The Photocatalytic Performance Research Of TiO₂ Nano-sheet Film Based On Light Conversion

This paper has synthesized up-conversion luminescence materials CeF₃ and CaF₂:Er³⁺ with regular morphology by using the microwave-assisted hydrothermal treatment. The shapes and sizes of two types of materials have been controlled by changing the reaction conditions, and the influence of reaction conditions as well as morphologies in the luminescence property of materials have been discussed. The morphology features and some other properties of the samples were characterized by XRD, SEM, PL, UV-vis and Raman, respectively. It can be seen that the CeF₃ exhibit fascinating chain structures which built from many nanodisks in a particular way of layer-by-layer. The mean thickness and diameter of the nanodisks are measured to be about 40 nm and 100 nm. Under 525 nm visible light excitation, a strong peak appear in the UV region center at 325 nm, which can be assigned to the 5D→2F7/2 transitions of Ce3+ ions, a relative weak UV emission peak at 325 nm can be also found under the excitation wavelength of 554 nm,781 nm and 852 nm. The CaF₂:Er³⁺ with monodisperse and uniform microcube were also synthesized by this way, and their main diameters are about 40 nm. Under 461 nm,480 nm 和 524 nm visible lights excitation, two peak appear in the UV region center at 330 nm and 368 nm. It is shown that 1.5 mol% of doping concentration of Er³⁺ ions in CaF₂:Er³⁺ is optimum. Finally, The UV-Vis was also used to analyse this up-conversion luminescence mechanism, the formation mechanism of sample was deduced as well.Moreover, anatase TiO₂NSF was fabricated using a facile hydrothermal synthesis, which consists of a large number of continuous distributed nanosheet films. It has a large surface area to provide more active sites for photoreaction. And the nanosheet film structure is regard as a wonderful substrate for the growth of UC materials. Hybrid architecture comprising up-conversion material dispersed on TiO₂NSF was fabricated using a facile one-step microwave-hydrothermal synthesis. Besides, there is no barrier between the up-conversion material and TiO₂NSF by the direct surface-to-surface contact, greatly facilitating the energy transfer between the two materials. Through the result of photocatalytic reaction we can see that when the amount of CeF₃ and CaF₂:Er³⁺ are 0.03 M and 0.05 M respectively, the hybrid system shows the highest degradation ability for methylene blue with 78.12% and 89.45% degradation ratio after reacting for 2 h on visible light. Finally, a photodegradation mechanism was proposed as well.In summary, this paper has made new attempt and exploration in the preparation and luminescence property of up-conversion materials. And we refer prepare two different upconversion luminescence agents to compound with TiO₂NSF, which can improve utilization efficiency of visible light, and enhance photocatalytic performances of photocatalyst.