The Preparation And Photocatalytic Properties Of TiO₂/SiO₂/Fe₃O₄Nanoparticles Modified By Quantum Dots

nanoparticles have photocatalytic properties of TiO2, it can degrade organic compounds under UV irradiation, and have the characteristic of magnetic loading, it can be recycled by its magnetic; SiO2middle layer can effectively protect the magnetic core, and suppress the recombination of photo-generated electron-hole pairs, SiO2middle layer is a good way to improve the photocatalytic properties of TiO2. TiO2/SiO2/Fe3O4nanoparticles modified by quantum dots can promote the photo-generated electrons and holes migrate to different field direction to improve the photocatalytic efficiency and also can broaden the scope of its light response and effectively use of solar energy by absorbing visible light.These advantages make it have a good prospect of application in the photocatalytic field of environmental protection.Fe3O4magnetic core was prepared by coprecipitation in this thesis, then was wrapped SiO2and TiO2layers by the hydrolysis and polycondensation of TEOS and isopropanol titanium. The package process conditions were changed, obtained nanoparticles’structural morphology and magnetic were characterized by XRD, TEM, EDS and VSM and then obtain the best process conditions. Prepared TiO2/SiO4/Fe3O4nanoparticles demonstrate the obvious diffraction peaks of anatase TiO2and Fe3O4, with an average particle size of15-20nm. its saturation magnetization is9emu/g, and it can be well recycled.For verifing TiO2/SiO2/Fe3O4nanoparticles photocatalytic properties under UV light, the methyl orange and methylene blue solution simulated organic wastewater. The rate of photocatalytic degradation was calculated by controlling the absorption peaks of the organic solution before and after the reaction to standard curve. TiO2/SiO4/Fe3O4nanoparticles have higher catalytic efficiency under alkaline conditions, compared with P25TiO2its photocatalytic efficiency is very close and it have higher photocatalytic efficiency compared with TiO2/Fe3O4nanoparticles. TiO2/SiO2/Fe3O4nanoparticles can well be used multiple times.TiO2/SiO2/Fe3O4nanoparticles modified by CdS, CdSe quantum dots were prepared by the chemical deposition method and the bridging role of mercaptopropionic acid, respectively. The morphology and composition of the particles were characterized by TEM and EDS. The absorption edges of the nanoparticles modified by quantum dots are around525nm and700nm in the visible region. The experiments of photocatalytic degradation under the visible light were did, the degradation rate was calculated by the absorption peak of the organic solution; nanoparticles modified by CdS, CdSe quantum dots have good degradation efficiency, but TiO2/SiO2/Fe3O4nanoparticles don’t have, nanoparticles modified by CdSe quantum dots have better photocatalytic efficiency.