SERS Substrate Fabrication via Rapid Triboelectrification-Driven Self-Assembly of Close-Packed Colloidal Monolayers.

Surface-enhanced Raman spectroscopy (SERS) amplifies Raman signals on nanostructured metallic surfaces, enabling the detection of trace analytes. There has been a spur on the precise fabrication of conventional planar SERS substrates with high performance and reproducibility. Common methods, such as ion beam and colloidal lithography, provide high-quality substrates but are often limited by high costs, complex processes, and challenges associated with mass manufacturing. Triboelectrification-driven self-assembly of dry colloidal powder offers a promising dry approach to attain ordered monolayer colloidal particles in < 20 $<20$  s rapidly. Here, we use this approach to produce high-performance SERS substrates with reproducible signals. By optimizing particle size and gold coating thickness, we found that self-assembled 500 nm particles with a 50 and 65 nm Au layer achieved a maximum enhancement factor (EF) of 1 × 10, and limit of detection (LOD) of 33-36 nM, in our initial characterization study without coordinate translation. Compared with commercial substrates (Silmeco; Hamamatsu) under matched conditions, this corresponds to 20-24 × lower LOD (33-36 nM vs. 680-800 nM) and 10-100 × higher maximum EF. These results highlight triboelectrification's ability to efficiently and cost-effectively produce homogeneous monolayers, offering a promising alternative to more complex or expensive methods and unlocking the opportunity for large-scale SERS substrate production with biosensing, diagnostics, and chemical detection applications.