-prepared products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and energy dispersive X-ray spectroscopy. The results show that the pure ZnO and the ZnO@ZnS appear a mesoporous structure and a hollow porous structure, respectively. Gas-sensing measurements show that the gas-sensing performance of the ZnO@ZnS based sensor is obviously higher than that of the pure ZnO, and it has a high selectivity, quick response-recovery and stability to ethanol. Its response reaches 114.2 to 100 ppm ethanol, and the response and recovery time is 3 s and 8 s to ethanol, respectively. The gas-sensing enhancement of the ZnO@ZnS can be attributed to the Schottky barrier at the interface of the ZnO@ZnS and the special hollow porous structure. The strategy put forward is generally applicable to design efficient ethanol sensors with optimized sensing performances. • A hollow porous ZnO@ZnS Heterostructures have been successfully synthesized. • The ZnO@ZnS sensor shows excellent gas-sensing performance to ethanol. • The gas-sensing mechanism of the hollow porous ZnO@ZnS is discussed in detail. [ABSTRACT FROM AUTHOR]