Synthesis and Characterization of Gold Nanoparticles Coated with Ultrathin and Chemically Inert Dielectric Shells for SHINERS Applications

We very recently reported a new spectroscopic application for expanding the versatility of surface Raman called "shell-isolated nanoparticle-enhanced Raman spectroscopy" or "SHINERS". The most important and most difficult part of the SHINERS experiment is the effective transfer of the strong electromagnetic field from a gold core through the isolating silica or alumina shell to the probed surface. For this it is essential that the chemically inert dielectric shell be ultrathin (2-5 nm) yet pinhole-free. Herein we describe experimental and theoretical aspects of our SHINERS method in more detail. We provide a protocol for the synthesis and characterization of optimized shell-isolated nanoparticles (SHINs), and we examine the advantages of SHINERS nanoparticles over bare gold nanoparticles. We also present high-quality Raman spectra obtained from gold and platinum single-crystal surfaces in an electrochemical environment by our SHINERS technique. SHINERS is a simple and cost-effective approach that expands the flexibility of surface-enhanced Raman scattering (SERS) for an unprecedented diversity of applications in materials and surface sciences.