Universal and Scalable Fabrication of Plasmonic Nanocrystals for Ultrasensitive SERS

Surface-enhanced Raman spectroscopy (SERS) enables the detection of molecular signatures at extremely low concentrations, even down to a single molecule, by using plasmonic nanostructures that support localized surface plasmon resonances (LSPRs). Nonetheless, fabricating highly sensitive nanostructures typically requires complex, time-consuming, and costly fabrication processes with limited scalability. In this work, we present a simple and universally applicable single-step method to fabricate plasmonic nanocrystals (NCs) from metals, such as Al, Ag, and Au. These NCs are directly grown over large surface areas on various substrates through heat-assisted growth from e-beam or magnetron sputter depositions. The LSPRs of the NCs can be tailored by selecting the metal, nanocrystal size, and surface morphology. The heat-assisted growth strategy enables the formation of NC matrices capable of detecting analyte molecules at ultralow, down to zeptomolar, concentrations via SERS, particularly when using Ag NCs. This versatile, cost-effective fabrication approach opens new opportunities for large-area plasmonic platforms in sensing, photocatalysis, and optoelectronic applications.