Spectroscopic investigations on metallo-dielectric Gold@silica composites

Optical properties of metallo-dielectric (Gold@silica) composites were measured using different characterizing techniques viz. UV–Visible and photoluminescence (PL) spectroscopy. Reflection spectra showed the Bragg reflection peak shifted to longer wavelength and was broadened with the shell growth. The PL spectra showed the presence of visible and infrared bands. While the visible emission is explained by radiative recombination caused by interband transitions, the infrared emission is accounted for by the intraband transitions. Raman spectroscopy of methyl red (MR) indicator dye adsorbed on metallo-dielectric films has shown an enhancement in the Raman signals on incomplete shells. The enhancement is ascribed to the surface roughness and nanogaps making the synthesized metallo-dielectric particles a potential substrate for surface enhanced Raman spectroscopy (SERS).