In-situ Preparation And Fluorescence Behaviors Of Polyacrylate/Perovskite Nanocomposites

Polymer/perovskite nanocomposites have drawn considerable attention and have been widely applied in the fields of lighting,display,anti-counterfeiting,sensing,and so forth,mainly due to that they exhibit outstanding fluorescence properties of perovskites along with the lightweight characteristic,ease of processing and environmental stability of polymers.However,the preparation of polymer/perovskite nanocomposites generally envolves considerable volatile organic solvents,which might cause environmental issues.In addition,it remains a challenge to precisely tune the fluorescence properties of the nanocomposites,limiting their applications in advanced anti-counterfeiting.In this thesis,a solvent-free and in-situ preparation method for polyacrylate/perovskite nanocomposites was developed.Furthermore,photo-induced halogen exchange reactions were demonstrated in the nanocomposites toward realizing a precise control of the fluorescence behaviors.Eventually,not only three-dimensional(3D)objects were fabricated via 3D printing,but also blue/green and green/red fluorescence patterns for anti-counterfeiting were achieved in the polyacrylate/perovskite nanocomposites,respectively.Main achievements are given bellow:(1)PbBr₂ and CH₃NH₃Br(MABr)were first dissolved in N,N-dimethylacrylamide(DMAA),followed by adding ligands of oleic acid and oleylamine,producing a homogeneous solution.Then,MAPbBr₃ nanoparticles were in-situ synthesized by adding the above solution into the monomer mixtures composed of 2-ethylhexyl acrylate(EHA)and di(trimethylolpropane)tetraacrylate(DTPTA)due to the solubility decrease.Sesequently,polyacrylate/perovskite nanocomposites were prepared by in-situ photopolymerization in the presence of photoinitiators without using solvents.The effects of the monomer composition on the properties of polyacrylate/perovskite nanocomposites were investigated.Results indicate that the nanocomposites show good fluorescence properties and environmental stability when the volume ratio of EHA/DTPTA is 4/6.3D objects were fabraciated based on the polyacrylate/perovskite nanocomposites via 3D printing.Interestingly,the incorporation of MAPbBr₃ nanoparticles led to a decrease in the light penetration depth from 2.4 to 1.4 mm in comparision with monomers,which improved the printing resolution.(2)The fluorescence emission of polyacrylate/perovskite nanocomposites were demonstrated to be adjustable in the range of 462?723 nm by changing the halogen composition in the solution of precursors.For precisely tuning the fluorescence behaviors,photo-induced halogen exchange reactions were conducted in polyacrylate/perovskite nanocomposites in the presence of specific halogenated alkanes.Both high exchange rate and conversion were obtained when using2-bromobutane as the source of Br during the photoinduced exchange of Cl with Br.The concentration of 2-bromobutane shows significant influences on the halogen exchange reactions while the irradiation intensity displays negligible impacts.Similarly,both high exchange rate and conversion were achieved when using2-iodobutane as the source of I during the photoinduced exchange of Br with I.Finally,fluorescence patterns for anti-counterfeiting in the color of blue-green and greed-red were achieved,respectively,in the polyacrylate/perovskite nanocomposites via photo-induced halogen exchange reations,providing new perspectives for unclonable anti-counterfeiting.