Physically Reshaped Silver Microplates Formed Monolayer Assemblies at Air/Water Interface as High-Performance SERS Substrates.

Surface-enhanced Raman scattering (SERS) holds great promise for ultrasensitive chemical analysis but is often limited by the trade-off between performance and fabrication simplicity. This work presents a facile strategy to prepare monolayer silver microplates combining the top-down and bottom-up fabrication concepts. Silver microplates with uniform nanoscale thickness (~93.5 nm) and micron-scale lateral size (D50 = 3.33 µm) are prepared via a scalable mechanical ball-milling process. These silver microplates served as building blocks for spontaneous interfacial self-assembly at the air/water interface to form a macroscopically continuous monolayer film. The silver microplate monolayer film is transferred onto a plasma-treated silicon wafer as a SERS substrate. The resulting SERS substrate exhibits a porous, network-like microstructure composed of densely packed microplates, which generates a high density of electromagnetic hot spots at the nanogaps. Using Rhodamine 6G as a probe molecule, the substrate demonstrates a SERS detection limit of as low as 1 nM and good spatial uniformity with a relative standard deviation of ~9.94%. This study provides a cost-effective and scalable self-assembly route of physically reshaped silver microplates to fabricate high-performance SERS substrates.