Preparation And Performance Of CsPbBr₃ Quantum Dots/MO（M=Si,Ti） Composites

All inorganic halide perovskite（Cs Pb X₃）has become a research hotspot due to its excellent photoelectric properties.However,the low stability and easy decomposition of Cs Pb Br₃quantum dots hinder their application.In order to improve the stability of Cs Pb Br₃quantum dots,we coated Cs Pb Br₃quantum dots with oxides MO（M=Si,Ti）and prepared Cs Pb Br₃/MO composite materials.The samples were characterized by XRD,TEM,EDX,UV-visible diffuse reflectance spectroscopy and PL fluorescence spectroscopy.The stability of Cs Pb Br₃/MO composite material in water system was explored.The specific research contents are as follows:（1）Cs Pb Br₃quantum dots were prepared by simple supersaturated recrystallization method.The optimum preparation scheme of Cs Pb Br₃quantum dots was determined by adjusting the preparation temperature.The morphology of Cs Pb Br₃quantum dots prepared at 30℃is similar to cubic shape.The prepared Cs Pb Br₃quantum dots have uniform distribution and good dispersion.The edge length is between 6 and 10nm,and the average size is 8nm.Cs Pb Br₃quantum dots have good visible light absorption performance and have a wide absorption band in the visible light region,extending the band edge to 530nm and showing excellent fluorescence intensity.（2）Cs Pb Br₃/Si O₂composites were prepared by sol-gel method using tetramethoxysilane（Si（OCH₃）₄）as silicon source and Cs Pb Br₃quantum dots coated with Si O₂.When the molar ratio of Cs to Si was 1:25,the crystallinity of the composites was the best.Si O₂coating does not affect the light absorption of Cs Pb Br₃quantum dots,and under the excitation of ultraviolet light emitting strong green light fluorescence characteristics.The prepared Cs Pb Br₃/Si O₂composite material has high stability and still retains good fluorescence intensity after being immersed in water for48h without decomposition.（3）Core-shell Cs Pb Br₃/Sn-Ti O₂composites were prepared by coating Cs Pb Br₃perovskite quantum dots with Sn doped titanium dioxide（Sn-Ti O₂）shells,and were applied to photocatalytic degradation of organic pollutants in water system.The prepared core-shell Cs Pb Br₃/Sn-Ti O₂composite has good dispersion and particle size distribution in the range of 15～30 nm.Sn-Ti O₂shell has good crystallinity and uniformly encapsulates Cs Pb Br₃perovskite quantum dots,providing better protection in aqueous solution.Compared with P25,the core-shell Cs Pb Br₃/Sn-Ti O₂composite showed significant light absorption in the visible region of a wide wavelength range,extending the optical absorption band edge to 536nm.The photocatalytic activity of Cs Pb Br₃/Sn-Ti O₂composite was investigated using Rh B aqueous solution as a simulated pollutant.Under simulated sunlight,the catalytic degradation rate of Cs Pb Br₃/Sn-Ti O₂composites reached 96.6%within 30min,and the degradation rate constant of Cs Pb Br₃/Sn-Ti O₂composites was 10.68×10^-2min^-1,which was 5 times higher than that of P25.Moreover,Cs Pb Br₃/Sn-Ti O₂composites had high stability and could work continuously for a long time in water system.Therefore,Cs Pb Br₃/Sn-Ti O₂composite materials have great advantages and application prospects in the treatment of organic pollutants in sewage by using sunlight.