Zirconium(IV) oxide: New coating material for nanoresonators for shell-isolated nanoparticle-enhanced Raman spectroscopy

One tool that can be used for determining the structure and composition of surfaces of variousmaterials (even in in situ conditions) is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). In SHINERS measurements, the surface under investigation is coveredwith a layer of surface-protected plasmonic nanoparticles, and then the Raman spectrum of the surface analysed is recorded. The plasmonic cores of the used core-shell structures act as electromagnetic nanoresonators, significantly locally enhancing the intensity of the electric field of the incident radiation, leading to a large increase in the efficiency of the generation of the Raman signal frommolecules in the close proximity to the deposited SHINERS nanoresonators. A protective layer (from transparent dielectrics such as SiO2, Al2O3 or TiO2) prevents direct interaction between the plasmonic metal and the analysed surface (such interactions may lead to changes in the structure of the surface) and, in the case of plasmonic cores other than gold cores, the dielectric layer increases the chemical stability of the metal core. In this contribution, we show for the first time that core-shell nanoparticles having a silver core (both a solid and hollow one) and a shell of zirconium(IV) oxide are very efficient SHINERS nanoresonators that are significantlymore stable in acidic and alkaline media than the silver-silica core-shell structures typically used for SHINERS experiments.