Protected hollow metal nanoresonators for Raman analysis of surfaces

In this contribution we report the first example of Raman analysis of various surfaces using hollow-silver and hollow-gold nanoparticles protected by the silica layer. In contrast to solid spherical gold nanoparticles typically used for construction of nanoresonators for shell-isolated nanoparticle-enhanced Raman spectroscopy (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 gold nanoparticles can be changed within broad range of the visible electromagnetic radiation. It suggests that silica-covered hollow-gold nanoresonators can be used in a broader frequency range than previously used “solid” nanoparticles. We also found that the samples of hollow Au or Ag nanoparticles induce, on average, stronger enhancement of the Raman signal than the respective samples of solid nanoparticles synthesized from the same amount of metal.