la403707j_si_001.pdf (2.73 MB)
Size Tunable Au@Ag Core–Shell Nanoparticles: Synthesis and Surface-Enhanced Raman Scattering Properties
journal contribution
posted on 2013-12-03, 00:00 authored by Akshaya
K. Samal, Lakshminarayana Polavarapu, Sergio Rodal-Cedeira, Luis M. Liz-Marzán, Jorge Pérez-Juste, Isabel Pastoriza-SantosWe
describe a simple and efficient methodology for the aqueous
synthesis of stable, uniform, and size tunable Au@Ag core–shell
nanoparticles (NPs) that are stabilized by citrate ions. The synthetic
route is based on the stepwise Ag reduction on preformed Au NPs. The
final size of the core–shell NPs and therefore their optical
properties can be modulated at least from 30 to 110 nm by either tuning
the Ag shell thickness or changing the size of the Au core. The optical
properties of the Au@Ag core–shell NPs resemble those of pure
Ag NPs of similar sizes, which was confirmed by means of Mie extinction
calculations. We additionally evaluated the surface-enhanced raman
scattering
(SERS) enhancing properties of Au@Ag core–shell NP colloids
with three different laser lines (532, 633, and 785 nm). Importantly,
such core–shell NPs also exhibit a higher SERS efficiency than
Ag NPs of similar size under near-infrared excitation. The results
obtained here serve as a basis to select Au@Ag core–shell NPs
of specific size and composition with maximum SERS efficiency at their
respective excitation wavelengths for SERS-based analytical and bioimaging
applications.