SERS performance of gold nanotubes obtained by sputtering onto polycarbonate track-etched membranes.

Surface-enhanced Raman scattering (SERS) is a powerful and versatile tool for studying molecules on metallic surfaces with great impact on areas such as electrochemistry, catalysis and related subjects. The search for new SERS-active substrates with high performance, namely high enhancement factors and reproducibility, is currently the main focus of several research groups. Here is shown an alternative easy and inexpensive synthetic approach to a SERS-substrate comprised of gold nanotubes obtained by the sputtering onto polycarbonate track-etched membranes used as template. Its SERS performance was evaluated by mapping (10 × 10) μm(2) areas and resulted in average enhancement factors that span from 2.3 × 10(3) to 1.2 × 10(5) with a maximum enhancement factor of 2.5 × 10(5). The enhancement depended strongly on the template pore diameter, with the best performance obtained when membranes with pore diameters of 400 nm were used as template. Further analysis showed that the larger enhancements came from coalesced gold nanotubes and detection of the dye rhodamine 6G at concentrations as low as 0.1 nM was possible. These results put this substrate as a valuable and easy-to-fabricate tool for studying and detecting molecules on surfaces. The proposed methodology could be easily adapted to other metals, such as silver and copper.