Potential Modulated Surface-enhanced Raman Spectroscopy of Tolmetin at Gold Nanoparticle Film Functionalised Polarisable Liquid-Liquid Interfaces

An aqueous colloidal suspension of gold nanoparticles (AuNPs) may be condensed into a thin fractal film at the polarisable liquid-liquid interface formed between two immiscible electrolyte solutions (ITIES) upon injection of millimolar concentrations of sodium chloride to the aqueous phase. By adjusting the interfacial polarisation conditions (negative, intermediate, and positive open-circuit potentials), the morphology of the film is modified, resulting in unique surface plasmon properties of the film, which enable in situ surface-enhanced Raman spectroscopy (SERS). Intense SERS signals are observed at the polarisable liquid-liquid interface when micromolar concentrations of tolmetin, a non-steroidal anti-inflammatory drug, are entrapped in the AuNP fractal film. The change in signal intensity, averaged over multiple spectra, with respect to the concentration of tolmetin, depends on the polarisation conditions and suggests the presence of chemical-induced damping effects on the surface plasmons of the gold film.