Artificial Regulation Of Luminescence And Photocatalytic Properties Of ZnGa₂O₄ And Ga₂O₃

With the rapid development of industry,the phenomenon of organic pollution in sewage is becoming more and more serious,and the use of traditional water treatment technology can not make the sewage meeting the recyclable standards.Using the semiconductor as a photocatalyst can effectively degrade organic pollutants,which has a good application prospects in the aspect of pollution controlling.Recently,there are some long afterglow material?which could absorb and store excitation energy,and releasing the transient storage of energy in the form of lighting after the stoping irradiation?been used as photocatalyst.Research has shown that the element?Ga,Zn,etc.?with a d10 electronic structure exhibits wonderful photocatalytic performance.In this paper,we study the Ga-containing compound with d10 electron structure as the object of study,via doping with different types of ions or loading noble metal to control the recombination efficiency of photogenerated electrons and holes,and discussing the inner relations between persistent luminescence and photocatalytic properties and analysising it from the aspect of separation and recombination of photogenerated electrons and holes.The specific research contents mainly include the following three aspects:Long persistent luminescent materials ZnGa₂O₄,ZnGa₂O₄:Dy³⁺0.02 and ZnGa₂O₄:Eu³⁺0.02 were prepared by high temperature solid phase method.The results of photocatalytic experiments show that the photocatalytic activity ZnGa₂O₄ decreased with Eu³⁺ doping,while was enhanced by Dy³⁺ doping.The doping of Dy³⁺ and Eu³⁺ did not change the morphology of the samples by testing scanning electron microscopy,also,with few other factors affecting our measurements when using the same host material?ZnGa₂O₄?,so,we analyzed that the doping of Dy³⁺/ Eu³⁺ ions leding to the number of photogenerated carriers captured in the ZnGa₂O₄ matrix get changed.Photoluminescence measurements show that compared to the matrix,Eu³⁺ doing into ZnGa₂O₄ appear an red emission peaks at 613 nm,and its show that Eu³⁺ ions acting as recombination centers in ZnGa₂O₄,however,there was no special emission for Dy³⁺ in the spectrum of ZnGa₂O₄ doped with Dy³⁺ ions,Dy³⁺ ions may induce the formation of traps instead of acting as luminescent centers.The thermoluminescence test confirmed that doping Dy³⁺ increased the trap concentration,while the Eu³⁺ doping reduced the trap concentration.At the same time,doping Dy³⁺ will enhance the afterglow luminescence performance,and Eu³⁺ doping will weaken the afterglow luminescence performance.Therefore,we believe that in ZnGa₂O₄,the electron-hole pairs will formed under the excitation of ultraviolet light,and these electron-hole pairs recombine at the luminescence center of Eu³⁺,resulting in reduced photocatalytic performance.In the Dy³⁺ doped material,due to the existence of multiple trap levels,the photogenerated electrons and holes may be trapped by the trap level,leading to the effective separation of electrons and holes,thereby enhancing the photocatalysis performance.Long persistent luminescent materials ZnGa₂O₄: x Ti?x=0,0.01,0.025,0.05?were prepared by high temperature solid phase method.XRD shows that the doping of Ti4+ ions does not change the crystal structure of ZnGa₂O₄,and the Ti4+ ions mainly occupy the sites of Ga ions.With the increase of Ti4+ concentrations,Ti doping ZnGa₂O₄ appear a decreasing photoluminescence,while show an excellent persisitent luminescence,this could be ascribed to the formation of new traps by the Ti4+ doping.At the same time,the photocatalytic test showed that the doping of Ti4+ could improve the photocatalytic activity.The new traps generated by Ti4+ doping,delaying the recombination of photogenerated electrons and holes,thereby enhancing the photocatalytic performance and exhibiting excellent afterglow performance.Also,the relationship between the long persistent performance and the photocatalytic performance of the material is discussed.Ag/Ga₂O₃,Ag/ZnO nanostrutures were synthesized by photochemical reduction.XRD showed that Ag+ was successfully reduced to Ag under the irradiation of ultraviolet light.Through measuring the X-ray photoelectron spectroscopy of the samples and observing the scanning electron microscope images,further confirms the generation of silver nanoparticles,also,Ga₂O₃ and ZnO respectively served as templates and growth of Ag nanoparticles over their surface in the photochemical reduction procedure,forming a metal-semiconductor heterojunction.The photocatalytic performance test showed that Ag/Ga₂O₃ and Ag/ZnO exhibited excellent photocatalytic performance compared with Ga₂O₃ and ZnO.The electron will diffuse in the contact surface,leding to the formation of schottky barrier or ohmic contact in the metal-semiconductor heterojunction,which can improve the photogenerated electrons and holes separation effectively,thereby enhancing the photocatalytic performance.