Synthesis, Optical Properties, and Multiplexed Raman Bio‐Imaging of Surface Roughness‐Controlled Nanobridged Nanogap Particles

Plasmonic nanostructures are widely studied and used because of their useful size, shape, composition and assembled structure-based plasmonic properties. It is, however, highly challenging to precisely design, reproducibly synthesize and reliably utilize plasmonic nanostructures with enhanced optical properties. Here, we devise a facile synthetic method to generate Au surface roughness-controlled nanobridged nanogap particles (Au-RNNPs) with ultrasmall (≈1 nm) interior gap and tunable surface roughness in a highly controllable manner. Importantly, we found that particle surface roughness can be associated with and enhance the electromagnetic field inside the interior gap, and stronger nanogap-enhanced Raman scattering (NERS) signals can be generated from particles by increasing particle surface roughness. The finite-element method-based calculation results support and are matched well wi…