Fabricating Au–Ag core-shell composite films for surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) integrates high levels of sensitivity with spectroscopic precision, and thus, has tremendous potential for chemical and biomolecular sensing. The key to the wider application of Raman spectroscopy using roughened metallic surfaces is the development of highly enhancing substrates for analytical purposes, i.e., for better detection sensitivity of trace contaminants and pollutants. Here, we have prepared Au, Ag, AuAg multilayer, and Au@Ag films on glass substrates for SERS-active substrates. The Au@Ag film shows a much stronger SERS signal for trans-bis(4-pyridyl)ethylene (BPE) molecules than those from pure Au, Ag, and AuAg films, indicating the Au@Ag film is more powerful than pure Au, Ag, and AuAg film as SERS active substrates. The enhanced surface Raman scattering signals were attributed to the local field enhancement in the core-shell structure.