Prepartion Of Er³⁺：Y₃Al₅O₁₂/TiO₂Composite Film And Studying On Visible-light Photocatalytic Activity

TiO₂is an ideal and excellent light catalyst semiconductor material with itsproperties of chemical stability than other metal oxide at room temperature, and it issuitable to be the high efficient photocatalyst due to its non-toxic, low price, broadspectrum antibacterial property and long-term for eliminating the pollutants in air andwater, in addition, it could reuse more times. Compared with other photocatalysts,TiO₂can degrade almost all organisms and also has a non-selective degradation,quick oxidation degradation speed and mild reaction conditions, which makes it oftenwidely used on industrial dye or wastewater treatment. However, there are twoproblems when TiO₂is used as photocatalyst scattered in wastewater. Firstly, thepowder of TiO₂photocatalyst is easy to condense and inactivate, difficult to separateand recycle, which limits the practical application of nanometer TiO₂catalyst to agreat degree; secondly, because of the TiO₂band gap is3.2eV wide and it can onlyuse ultraviolet light （λ <387nm） to be activated, so the use efficiency of solar energyis limited accordingly.In order to make up for the shortcomings, this paper uses sol-gel method anddip-coating method to immobilize TiO₂catalyst onto glass as thin films, which can be thebetter way to solve problem of the catalyst is difficult to separate, so that we canreduce the difficulty of the processing steps after degradation reaction. And we addupconversion luminescence agent Er³⁺：Y₃Al₅O₁₂to the TiO₂sol and prepared theEr³⁺：Y₃Al₅O₁₂/TiO₂composite film. The upconversion luminescence agent canabsorb visible light which has low energy in visible light and can stimulate ultravioletlight with high energy, so that it could improve the utilization rate of solar energy byusing TiO₂in the catalytic reaction. After adding the upconversion luminescenceagent into TiO₂thin film, it has been excitated by more high-energy ultraviolet lightand the effect of catalytic is greatly improved.In this study, we add upconversion luminescence agent Er³⁺：Y₃Al₅O₁₂into theTiO₂sol to prepare composite film by dip-coating method. The Er³⁺：Y₃Al₅O₁₂/TiO₂ composite film was characterized by X-ray diffraction （XRD） and scanning electronmicroscope （SEM）. Its photocatalytic activity was examined through the degradationof some organic dyes under visible-light irradiation. The degradation process oforganic dyes was monitored by UV-vis spectrophotometer. Some main influencefactors on the photocatalytic activity of Er³⁺：Y₃Al₅O₁₂/TiO₂composite film such asEr³⁺：Y₃Al₅O₁₂/TiO₂mass ratio, layer number, heat-treated temperature andheat-treated time were studied, recycling used times will also be taken into account.The effects of initial organic dyes concentration and visible-light irradiation time onphotocatalytic degradation were also researched. In addition, we are working toexplore the relationship between photocatalytic activity and layers number, sequencein chapter three of this article. We have prepared10kinds of different forms ofcoating film related to the layer number and8kinds of different forms of coating filmrelated to the sequence. Then, the relationship between photocatalytic activity andlayers number, layers sequence is obtained. The effects of heat-treated temperatureand heat-treated time on the photocatalytic activity of Er³⁺：Y₃Al₅O₁₂/TiO₂compositefilm was considered. Finally, the results show that the Er³⁺：Y₃Al₅O₁₂/TiO₂compositefilm displays a good and broad-spectrum photocatalytic activity for degradation ofmost organic dyes.