3D Nanoporous Metallic Networks for SERS-Based Detection of Water Contaminants

We investigated the formation of nanoporous metallic networks through a physical vapor deposition (PVD) process. Utilizing transmission electron microscopy (TEM), we observe the early stages of growth, revealing the presence of large pores and pillars. Our findings highlight the significant influence of the electrostatic nature of the substrate on the metallic network growth, where repulsion and attraction mechanisms come into play during the deposition process. We extend the applicability of this method, demonstrating its versatility in fabricating macroscopic metallic networks composed of submicrometer building blocks on different substrates, among them an amber stone, in a one-step process. The resulting three-dimensional (3D) networks display distinctive nonlinear optical properties, including enhanced second harmonic generation (SHG) and surface-enhanced Raman scattering (SERS) responses. The latter is used to detect contamination in water down to 10^-8 M.