Robust SERS substrates generated by coupling a bottom-up approach and atomic layer deposition

This paper reports on the development of a novel thermally stable surface enhanced Raman scattering (SERS) substrate. Specifically, these substrates can withstand high temperatures in air for an extended period of time without the loss of their enhancement capabilities. To accomplish this, we utilized a bottom-up approach, where the polyol reduction process was used to synthesize silver nanowires (NW) that were roughly 90 nm wide to act as the SERS active moiety. Subsequently, the NW were deposited onto a glass substrate and then coated with a thin protective layer of Al₂O₃ via atomic layer deposition (ALD). After heating these SERS substrates at 400°C for 24 h in air, it was found that the coated samples maintained a significant enhancement of the Raman signal, with further heating resulting in effectively no change in the SERS spectrum. The stability imbued by the ALD coating stems from limiting surface oxidation along with impeding aggregation that occurs at the higher temperature, which would otherwise lead to the destruction of the nanomorphology and complete loss of the SERS capabilities. These highly stable SERS substrates highlight the potential application of SERS in investigation of high-temperature chemical reactions and catalytic processes.