Fabrication of Au@Ag core-shell nanoparticles using polyelectrolyte multilayers as nanoreactors.

A new synthetic strategy has been developed for the fabrication of Au-Ag bimetallic core-shell nanoparticles (NPs) using polyelectrolyte multilayers (PEMs) as unique nanoreactors. Bimetallic NPs composed of Au core and Ag shell were successively incorporated into PEMs by repeating anion/cation exchange/reduction cycle multiple times in a stepwise manner. The strategy described here allows for the facile preparation of Au@Ag core-shell NPs with well-controlled core and shell dimensions and geometrically tunable optical properties by simply varying the number of ion-exchange/reduction cycles in the PEM matrix. The strategy can be extended to synthesize in situ other core-shell NPs in polymer matrix.