Multiband SERS substrate using switchable hot spots of the inline graphene-wrapped nanoparticle chains.

This paper discusses the applicability of graphene-based inline spherical trimers for the triple band single molecule detection of the analytes. The extension of the performance to the few particles' linear array assemblies with the aim of increasing the number of frequency bands and conducting hot-spot engineering is correspondingly provided. Numerical simulations show that the observed multi-band electric field intensities at the hot spots are adequately high to be used in single-molecule detection through surface-enhanced Raman scattering (SERS). Meanwhile, the few particles' linear array offers the hot spot switching capability regarding different frequencies. The generation of multiple resonances in the proposed devices is the consequence of strong coupling among the nanoparticles in the array. It is observed that to survive the higher-order resonance' detection capability, high-quality graphene shells are demanded, which is the main challenge of the experimental realization due to the imperfections introduced by the curvature of the particles. Also, to reach the single-molecule detection criteria, the use of hollow nanoparticles is a must. Importantly, multiple resonance generation employing multiple nanoparticles in the chain is not observed in the chains of plasmonic metallic particles. It is the outcome of electing graphene as the design platform since the plasmon lifetime and dissipation engineering are viable in the graphene-based devices.