Preparation And Fluorescence Stability Of Polymer/Inorganic Perovskite CsPbBr₃ Nanocrystalline Composites

In recent years,all inorganic perovskite nanocrystalline materials have attracted extensive research focus in optoelectronic devices,semiconductor materials,laser,light emitting diodes,and other fields because of their high photoluminescence quantum yield（PLQY）,narrow emission spectrum,adjustable composition and size,simple preparation,low raw material prices.However,they are vulnerable and can be degraded under the stimulation of oxygen,ultraviolet light,heat,water and polar organic solvents.The intrinsic instability of all inorganic perovskite nanocrystalline materials has greatly hindered their practical application.Therefore,it is of great significance to prepare all-inorganic perovskite nanocrystalline materials with excellent performance and high stability.In this dissertation,two kinds of polymer-inorganic perovskite CsPbBr₃ nanocrystalline composites（NCCs）were designed and prepared,and their stability was scrutinized.The main research contents and results are as follows:（1）Preparation and stability of SiO₂-CsPbBr₃-SiO₂ NCCs based on SiO₂-PDMAEMA nanoreactor.Firsf,monodispersed SiO₂ microspheres with a diameter about 300 nm were prepared by sol-gel method,which were modified with3-aminopropyl triethoxysilane（APTES）to obtain amino-functionalized silica microspheres.ATRP-active SiO₂ microspheres with bromo-terminal group（SiO₂-Br）were then obtained through the acylation reaction between amino group and bromo-iso-butyryl bromide（BIBB）,and the polymer PDMAEMA was grafted on the surface of SiO₂ by ATRP reaction to yield the target nanoreactor od SiO₂-PDMAEMA.Subsequently,perovskite nanocrystals were in situ grown on the polymer domain by supersaturation precipitation method at room temperatureowing to interaction between PDMAEMA and precursors（i.e.,Cs Br,Pb Br₂）.Next,with the addition of3-aminopropyltrimethoxysilane（APTMS）,SiO₂-CsPbBr₃-SiO₂ NCCs were yielded by the hydrolysis of APTMS,which serves as both ligand and precursor of SiO₂.Finally,the stability of SiO₂-CsPbBr₃-SiO₂ NCCs towards UV light,heat,long-term storage,water and polar organic solvents was examined.The results showed that the PL intensity and the environmental stability of SiO₂-CsPbBr₃-SiO₂ NCCs were much higher than the control sample of OA/OAm-CsPbBr₃ prepared in conventional method（i.e.,capped by OA and OAm）.This possible reason is that the CsPbBr₃nanocrystals in SiO₂-CsPbBr₃-SiO₂ NCCs have interior and exterior SiO₂ shell,which can separate the CsPbBr₃ nanocrystals from external environment.In addition,APTMS used to form the outer SiO₂ shell is an effecient ligand,which can effectively passivate the surface defects of CsPbBr₃ NCs and thus lead to enhanced PL emission.（2）Preparation and stability of MPC/PMPC capped CsPbBr₃ NCs.First,poly（2-methacryloyloxyethyl phosphorylcholine）（PMPC）was synthesized by photopolymerization.Then,MPC,PMPC and MPC/PMPC mixture of equal mass were added to the dispersion of DMF solution containing cesium bromide and lead bromide respectively.The coressponding precursor solutions were obtained by stirring overnight due to the interaction between phosphorylcholine group and perovskite precursors.MPC-CsPbBr₃ NCCs,PMPC CsPbBr₃ NCCs,and MPC/PMPC coapped-CsPbBr₃ NCCs were yielded when the certain amount of precursor solutions were quickly added to toluene,respectively.The stability of the resulting CsPbBr₃NCCs against UV light,heat,lont-time storage,water and polar solvents were investigated systematically.The results showed that the three as-prepared CsPbBr₃NCCs have mucher better stability and than the control sample of OA/OAm-CsPbBr₃.The polymer-capped CsPbBr₃ NCCs have better stability than the monomer or small molecule ligand capped CsPbBr₃ NCs owing to the better protection of polymer,however,the PL intensity of polymer capped CsPbBr₃ NCs is low compared with small ligand.This may attributed to that phosphorylcholine group can not efficient bind with CsPbBr₃ NCs owing to the steric hindance of the long polymer chains.When monomer MPC and polymer PMPC were used to co-cap the CsPbBr₃ NCs,CsPbBr₃ NCCs with excellent fluorescence intensity and stability were obtained owing the combination of advantages in both ligands.