Facile synthesis of large-scale Ag nanosheet-assembled films with sub-10 nm gaps as highly active and homogeneous SERS substrates

We report a facile low-cost synthetic approach to large-scale Ag nanosheet-assembled films with a high density of uniformly distributed sub-10   nm gaps between the adjacent nanosheets on Si substrates via galvanic cell reactions. The distribution density of Ag nanosheets on substrates could be tailored by tuning the duration of the HF-etching and the concentration of citric acid in the solution. Furthermore, in conjunction with a conventional photolithography, highly uniform patterned Ag nanosheet-assembled structures with different morphologies can be achieved on Si substrates via galvanic-cell-induced growth. By using rhodamine 6G as a standard test molecule, the large-scale Ag nanosheet-assembled films exhibit highly active and homogenous surface-enhanced Raman scattering (SERS) effect and also show promising potentials as reliable SERS substrates for rapid detection of trace polychlorinated biphenyls (PCBs).