Graphitic Carbon Nitride Sensitized with CdS Quantum Dots for Visible-Light-Driven Photoelectrochemical Aptasensing of Tetracycline

Abstract

Graphitic carbon nitride (g-C₃N₄) is a new type of metal-free semiconducting material with promising applications in photocatalytic and photoelectrochemical (PEC) devices. In the present work, g-C₃N₄ coupled with CdS quantum dots (QDs) was synthesized and served as highly efficient photoactive species in a PEC sensor. The surface morphological analysis showed that CdS QDs with a size of ca. 4 nm were grafted on the surface of g-C₃N₄ with closely contacted interfaces. The UV–visible diffuse reflection spectra (DRS) indicated that the absorption of g-C₃N₄ in the visible region was enhanced by CdS QDs. As a result, g-C₃N₄–CdS nanocomposites demonstrated higher PEC activity as compared with either pristine g-C₃N₄ or CdS QDs. When g-C₃N₄–CdS nanocomposites were utilized as transducer and tetracycline (TET)-binding aptamer was immobilized as biorecognition element, a visible light-driven PEC aptasensing platform for TET determination was readily fabricated. The sensor showed a linear PEC response to TET in the concentration range from 10 to 250 nM with a detection limit (3S/N) of 5.3 nM. Thus, g-C₃N₄ sensitized with CdS QDs was successfully demonstrated as useful photoactive nanomaterials for developing a highly sensitive and selective PEC aptasensor