Preparation And Surface Enhanced Raman Scattering(SERS) Characterization Of Au-Ag Nanostructures

Surface enhanced Raman scattering(SERS)can be used to detect and diagnose trace molecules by effectively amplifying Rahman signal,which promises SERS important applications in drug research,food safety and environmental monitoring.Therefore,it is of great importance to prepare stable SERS substrates and figure out the effect of the substrates'morphology on the SERS performance.The SERS activity of the substrate mainly depends on its composition and structure.It has been found that noble metals,such as gold,silver and copper,exhibit the best SERS performance.Besides that,micro-nano sharp protrusions and gaps below 10 nm are believed to create strong SERS activity.Therefore,Au-Ag micro/nano-structures have attracted great attention in the field of SERS due to their high plasma efficiency and localized electromagnetic field enhancement.In the presented study,Au-Ag nanostructures were prepared by physical and chemical methods,respectively.Their microstructure,composition and SERS properties were characterized,and the effect of Au-Ag nanostructure substrate morphology on the SERS properties was studied.The effective adjusting of the morphology and composition of Au-Ag nanostructure substrate was realized,and enhanced SERS properties were obtained.Au-Ag alloy ingots were prepared by induction melting and copper mold casting.Au-Ag nanowire arrays were prepared under relatively low temperature by superplastic embossing.The effects of molding time,temperature and pressure on the morphology of Au-Ag nanowire arrays were systematically studied.It was found that the aspect ratio of the nanowire increases with increasing temperature,pressure and molding time,and the Au-Ag nanowire arrays become more aggregated.The length of Au-Ag nanowire up to 24?m,and the aspect ratios up to 69.The prepared Au-Ag nanowire arrays exhibit good SERS properties,and the highest enhancement factor is 1.89×10~8.Au-Ag thin films with smooth and uniform surface were deposited on silicon wafers by magnetron sputtering,which then dealloyed by electrochemistry method.The effect of the electrochemical dealloying voltage and time on the morphology and composition of the Au-Ag nanoporous film was systematically studied.Nano-porous film with average pore size of 10?12 nm was obtained.The adjusting of film's composition with stable fine pore size was realized by controlling the dealloying voltage.The prepared Au-Ag nano-porous film exhibit good SERS properties,and he highest enhancement factor was 1.05×10~7.In this paper,Au-Ag nanostructures were prepared by physical forming and chemical etching,respectively.This work provides insights into the preparation of stable and efficient SERS substrates and a reference for the practical application of SERS technology.