Preparation,organic Amine Gas Induced Dimensional Transformation And Photoactive Properties Study Of Lead And Cadmium Halides

Organic-inorganic hybrid metal halides materials have withdrawn extensive research attention in photoelectric and photoactive areas due to their diversities in composition,structure and function.In recent years,organic-inorganic hybrid lead halides perovskites and other low-dimensional hybrid metal halides have shown great promise in light-absorbing,fluorescent,X-ray scintillator and other researches because of their excellent photoelectric property.This thesis focuses on exploring the mechanism of compositional and structural evolution of hybrid lead halides perovskites in the gas-solid reaction with volatile organic amines,new design of low-dimentional organic-inorganic hybrid cadmium chloride material with photochromic and fluorescent properties,and developing new synthetic or post-modification method for the new hybrid metal halides compounds.The main results are as follows.1.Explore the mechanism for the reaction difference of organic-inorganic hybrid lead halides perovskites with primary and tertiary amine due to their different molecular structure,and the influence of synergistic and competitive approaches of mixed amine for the gas induced structural transformation.The MAPb I₃（MA⁺=methylammoniu）film was exposed to gaseous amines isomers hexylamine and triethylamine.Experiment results shown that hexylamine could take place of MA⁺cation and indue the three dimentional to two dimentional transformation of MAPb I₃.In comparison,triethylamine could hardly coordinate with the Pb²⁺and thus collapse of lead halide framework for the further proton transfer reaction due to the lack of-NH₂ functional group,failing to induce the dimensional transformation.Base on the mechanism above,synergistic transformation method with mixed amines atmosphere of methylamine and triethylamine was developed,which led to the successful transformation of the three dimentional MAPb I₃ to one dimentional(C₆NH₁₆)Pb I₃hybrid lead halides.With MA as coinduction conversion agent to influence the chemical equilibrium,the MAPb I₃ film transfers to quasi-2D perovskite structures within MA and C6mixed atmosphere,displaying tuneable absorption and emission luminescent characters and showing a competitive transformation feature.In addition,by exploring the transformation in single gas and mixed gases atmosphere under different thermal effect,we concluded that when temperature is increased,hybrid lead halides perovskites with higher dimensions tend to generate.2.We prepared a low-dimensional hybrid metal halide crystalline compound Cd₂（TERPy）₂Cl₄（TERPy=4’-（4-Pyridinyl）-2,2’:6’,2’’-terpyridine）.The characterized single crystal structure shown that it was a binuclear structure where every Cd atom was bridged by two Cl atoms,and coordinated with three N atoms of the TERPy molecule.Cd₂（TERPy）₂Cl₄shown intriguing photochromic property due to the present of both the electron donor Cl atom to the electron acceptor pyridine moiety,where photoinduced electron transfer could undergo with irritation.Cd₂（TERPy）₂Cl₄ changed its color from white to pale yellow under the 1 min irritation of mercury lamp.And before irritation,Cd₂（TERPy）₂Cl₄ shown no obvious fluorescence,while it shown strong blue fluorescence after the photochromic process,which endowed Cd₂（TERPy）₂Cl₄ both photochromic and turn-on fluorescent properties.3.Prepare fluorescent hybrid lead halides perovskites thin film from lead halides Pb X₂（X=Br,I）with combination of methylamine and butylamine gas.The gas-solid reaction between lead halides and methylamine gas was used to synthesize three dimensional hybrid lead halides perovskites MAPb I₃ and MAPb Br₃,of which the structure and fluorescent property were subsequently modulated successfully with the combination of butylamine gas;Explore the gas-solid reaction between Cu I and ammonia.The results shown that hybrid Cu I material generated when ammonia gas contacted with Cu I,of which the emission peak of fluorogram shifted from near ultraviolet light to visible light area.This process was reversible,when hybrid Cu I material changed back into original Cu I under heating.