Nanoporous Au/SnO/Ag heterogeneous films for ultrahigh and uniform surface-enhanced Raman scattering

There is a strong interest in plasmonic nanostructures that uniformly enhance Raman signals of chemical and biological molecules using surface-enhanced Raman spectroscopy (SERS) for trace detection. Although the resonant excitation of localized surface plasmons of single or assembled metallic nanoparticles can generate large electromagnetic fields, their SERS effects suffer from poor reproducibility and uniformity, limiting their highly reliable and stable applications. Here, we report self-supported large-scale nanoporous hybrid films with high density and uniform hot spots, produced by the implantation of SnO nanoparticles into nanoporous Au/Ag bimetallic films (NP Au/SnO/Ag) for the trace detections of both resonant and non-resonant molecules. The NP Au/SnO/Ag films exhibit extraordinary SERS enhancements, which increase with the increasing density of Au/SnO/Ag sandwich protrusions, as a result of the formation of abundant and uniform hot spots. The nanogaps in their wrinkled films further improve the capability to detect molecules at single molecular levels, making the hybrid films promising SERS-active substrates with superior reproducibility and reliability for applications in life science and environment protection.