Raman and SERS responses were collected using a Labram HR800 (Horiba JobinYvon, France) spectrometer equipped with a diffraction grating of 600 groves/mm and a Peltiercooled CCD detector. All Raman and SERS spectra were excited in a back-scattering mode using a diode-pumped frequency-doubled Nd:YAG laser providing 532 nm radiation. Spectra were acquired at room temperature. The spectrometer was calibrated using the 520 cm Raman band of crystalline silicon prior to each experimental session.