Multi-channel SERS enhancement using graphene-based trimeric molecule in triangular configuration

• Multiple hybridized resonance generation using graphene-coated particles with triangular configuration for multiplexed detection of the analytes. • Increasing the number of frequency bands by opening the vertex of the triangle. • Extracting the high-quality graphene material requirement as a design key point and exhibiting the possibility of reconfiguring the optical response. • Revealing the modulation of the response with respect to geometrical parameters, beneficial for optimization of the design for different analytes. In this paper, a graphene-based trimeric plasmonic molecule with a triangular configuration is proposed for the multi-channel surface-enhanced Raman scattering (SERS). It is observed that the equilateral triangular nanoparticle arrangement provides multiple intense resonance channels with giant near-field enhancement at the three hot spots, fulfilling the single-molecule detection criteria, which makes it superior with respect to noble metal counterparts. The operating mechanism of the device is discussed based on the spherical multipoles, quantitatively illustrated by the normal electric field on the nanoparticle surface. The generated resonances can be reconfigured by applying different chemical potentials to the graphene shells. Furthermore, thanks to the wideband resonance excitation in the graphene material, the design can be extended to devices with other geometrical dimensions, suggesting the applicability of the sensor for a wide range of analyte detection. Importantly, the resonance generation is susceptible to geometrical symmetry, such that by opening the equilateral triangle vertex, the number of observed resonances increases. The multi-channel performance of the device can be employed for the precise detection of the mixture of the analytes with more certainty since the multiple frequencies and hot-spots increase respectively the chance of experiment double-checking and the molecule binding to the hot spot.