Preparation And Properties Of Tm³⁺ And Yb³⁺ Co-doped Calcium Fluoride Nanocrystalline Composites Supported By Porous TiO₂ Array

Nowadays,rivers are increasingly polluted and harmful microorganisms are everywhere.Degradation of harmful substances,inhibition of bacterial growth,treatment of river pollution,purification of living enviro nment,is related to the survival of mankind.Photocatalyst materials can effectively degrade pollutants and inhibit or even kill bacteria through photocatalytic effect.Nano TiO₂has been widely used because of its high catalytic activity.However,at present,the nano-TiO₂material are easy to agglomerate,and cannot be used for the treatment of natural water due to its nano-toxicity.Moreover,it can only utilize ultraviolet light and short-wave visible light in natural light,but cannot effectively utilize infrared light,which accounts for about40%of natural light.So its photocatalytic efficiency is greatly reduced.Aiming at the above disadvantages of nano TiO₂,this study prepared porous array TiO₂with nano-level defects by PMMA template method.The morphology,adsorption capacity and photocatalytic capacity of porous TiO₂array were compared with that of ordinary sol-gel TiO₂.Upconversion calcium fluoride nanocrystals were prepared by hydrothermal method.Upconverted calcium fluoride nanocrystals are supported by porous TiO₂.Six new photocatalyst composites with different composite ratios were successfully prepared.The composition and structure of the composite were studied.The photocatalytic properties of TiO₂/（CaY）F₂:Tm³⁺,Yb³⁺composites were studied by placing the composite material under 980 nm nir light to degrade methyl orange.The effects of different composite ratios of TiO₂and（CaY）F₂:Tm³⁺,Yb³⁺on its photocatalytic efficiency were discussed.The bacteriostatic properties were also studied.Finally,the preparation experiment of array porous TiO₂is amplified to explore the possibility of realizing mass production.1 kg array of porous TiO₂was successfully prepared.The cost was estimated.Its composition and morphology were analyzed.The porous TiO₂array was compounded with nanocrystals at a ratio of 2:1 to investigate the photocatalytic properties of the composites.Finally,its bioco MPatibility was evaluated.The results showed that:（1）The pore diameter of array porous TiO₂was about 300nm,with nano-scale defects.The toxicity and agglomeration of nano TiO₂were eliminated,and the internal pores of the array porous TiO₂were connected with each other,which enhanced the mass transfer efficiency and adsorption capacity.Under the uv lamp with the main peak of 365 nm and power of 170 W,the array of porous TiO₂degraded methyl orange.After 10 h,the degradation rate was 85%,while that of ordinary sol-gel TiO₂was only 70%.The photocatalytic capacity of porous array TiO₂was greatly improved.（2）Under the infrared lamp with the main peak of 980 nm and the power of275 W,the array porous TiO₂supported（CaY）F₂:Tm³⁺,Yb³⁺nanocrystalline composite material has a good degradation effect on methyl orange.When the TiO₂/（CaY）F₂:Tm³⁺,Yb³⁺mass composite ratio is 2:1,the degradation efficiency is the highest,and the degradation rate can reach 70%.When the ratio was 2:1,the minimum inhibitory concentration was 125 ppm,and the inhibitory rate was up to 90%.（3）After amplification of the experiment,the degradation rate of 2:1 composite material on methyl orange could reach 65%,and there was no cytotoxicity.The production of 1 kg array porous TiO₂has controllable cost and low price,so it is possible to realize mass production.