Tuning the plasmonic properties of bimetallic core–shell
rods for surface-enhanced Raman spectroscopy. (a) Experimentally measured
extinction spectra of Au@Ag@SiO2, Au@SiO2 NRs,
and Au@Pd@SiO2 NRs with XAg = 0.42 (orange), XAg = 0.20 (red), XAu = 1.0 (black), XPd = 0.21 (blue), and XPd = 0.32 (turquoise)
in a 3:1 (by volume) EtOH/H2O mixture. For the experimental
spectra, an equal Au concentration of [Au] = 0.1 mM was used. (b)
Raman spectra of crystal violet measured in the presence of Au@Ag@SiO2, Au@Pd@SiO2 NRs, and Au@SiO2 NRs. The
SERS measurements were performed in a 3:1 (by volume) EtOH/H2O mixture containing a constant metal concentration of [Au] = 0.5
mM and 1 μM crystal violet (CV). FDTD-calculated extinction
(c), scattering (d), and absorption (e) spectra of the Au@X@SiO2 NRs. (f) FDTD-calculated local field around the Au@Ag@SiO2 (left), Au@SiO2 (middle), and Au@Pd@SiO2 NRs (right) when using a 633 nm light source. In Table S6, the maximum local field enhancements are listed.