Surface sol–gel growth of ultrathin SiO2 films on roughened Au electrodes: Extending borrowed SERS to a SERS inactive material

We report the application of borrowed SERS to SERS-inactive SiO2, which is achieved by coating an ultrathin, pinhole-free SiO2 layer on a roughened Au electrode. The ultrathin SiO2 layer allows the transfer of the long-range electromagnetic fields created by the underlying Au to the SiO2 surface, achieving SERS therein (i.e., borrowed SERS). The pinhole-free nature of the SiO2 layer avoids spectral contamination from the underlying Au substrate. The roughened Au/SiO2 overlayered electrode thus enables acquiring vibrational spectra for molecules adsorbed at SERS-inactive SiO2, and such an overlayered strategy could be extended to enable borrowed SERS to be realized on more SERS-inactive materials.