Plasmonic ladder–like structure and graphene assisted high surface enhanced Raman scattering detection

Abstract

Surface enhanced Raman scattering (SERS) study is an interesting active area of research, where periodically patterned plasmonic substrates play a key role in SERS enhancement. Surface plasmon resonance excitation generates tremendous electromagnetic near-fields (E) in the form of localized or propagating near-fields contributing to the Raman signal (E4 process) to a great extent and overall enhancement is reported to be as high as 1010 or even more. Independently, graphene alone can enhance the Raman signal due to chemical enhancement. In the present study, we have attempted to achieve high SERS from the R6G Raman active probe using plasmonic patterned substrates in the presence and absence of graphene oxide. Plasmonic ladder-like patterned substrates are fabricated using laser interference lithography, which is cost effective, simple to operate, and has potential for large scale nanofabrication. By combining graphene oxide with R6G, we have found additional two time enhancement compared to that obtain from R6G alone on the plasmonic patterned substrate. Further, we have also attempted to understand the underlying mechanism to correlate the uniform and reproducible SERS through Raman mapping and Finite difference time domain computation. Our finding can potentially be applied for SERS investigation at a low molecular concentration.