Ag-Ni Alloy Nanocluster:Crystal Structure And Insights Into The Nature

Nanomaterials refers to all kinds of materials at the nanoscale assembly,in general,when the size of the material down to the nanometer level,the nature will happen big change,even tend to present a completely opposite properties and macro condition.At the same time,due to the large specific surface area of nanomaterials and other factors,such as quantum size effect,nanomaterials will be one of the important factors that people change the future life.Precious metals nanoclusters?nanoclusters?as a new nanometer material,in biomedical,photochemical catalysis,research in areas such as chiral gradually showed its positive effect,has been the scientists research in recent years.These precious metals nanoclusters can be divided into gold,and silver nanoclusters,other metal clusters and alloy nanoclusters.Among the most widely studied when several gold nanoclusters,because gold itself stability and good compatibility with biological,makes it both in theoretical research or practical application can perform,and was deeply loved by scientists.Silver nanoclusters were found in recent years has been gradually nanoclusters,its main composition is silver atoms.The early stability of silver nanoclusters because itself is not good,so has been,difficult to characterize.Bored with unremitting efforts by scientists in recent years,a batch of silver nanoclusters have been reported,its special physical and chemical properties and molecular structure is becoming more and more attracted people's interests.Alloy nanoclusters refers to two or more metal elements of nanoclusters,the metallic elements will not only precious metal elements,also includes a lot of cheap comes easily to the element.Alloy clusters make precious metals nanoclusters study and production cost reduction,which is beneficial to people on the extensive and in-depth research.At the same time,its unique metal synergies will largely improve the nature of the single metal nanoclusters,at present has been reported in many alloy nanoclusters,sometimes only one or two atoms of change will make the whole photochemical properties of clusters,get a lot of properties such as catalytic activity.In general,the gold nanoclusters as the first step to the new world nanoclusters,and most important step;Silver clusters continue to carry forward the nanoclusters,provides more theoretical research opportunities;Alloy nanoclusters is one of the important foundation of theory to the practical application of leap.Therefore,for metal nanoclusters research,can not only to the theoretical development of nanometer materials,but also to remake nature for the benefit of humanity.For alloy nanoclusters,the most fascinating is the mysterious metal synergy is its characteristic is changed and 92 kinds of metal elements in the periodic table permutation and combination of diverse.If you can clearly understand the metal synergy,certainly will be the revolutionary discovery of is the metal material;If can enrich of element types of nanomaterials,must provide more opportunities for theoretical research and practical application.Atomically precise pieces of matter of nanometer dimensions composed of metals,which are called nanoclusters,have attracted especial research interest as a consequential frontier in nanoscience research.These nanoclusters exhibit unique natures which make them propitious to wide applications in fields such as medical treatments and catalysis.Studies in nanoclusters have been greatly benefited by the use of advanced instrumentation,especially adaptation of mass spectrometry?e.g.,matrix assisted laser desorption ionization time of flight mass spectrometry?MALDI-TOF MS?and electrospray ionization mass spectrometry?ESI MS??.However,mass spectrometry could not explain the bonding details between metals and ligands;therefore,single crystal x-ray diffraction?SC-XRD?analysis has been applied.SC-XRD is significant for the development of the nanocluster range for uncovering the precise structure of nanoclusters as well as moving forward to fully understand the relationship between structure and property.Furthermore,understanding the surface status of nanoclusters has provided possibility to embellish surface structure of nanoclusters and improve their performance.Nowadays,alloy nanoclusters play an important role in catalyst,biology,and material.Previous reports have synthesized and predicted the alloy structure composed by silver and nickel in ultra-small size?Ag₄Ni₂?DMSA?₄,?DMSA = meso-2,3-dimercaptosuccinicacid??.However.no precise crystal structure has been reported.Herein,we reported the crystal structure of Ag-Ni alloy nanocluster Ag₄Ni₂?DMSA?₄.The structure was further confirmed by Single Crystal X-ray Diffraction?SC-XRD?,X-ray photoelectron spectroscopy?XPS?,Matrix assisted laser desorption ionization time of flight mass spectrometry?MALDI-TOF MS?,Electro spray ionization?ESI?MS and Thermo gravimetric analysis?TGA?measurements.The stability experiment suggested that the Ag₄Ni₂ nanocluster could be stable in ultra-small sizes.This scientific research on Ag-Ni alloy nanoclusters will contribute to the understanding of the alloy in ultra-small size.Specifically,based on the structure determination by SC-XRD,the structure of Ag₄Ni₂?DMSA?₄ could also be divided into three layers:upper and lower layers with Ni?SPhMe₂?₄ complexes constituting a parallelogram,middle layer with four silver atoms constituting a parallelogram like a sandwich.The bonds distance of Ag-Ni,Ag-S and Ni-S were from 0.31 to 0.32 nm,0.23 to 0.24 nm and 0.22 to 0.23 nm,respectively.XPS analyses revealed that the Ag/Ni atomic ratio was 5.19/2.55 and the Ag/Ni/S atomic ratio was 5.19/2.55/10.28,consistent well with the expected ratio of 4/2 and 4/2/8 in Ag₄Ni₂?DMSA?₄.In addition,the Ag 3d3/2 and Ag 3d5/2 binding energy peaks were located at 375.0 and 369.0 eV,and the Ni 2p1/2 and Ni 2p3/2 are located at 871.50 and 853.90 eV,respectively.Moreover,combined with ESI,the Ag 3d3/2 and Ag 3d5/2 binding energies of Ag₄Ni₂?DMSA?₄ were close to the +1 valences according to previous reports;meanwhile,the spectra of Ag₄Ni₂?DMSA?₄ illustrated that the valences of nickel was +2.Additionally,the test result of MALDI-TOF MS was in good agreement with ESI.Weight loss upon heating?Thermo gravimetric analysis,TGA?was used to confirm the percentage of organic material in nanoclusters?66.31%loss was observed in TGA,which was consistent with the calculated loss 66.67%according to the formula?.In the liquid state,the UV-Vis spectra showed no change after contacting with oxygen for a few weeks.Meanwhile,we used UV-Vis spectra under 80 ? to test the stability of the Ag₄Ni₂?DMSA?₄.The absorption peaks were almost identical with each other which suggested the high stability of the Ag₄Ni₂?DMSA?₄.Our work prove that the small-sized alloy also has the possibility of diversification,which will play an important role in the synthesis of the alloy nanocluster.Moreover,this scientific research on Ag-Ni alloy nanoclusters will contribute to the understanding of the alloy in ultra-small size.In Au₄Ni₂?DMSA?₄,on the basis of synthetic methods,we expanded the types of precious metals,successfully synthesized Au₄Ni₂?DMSA?₄?SPhMe₂ = 2,4-dimethyl thiophenol?nanoclusters,and by X-ray single crystal diffraction and ESI testing technology are verified.