Synthesis And Thermodynamics And Electrochemical Properties Of(Au,Ag)-Cu Alloy Nanoparticles

Widely range of nanomaterials have been applied to daily life and are affected by the rapid development of nanotechnology.Therefore,it's necessary to explore the preparation methods and related properties of nanoparticles(NPs).In this paper,the polymeric pecursor solution of component Au and Cu was reduced by chemical co-reduction method with sodium borohydride reductant under the protection of sodium citrate stabilizer.Au-Cu@Si O₂NPs were synthesized by St(?)ber method based on the obtained nano colloid,then the particle size and phase transition temperature of nanoalloy were obtained by TEM and DSC method.The surface tension,surface segregation and surface energy of NPs as a function of particle size and temperature were calculated by the theoretical model based on the thermodynamic properties of pure component NPs.The thermodynamic parameters of Au-Cu nano phase diagrams with different particle sizes were optimized on the basis of experimental and theoretical results,and the thermodynamic properties of the Au-Cu nanoalloys were constructed.The supported Au-Cu/GO and Ag-Cu/GO NPs were synthesized by different preparation methods,and their electrocatalytic properties of nanoalloys in different sweep rates and four kinds of concentration of glucose solution were studied by cyclic voltammetry method,and the relationship between the composition ratio of nanoalloys and their electrocatalytic properties were explored.(1)Au-Cu@Si O₂ NPs with different composition ratio were obtained based on the chemical co-reduction method and the results of TEM,UV-Vis and FT-IR confirmed the formation of the nanoalloy.We have employed the DSC method to determine the liquidus and solidus temperature of Au-Cu@Si O₂ NPs and its alloy,where Au₅Cu₅@Si O₂has the superb DSC performance and its melting temperature are 1028.6 K,1041.3 K for NPs and1183.5 K,1189.5 K for the bulk,respectively.It's show that the melting temperature of NPs shows a certain degree of depression with the decrease of particle size.(2)The function relationship among particle size,alloy composition and temperature with surface tension was calculated combine with Butler's equation on the basis of thermodynamic data of pure component,so as surface energy and surface segregation.The value of surface tension and surface energy in the equation before and after the modification of the model were compared.Their value shows a decrease trendency with the decrease of particle size before the modification without the influence of surface effect.Both of surface tension and surface energy increase with the decrease of particle size which is attributed to the effect of atoms at the edges and vertices of NPs.In addition,the surface tension and surface energy have the same trend with the change of alloy composition and temperature.One concentration of alloy with lower syrface energy tends to be enrichment on the surface,and then surface segregation occurs.With the increase of temperature,the particle surface concentration tends to change to the ideal value.(3)On the basis of Nano-Calphad model,the thermodynamic parameters of the Au-Cu NPs are obtained by theory calculation and shows agreement with the experiment data.Then,the nano phase diagram with the radii of 5 nm and 10 nm were obtained.With the decrease of the particle size for Au-Cu NPs,the results show that the minimum melting temperature is shifted towards Au component and the liquidus and solidus possess the mixing enthalpy of liquid phase is more negative value under smaller particle size.(4)Different components of Au-Cu/GO and Ag-Cu/GO NPs were synthesized based on the chemical co-reduction method,combined with hydrothermal synthesis and the addition of different nonionic surface active agent,and observed through scanning electron mirrors and transmission mirrors.In the alkalescent environment(p H=7.4),we employed cyclic voltammetry method to obtain the determination of electrocatalytic properties of NPs in glucose solution.Au-Cu/GO NPs on electrocatalytic properties of glucose solution shows good regularity,especially for the Au-Cu(7:3)NPs showing the best electrochemical response.The electrocatalytic activity of Au-Cu/GO NPs is related to the composition of alloy,its response current decrease with the decrease of the concentration of Au,but the response current of Au-Cu/Go NPs is generally low.Three different methods of preparation for Ag-Cu/GO show high electrocatalytic properties and larger response current to glucose solution.The Ag-Cu/GO NPs synthesized by adding polyvinylpyrrolidone as nonionic surface active agent present a better regularity with different concentration of glucose solution.With the decrease of the concentration for glucose solution,the response current show a depression tendency under the same sweep speed.The response current with the increase of the concentration of glucose solution showed a trend of increase direct ratio under the same sweep speed.The results about a test of different alloy composition show that the catalytic oxidation performance of Ag-Cu/Go NPs decrease with the decrease of Cu concentration under the same sweep speed.