A simulation-based plasmonic terahertz nanosensor with graphene-enhanced sensitivity for diabetes monitoring.

We report a dual-mode terahertz plasmonic nanosensor based on a novel graphene-SiO₂-gold multilayer architecture, engineered for rapid and highly sensitive non-invasive detection of blood glucose concentration via refractive index sensing. This is the first sensor that simultaneously achieves two sharp, independently tunable resonant modes at 2.48-2.50 THz (mode one) and 6.01-6.12 THz (mode two) through the synergistic interaction of localized surface plasmon resonance (LSPR) and near-perfect impedance matching. The second mode exhibits an outstanding sensitivity of 4.5 THz /RIU and a figure of merit (FoM) of 40.9 among the highest reported in terahertz glucose sensing along with a limit of detection (LOD) of 6 × 10⁻³ RIU across the physiologically relevant refractive index range (n = 1.33-1.378). The dual-mode operation offers inherent self-referencing capability against environmental variations, while the validated equivalent circuit model provides deep physical insight and design flexibility. Compared with previously reported terahertz and metamaterial sensors, the proposed device achieves a superior combination of sensitivity, FoM, linearity, and robustness, indicating strong potential for integration into future wearable, real-time, non-invasive diabetes monitoring platforms.