Research On Ligand-modulated Au₁₁?PR₃?₇Cl₃ And Au_25-xAg_x?PR₃?₇?PET?₅ Nanoclusters Properties:Nanocluster Assembly And Fluorescence Properties

Precisely noble nanoclusters have attracted more and more attention due to their unique physical and chemical properties as well as stable structure,ultra-small size and fluorescence et.Noble nanoclusters are expected to be used in various filed,like energy conversion,biomedicine other fields.The physical and chemical properties of nanocluster can be changed through the assemblies/self-assemblies of the nanocluster.Non-covalent interactions between nanocluster ligands play an important role in the nanocluster assembly process.In addition,fluorescent nanoclusters play an important role in the development of fluorescence-based imaging techniques,cell labelling and other fields.The rod-shaped Au_25-xAg_x nanocluster has attracted researchers'attention because of its excellent fluorescence performance.Whether it is possible to adjust its fluorescence properties through ligands and understand its luminescence mechanism remains to be further studied.Based on this,this paper mainly studies the surface modification of the space group in Au₁₁ clusters and the fluorescence performance of Au_25-xAg_x by changing the ligands.The main contents are as follows:1.We present an example of a crystal system transformation of Au₁₁?PR₃?₇Cl₃ from monoclinic?M?to trigonal?T?by surface modification.Atomically-resolved gold nanoclusters containing tris?4-chlorophenyl?phosphine and chloride ligands were synthesized and determined to be Au₁₁?p-ClPPh₃?₇Cl₃?p-ClPPh₃=tris?4-chlorophenyl?phosphine?by X-ray crystallography.Crystal data demonstrated that the C-H···Cl-C interaction is dominant in a trigonal crystal system of Au₁₁?p-ClPPh₃?₇Cl₃ with an R3?space group.However,the C-H···?interaction is the major driving force to form monoclinic crystal system of Au₁₁?PPh₃?₇Cl₃?PPh₃=triphenylphosphine?with a P2?1?/n space group.Moreover,UV-vis absorption spectra and X-ray photoelectron spectra reveal that the electronic structure of Au₁₁?p-ClPPh₃?₇Cl₃ nanocluster are greatly influenced by p-ClPPh₃.This work provides critical implications for the crystallization of metal nanoclusters,as well as a better understanding of the non-covalent interaction on the nanocluster assembly and the crystal engineering by surface modification.2.Rod-shape[Au25-xAg_x?PR₃?₁₀?SC₂H₄Ph?₅Cl₂]²⁺(abbreviated as Au_25-xAg_x)has attracted increasing interest due to high quantum yield,but how to modifying the fluorescence of nanoclusters remains a challenge.Ligand-engineering strategies have been developed to NCs.In this work,we modulated the luminescence of Au_25-xAg_x nanoclusters by using the withdrawing substituents ligands such as the tris?4-fluorophenyl?phosphine?abbreviated as p-FPPh₃?.It has been observed that the fluorescence quantum yield was significantly modulated from the Au_25-xAg_x-PPh₃?QY=40%?to those with p-FPPh₃ ligands?QY=1.1%?.The fluorescence peak of Au_25-xAgx protected by p-FPPh₃ obviously red-shifts compared to that of Au_25-xAg_x protected by PPh₃.In addition,the fluorescence lifetime of Au_25-xAg_x-PPh₃?8.6?s?decreased to that of Au_25-xAg_x-?p-FPPh₃??5.20?s?.The UV-vis absorption spectra and X-ray photoelectron spectra of these Au_25-xAg_x NCs reveal that the effect of withdrawing ligands on the optical absorption and the electronic structure.This study presents a controllable strategy for modifying the fluorescence properties of NCs via electron-withdrawing ligands.