Synthesis And Photocatalytic Activity Study Of Plasmon Enhanced Upconversion Luminescence Photocatalytic Composites

Upconversion photocatalytic composites are prepared by the combination of"up conversion"and"photocatalytic technology".Because of the wide light response range,it has a good application prospect in the direction of photocatalytic degradation of wastewater.However,its upconversion luminescence intensity is low,thus limiting its application and popularization.In recent years,the surface plasmon resonance effect?LSPR?of precious metals has been studied much,and found that the combination of noble metal nanomaterials and upconversion materials can increase the luminous quantum yield and luminescence stability of the upper conversion materials and reduce the luminescence life.The mechanism above has a significant effect on the luminescence enhancement of the upconversion material.The study of plasma resonance enhanced up conversion technology can further improve the luminescence intensity of the upconversion materials,further improve the photocatalytic efficiency of the composites,and further promote the application and popularization of the upconversion photocatalytic composites.In this paper,the excitation light range of the upconversion material YF₃:Ho³⁺is analyzed first,and then the Ag@SiO₂ nuclear shell structure model is constructed by using the finite difference time domain?FDTD?simulation software,and the best parameters?Ag particle size,SiO₂ shell thickness?of the LSPR resonance peak that show the most improvement on the luminous intensity of upconversion material are calculated theoretically,and the corresponding Ag@SiO₂ core shell structure was prepared by the simple experimental method,,then the upconversion material YF₃:Ho³⁺was applied load on its surface successful,Finally,the composite photocatalyst,Ag@SiO₂@YF₃:Ho³⁺@TiO₂,with better photocatalytic activity was obtained by combining the LSPR enhanced upconversion material with the photocatalyst TiO₂,In order to study the surface microstructure,element composition,luminescence and photocatalytic activity of the synthesized photocatalyst are investigated by various characterization and experiments,and the following conclusions are obtained:?1?FDTD simulation results show that when the diameter of Ag is 150-250nm and the thickness of SiO₂ shell is 20nm,it is the strongest to enhance the luminous of the upconversion material YF₃:Ho³⁺as it deposits on the shell structure.?2?When dosage of PVP is 2.500g,ethylene glycol dosage is 200.0mL and dosage of TEOS is 0.16mL,core-shell structure Ag@SiO₂ is successfully prepared.When the mole ratio of Ag to YF₃:Ho³⁺n(Ag/YF₃:Ho³⁺)is 1:0.05,the upconversion material Ag@SiO₂@YF₃:Ho³⁺+is successfully prepared.When the dosage of TBOT is 1.0mL,TiO2 is successfully combined with up conversion material,and the core-shell structure composite photocatalytic materialAg@SiO₂@YF₃:Ho³⁺@TiO₂ is prepared.?3?The result of scanning electron microscope?SEM?,transmission electron microscope?TEM?and energy spectrum analysis?EDS?show that:the upconversion materialAg@SiO₂@YF₃:Ho³⁺andthecompositephotocatalystAg@SiO₂@YF₃:Ho³⁺@TiO₂ were all core-shell structure and the core is Ag particles,the shell from inside to outside is SiO₂,YF₃:Ho³⁺and TiO₂ layer respectively,the thickness of the whole shell is about 30nm,YF₃:Ho³⁺and TiO₂ layer is found in the outermost layer with a thickness of about 10nm,and shouwn as the stratified granular structure,the SiO₂ shell exists in the innermost layer with a thickness of about 20nm.The results of photoelectron spectroscopy?XPS?and X ray diffraction?XRD?show that Ag,SiO₂,YF₃:Ho³⁺,TiO₂ and other substances exist in the experimental samples,and Ho elements exist in the form of Ho3+in the matrix YF₃.The results show that the work of the upconversion materials and composite materials is prepared.?4?The UV-Vis DRS characterization shows that the upconversion material Ag@SiO₂@YF₃:Ho³⁺and the composite photocatalyst Ag@SiO₂@YF₃:Ho³⁺@TiO₂ have obvious absorption of ultraviolet and visible light,and the double logarithmic relation of luminescence intensity and luminescence power is calculated by the upconversion luminescence spectrum,comparing the Ho3+level diagram,we find that the upconversion of the upconversion material is two-photon upconversion.The luminescence ability of the composite photocatalyst is weaker than that of the upconversion material,but the emission peak is not offset,indicating that the load of TiO2does not affect the luminescence properties of the material,and the partial emission light is used by the TiO₂.?5?The degradation experiment of RhB for simulated wastewater was carried out to study the photocatalytic degradation ability of the composite photocatalytic material Ag@SiO₂@YF₃:Ho³⁺@TiO₂ under the simulated sunlight.When the TBOT dosage of composite photocatalyst is 1.0mL,the degradation effect can be better,the dosage of photocatalytic material and the concentration of RhB have prominent effect on the photocatalytic degradation,the dosage of photocatalyst is 0.1g/L,the best photodegradation effect is obtained when the concentration of RhB is 2.5mg/L?78%?,and the decolorization rate of the dark reaction is only 3%.