nitrogen-dioxide and stannic-oxide

In the pandemic era, the development of high-performance indoor air quality monitoring sensors has become more critical than ever. NO

Topics: Cysteine; Light; Nanoparticles; Nitrogen Dioxide; Sulfur; Tin Compounds

γ-Ray radiolysis was applied to the synthesis of Au nanoparticles. The growth behavior of Au nanoparticles was systematically investigated as a function of the processing parameters under γ-ray radiolysis. The surface of the networked SnO(2) nanowires fabricated through the vapor-phase selective growth process was uniformly functionalized with the Au nanoparticles by the γ-ray radiolysis process. Au nanoparticle-functionalized SnO(2) nanowires were compared to bare SnO(2) nanowires in terms of the NO(2) sensing characteristics. Au functionalization sharply improved the sensitivity and response time of SnO(2) nanowire-based gas sensors, most likely due to the spillover and the catalytic effects of Au nanoparticles. The methodology used in this work can be easily extended to synthesize various combinations of metal nanoparticles and oxide nanowires, which may be useful materials for use in detecting hazardous substances.

Topics: Gamma Rays; Gold; Metal Nanoparticles; Microscopy, Electron, Transmission; Nanowires; Nitrogen Dioxide; Tin Compounds

Mesoporous and/or macroporous SnO(2)-based powders have been prepared and their gas-sensing properties as thick film sensors towards H(2) and NO(2) have been investigated. The mesopores and macropores of various SnO(2)-based powders were controlled by self-assembly of sodium bis(2-ethylhexyl)sulfosuccinate and polymethyl-methacrylate (PMMA) microspheres (ca. 800 nm in diameter), respectively. The introduction of mesopores and macropores into SnO(2)-based sensors increased their sensor resistance in air significantly. The additions of SiO(2) and Sb(2)O(5) into mesoporous and/or macroporous SnO(2) were found to improve the sensing properties of the sensors. The addition of SiO(2) into mesoporous and/or macroporous SnO(2) was found to increase the sensor resistance in air, whereas doping of Sb(2)O(5) into mesoporous and/or macroporous SnO(2) was found to markedly reduce the sensor resistance in air, and to increase the response to 1,000 ppm H(2) as well as 1 ppm NO(2) in air. Among all the sensors tested, meso-macroporous SnO(2) added with 1 wt% SiO(2) and 5 wt% Sb(2)O(5), which were prepared with the above two templates simultaneously, exhibited the largest H(2) and NO(2) responses.

Topics: Antimony; Crystallization; Gases; Hydrogen; Microscopy, Electron, Scanning; Nanotechnology; Nitrogen Dioxide; Oxides; Porosity; Powders; Surface Properties; Temperature; Tin Compounds; X-Ray Diffraction

The paper presents a quantitative model to elucidate the role of impinging photons on the final response towards oxidizing gases of light-activated metal oxide gas sensors. The model is based on the competition between oxygen molecules in air and oxidizing target gases (such as NO(2)) for the same adsorption sites: the surface oxygen vacancies (OV). The model fairly reproduces the experimental measurements of both the steady-state and the dynamic response of individual SnO(2) nanowires towards oxidizing gases. Quantitative results indicate that: (1) at room temperature NO(2) adsorbs onto OV more avidly than oxygen; (2) the flux of photons and the NO(2) concentration determine the partition of the two gas populations at the surface; and (3) the band-to-band generation of electron-hole pairs plays a significant role in the photodesorption process of gas molecules. The model also offers a methodology to estimate some fundamental parameters, such as the adsorption rates and the photodesorption cross sections of oxidizing molecules interacting with the nanowires' surface. All these results, enabled by the use of individual nanowires, provide deep insight about how to control the response of metal oxide nanowires towards oxidizing gases, paving the way to the development and consolidation of this family of low consumption conductometric sensors operable at room temperature.

Topics: Gases; Models, Chemical; Nanowires; Nitrogen Dioxide; Oxidation-Reduction; Temperature; Tin Compounds; Ultraviolet Rays