Study On The Coating And Photocatalytic Performance Of Lead-cesium Halide Perovskite Quantum Dots

The all-inorganic perovskite quantum dot Cs Pb X₃(X=Cl,Br,I)has attracted wide attention of researchers due to its high absorption coefficient,high luminous efficiency,adjustable luminescence range,and narrow emission line.As a new type of luminescent material,it has broad application prospects in the fields of light-emitting diodes,solar cells,light detection and lasers,so it has become a research hotspot in optoelectronic materials in recent years.However,perovskite quantum dots have their own special ionic structure.When they are exposed to the air,the water and oxygen in the air will cause the material to rapidly decompose,destroying its ionic structure and causing irreversible fluorescence quenching.Therefore,these stability issues limit the applications of perovskite quantum dot materials in water as a medium,such as photocatalysis,photoelectrocatalysis,and biological detection.Based on this,the development of water-stable perovskite quantum dots is of great significance for further expanding the application of all-inorganic perovskite quantum dots in water environments.In this project,by trying to encapsulate lead-cesium halide perovskite quantum dots with different materials,the stability of lead-cesium halide perovskite quantum dots in water was improved significantly,and its photocatalytic performance has also been improved to a certain extent.The main research contents are as follows:1.The CsPbBr₃ perovskite quantum dots were prepared,and a series of characterizations of the prepared CsPbBr₃ quantum dots were carried out,including X-ray diffraction(XRD),transmission electron microscope(TEM)and so on.The characterization results showed that the synthesized lead cesium halide perovskite quantum dots had a monoclinic structure,and exhibited high crystallinity and monodispersity;2.The CsPbBr₃/TiO₂composite material was prepared.UV-vis absorption spectra,TEM,XPS and FTIR showed that the CsPbBr₃ perovskite quantum dots were successfully coated into the Ti O₂ shell.The photocatalytic performance of the CsPbBr₃/Ti O₂ composite was investigated by the degradation of rhodamine B(Rh B)in water under visible light irradiation.The result showed that the CsPbBr₃/TiO₂ composite exhibited much enhanced photocatalytic activity than pure TiO₂ and CsPbBr₃ perovskite quantum dots.After photocatalytic degradation of pollutants,the recovered CsPbBr₃/TiO₂ composite retained its original structure and morphology;3.The CsPbBr₃ quantum dots were fixed on ultrathin g-C₃N₄nanosheets(UCN),and the CsPbBr₃/UCN composite was prepared.In this composite,the CsPbBr₃ quantum dots and UCN were chemically bonded through N-Br.A series of characterizations such as XRD?TEM and UV-vis absorption spectra have been carried out.The photocatalytic performance of the CsPbBr₃/UCN composite was investigated by the degradation of Rh B under visible light irradiation.The results showed that the environmental stability and photocatalytic performance of CsPbBr₃/UCN composite materials have been improved to a certain extent,which was better than both UCN and CsPbBr₃ quantum dots;The enhanced photocatalytic performance can be ascribed to the facilitated photo-generated charge separation and transportation,as disclosed by the PL spectra and the photoelectrochemical measurements.4.The CsPbBr₃/C₆₀composite material was prepared.XRD,TEM,XPS and FTIR characterizations showed that the C₆₀thin layer was uniformly coated on the surface of the CsPbBr₃quantum dots.The UV-vis absorption spectra showed that the CsPbBr₃/C₆₀ composite material exhibited increased optical absorption intensity in the visible light region.Photocurrent tests and electrochemical impedance spectroscopy showed that the introduction of C₆₀to CsPbBr₃ quantum dots greatly improves the separation efficiency of photogenerated electrons and holes in the composite material,and at the same time suppresses electron holes recombination.Therefore,the photocatalytic performance of CsPbBr₃/C₆₀composite for CO₂ reduction under visible light was significantly improved than that of CsPbBr₃ QDs.