Green synthesis of Au@Ag nanostructures through a seed-mediated method and their application in SERS

A facile bottom-up "green" synthetic route is reported by using epigallocatechin gallate (EGCG) extract from tea leaves as a reducing and stabilizing agent in aqueous solution to produce silver nanostructures through a seed-mediated method at room temperature. The obtained gold core silver shell nanostructures (Au@Ag), whose sizes can be tuned through adjusting the amount of seeds, present polygonal morphologies. Meanwhile, the formation mechanism of Au@Ag nanoparticle has been investigated, in which Au-seeds act as nucleation sites for the formation of silver nanoparticles. The as-prepared Au@Ag nanostructure deposited on the glass plate can become the substrate of surface-enhanced Raman scattering (SERS), which has the obvious SERS effect when rhodamine 6 G (R6G) is used as the probe molecular. The above results indicate that the more irregular the shape of Au@Ag nanostructure becomes and the larger the size of nanoparticle gets, the stronger the SERS signal is. (C) 2016 Elsevier B.V. All rights reserved.