A novel visible light photoelectrochemical (PEC) aptasensor was fabricated for label-free determination of bisphenol A (BPA) using graphitic carbon nitride (g-C3N4) nanosheets and gold nanoparticles (AuNPs). The flourin tin-oxide (FTO) glass plates were prepared by spray pyrolysis method and they were modified with g-C3N4 and AuNPs. The SH-terminal aptamer was then adsorbed on the surface of AuNPs /g-C3N4/FTO electrode through formation of thiol–gold (S–Au) bonds. In the presence of bisphenol A molecules, the structure of the aptamer molecules changes to G-quadruplex which limits the electron transfer on the electrode surface. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and time-based photocurrent measurements were carried out to investigate the changes of the surface of the FTO electrode in each step. Under the optimal experimental conditions, the constructed PEC aptasensor displayed a linear response to bisphenol A within the concentration range of 0.1–1000 nM with a detection limit of 0.03 nM. The PEC aptasensor did not show any cross-reactivity towards the analogues which are similar to BPA molecules. In addition, the proposed aptasensor was employed for determination the low concentration of BPA in real samples such as mineral water, milk, baby bottle, food storage container and urine with satisfactory results

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