Deposition of Ag Films on Liquid Substrates via Thermal Evaporation for Surface-Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) substrates were prepared by depositing Ag atoms on liquid surfaces via thermal evaporation at room temperature. These free-sustained substrates result in the formation of uniform Ag films, in which ramified Ag aggregates consist of substantial Ag nanoclusters with narrow gaps of several nanometers in between. SERS spectra of rhodamine 6G were investigated for this substrate to evaluate the SERS performance of this characteristic film morphology, and the results indicated that the SERS intensity from the closely-packed Ag nanostructures and small intervals were significantly enhanced. The dependence of SERS enhancement on the film thickness, nanoparticle size, and gap width was studied. An analytical model was proposed to simulate the electric field distribution during SERS detection, and the results validated the experimental observations.