Electrolyte-gated Graphene FETs for Acetylcholine Detection via Layer-assisted Transfer Approach

Acetylcholine (ACh) detection is essential for studying the cholinergic system and diagnosing neurodegen erative disorders. Here, we present a graphene field-effect transistor (GFET) biosensor functionalized with acetyl cholinesterase (AChE) enzyme for label-free ACh sensing. To preserve the intrinsic properties of graphene and enhance biosensor performance, we employ a Functional Layer-assisted Transfer (FLaT) strategy. This approach enables direct post-growth functionalization of graphene with a perylene bisimide (PBI) linker, preventing contamination during transfer and serving as a stable, non-covalent anchoring layer for biofunctionalization. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses confirm a cleaner and more uniform surface for FLaT-treated graphene compared to non-functionalized graphene, while Raman spectroscopy verifies the high quality of the CVD-grown material. AChE enzymes are covalently attached to the PBI layer using carbodiimide cross-linker chemistry. The successful surface chemistry was confirmed by AFM and X-ray electron spectroscopy (XPS). The resulting enzyme-functionalized, electrolyte-gated GFETs operate at low gate voltages (∼1V), making them well-suited for biosensing in aqueous environments. They exhibit calibrated responses to ACh concentrations ranging from 0.1 to 1000 μM, effectively covering the physiologically relevant range found in the central nervous system. This work demonstrates the potential of the FLaT based GFET platform for sensitive, stable, and scalable neurotransmitter detection.