The SERS Activity of a Supported Ag Nanocube Strongly Depends on Its Orientation Relative to Laser Polarization

Silver nanocubes with sharp or truncated corners were synthesized, deposited on silicon substrates, and functionalized with Raman-active thiols for surface-enhanced Raman scattering (SERS) studies. The use of substrates with registration marks allowed us to correlate the SERS spectra from individual nanocubes to their physical parameters revealed by high-resolution SEM imaging. We observed dramatic variations in SERS intensity when the nanocubes were oriented at different angles relative to the polarization of excitation laser. This angular dependence was less significant when the nanocubes were truncated and became nearly spherical in profile. Numerical calculations were employed to confirm our observations, and to attribute the source of variation to the difference in near-field distribution between different laser polarizations.