Synthesis And Application Of Organic Metal Perovskite Quantum Dots In Aqueous Phase

Organic metal perovskite（CH₃NH₃Pb X₃）has aroused a research upsurge in new materials field,due to it has unique and excellent photophysical properties,micro-tunable and multi-dimensional controllable structure,it has been widely used in optical devices,catalysis,sensing fields.However,organic metal perovskite cannot be produced on a large scale due to the unsustainability and toxicity of synthetic raw materials,and high precision requirements of the process.In this study,dedicated to search for a more green economy of polymer ligand to prepare organic metal perovskite quantum dots（QDs）in aqueous phase to achieve the purpose of industrial production.At the same time,using the hydrogel properties of polymer to the improve the dispersion and stability of organic metal perovskite QDs.This polymer ligand aqueous method was extended to the whole organic metal perovskite system to prepare doped organic metal perovskite QDs.Then explore the application of QDs in trace water of organic solvents.Firstly,researching the green-friendly synthesis of organic metal perovskite QDs in aqueous phase.Four common polymer materials were preliminary chosen,due to they have containing groups and elements that can coordinate with Pb（Ⅱ）in organic metal perovskite,they are polyethylene pyrrolidone（PVP）,polyvinyl alcohol（PVA）,polyethylene glycol（PEG）and polyethylene imine（PEI）.These polymer ligands are different from the oleic acid,octylamine and other organic ligands used in organic metal perovskite synthesis.They are green,friendly,low-cost,readily available materials.The experimental results show that only when PVP and PVA are used as ligands can prepared organic metal perovskite QDs in the aqueous phase,when PVP is ligands the photoluminescence of QDs is the strongest.When PVP was 5 wt%,the photoluminescence quantum efficiency（PLQY）of PVP-CH₃NH₃Pb Br₃ QDs reached 52%and the fluorescence lifetime was 333.3 ns.The interaction mechanism between PVP and CH₃NH₃Pb Br₃ QDs was analyzed by X-ray photoelectron spectroscopy（XPS）and Fourier transform infrared spectroscopy（FT-IR）.The results show that there is an obvious interaction between C=O in PVP and Pb（Ⅱ）in CH₃NH₃Pb Br₃.The size of CH₃NH₃Pb Br₃can be controlled effectively by flexible linkage and intermolecular force.The lattice structure of PVP-CH₃NH₃Pb Br₃ QDs was analyzed by X-ray diffraction analysis（XRD）and high resolution transmission electron diagram（HR-TEM）,and the average particle size of QDs was about 8 nm.In order to further improve the dispersion and stability of PVP-CH₃NH₃Pb Br₃ QDs,this study embedded PVP-CH₃NH₃Pb Br₃ QDs into PVA/PVA polymer hydrogel network structure.The optimization results showed that the PVA/PVP-CH₃NH₃Pb Br₃ QDs hydrogel can obtain green uniform PLQY 52%when the PVA is 1wt%.Secondly,the applicability of PVP as ligand in the preparation of organic metal perovskite QDs was explored.Successful preparation of PVP-CH₃NH₃Mn_1-xPb_xBr₃ QDs,and it was found that the doping of trace Mn（Ⅱ）could improve the photoluminescence intensity of aqueous organic metal perovskite QDs.The optimal doping concentration of Mn（Ⅱ）is 15%,and PLQY of CH₃NH₃Mn_1-xPb_xBr₃ QDs reaches 52.4%.The morphology and lattice structure changes of CH₃NH₃Mn_1-xPb_xBr₃ QDs were observed by XRD and TEM.The morphology changed from round to long elliptic or irregular geometry,and the lattice gradually transformed with the increase of Mn（Ⅱ）content.XPS showed that the interaction mechanism between CH₃NH₃Mn_1-xPb_xBr₃ QDs and Mn（Ⅱ）was different from that between CH₃NH₃Pb Br₃ QDs and Pb（Ⅱ）.Finally,the application of CH₃NH₃Pb Br₃ QDs in the detection of trace water in organic solvents was studied.Based on the high sensitivity of organometal perovskite to water,a small amount of water in ethanol and trace water in toluene can be detected.Up to now,organic metal perovskite materials have made breakthroughs in the fields of optoelectronics and catalysis,but also in temperature and humidity sensing applications.