Facile fabrication of ultrathin freestanding nanoporous Cu and Cu-Ag films with high SERS sensitivity by dealloying Mg-Cu(Ag)-Gd metallic glasses

Nanoporous metals prepared by dealloying have attracted increasing attention due to their interesting size-dependent physical, chemical, and biological properties. However, facile fabrication of metallic ultrathin freestanding nanoporous films (UF-NPFs) by dealloying is still challenging. Herein, we report a novel strategy of facile preparation of flexible Cu, Cu₃Ag, and CuAg UF-NPFs by dealloying thick Mg-Cu(Ag)-Gd metallic glass ribbons. During dealloying, the local reaction latent heat-induced glass transition of the precursor ribbons leads to the formation of a solid/liquid interface between the initially dealloyed nanoporous layer and the underlying supercooled liquid layer. Due to the bulging effect of in situ generated H₂ on the solid/liquid interface, Cu, Cu₃Ag, and CuAg UF-NPFs with thicknesses of ∼200 nm can self-peel off from the outer surface of the dealloying ribbons. Moreover, it was found that the surface-enhanced Raman scattering (SERS) detection limit of Rhodamine 6G (R6G) on the Cu and CuAg UF-NPF substrates are 10⁻⁶ M and 10⁻¹¹ M, respectively, which are lower than most of the Cu and Cu-Ag substrates prepared by other methods. This work presents a reliable simple strategy to synthesize a variety of cost effective and flexible metallic UF-NPFs for functional applications.