Graphene-doped Bi2S3 nanorods as visible-light photoelectrochemical aptasensing platform for sulfadimethoxine detection

Bismuth sulphide (Bi2S3) nanorods doped with graphene (G) were synthesized and explored as photoactive materials for constructing a photoelectrochemical (PEC) aptasensor for sulfadimethoxine (SDM) detection. The formation of Bi2S3 nanorods and G nanosheets was observed by scanning electron microscopy (SEM) and further characterized by X-ray diffraction (XRD) spectroscopy. The PEC measurements indicated that the photocurrent response of Bi2S3 was obviously improved by doping suitable amount of G. The G-Bi2S3 composite coated electrode was utilized for fabricating a PEC aptasensor by covalently immobilizing a 5′-amino-terminated SDM aptamer on the electrode surface. Based on the specific interaction between SDM and the aptamer, a PEC sensor responsive to SDM was obtained. Under optimal conditions, the proposed sensor showed a linear photocurrent response to SDM in the concentration range of 1.0-100 nM, with a low detection limit (3S/N) of 0.55 nM. Moreover, the sensor showed high sensitivity, stability and reproducibility. The potential applicability of the PEC aptasensor was confirmed by detecting SDM in veterinary drug formulation and milk.