Study On The Preparation Of Nano Semiconductor At Low Temperature And Their Properties

Both WO3 and Bi2WO6 are n-type semiconductor materials, wherein the band gap of WO3 is about 2.4-2.9 eV, and Bi2WO6 is 2.8 eV. Bi2WO6 crystal structure is composed of [Bi2O2]2+ layers and WO6 octahedral sheets alternately. This layered structure makes for conducive to charge transfer, and therefore, Bi2WO6 shows excellent photocatalytic activity. As the important physical and chemical properties material, WO3 is a very important semiconductor material. Compared with traditional WO3 material, WO3 nanowires have a larger surface area, and they have important application in aspects of gas sensing, electroluminescence, photoluminescence, conductivity electrode and photocatalysis. With these advantages(simple, easy to operate, and low power consumption), this method breaks the conventional hydrothermal method in the stringent requirements of the reaction vessel and the reaction conditions. Besides a variety of morphologies of samples were characterized. Biological applications and photocatalytic experiments were also carried out. The related mechanisms were explored, too. Details are as follows:(1) Surfactants have a major impact on the morphology and size of Bi2WO6 in this low-temperature hydrothermal method. There are two possible reasons, one is the guiding role of different surfactants, and the other one is that solvents affect mass transfer rate in Oswald ripening process, thereby affecting the performance and micro-crystalline structure of the sample. Compared with traditional methods, Bi2WO6 prepared by low temperature hydrothermal method still has excellent photocatalytic ability.(2) Bi2WO6 can be synthetized at 95℃ low temperature conditions by hydrothermal method when Bi(NO3)3?5H2O and previously synthesized WO3?nH2O are used as raw materials. Bi2WO6/WO3 heterojunction has a strong absorption characteristic in the UV-visible region and can significantly improve the activity of photocatalytic degradation of methyl orange. Bi2WO6/WO3 is better than a single WO3 or Bi2WO6 as photocatalyst in the degradation of methyl orange. This enhancement can be attributed to that the intimate contact heterojunction is beneficial to photogenerated electron transport and the electron-hole pair separation.(3) WO3 with different morphologies are prepared by chemical precipitation and hydrothermal method below 95 ℃ via changing various test parameters. Nano-acicular WO3 is prepared with(NH4)2SO4 as surfactant. WO3 nanowires with 400 slenderness ratio are obtained by one-step annealing method. WO3 nanowires have many important applications in many aspects such as electrochemical and biological fields.(4) The experiments show that nano Ag with different concentrations and WO3 with different nanostructures have the effect of antibiosis and sterilization. Nano Ag particles with diameter of about 50 nm and concentration of 0.067 M, has the best antibacterial and bactericidal effect. WO3 with different morphologies show different antibacterial and bactericidal effect, thereinto needle-WO3 has the best effect. Presumably those WO3 nanowires produce strong oxidizing substances under light irradiation as a semiconductor catalyst.