Multilayer enhanced SERS active materials: fabrication, characterization, and application to trace chemical detection

Abstract

A multilayer surface-enhanced Raman scattering (SERS) substrate geometry providing significantly greater SERS enhancements, longer active lifetimes, better reproducibility, and lower detection limits for trace chemical analysis than traditional SERS substrates has been developed. We have fabricated and characterized this novel class of multilayered metal film-based SERS substrates, which are capable of enhancing SERS signals over an order of magnitude relative to conventional metal film over nanostructure substrates. These multilayer enhanced metal film substrates are fabricated by repeated vapor deposition of metal films over nanometer sized structures. Different sizes of nanostructures were evaluated in order to obtain the optimal SERS enhancements. Meanwhile, different dielectric coatings were fabricated between silver layers, and SERS enhancements were evaluated for each type. Additionally, different metals, such as gold, were used to further optimize the stability and reproducibility of these novel substrates. Silver oxide layers produced at elevated temperatures were also investigated to accelerate the fabrication rate of these multilayer substrates. Finally, this paper also discusses the application of these novel multilayer substrates for trace detection of chemical agents and simulants.