An Innovative Approach to Fabricate Wrinkled Silver-Based Nanoporous Materials for SERS Detection

Accepted manuscript of an article published in ACS Applied Nano Materials. Abstract: Nanostructured porous surfaces exhibit remarkable properties suitable for a diverse range of applications, such as surface-enhanced Raman scattering (SERS). Nevertheless, the facile engineering of these nanoscale materials is constrained by limitations inherent in the current synthesis methodologies employed for their fabrication. In this work, we present an innovative plasma-derived technique for the fabrication of silver-based nanoporous wrinkled surfaces. First, by depositing a magnetron-sputtered Ag–Al thin film onto a liquid plasma polymer film (PPF), we exploit the spontaneous wrinkling phenomenon that occurs in bilayer systems composed of a soft and stiff layer. Notably, the thickness of the PPF influences the nanowrinkle amplitude (ranging from 280 to 520 nm) while the wavelength remains constant (approximately 2 μm). This behavior is attributed to the pinning of the metal layer onto the silicon substrate. Then, the wrinkled surface is further nanostructured by dealloying, which involves etching of the less noble element of the alloy, here aluminum, resulting in the formation of a silver-based nanoporous structure that retains the wrinkled morphology. An increase in dealloying time, while increasing the nanopore dimensions, results in a loss of wrinkle amplitude, which can be explained by the shrinking of the metal layer during the dealloying process, leading to tensile strain. Our results clearly demonstrate the attractiveness of this innovative method for fabricating wrinkled nanoporous materials with customizable dimensions. Furthermore, this substrate applicative potential as a SERS platform has been evaluated considering the rhodamine B molecule, demonstrating a detection limit of 10^–9 M.