Ordered Au: Ag Nanoshell Array For Surface-enhanced Raman Scattering

Since the discovery of the surface-enhanced Raman scattering(SERS)for the EM mechanisms about 30 years ago,the noble metal silver(Ag)and gold(Au)have been the promising materials as SERS-active substrate due to their remarkable surface plasmon characteristics.In this article,we used the ordered two-dimensional polystyrene(PS)colloidal array as the substrate for magnetron sputtering to build Au: Ag patterned composite nanostructure array,which suitable for high sensitivity of the application of SERS effect.We fabricated Au: Ag nanocap arrays by co-sputtering Au and Ag onto two-dimensional polystyrene(PS)colloidal sphere templates in a magnetron sputtering system for the SERS substrate.This Au: Ag bimetal array formed the protrusion network of Ag and Au nanoparticles,which contributed to Raman enhancement in thewaxberry-like structure.The metal protrusions formed waxberry-like shell in which the PS beads were encapsulated.At the same time,the Au: Ag bimetal arrays exhibit more enhancement in the SERS signal intensity of Rhodamine 6G at the 1650 cm-1than Au/Ag bilayer array,which is ascribed to the plasmon coupling between the nanoparticles of Au and Ag on the sample,and the more roughness of the Au: Ag bimetal array.And This Au: Ag bimetal array is a promising material SERS substrate.By changing the surface structure of the substrate,to the adjusted the surface plasmon absorption to produce an enhanced magnetic field,leaving a significantly enlarged SERS intensity.We co-sputtering different thickness of Au and Ag on different sizes respectively,To adjust the surface roughness of the substrate.While gradually increasing the thickness,the surface roughness of substrate showing a decreasing trend after the first increase,thus affecting the intensity of SERS.By SEM,AFM and a series of characterization methods,we obtain the relation of the spurting thickness to the surface roughness,thereby optimized the Au: Ag bimetal arrayFinally,the PS colloidal particle templates were etched by O2-plasma before sputtering process,the SERS signal intensity is strongly dependent on the etching time of the ball because of the nanogaps affected the surface plasmon resonance(SPR),and the optimalgaps between adjacent Au: Ag nanocaps generated even stronger SERS enhancements.We also prepared the particle-in-ball structure by annealing process,and temperature of annealing changed the nanogaps and SERS intensity.Further proofed the impact of nano-gap on SERS signals.