All-Armchair Graphene Nanoribbon Field-Effect Uridine Diphosphate Glucose Sensor: First-Principles In-Silico Design and Characterization

Label-free sensors capable of detecting low concentrations of significant biomolecular substances without inducing immune response would simplify experiments, minimize errors, improve real-time observations, and reduce costs in probing living organisms. This paper presents a first-principles, in-silico derived, all-armchair graphene nanoribbon field-effect transistor (g-FET) device for the detection and measurement of low-concentration (pM-nM) uridine diphosphate glucose, UDP-glucose. UDP-glucose is an intermediate reactant in the synthesis of sucrose in a plant cell's cytoplasm and an extracellular signaling molecule capable of activating downstream defense mechanisms. The unique g-FET configuration for the semiconducting channel and electrodes favors the fabrication of high-density nanoarray sensors. Optimal device electronic transport and switching properties are predicted by screening configurations with different widths, to control bandgap, and lengths, to control thermionic versus tunneling transport across the semiconducting junction. A self-assembled monolayer (SAM) of pyrene derivatives, 1-pyrenebutyric acid, is used to noncovalently functionalize the graphene surface on one end and to covalently ligate the target analyte on the other while providing mechanical, chemical, and electronic signal sensing stability. We find that the device offers a predicted limit of detection (LOD) of 0.997/$n$ mM/L (where $n$ is the number of sensor units in an array), with high transconductance sensitivity, 0.75-$1.5\mu\text {S}$ for 1-3 UDP-glucose molecules, at low input ($V-{G}= 0.9$ V) and output voltages $V-{\text {DS}}=0.1$ V. Thus, a $1000\times1000$ nanoarray sensor would yield an LOD = 0.997 nM/L. This low-power, all-armchair g-FET sensor with SAM ligands that may be chosen to bind different biomarkers provides a unique opportunity for high throughput, real-time, low-cost, high-mobility, and minimal-calibration sensing applications.