Synthesis And Stability Of [Ag_62-xCu_xS₁₂(SBu^t)₃₂]⁴⁺ Nanoclusters By Copper Doping

Gold element and silver element are very chemically inert and can exist in the form of element in nature.Since ancient times,they have been one of the main means of currency.They have a certain liquidity advantage in the market and are easy to attract people's attention..The atomically accurate precious metal nanoclusters are ultrafine particles(1-3 nm in size)composed of tens to hundreds of metal atoms.Such atomically precise noble metal nanoclusters with a size below 3 nm are a new class of promising functional materials.In recent years,their synthesis,molecular formula,structure,properties and potential applications have been extensively studied.Compared with other precious metals,the chemical energy barriers of gold and silver are easier to break through to meet the requirements of chemical reactions.Silver and gold belong to the same group and have almost the same atomic radius.However,zero-valent silver is more reactive than gold and is easier to be oxidized,which makes the preparation and performance research of silver nanoclusters more difficult.Because the crystal structure of silver nanoclusters is often disordered and the stability is not as good as that of gold nanoclusters,it is very challenging to determine the crystal structure of silver nanoclusters.Moreover,although single metal nanoclusters show certain effects and performance in the reaction,there are still a series of problems such as low activity,low selectivity and unsatisfactory stability.Therefore,researchers have adopted the method of adding other metals to single metal nanoclusters to form alloy nanoclusters to improve its performance.For example,Wu's research group found that by doping with copper atoms,anion Au₂₅ nanoclusters can be oxidized into neutral Au₂₅,cation Au₂₅,and even new cluster Au₄₄.As the valence electrons or free electrons of the nanoclusters change,the unexplored properties can be enhanced or explored.I started my work on the basis of previous studies,and took the[Ag₆₂S₁₂(SBu^t)₃₂]²⁺nanocluster(4 free electrons)with the highest reduction state as the precursor,and reacted with+2 valent copper ions to obtain new silver copper The alloy nanoclusters[Ag_62-xCu_xS₁₂(SBu^t)₃₂](BPh₄)₄(x=13-21,referred to as AgCu₆₂)were studied.Its structure was characterized by X-ray photoelectron spectroscopy and its optical properties were characterized by UV-visible absorption spectroscopy,and its molecular formula was successfully characterized by electrospray ionization mass spectrometry([Ag₆₂S₁₂(SBu^t)₃₂]²⁺referred to as Ag₆₂ nano-cluster The clusters are unstable during the electrospray ionization mass spectrometry test and are easily broken into smaller fragments,so the complete molecular ion peaks can not be observed in the electrospray ionization mass spectrometry of Ag₆₂ nanoclusters).The main research contents of this paper are as follows:A three-step reaction was used to successfully synthesize AgCu₆₂ nanoclusters.The steps are as follows:the first step is to synthesize polydisperse Ag_n(SG)_m water-soluble clusters;the second step,two-phase ligand exchange induces monodisperse oil-soluble Ag₆₂ nanoclusters Clusters;in the third step,+2 valence copper ions are doped into monodisperse Ag₆₂nanoclusters to prepare AgCu₆₂ nanoclusters.The structural framework of AgCu₆₂nanoclusters is very similar to Ag₆₂ nanoclusters,and all Cu atoms are selectively doped on the surface of AgCu₆₂ nanoclusters.Interestingly,there are 2 free electrons in AgCu₆₂nanoclusters,indicating that copper atom doping changes the superatomic structure of Ag₆₂nanoclusters.Compared with Ag₆₂ nanoclusters,AgCu₆₂ nanoclusters are more stable under heating and electrochemical conditions,which is caused by copper doping.This work provides a new perspective for the electron transfer of nanoclusters.