| In this paper,the ZnO foam with exposed {001} facets and the ZnO foam doped with A1 were produced by the solution of rapid thermal decomposition.The hydrogenated ZnO foam was obtained by hydrogenation.The ZnO thin films with different[001]orientation were obtained by using sol-gel spin coating.The composition,morphology,crystal structure,specific surface area and surface structure of the products were analyzed by means of various detection methods.The gas sensing properties of the ZnO foam exposed with {001} facets,hydrogenated ZnO foam,commercial ZnO particles and ZnO foam doped with A1 were tested.The relationship between ZnO crystal structure and the structure change of {001} facets and sensing properties was studied,and the gas sensing mechanism was proposed.The photovoltaic properties of the ZnO thin film with different[001]orientation were tested.The relationship between the structure of[001]oriented ZnO and the photovoltaic properties is studied,and the separation mechanism of photogenic charge of its[001]oriented film was presented.The detailed exploration results are as follows:(1)The 3D ZnO foam structure with exposed the {001} facets was synthesized by heating Zn(NO3)2 aqueous solution containing polyvinyl pyrrolidone(PVP)at 650 ?for 10 min in the air.The hydrogenated ZnO foam products were obtain by heating in H2 gas flow at 500 ? for different time period.The gas-sensing properties of the ZnO products indicate that the hydrogenated ZnO foam products show better gas sensing response than non-hydrogenated ZnO foam for acetone,ethanol,n-Butylamine and its performance is improved with hydrogenated time longer.The relationship between the hydrogenation time and the adsorption oxygen content on the {001} facets of the products was investigated.The 3-fold coordinated Zn atoms with one dangling bond are regarded as reaction active sites in the gas-sensing reaction,and the gas sensing properties difference between the hydrogenation and non-hydrogenation products was explained.(2)The different amounts of aluminum nitrate were dissolved in the aqueous solution of PVP(polyvinylpyrrolidone)containing zinc nitrate and the ZnO foam samples with different Al doping amount were produced by fast thermal decomposition of the mixed solution at 650 ?.The gas-sensing properties of the products of different A1 doping concentration were tested.It was found that the gas-sensing properties of the samples with doped Al to methanol,formaldehyde and toluene were better than the samples without doped Al,and the gas sensing property of the sample doped with the 3%Al was the best.The relationship between the Al doping concentration and the specific surface area and crystal structure of the ZnO foam was investigated.The effect of the crystallinity,morphology,special surface area and the exposed crystal facet on the adsorbed oxygen amount on the sample surface was explored,and the gas-sensing reaction mechanism was proposed.(3)By using sol-gel spinning method,ZnO thin films with the different[001]orientation on the FTO substrate were produced by changing the forming temperature of gel.The crystal structure and morphology were analyzed.The thin film is composed of a lot of tiny ZnO particles,and the thin film surface is very dense.The photovoltaic properties of the ZnO thin films with[001]orientation are tested,and it is found that the photovoltaic properties of the thin films are better with the[001]orientation enhancement.The ZnO crystal structure was analyzed by DFT(density functional theory),it was found that the {001} crystal plane is a polar crystal plane,and the charge separation mechanism between the {001} polar crystal plane was propose. |
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