Facile synthesis of AgPt@Ag core-shell nanoparticles as highly active surface-enhanced Raman scattering substrates

The well-defined bimetallic AgPt@Ag core-shell nanoparticles (AgPt@Ag NPs) were prepared by a seedless and template-free wet-chemical method, using poly(ethylene imine) (PEI) as the shape-directing and stabilizing agents. The concentration of PEI played the key role in the current synthesis. The obtained AgPt@Ag NPs exhibited superior surface-enhanced Raman scattering (SERS) enhancement for 4-mercaptopyridine (4-MPY) with the enhancement factor (EF) of 5.0 x 10(7) and a low detection limit of 0.008 mu M (S/N= 3), coupled with the significant SERS enhancement for the other Raman probes (e.g. 4-nitrothiophenol, 4-mercaptobenzoic acid, and 4-mercoptophenylboronic acid). AgPt@Ag NPs can be employed as a promising candidate for in-situ SERS determination of trace analytes in environment, food and even clinical analysis. The dramatically improved SERS performances were mainly attributed to the specific core-shell structures and electromagnetic coupling effects between the bimetallic AgPt alloyed core and the Ag shell. This synthetic strategy provided a facile and environment friendly method to prepare other metallic architectures with novel properties. (C) 2017 Elsevier B.V. All rights reserved.