Sculpted substrates for SERS

Sculpted SERS-active substrates are prepared by assembling a closed packed monolayer of uniform polystyrene colloidal particles (diameter 350 to 800 nm) onto an evaporated gold surface and then electrodepositing gold through this template to produce films with controlled thicknesses, measured as fractions of the sphere diameter, d. The resulting surfaces consist of a regular hexagonal array of interconnected spherical cross-section dishes. The role of localised plasmons in determining the SERS enhancement factor obtained for benzene thiol adsorbed onto the surfaces is then investigated by correlation of the UV-visible reflectance spectra, 400 to 900 nm, measured at the same positions on the substrate surfaces, with the SERS spectra. The results are interpreted in terms of the relative contributions of plasmons that are free to propagate across the top surface and those trapped within the dishes of the sculpted surface.