Ultrasensitive Graphene-TMD Heterostructure Optical Biosensors Integrated with Silicon Photonics for Label-Free Detection

Abstract This work presents a breakthrough optical biosensing platform utilizing graphene–transition metal dichalcogenide (TMD) heterostructures monolithically integrated with silicon photonic waveguides. The engineered van der Waals heterostructure exploits synergistic light-matter interactions between graphene’s tunable plasmonic properties and TMD’s direct bandgap characteristics to achieve unprecedented detection sensitivity. Our platform demonstrates label-free biomolecule detection with an exceptional limit of detection of 10⁻ ¹⁸ M—three orders of magnitude superior to conventional surface plasmon resonance biosensors (10⁻ ¹² M) and two orders better than existing graphene-based sensors (10⁻ ¹⁷ M). The heterostructure exhibits voltage-tunable optical properties through electrostatic gating, enabling dynamic sensitivity optimization via epsilon-near-zero condition manipulation with up to 30% transmission modulation depth. Comprehensive characterization confirmed high-quality monolayer materials (I₂D/IG > 2, ID/IG < 0.1) with optical measurements perfectly matching theoretical predictions. Biosensing performance was validated using clinically relevant biomarkers including cardiac troponin I, PSA, miRNA-21, IL-6, and SARS-CoV-2 spike protein, demonstrating exceptional specificity (> 95%), rapid response kinetics (2–15 seconds), and remarkable 30-day operational stability in complex biological matrices. Silicon photonics integration enables unprecedented miniaturization (footprint < 100 µm²) and multiplexing capabilities with ultralow energy consumption (< 1 fJ/bit). Surface functionalization using pyrene derivatives preserves 2D material properties while providing selective biomolecule recognition. The scalable CVD-based fabrication achieves > 80% yield and full CMOS compatibility for cost-effective mass production. This research addresses critical biosensing limitations—insufficient sensitivity for early disease detection, bulky instrumentation, and high costs. Our graphene-TMD platform represents a paradigm shift toward portable, multiplexed, ultrasensitive diagnostic tools capable of detecting biomarkers at physiologically relevant concentrations, establishing a new benchmark for next-generation point-of-care diagnostics and personalized medicine applications.