Combining PVD structuration with dealloying for the creation of a highly efficient SERS platform

Abstract

Nanostructured noble metal thin films are highly studied for their interesting plasmonic properties. The latter can be effectively used for the detection of small and highly diluted molecules by the surface-enhanced Raman scattering (SERS) effect. Regardless of impressive detection limits achieved, synthesis complexity and the high cost of gold restrict their use in devices. Here, we report on a novel two-step approach to design and fabricate efficient SERS platforms that combines the deposition of a silver-aluminum thin film with dealloying. The magnetron sputtering technique was used for the deposition of the alloy thin film to be dealloyed. After dealloying, the resulting silver nanoporous structures revealed two degrees of porosity: a macroporosity, associated to the initial alloy morphology and a nanoporosity, related to the dealloying step. The resulting nanoporous columnar structure was finely optimized by tuning the deposition (i.e., the alloy chemical composition) and dealloying (i.e., dealloying media) parameters to reach the best SERS properties. These are reported for the samples dealloyed in HCl and with 30 at.% of silver at the initial state with a detection limit down to 10-10 mol.L-1 for a solution of Rhodamine B.