Graphene-based Field-Effect Transistor Biosensors for Photosensory Biomolecular Detection

Biosensors play a crucial role in science and healthcare. Current research focuses on improving detection limit, response time, selectivity, and label-free sensing capabilities of biosensors. Graphene Field Effect Transistors (GFETs) have advanced optical and electrical properties that can be utilized for detecting biomolecules with both high sensitivity and fast response times. Here we demonstrate the capabilities of GFETs for detecting Photoactive Yellow Protein (PYP) without the need for chemical functionalization. Due to the presence of the p-coumaric chromophore, PYP molecules undergo a cyclic photochemical reaction when illuminated with blue (450 nm) light. The photochemical process leads to protonation which causes changes in the conductance of the GFET when the biomolecules interact with the graphene surface. Protonation occurs in the millisecond timescale, inducing charge circulation in the graphene channel and leading to a photoconductive gain. Due to the ultra-high carrier mobility and high surface sensitivity of graphene, the photogating effect in GFETs allows for the fast detection of these conduction changes at extremely low protein concentrations. Experimental results demonstrate that GFETs are capable of detecting PYP molecules in solutions at concentrations as low as 5.8 fM in the millisecond timescale.