Synthesis And Photocatalytic Application Of Metal Nanocluster Matrix Composites

Metal nanoclusters（MNCs）are ultra-small nanoparticles（<3 nm）containing metal nuclei and surface protective ligands.Because the core size is equivalent to the wavelength of electron de Broglie,MNCs exhibit strong quantum limiting effects and interesting physicochemical properties,such as the transition between the highest occupied molecular orbital（HOMO）and the lowest unoccuated molecular orbital（LUMO）,adjustable optical absorption,strong fluorescence,large Stokes shift and extremely long fluorescence lifetime.Meanwhile,the diversity of ligands gives MNCs rich surface chemistry and good biocompatibility.Therefore,MNCs are described as a new photocatalyst,showing great application potential in the field of photocatalysis.Similar to traditional semiconductor photocatalysts,MNCs can absorb photon energy and stimulate HOMO electron transition to LUMO under light,thus realizing electron（e^-）-hole（h⁺）separation.At the same time,MNCs have atomically accurate structure,which can explore the mechanism of photocatalysis at atomic and molecular scales,thus contributing to the development of photocatalysis technology.However,single MNCs still have some shortcomings,such as high carrier recombination rate,easy aggregation and poor photostability,which greatly limit its application in photocatalysis.In summary,this paper solves the problem of the application process of MNCs in photocatalysis by constructing MNCs based composites,and applies the composites to photocatalytic dye degradation,antibacterial and photocatalytic hydrogen peroxide（H₂O₂）production.The main research contents are as follows:（1）In order to solve the problem of high carrier recombination rate and poor optical stability of MNCs,gold nanoclusters（Au NCs）protected by reducing glutathione（GSH）were combined to the surface of Bi OCl by physical mixing,and Z-type Bi OCl/Au NCs heterojunction was successfully prepared.Studies have shown that the appropriate valence band matching between Au NCs and Bi OCl enables the e-of Bi OCl guide band to be transferred to the HOMO orbital of Au NCs,thus effectively consuming h+of Au NCs,improving the stability of the system and carrier migration ability.The reactive oxygen species（ROS）production of Bi OCl/Au NCs was increased by 10 times.The Z-type Bi OCl/Au NCs heterojunction showed excellent photocatalytic degradation of organic matter,and the degradation rate was 3 times that of pure Bi OCl.This provides a solid foundation for the development of high performance MNCs photocatalysts for the degradation of organic pollutants.（2）MNCs have excellent photocatalytic antibacterial properties,but the problems such as easy aggregation and poor photostability limit the application of MNCs in photodynamic antibacterial.In this study,Ag₂₈Au₁-DHLA₁₂ was encapsulated into zeolite imidazolate skeleton material（ZIF-8）through coordination assisted self-assembly,and Ag₂₈Au₁-DHLA₁₂@ZIF-8 composite photocatalytic antibacterial agent was constructed.It was found that the ZIF-8 shell can restrict the migration and aggregation of Ag₂₈Au₁-DHLA₁₂,thus effectively improving the stability of Ag₂₈Au₁-DHLA₁₂,enabling it to destroy 99.9%of bacteria within 20 min.It was found that the excellent antibacterial performance of Ag₂₈Au₁-DHLA₁₂@ZIF-8 was due to its high ROS yield(H₂O₂yield was 520μM,9 times that of ZIF-8 and Ag₂₈Au₁-DHLA₁₂).The ROS produced by Ag₂₈Au₁-DHLA₁₂@ZIF-8 had strong oxidation ability and could destroy the structure of bacteria,thus achieving efficient bacteria-killing.This paper provides a reference for the development of efficient MNCs based nano antibacterial agents.（3）In order to solve the problems of high efficiency and poor photostability of MNCs carrier composite caused by the accumulation of photogenic holes,C₃N₄-BPEI@Au Ag NCs nanocomposites were prepared by cross-linking Au Ag NCs on the surface of polyvinylimide（BPEI）functionalized C₃N₄.Among them,BPEI can be a hole sacrificial agent,which can reduce h⁺produced in the reaction,thus improving the stability of the photocatalyst and thus the catalytic ability.In addition,the amide bond formed between C₃N₄-BPEI and Au Ag NCs improves the photostability of Au Ag NCs and promotes charge transfer.The results show that the H₂O₂ yield of C₃N₄-BPEI@Au Ag NCs composite is 82μM and 3.5 times that of C₃N₄（22.8μM）.This study provides reference for improving the stability of MNCs and photocatalytic production of H₂O₂.