Graphene Quantum Dot‐Doped PEDOT for Simultaneous Determination of Ascorbic Acid, Dopamine, and Uric Acid

Abstract We propose a novel strategy to prepare poly(3,4‐ethylenedioxythiophene) (PEDOT) thin films (PEDOT‐GQD) doped with graphene quantum dots (GQD) as an electrode active material for an electrochemical biosensor. The PEDOT‐GQD was prepared through simultaneous electropolymerization and doping of EDOT using an ionic complex composed of several Li + cations and one multivalent GQD anion (Li‐GQD) by potential cycling without any additives. The Li‐GQD, acting as a supporting electrolyte and an anionic dopant, leads a conformational change in the PEDOT chains into an expanded‐coil structure. This led to the formation of the PEDOT‐GQD with expanded‐coil polymeric chains which increases not only intramolecular electron transfer among PEDOT chains but also interfacial charge transfer between the aromatic moieties of target molecules and that of PEDOT through π–π interaction. Moreover, PEDOT‐GQD revealed a porous structure with interconnected 3D networks, as GQD doped into the PEDOT backbone affects the growth mechanism of PEDOT. Interestingly, applying a potential of more than +1.2 V in the electropolymerization caused the mixed formation of oxidized PEDOT and overoxidized PEDOT, leading to the high electrocatalytic activity of PEDOT‐GQD. The resulting PEDOT‐GQD based electrochemical sensor exhibited excellent electrochemical performances in the simultaneous detection of ascorbic acid, dopamine, and uric acid, such as high sensitivity, selectivity, reproducibility, stability, also in real sample analysis.