Silica-Protected Hollow Silver and Gold Nanoparticles: New Material for Raman Analysis of Surfaces

Abstract

The first example of Raman analysis of various surfaces using hollow-silver (h-Ag) and hollow-gold (h-Au) nanoparticles protected by the silica layer has been reported. Synthesized h-Ag@SiO2 and h-Au@SiO2 nanoparticles are efficient electromagnetic resonators, which locally enhance the electric field of the incident radiation. This effect leads to an increase of the efficiency of Raman scattering for molecules being in the close proximity to h-Ag@SiO2 and h-Au@SiO2 nanoresonators. In contrast to solid spherical Au nanoparticles typically used for construction of nanoresonators for shell-isolated nanoparticle-enhanced Raman scattering (SHINERS) measurements, for which a change of the diameter of the nanoparticle causes only a small change of the position of its plasmon band, the plasmon band for hollow spherical Au nanoparticles can be changed within broad range of the visible electromagnetic radiation. It suggests that silica-covered h-Au nanoparticles can be used in the broader wavelength range of the el...