Selectivity interaction semiconductor nanocrystalline oxide gases : catalytic role of clusters

   The project aims to develop methods to improve the specificity of the interaction of nanocrystalline oxide semiconductor SnO₂, ZnO, In₂O₃ gases to create selective gas sensors. The proposed approach is to modify the surface of the nanocrystalline oxide clusters of catalytically active noble metals (Ru, Pd, Pt, Au), and their oxides. The advantages of the developed materials are the selectivity of the reducing gas , as well as the touch sensitivity at relatively low temperatures (25 - 200^oC) . Preliminary studies have shown that the catalytically active additives help to increase the specificity of the interaction of tin dioxide gases, thanks to the combined participation in the process of forming the sensor signal (chemisorption of gas molecules - redox interaction with the surface adsorbates - electron transport).

    Nanocrystalline semiconductor oxides are synthesized by the modified sol- gel method, aqueous solutions of salts of the corresponding metals. Morphology and size of nanoparticles will be monitored pH selection and deposition conditions of heat treatment of the xerogels. Immobilization catalytic clusters of noble metals and their oxides is performed by two methods: impregnation of the modifier precursor solution in an organic solvent and adsorption of colloidal noble metal hydroxides, on the carrier surface in an aqueous suspension. Dimensions catalytic clusters are determined by the temperature and annealing conditions applied precursors. Phase , elemental composition and microstructure of the materials will be investigated by X-ray and electron diffraction, scanning and transmission electron microscopy, high-resolution X-ray fluorescence. The oxidation state of the modifier and crystal structure of the catalytic clusters will be determined by X-ray photoelectron spectroscopy, electron paramagnetic resonance, X-ray absorption spectroscopy .

    The focus of the work will be paid to the study of nature and the concentration of surface active sites and their interaction with gases using special methods: thermoprogrammed probe techniques, in situ analysis methods directly into the atmosphere in the presence of toxic gases at the MPC (synchronous measurements of conductivity and work function in situ infrared spectroscopy). Be established correlations between the physicochemical properties of the surface : the concentration and reactivity of the active sites on the surface of the semiconductor oxide materials and the nature of the interaction with the gas molecules and sensory properties in relation to the reducing gas (NH₃, CO, H₂). Special attention will be paid to the influence of catalytic clusters interaction of materials with oxygen isotope exchange method thermoprogrammed .
As a result of the material will be obtained for the active elements of fire detectors and prototypes of selective gas detectors.