Silica-Covered Silver and Gold Nanoresonators for Raman Analysis of Surfaces of Various Materials

摘要

Silver and gold colloids have been coated with ca. 3-6 nm thick layer of silica to form nanoparticles with core-shell structure. Synthesized Ag@SiO2 and Au@SiO2 nanoparticles are efficient electromagnetic resonators and can locally significantly enhance the electric field of the incident electromagnetic radiations, which leads to a very large increase of the Raman signal from species being in the close proximity to nanoresonators. In this contribution we report the first example of surface shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) analysis with Ag@SiO2 nanoresonators. Ag@SiO2 nanoresonators enhance locally the intensity of the exciting electromagnetic radiation in a significantly broader frequency range than the previously used Au@SiO2 nanoparticles; therefore, combination of the SHINERS technique with the resonance Raman effect is significantly easier with Ag@SiO2 clusters.