| With the development of society, the problem of environment pollutions becomes more and more serious, how to control environment pollutions is an important question for human beings. Titanium dioxide (TiO2) has become the most important photocatalyst towards all scholars because of its incomparable advantages compared with other photocatalysts. But the energy gap of anatase is about 3.2eV, only ultraviolet light which occupy about 4% of the solar light can be absorbed by pure TiO2, so it is very difficult to put TiO2 into reality. Therefore, many methods have been adopted, such as doping of ions, aggradation of noble metals and combination with other semiconductors and so on. All of these methods do its work in extending the range of absorption wavelength of TiO2, at the same time they obtained some achievements. However, the ability of oxidation of the cavities generated by excitation of various wavelength lights is different, the oxidation potentials of the cavities generated by ultraviolet lights must be higher than those generated by visible lights. Meanwhile, the hydroxyl radicals (·OH) which have high oxidative ability can generated through oxidizing the H2O molecules by cavities, both of the cavities and the·OH can decomposed pollutions thoroughly. In this thesis, on the foundation of the summarizing the results of other people, we study the upconversion luminescence agents of oxide, fluoride, phosphate which can transfer visible light into ultraviolet light compounded with TiO2 to improve the photocatalytic activity of TiO2.1. Upconversion luminescence agent CaF2(Er3+) is obtained by combustion method, when it was excited by 480nm wave, there are two evident emission peaks in the range of 320-380nm, locate at 332nm and 376nm respectively. It means that CaF2(Er3+) can transfer visible light into ultraviolet light successfully. Upconversion luminescence agent compounded with TiO2 (named CaF2(Er3+)/TiO2) by the way of sol-gel method. Through the result of photocatalytic reaction we can see that when the amount of CaF2(Er3+) is 15%, CaF2(Er3+)/TiO2 shows the highest degradation ability for methylene blue with 52% degradation ratio after reacting for 180 min on visible light, while it is only 17.6% of TiO2 at the same condition.2. We prepare ZrO2(Er3+) upconversion luminescence agent by the precipitation method, research shows that the luminous efficiency of ZrO2(Er3+) is strong, and it can emit ultraviolet light when it is excited by 522nm wave. After prepared ZrO2 (Er3+)/TiO2 photocatalyst, we characterize the phase, the grain size, morphology, surface area and absorption edge of ZrO2(Er3+)/TiO2 by XRD, TEM, BET and ultraviolet-visible spectrophotometer. It can be seen that when the mol ratio of ZrO2(Er3+) and TiO2 is 30% ZrO2 (Er3+)/TiO2 shows the best degradation ability for methyl orange.3. Ca3(PO4)2:Tm3+ upconversion luminescence agent and Ca3(PO4)2:Tm3+/TiO2 photocatalyst are prepared by high temperature solid process and sol-gel method respectively. Through the excitation spectrum and emission spectrum of Ca3(PO4)2:Tm3+ we discover that Ca3(PO4)2:Tm3+ can emit ultraviolet light which can be absorbed by TiO2 when it is excited by visible lithe. Then, we characterize all samples, thanks to the high temperature the morphology of samples have been destroyed. The structure of Ca3(PO4)2:Tm3+/TiO2 is TiO2 aggradated on the surface of Ca3(PO4)2:Tm3+. Compared the result of photocatalytic reaction to phenol of Ca3(PO4)2:Tm3+/TiO2 on visible light and ultraviolet light respectively we know that the utilization of visible light of Ca3(PO4)2:Tm3+/TiO2 is much higher than pure TiO2, while, we analysis the influence of structure towards photocatalytic activity.In summary, we refer many articles and prepare different upconversion luminescence agents to compound with TiO2, analysis the photocatalytic ability of photocatalysts. A systematic investigation has been conducted on our work. Many significance and novel results have been obtained. At the same time, this work laid the foundation for put TiO2 into industrial production to a certain extent.
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