Synthesis And Research On Optical Properties Of Au₁₃Cu₂ And Au₁₁Ag₆ Alloy Nanoclusters With M₁₃ Core

Due to the complexity of structure and composition,alloy nanoclusters have attracted much attention in recent years.The electronic structure and even the geometric structure of the nanocluster are greatly affected for the synergistic effect of the two metals(or more than two).The structure and composition of nanoclusters have a decisive influence on their physicochemical properties.Compared with single metal nanoclusters,alloy nanoclusters exhibit new or better physical and chemical properties(such as optics,catalysis,magnetism,electrochemistry,stability,etc.)due to their unique electronic structure,which significantly expands the practical application of such nanomaterials.Because of its important significance in chemical sensing and biological imaging applications,optical properties of nanocluster have been widely studied.The icosahedral structure M₁₃ has been the focus of researchers,12 metal atoms form a closed icosahedral shell,another metal atom is in center of the icosahedron.Icosahedral M₁₃ core is often observed in metal nanoclusters due to its high symmetry and stability.The alloying of nanoclusters containing icosahedral cores alters the metallic composition of the nanoclusters and may further affect their geometric/electronic structures,which reflected in their different optical properties.In this paper,we aim to synthesize nanoclusters containing icosahedral M₁₃ core and study their optical properties,which can be divided into two parts as following:1.In this work,a new Au₁₃Cu₂ nanocluster protected by phenylethanethiol(PET)and triphenylphosphine(TPP)was synthesized by metal doping and structurally determined by X-ray single crystal diffraction.And electrospray mass spectrometry(ESI-MS)was further verified,formula as[Au₁₃Cu₂(PPh₃)₆(SC₂H₄Ph)₆]⁺.The Au₁₃Cu₂ nanocluster has an icosahedral Au₁₃ core covered by two Cu atoms,and the two Cu atoms follow one of the triple axes of the Au₁₃.Combined with previous work,a comparable system was formed—only the surface coordination of Cu atoms changes from Cu-N to Cu-S.The optical properties of the two clusters changed significantly due to different coordination modes,DFT theoretical calculation results further confirm that different coordination modes have significant effects on the electronic structure of the nanoclusters.This work provides new insights into the ligand engineering.2.In this work,we obtained Au-Ag nanoclusters protected by diphenylphosphine methane(DPPM)and adamantanethiolate(Adm SH)by simply modulating the Au/Ag molar ratio in the synthetic precursors.The crystal structure was determined by single crystal X-ray diffraction with the molecular formulas Au₉Ag₁₂(SAdm)₄(DPPM)₆Cl₆]³⁺and Au₁₁Ag₆(DPPM)₄(SAdm)₄(CN)₄.The single crystal results were further confirmed by ESI-MS,XPS,PXRD and EPR.Both nanoclusters have a M₁₃ core,but degree of Ag doping is different.The structure of Au₁₁Ag₆ is composed of an icosahedral M₁₃ core,which wrapped by four Au atoms,four dppm,four Adm S and four CN.Although the two nanoclusters had the same synthesis method and similar structure,their optical properties were obviously different.Au₁₁Ag₆ shows strong red fluorescence with a high absolute QY of 14.03%in CH₂Cl₂ solution whereas the Au₉Ag₁₂ is non-emissive.Au₁₁Ag₆ nanoclusters have become a new member of Au-Ag alloy fluorescent nanoclusters family,and are expected to become potential fluorescent functional materials.