Modeling of a Plasmonic Biosensor Based on a Graphene Nanoribbon Superlattice

Abstract

A semi‐analytical theoretical model is presented, which describes the operation of a selective molecular sensor 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 equations 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 2D, 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 by Rodrigo et al. [Science 2015, 349, 165], 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 these sensing principles are discussed.