Preparation Of High Stability Perovskite Nanomaterials And Its Application In Fluorescence Detection

Perovskite（CsPbBr3）nanocrystals（NCs）have attracted the attention of many researchers due to their high photoluminescence quantum yield（PLQY）,narrow emission half-peak width（FWHM）,low carrier recombination rate and high defect tolerance,the advantages make it a new type of fluorescent material.it has broad application prospects in the fields of fluorescence detection,lightemitting diode（LED）,solar cells and so on.However,the poor stability of perovskite nanocrystals to water,light and heat environment leads to the reduction of their fluorescence intensity,which seriously hindrance the wide application.Therefore,this paper takes the improvement of the stability of perovskite nanocrystals as the starting point,and adopts different strategies to prepare highstability perovskite composites through different methods and apply them to fluorescence detection and other aspects.The specific research contents are as follows:1.Improving the stability of perovskite nanocrystals based on polymer coating method.The CsPbBr3 NCs materials were encapsulated in polystyrene（PS）microspheres by the expansion-shrinkage method,and the effect of different experimental conditions on their fluorescence intensity was studied,and the CsPbBr3@PS NCs composites with superior optical properties and high stability were constructed.The structure and morphology of the materials were further analyzed by X-ray diffraction（XRD）,transmission electron microscopy（TEM）and scanning electron microscope（SEM）.The results show that the initial PL intensity of the CsPbBr3@PS material remains at 3 8%after being irradiated by a 365 nm UV lamp for 4 h,while the fluorescence intensity of the unencapsulated CsPbBr3 material only reaches 18%.And under high temperature conditions,the new perovskite Polymeric nanomaterials also exhibit unprecedented fluorescence stability.2.In situ synthesis of highly stable CsPbBr3@ZIF composites via doping of ZIF materials for iodide detection.CsPbBr3 NCs grows in situ in the pores of ZIF material.ZIF material provides a protective shell for CsPbBr3 NCs,which not only improves the luminescence intensity of CsPbBr3 NCs.but also improves its stability,so that the water stability of CsPbBr3 nanocrystals can still reach 57%after 7 days.The photostability and thermal stability are also improved in different degrees.In addition,a fluorescence sensor based on CsPbBr3@ZIF NCs material was successfully prepared,which can be used for high sensitivity and selective detection of I-with a detection limit of 0.17 mM.Therefore.the fluorescence sensor based on CsPbBr3@ZIF NCs material has a broad application prospect in the field of sensing.3.The highly water-stable CsPbBr3-mPEG@SiO2 NCs material was prepared through the synergistic effect of polymer ligand engineering and silica encapsulation and used as a novel "on-off-on" fluorescent probe for the highly sensitive and selective detection of mercury ions（Hg2-）and glutathione（GSH）in aqueous solution.In this study,the effects of methoxypolyethylene glycol amine（mPEG-NH2）ligand and silica coating on the stability and aqueous fluorescence of CsPbBr3 NCs were investigated.The results showed that the fluorescence intensity of the perovskite nanomaterials in aqueous solution was increased by 2.59 times,and the water stability was also greatly improved,maintaining 73%of the original fluorescence after 30 days of storage in water.Based on this,a novel "on-off-on" fluorescent probe was used to detect Hg2+ and GSH with high sensitivity with low detection limits of 0.08 nM and 0.19 μM,respectively.Therefore,the efficient and sensitive CsPbBr3-mPEG@SiO2 fluorescent probe shows great potential in environmental and biosensing.