Nano-semiconductors(ZnO,TiO₂,Ag@AgI): Synthesis And Photocatalytic Property

With the development of the economy, the environmental pollution, especially the water pollution, more and more become one of the most urgent problem of the world. Sewage treatment has already been a global consensus, as well as a research hot spot. Although various methods had been used to treat sewage, the application of these methods is restricted due to high cost, poor degradation efficiency, second-pollution and complicated technology. As a result, it is significant to develop the new method which is more economical and efficient.The semiconductor photocatalysis is a new method of sewage treatment which was developed in 1972. It has attracted much attention for its advantages such as low cost, nontoxic, high degradation efficiency. TiO₂ nanophotocatalyst became the most widely used photocatalyst for it possesses many characteristics such as high photocatalysis activity, excellent stability, harmless to human beings, low cost and so on. However, the photocatalysis application of the TiO₂ is restricted due to the poor quantum efficiency and the fact that it could only absorb the UV light which is just the 4% of sunlight. To solve these problem, many mechods, including noble metal deposition, coupled semiconductor, ion modification, were proposed to enhance the photocatalysis efficiency by scientist.This paper focuses to the follow two aspects:(a) Search for the new photocatalyst which could replace the conventional TiO₂ photocatalyst.ZnO could be a substitute for the superior quantum efficiency than TiO₂ as well as the nontoxic and cheapness. The plasmonic photocatalyst Ag@Ag halidesis is efficient and stable under visible light and is promising candidates for the development of highly efficient and stable photocatalysts active under visible light.(b) Prepare the three-dimensionally ordered macroporous TiO₂ structureThree-dimensionally ordered macroporous TiO₂ structure possess high surface area which is favorable for photocatalysis. In addition the slow photons effect, a characteristic of the three-dimensionally ordered macroporous structure, could enhance the optical absorption of material. Therefore, compared with the conventional TiO₂, the photocatalysis activity of three-dimensionally ordered macroporous TiO₂ structure is promising to improve largely.The main content of my paper are as follow:(a) The flowerlike ZnO nano/microstructures had been successfully prepared in high yield via a hydrothermal process at 95°C. The possible formation mechanism of this nano/microstructure has been proposed. Our experimental results demonstrated that the flowerlike morphology could be controlled by adjusting reaction time. Heat treatment, as well as reducing the size of the rods of flowerlike ZnO nano/microstructures could obviously enhance their photocatalytic activity. Our results demonstrated that flowerlike ZnO nano/microstructures had a promising application for photocatalytic degradation.(b) SiO₂ opal structure was prepared by vertical deposition method. Then, TiO₂ inverse opal which has photonic band gap was obtained via dip-coating method. the tetrabutyl titanate was replaced by titanium tetrachloride to use as precursor. The prepareed inverse opal has smooth surface and few crack was observed in a large range. It is found that the film thickness of the TiO₂ inverse opal could be controlled by adjusting the deposition temperature.(c) The plasmonic photocatalyst Ag@AgI had been successfully synthesized by a simple method. The synthesized Ag@AgI was stable under light and exhibit excellent photocatalytic activity. We found that the surface plasmonic intensity which could enhance photocatalysis activity could be controlled via adjusting the prepare reaction temperature of the AgI.