Pralidoxime-probed solution-gated graphene field-effect transistors for enzyme-free organophosphorus pesticide detection

The conventional electrochemical detection of organophosphorus pesticides (OPs) predominantly relies on acetylcholinesterase-based sensing strategies, which often suffer from poor operational stability and limited robustness. Herein, we report a conceptually new, enzyme-free sensing paradigm based on a solution-gated graphene field-effect transistor (SGGT) functionalized with a graphene-MXene‑cerium dioxide (Gr-M-Ce) nanocomposite, enabling ultrasensitive and broad-spectrum detection of OPs via a molecular-gating mechanism. In this platform, pralidoxime (PAM) is employed as a broad-spectrum molecular probe that interacts with the phosphate ester moieties commonly present in OPs. Upon exposure to OPs, PAM rapidly undergoes phosphorylation to form an electrochemically inert derivative (PAM-OPs), which adsorbs onto the Gr-M-Ce surface and selectively suppresses its catalytic activity toward PAM oxidation. This chemical conversion-catalytic inhibition cascade induces an effective gating modulation along the gate-source pathway of the SGGT, which is transduced and amplified by the device, yielding a pronounced shift in the source-drain current (I_DS). As a result, the sensor achieves ultrahigh sensitivity over a wide linear range from 1 × 10⁻¹² to 1 × 10⁻⁷ M, with a detection limit down to 0.24 pM. More importantly, this work establishes a generalizable molecular-gating strategy that integrates solution-phase chemical recognition with transistor-based signal amplification, offering a new design principle for constructing high-performance enzyme-free sensors for small-molecule analysis.