Preparation, Characterization And Photocatalytic Properties Of Au-TiO 2 Composite Nanoparticles

As two emerging disciplines and fields, nanotechnology and nanomaterials are supposed to greatly promote the social development in the 21 st century. Nanomaterials are endowed with broad development prospective in terms of governing the environmental pollution, and the photocatalyst such as TiO₂ nanoparticles have been widely applied in the fields including organic wastewater treatment, air purification, mould proof, sterilization, deodorization and so on. TiO₂ nanoparticles have won the favor of the researchers due to its advantages including favorable stability, high catalytic activity, strong oxidation ability, mild reaction conditions, rapid degradation speed and degradation of non-selectivity. Meanwhile, they are likely to generate the catalytic oxidation reaction when irradiated by the ultraviolent light or sunlight, and they give rise to no secondary pollution. In the contemporary field of catalysis science, Au nanoparticle catalyst is one of the active frontiers. Relevant studies demonstrated that the catalysts obtained by doping the nano-Au particles into the nano-TiO₂ exhibit better catalytic effect than that of pure TiO₂, and they present potential application in the fields of optics, catalysis, electric, etc. The functional materials of the nanoscale composite structures are supposed to become the hotspot and emphasis for many scientific workers in the future.In this paper, the simple chemical synthesis method was utilized to prepare the Au-TiO₂ composite nanoparticles. Meanwhile, the instruments including the transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, UV-visible spectrophotometer （UV-VIS）, infrared spectroscopy （IR） were employed to characterize the size, surface morphology, crystal form and morphology, absorption spectra and chemical composition of the TiO₂ nanoparticles and Au-TiO₂ particles, the appearance morphology. In addition, the catalytic properties of the pure TiO₂ and Au-TiO₂ were analyzed through the experiment of photocatalytic degradation. This paper consists of three parts:The first part:Sol-gel method was used to synthesize the sphere-like TiO₂ nanoparticles with uniform particles and irregular morphology. Meanwhile, the Au-TiO₂ composite nanoparticles that were uniformly doped and endowed with insignificant agglomeration were prepared by controlling the amount of the ammonia water and the adding speed of Au. The experimental results showed that in case the amount, adding and stirring rates of the ammonia water were appropriate and the KH-550 existed, as the Au nanoparticles were doped in the TiO₂ nanoparticles uniformly, the composite particles presented uniform size and favorable dispersibility.The second part:the TiO₂ nanoparticles and the Au-TiO₂ composite nanoparticles were roasted in the high temperature furnace at 500℃ to obtain the targets with favorable crystal form. The experimental results indicated that the particle size of the Au nanoparticle was about 4.5-7.5 nm, and the crystal form of the TiO₂ nanoparticles belonged to the anatase type. Besides, Au and TiO₂ remained their own chemical characteristics after being doped with each other, but presented slightly changed chemical characterization on the whole. This was because there existed the Schottky junction between the Au and TiO₂.The third part:the rhodamine B and acridine orange were used to simulate the pollution sources in water pollution. The TiO₂ and Au-TiO₂ were regarded as the catalysts to degrade the rhodamine B and acridine orange with the same concentration. Then, the photocatalytic performance of the samples was evaluated by measuring the variations of the concentrations of the rhodamine B and acridine orange using the ultraviolet-visible spectrophotometer. The results show that:the photocatalytic performance of Au-TiO₂ is better than that of the pure TiO₂. Afterwards, the decomposition products of the rhodamine B and acridine orange were predicted, and then detected using the high performance liquid chromatography （HPLC）, so as to check whether or not TiO₂ and Au-TiO₂ can lead to the decomposition of the rhodamine B and acridine orange products.The results confirm that this catalyst has great reference for the further research in terms of governing the waste water.