Characterizing planar SERS substrates: Unraveling the link between physical characteristics and performance metrics

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a powerful optical sensing technique used in various applications, including medicine, microbiology, and environmental analysis. Planar SERS substrates are of particular interest due to their ease of integration in lab-on-chips and better reproducibility compared to colloidal SERS. The performance of these SERS substrates is quantified using metrics such as enhancement factor, sensitivity, and reproducibility. However, there is yet to be a consensus on how to practically compare and interpret such metrics in publications and experiments. These performance metrics are strongly influenced by the nanostructures’ material, architecture, element sizes, as well as the circumstances surrounding the experiments. Understanding the effect of these characteristics on the SERS substrates’ performance could not only enable a better performance but also direct their development for different applications. Thus, we developed a planar SERS-substrate characterization protocol to explore the correlation between the nanostructures’ physical characteristics and the performance metrics through coordinate-transformed spectroscopic measurements over structure-characterized areas. Seven commercial SERS substrates, with various surface architectures fabricated using different fabrication technologies, were studied using this benchmarking protocol. The results demonstrated how this protocol can indicate a SERS substrate’s suitability for a specific application, thus, guiding the substrate's further adaptations or development.