A graphene-based toxic detection approach

Periodic arrays of graphene disks are leveraged to form a toxic gas detector. The operational frequency range is the THz gap. The idea stems from the middle air gap which is surrounded by graphene-spacer layers while a fully reflecting metallic surface is placed underneath. The change in the refractive index of the air gap due to the presence of some toxic gases leads to absorption deviations. Interpreting the known deviations can define a detection protocol in the THz spectrum. This work proposes a three-layer wave absorber based on the graphene patterns, TOPAS spacer, and the golden surface. Each component is modeled by the passive circuit element and the total impedance of the structure is calculated. Additionally, the impedance matching concept is investigated to predict absorption response. Furthermore, full-wave simulation is performed to compare with the circuit model approach. Based on the simulation results, a multi-band absorption response experiences considerable frequency shifts when exposed to some toxic gases including SO₂, N₂, NO₂, O_3, and CO. More importantly, the capability of being tuned via external chemical potential makes the proposed absorber an ideal basic building block for healthcare-based optical systems.