Study On Upconversion Luminescence Modulation And Photocatalytic Properties Of Sc³⁺-based Oxide Nanocrystals

In recent years,rare-earth doped upconversion luminescent materials have shown excellent application value in the fields of photocatalysis,bioimaging,photosensitized solar cells,and display anti-counterfeiting due to their unique luminescent properties.However,the luminous efficiency of upconversion materials is generally low,which affects its practical application.The choice of host material strongly affects the upconversion luminescence intensity.Therefore,it is of great significance to develop excellent host materials and enhance their luminous intensity.Efficient upconversion luminescent materials can effectively convert near-infrared light into visible or ultraviolet light.Composite TiO₂semiconductor materials can improve the utilization of sunlight,increase the photocatalytic degradation rate of TiO₂ semiconductor materials to organic pollutants,and improve catalytic efficiency.Provide a new way to control the environmental problems of water pollution and air pollution.In this paper,the rare-earth doped scandium based oxide material Sc₂O₃、CaSc₂O₄ as the research object.Small-scale Sc₂O₃ and CaSc₂O₄ nanocrystals are prepared to study the upconversion luminescence characteristics and luminescence mechanism of the materials.And the preparation of CaSc₂O₄:Er³⁺,Yb³⁺@TiO₂ nanocomposites beneficial to improve the photocatalytic efficiency.The research content and results of this paper are as follows:（1）Sc₂O₃:Er³⁺,Yb³⁺upconversion nanocrystals of about 19 nm were prepared by a simple oleic acid-mediated hydrothermal method.Compared with Sc₂O₃ samples prepared by the two-phase solvothermal method with the same optimized concentration,Sc₂O₃:Er³⁺,Yb³⁺upconversion nanocrystals of hydrothermal synthesis method showed stronger upconversion luminescence performance,in which red light was enhanced by 4 times.The upconversion luminescence enhancement in this experiment can be attributed to the reduction of surface groups and longer lifetime.（2）Preparation of different alkaline earth scandate MSc₂O₄（M=Mg,Ca,Sr,Ba）nanocrystals to obtain the best host material CaSc₂O₄.By selecting organic additives（Cit-3Na,EDTA,CTAB,etc.）to change the structure,crystallinity,morphology and up-conversion luminescence properties of CaSc₂O₄ nanocrystals.At the same time,we also studied the upconversion luminescence characteristics and mechanism of CaSc₂O₄nanocrystals doped with Ln³⁺,Yb³⁺(Ln³⁺=Er³⁺/Tm³⁺/Ho³⁺).（3）CaSc₂O₄:Er³⁺,Yb³⁺@TiO₂ composite materials were prepared by hydrothermal method,to simulate the photocatalytic degradation experiment of methylene blue solution under simulated sunlight and compared the catalytic degradation performance of different samples.The experimental results show that the presence of upconversion luminescent materials can improve the photocatalytic degradation ability of TiO₂ and increase the industrial application value of photocatalysts for degradation of organic pollutants.