Field Effect Transistor Enable Remote Label-Free Enzyme Measurements*

We have fabricated and characterized ionic liquid-gated 2D-MoS2 field effect transistors (2D-ILFETs) that operate at the quantum capacitance limit of the 2D channel material. These devices were used to measure pH with high sensitivity (~75 times higher than the Nernst value of 59 mV/pH) and low noise (~2 orders of magnitude higher signal-to-noise ratio over ion-sensitive FETs) at room temperature. This high device performance in pH sensing is attributed to the large asymmetric capacitive coupling between the top ionic liquid gate and bottom silicon gate to the 2D semiconducting channel. This behavior is fundamentally different from dual-gate silicon FET pH sensors that control two coupled channels. To demonstrate the usefulness of ultra-sensitive pH measurements based on 2D-ILFETs, we experimentally quantified the function of enzymes implicated in Alzheimer’s disease at physiological concentrations and with sufficient time-resolution to allow the estimation of both steady-state and kinetic parameters in a single experiment.