Graphitic
carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) is a new
type of metal-free semiconducting material with promising applications
in photocatalytic and photoelectrochemical (PEC) devices. In the present
work, g-C<sub>3</sub>N<sub>4</sub> 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-C<sub>3</sub>N<sub>4</sub> with closely contacted interfaces. The UV–visible
diffuse reflection spectra (DRS) indicated that the absorption of
g-C<sub>3</sub>N<sub>4</sub> in the visible region was enhanced by
CdS QDs. As a result, g-C<sub>3</sub>N<sub>4</sub>–CdS nanocomposites
demonstrated higher PEC activity as compared with either pristine
g-C<sub>3</sub>N<sub>4</sub> or CdS QDs. When g-C<sub>3</sub>N<sub>4</sub>–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-C<sub>3</sub>N<sub>4</sub> sensitized
with CdS QDs was successfully demonstrated as useful photoactive nanomaterials
for developing a highly sensitive and selective PEC aptasensor
