Study On Green Chemical Synthesis And Fluorescence Properties Of Cesium-lead Halite Perovskite/Silica Composite Luminescent

All-inorganic cesium lead halide perovskite nanoparticles have recently become a new class of luminescent materials,which have the advantages of adjustable luminous color and high quantum yield.In contrast to conventional quantum dots（such as CdSe and InP Nanocrystallines（NCs））,perovskite NCs are unusually resistant to defects.Specifically,surface dangling bonds and intrinsic point defects（such as vacancies）do not form a known intermediate.Therefore,perovskite-type NCs do not require electronic surface passivation（for example,using ligands and wider interstitial materials）,and are not significantly exposed to photooxidation.They can be used in lighting,nanolasers,solar cells,and light-emitting diodes.However,there are currently two main methods for the synthesis of fluorescent cesium lead halide perovskite nanoparticles:one is the method of hot injection,but the synthesis process of this method is cumbersome and needs to be performed under the protection of an inert gas.Pretreatment and synthesis require high temperature and require a certain amount of energy input,which is not suitable for large-scale production.Another method is room temperature recrystallization,which can be performed at atmospheric environment,but in this method,the reaction process requires organic solvents such as toluene,DMF,or DMSO,and these solvents are toxic and could be harmful to the human body after volatilization.Furthermore,if industrial level production is required,a large amount of waste liquid will be generated,which will not only cause harm to the environment,but also increase waste liquid treatment.So,the purpose of this paper is to synthesize perovskite nanoparticles with high fluorescence properties by using an environmentally friendly method,and to systematically study the formation processes,controllable preparation,and fluorescence properties.The main research contents include:1.We describe an eco-friendly two-step immersion-evaporation（TSIE）approach for the synthesis of ligand-free perovskite clusters.Firstly,immerse CsBr aqueous solution in the pores of mesoporous SiO₂ matrix and evaporate water at 40^oC under vacuum and prepare CsBr/SiO2 mesoporous composites.Then,PbBr2 DMF solution is added to the pre-formed CsBr/SiO2 mesoporous composite material to obtain Cs4PbBr6 ultrafine nanoparticles（NPs）in the mesoporous Si O2 matrix.During the synthesis process,washing and purification processes that remove surface ligands are not involved.In the ligand-free Cs₄PbBr₆/SiO₂perovskite powder,Cs4PbBr6 NPs are highly dispersed on the silica matrix,and only by increasing the initial amount of silica and perovskite precursors,batch production can be achieved.The amount of solvent is not only less,but also can be recycled and used to prepare new Cs4PbBr6/SiO2 perovskite powder with high luminous properties.Its excellent photothermal stability provides a good basis for further applications,and its applications on WLEDs show that the prepared Cs₄PbBr₆/SiO₂ composite material has great potential as a green emitter for solid-state display devices.The TSIE method provides an environmentally friendly and low-cost way for large-scale production of high-radiation perovskite phosphors.2.Green-emitting CsPbBr3/SiO2 composite material is synthesized by grinding method at room temperature,water is used as the reaction solvent,KBr is introduced as a bromine source,Pb（NO3）2 is used as a lead source,and CsBr is used as a cesium source.First,CsBr,KBr/SiO₂ composites and Pb（NO₃）₂/SiO₂ composites were prepared by immersing SiO₂ in the precursor solution and then evaporating the water under vacuum at 40^oC.Then,the obtained CsBr,KBr/SiO2 and Pb（NO3）2/SiO2 powders are ground in a mortar to obtain CsPbBr3perovskite quantum dots attached to the surface of solid SiO2,with a strong green emission under ultraviolet light.By adjusting the halogen ratio in the precursor solution,the emission color of the product fluorescence can be adjusted.It exhibited excellent photothermal properties and extraordinary thermal stability reversible characteristics.