Design of Plasmonic Platforms for Selective Molecular Sensing Based on Surface-Enhanced Raman Spectroscopy

While the high sensitivity of plasmonic metal nanoparticles in Surface-Enhanced Raman Spectroscopy (SERS) is well established, applications of SERS in the selective identification of trace quantities of targeted molecules in a mixture of species remain to be a challenge. In this contribution, we demonstrate the design of plasmonic substrates that selectively enhance specific Raman vibrational bands, thereby offering high molecular sensitivity. We show that by changing the density and shape of plasmonic Ag nanostructures in Ag aggregates we can selectively control their optical properties and the degree to which they enhance different vibrational bands. By correlating the optical extinction spectra of substrates and the enhancement factors for different Raman vibrational bands, we demonstrate that the observed difference in the enhancement of vibrational modes is due to the difference in the localized surface plasmon resonance intensity at the Stokes Raman shifted wavelengths. We also shed light on critical design parameters for the synthesis of plasmonic nanosubstrates for selective detection of a molecule in a mixture of compounds.