Host-guest assisted carbon quantum dots/WS₂ photoelectrochemical solution-gated graphene field-effect transistor for diquat detection

An innovative photoelectrochemical solution-gated graphene transistor (PEC-SGGT) was developed in this work for the sensitive detection of diquat (DQ). In this system, DQ acts as a molecular bridge that directs the pre-formation of a DQ@carbon quantum dots (DQ@CQDs) complex in solution and subsequently guides its assembly onto the WS₂ quantum dots–gold nanoparticles–cyclodextrin (WS₂/Au/CD) substrate. This process leads to the formation of a WS₂/Au/CD@DQ/CQDs photosensitizer with enhanced photoelectronic properties. When integrated as a PEC gate electrode, this material effectively modulates the channel current of the PEC-SGGT device, enabling accurate quantification of DQ with an ultralow detection limit of 0.45 pM. The sensing strategy combines host–guest recognition with electrostatic self-assembly to achieve selective DQ capture while generating robust, device-compatible gating signals. Overall, this work presents a promising paradigm for the ultrasensitive detection of small-molecule toxins.