Synthesis And Characterization Of Fe ₃ 4 -Au Magnetic Composite Nanoparticles And Their Catalytic Degradation Of Organic Dyes

Au composite nanoparticles have received considerable attention because of their advantageous properties arisen from both individual Au and Fe3O4 nanoparticles. At present, various structures of Fe3O4/Au hybrid nanoparticles have developed, such as nuclear/satellite, core shell, dumbbell, nanostar and nanoflower etc., which have offered widely applications in biomedical and chemical catalysis field. In this thesis the Fe3O4-Au composite nanoparticles was firstly prepared in water and characterized, then used as catalyst to oxidative degradation organic dyes. The mechanism of catalysis was also discussed and the detail results are as follows:(1) Fe3O4-Au composite nanoparticles were synthesized in aqueous solution, then characterized by Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectrometer (FTIR) and Vibrating Sample Magnetometer (VSM) etc. The experimental results showed that the size of Fe3O4-Au composite nanoparticles was ranged from 10 to 30 nm and its saturated magnetization was 31 emu/g. These nanoparticles possessed well-dispersed and long-term stability in aqueous solution.(2) Fe3O4-Au composite nanoparticles were served as catalyst in oxidative degradation of methyl orange (MO) in the presence of H2O2, and their catalytic condition were optimized. The optimization condition was m(catalyst)=4 mg, C(H2O2)=0.65 mol/L, the ratio of Au/Fe=1.52, pH=7 and C(MO)=8 mg/L, which degradation rate was higher than 95% within 40 min. Meanwhile, it followed the first-order reaction kinetics equation and the reaction rate constant was 6.30x10-2 min-1. More importantly, the catalyst can be recycled and reused for 10 times with catalytic activity still greater than 86%.(3) By using Fluorescence Spectrophotometry, Raman Spectroscopy, and Fourier-transform Infrared spectrometer, the mechanism of Fe3O4-Au with H2O2 system degradating methyl orange solution was explored. The results indicated that homolytic cleavage of H2O2 produced the hydroxyl radicals in reaction system was the main reactive oxygen species, and the rate of formation of hydroxyl radicals catalyzed by Fe3O4-Au was over 6 times than that of the control group (Fe3O4+Au).(4) The degradation of methylene blue (MB) catalyzed by Fe3O4-Au in H2O2 reaction system under neutral condition MB was also discussed. The optimized condition was C(MB) =8 mg/L, m(catalyst)=3 mg, C(H2O2)=0.33 mol/L and the degradation rate of MB solution was more than 95% within 60 min. The capability of catalysts were more than 90% with recycling 5 times, suggesting Fe3O4-Au composite nanoparticles could be applied in oxidative degradation of different organic dyes.