Synthesis And Properties Of Semiconductor Nancomposite Photocatalysts

With the development of technology and industry, the water environment pollution becomes a global problem to be solved. Wastewater containing many kinds of organic dye, which not only is harm to environment and human body, but also is difficult to degradation through traditional microbe treatment, physics, or chemical methods in natural conditions. Thus, it is the requirments for us to look for an effective strategye for removal of pollutes. In recent years, semiconductor photocatalyst provides a kind of effective route to solve this problem. It is a kind of environment-friendly technology, and could degrade pollutes completely into harmless normally substance, such as CO2and H2O without secondary pollution under atmospheric conditions. This paper focuses on the preparation of a seirs of semiconductor nanocomposites. Furthermore, the photocatalytic activity for the degradation for the orgnic pollutes using the as-prepared nanocomposites as photocatalyst was further investigated. The contents of this paper were as following:1. Microwave-assisted rapid synthesis of ZnO/ZnS core-shell nanostructures via controllable surface sulfidation of ZnO nanorodsThis chapter demonstrated a new strategy for preparation of ZnO/ZnS core-shell nanorods via microwave-assisted in-situ surface sulfidation of ZnO nanorods. This is a facile and rapid process, requiring only a low level of microwave irradiation (400W), through which a conformal ZnS nanoparticle layer is deposited onto the ZnO nanorods, while retaining the uniformity of the original ZnO nanorods in the as-prepared ZnO/ZnS hybrid structures with excellent fidelity. Furthermore, the thickness and nanoparticle size of the ZnS shell can be conveniently varied or controlled by the concentration of the organo-sulfur source thioacetamide (TAA). The as-prepared products exhibit narrowed band gap and strong orange luminescence at621nm, due to the interstitial oxygen ion defect present in hydrothermally grown ZnO. However, the PL intensity gradually decreases with the increase of the thickness of ZnS shell, indicating charge transfer between the two components of the ZnO/ZnS hybrids. Further investigation has revealed that the hybrid nanostructures possess significantly higher visible light photocatalytic activity which is twice that of the original ZnO nanorods.2. Facile low-temperature synthesis of carbon nanotubes/TiO2heterostrutures with enhanced visble-light-driven photocatalytic activityIn this work, we demonstrate a facile and novel chemical precipitation strategy for the accurate coating of TiO2nanoparticles on the surface of carbon nanotubes (CNTs) to form CNT/T1O2heterostrutures, which only require titanium sulfate and CNTs as starting materials and react in the alkaline solution at60℃for6h. Additionally, TiO2nanoparticles were obtained without addition of CNTs in the reaction process, while the other conditions remain unchanged. Furthermore, the CNT/TiO2nanohybrids show an exhibit significantly enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation under the same conditions.3. Electrostatic self-assembly of TiO2nanoparticles onto carbon spheres with enhanced adsorption capability for Cr (VI)A rapid electrostatic assembly method has been developed for deposition of highly dispersed TiO2nanoparticles on the surface of carbon spheres. Surface charges on carbon spheres are found to facilitate the spontaneous deposition of the TiO2nanoparticles, in which no additional chemicals are required in this assembling process. In the formed C/TiO2hybrid structure, carbon microspheres not only reduce the agglomeration of TiO2nanoparticles, but also allow easy separation from the reaction medium for reuse. Remarkably, the as-prepared C/TiO2hybrid microspheres exhibit a superior adsorption capacity for Cr (VI), which is3.6times greater than that of commercial Degussa P25TiO2nanoparticles. The effect of pH value in solution on the adsorption capacity of the products has also been systematically investigated.4. A magnetically separable photocatalyst based on Fe3O4/C/TiO2sandwich-nanostructures as highly efficient and reusable photocatalysts for water treatment.A novel strategy was developed for fabrication of Fe3O4/C/TiO2sandwich-nanostructures via an electrostatic self-assembly method. First,Fe3O4/C core-shell structures are successfully synthesized during the hydrothermal reaction of Fe3O4nanospheres and glucose in water. Afterwards, TiO2nanoparticles are facilely deposited onto the Fe3O4/C via electrostatic self-assembly route to form Fe3O4/C/TiO2sandwich nanostructures. Further investigation has revealed that these magnetic nanocomposites possess significantly improved activity as a recyclable photocatalyst for the degradation of organic pollutants when exposed to light irradiation. This new synthesis strategy is not restricted to the specific material discussed in this work and should be versatile for a wide range of magnetically separable photocatalysts containing sandwich-nanostructures as the support and an outer layer of active semiconductor nanocrystals.