Bi-analyte demonstration of non-resonant, single-molecule SERS with isolated lithographic enhancement structures

of a monolayer coverage. Raman spectra are obtained with 633 nm excitation. The spectra show truncated Pareto distribution statistics with individual spectra showing: only A; only C; and A & C features demonstrating single molecule sensitivity. Over 90% of the spectra are null spectra without either A or C features. Importantly, the enhancement structures are isolated from each other, no close approach is required as in the case of spherical nanoparticles where ~ 1 nm gap modes are responsible for the large enhancement required for non-resonant single molecule sensitivity. These enhancement structures are readily fabricated by volume manufacturing lithography (optical and nanoimprint).