Synthesis And Properties Of Noble Metal-perovskite Nano Crystals Heterostructures

All-inorganic Cs Pb X₃（X=I,Br,Cl）perovskite nanocrystals（PNCs）have attracted extensive attention in the fields of solar cells and light-emitting diodes due to their excellent optoelectronic properties.PNC heterostructures include heterostructures composed of two or more materials with different properties,which can exhibit better performance than pure PNCs.For example,heterostructures can efficiently confine or transport photogenerated charge carriers from one material to another,where both materials can share electrical and optical properties.Although heterostructures have been extensively studied in metal and chalcogenide semiconductor nanocrystals,reports on perovskite nanocrystal heterostructures are still limited.This is because the perovskite nanocrystal formation process is rapid and requires a specific environment,making it difficult to grow other materials on its surface or vice versa.Aiming at the above problems,this thesis mainly developed two methods to prepare PNC/noble metal heterostructures:1.On the basis of preparing Cs₄Pb Br₆nanocrystals by thermal injection,PNC/Au（or Pt）was prepared by oil/water interface photoreduction method.Heterostructure;2.First prepare Cs X nanocrystal/noble metal heterostructure,and then convert it into PNC/noble metal heterostructure.In addition,the photocatalytic properties of PNC/noble metal heterostructures were also investigated.The specific work is as follows:1.Preparation of Perovskite/Noble Metal Heterostructures by Photoreduction at Oil/Water Interface.First,Cs₄Pb Br₆nanocrystals were synthesized by hot injection method,and then the aqueous phase solution of noble metal precursor（chloroauric acid or chloroplatinic acid）was stirred and reacted with Cs₄Pb Br₆nanoparticle oil phase dispersion under the protection of ultraviolet light and inert gas,and finally obtained PNC（Cs Pb X₃）/noble metal（Au,Pt,etc.）heterostructures.During this process,the reaction atmosphere and the type of light source can affect the process of precious metal reduction and the composition of the final product.XRD,TEM,X-ray photoelectron spectroscopy and UV-Vis spectroscopy data show that Cs Pb Br₃/noble metal heterostructure can be obtained under inert atmosphere and UV illumination,while Cs₂Au₂Br₆by-product is generated under air atmosphere,and Cs Pb Br₃under visible light illumination There will be some halogen anion exchange with HAu Cl₄.The properties of noble metal nanoparticles,such as localized surface plasmon resonance effect and easy charge separation,provide more possibilities for perovskite nanocrystals in multiple application fields,such as solar cells,detection,and LEDs.2.From cesium halide/noble metal heterostructures to PNC/noble metal heterostructures and their photocatalytic properties.Firstly,Au Cl was reduced on the surface of Cs X（X=Cl,Br,I）nanoparticles,the precursor of PNC,to deposit Au nanoparticles and obtain a Cs X/Au heterostructure;then Cs X and lead oleate（Pb（OA）₂）,and finally the PNC/Au heterostructure was generated.The reaction at room temperature does not require inert gas protection,which simplifies the preparation process and is beneficial to overcome the by-product Cs₂Au₂Br₆NCs produced by PNC in the process of preparing heterostructures.Transmission electron microscopy and X-ray photoelectron spectroscopy data showed that the noble metal was successfully reduced to zero valence and deposited on the surface of NCs.The photocatalytic performance of Cs Pb Br₃/Au nanocrystals for the degradation of water-insoluble carcinogen Sudan Ⅲ under visible light irradiation was characterized by UV-Vis absorption spectroscopy.The Cs Pb Br₃/Au heterostructure exhibits good photocatalytic activity and can degrade about69%of Sudan red Ⅲ within 5 h.This study explores the photocatalytic applications of perovskite nanocrystal/noble metal heterostructures.