Target-enhanced photoelectrochemical aptasensor for Cd(II) detection using graphite-like carbon nitride as sensitizer with high sensitivity

Abstract

In this paper a photoelectrochemical (PEC) aptasensor based on specific recognition between aptamer and target cadmium ion (Cd(II)) with change of the sensing interface structure was constructed. A ZnO-TiO2 nanocomposites and Au nanochains (Au NCs) modified electrode as photosensitive substrate was prepared and further covalently bound with graphite-like carbon nitride (g-C3N4) on the free end of the aptamers to amplify the detection signal, which was applied to Cd(II) detection. Graphite-like carbon nitride with narrow band gap exhibited unique photoelectric property under UV and visible light irradiation. When the target Cd(II) was detected by the modified interface of the aptasensor, the structure of sensing interface was changed with the signal sensitizer g-C3N4 closed to the interface, which caused the changes of photocurrent signal more sensitive and exhibited a good linear relationship with the Cd(II) concentration, so as to realize the quantitative analysis of the target. This PEC aptasensor showed a high sensitivity with a detection limit as 1.1 × 10−11 mol/L and was further applied to the water sample detection successfully.