The Synthesization And Gas Sensitivity Rearch Of Au@SnO₂ Core/shell Nano-particles Film

Functional metal oxides have been concerned owing to their unique physical properties. Tin oxide (SnO₂) which with forbidden band energy Eg=3.6eV at 300 K is a n-type wide band oxide semiconductor. It is widely used in dye-sensitized solar cells, Li-ion batteries, transparent conductive electrodes and gas sensors.In gas sensor, SnO₂ is one of the most attractive materials because of high sensitivity and chemical stability to different gases. The sensing performance of SnO₂ can be significantly improved, when its size is in nanometer with large surface area and high surface activity. The application of nanotechnology expands a new method to improve the performance of gas sensors. Moreover, the appropriate additives can also improve the performance of the sensors.In this paper, AuSn nano-particles have been synthesized by the reduction of Sn2+ in the pre-gel solution of Au nano-particles, and then the film of the Au@SnO₂ core/shell nano-structure was obtained, by gradual elevation of temperature oxidation in oxygen atmosphere. The XRD, TEM were employed to investigate the morphology, structural and composition of these samples. The factors influencing the grain size of Au@SnO₂ nano-particles is discussed over this basis.Results show that the particles'size increase with the molar ratio of Au and Sn decreasing.By means of the studies of gas sensitivity about Au@SnO₂ core/shell nanoparticles film to the reducible gas (ethyl alcohol) and the oxidized gas (oxygen), the mechanism of Au influence the performance of SnO₂ semiconductor has been initially discussed. Compared with SnO₂, the Au@SnO₂ core/shell nanostructure has advanced the sensitivity to the oxygen, while reduced the sensitivity to the ethyl alcohol due to the changes of energy band induced by Au contacting with the SnO₂ semiconductor, forming a metal semiconductor junction. The impact of metal-semiconductor junction and electron tunneling effect to electrical properties of the film has been analyzed, providing some theoretical support to the new SnO₂-based gas sensitive materials.