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High-performance dual-gate graphene pH sensors

Field-effect transistors (FETs) are versatile tools for high-precision biophysical measurements, and their measurement sensitivity and resolution can be improved by using innovative materials and device designs. Here, we report on the sensitivity and noise performance of dual-gated graphene FETs. When measuring pH, our devices exhibit a sensitivity of up to 30 V per unit change in pH, ≈500-fold greater than the Nernst value at room temperature, and noise-limited resolution of 2 × 10−4 in the biomedically relevant 0.1–10 Hz bandwidth. This level of performance is obtained due to a highly asymmetric dual-gate design utilizing an ionic liquid top-gate dielectric coupled with graphene's large intrinsic quantum capacitance (≈15  μC/cm2). Our results improve upon the sensitivity and resolution of previously demonstrated Si- and MoS2-channel FET biosensors.