“…Hence, the upgrade of metal films with controlled nanostructure and composition is of pivotal importance and is currently intensely investigated [6,7,37]. There is a variety of methods for the fabrication of SERS substrates, such as pulsed laser deposition (PLD) [38], metal evaporation [39,40], chemical or electrochemical etching or deposition on smooth surfaces [41][42][43][44], and deposition or assembly of metal nanoparticles from solution (dried droplet (DD) method) [45,46]. However, for a given excitation wavelength, SERS effect is nearly absent in isolated particles, while the coupling of transition dipoles in aggregates enhances relatively this effect in the nanoscopic scale [47].…”