Modeling of a plasmonic biosensor based on a graphene nanoribbon superlattice

We present a semi-analytical theoretical model, which describes the operation of a selective molecular sensor [1] employing a double resonance between a dipole-active molecular vibration mode, tunable surface plasmons in a periodic structure of graphene nanoribbons (NRs), and the incident light, in the THz-to-IR range, used for testing. The model is based on the solution of Maxwell’s equa tions for the NR structure deposited on a dielectric substrate, using the electromagnetic Green’s function, and is extended to the case of an additional (buffer) layer present between the NRs and the substrate. Both the graphene NRs and the layer of adsorbed molecules are considered as two-dimensional, since their thicknesses are very small in comparison with the wavelength of the incident light. The model is applied to different molecular systems, the protein studied in Ref. [1], for which an excellent agreement with experimental data is obtained, and an organometallic molecule Cd(CH3)2. Two different assumptions concerning the way of sticking of the analyte molecules to the sensor’s surface are considered and the limitations of this sensing principles are discussed. Funding from the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2019. Authors also acknowledge FEDER and the Portuguese Foundation for Science and Technology (FCT) for support through projects POCI-01-0145-FEDER-028114 and PTDC/FIS-MAC/28887/2017. MIV also acknowledges support from the European Commission through the project “Graphene-Driven Revolutions in ICT and Beyond”- Core 3 (Ref. No. 881603).