De-wetted gold nanostructures for SERS-based sensing of static and dynamic targets

De-wetting of metal thin film is one of the simplest fabrication techniques to produce metallic nanostructures for Surface-Enhanced Raman Spectroscopy (SERS)-based sensing. In this manuscript, we explore the sensitivity of a de-wetted metal SERS substrate by testing it with the organic dye Rhodamine 6G (R6G) as well as with the single amino acids (Glycine, Serine, and Histidine) and a binary mixture of Glycine and Serine mixture. We observe that repeated de-wetting of the metal thin film provides a more than ten times higher SERS enhancement factor compared to a single de-wetting. This is attributed to the presence of more closely spaced metal nanoclusters, enabling a higher electromagnetic field enhancement at the hotspots. We characterized the sensing capability of our SERS substrates by detecting R6G dye drop-casted onto the substrates at sub-femtomolar concentrations. We were also able to detect R6G in a dynamic state while it was transported across a 500 nm diameter pore with a nanomolar detection limit. Finally, we were also able to detect amino acids with a micromolar detection limit using our SERS substrate. These results indicate the promise in the integration of our SERS substrate with solid-state nanopores for SERS-based signal readout where concentrations higher than nanomolar exist in the pore due to high confinement. © 2024 Elsevier B.V.