A novel photoelectrochemical strategy for lead ion detection based on CdSe quantum dots co-sensitized ZnO-CdS nanostructure

A novel photoelectrochemical (PEC) aptasensor for lead ion (Pb 2+ ) detection was proposed on the basis of the CdSe quantum dots (QDs) co-sensitized ZnO-CdS nanostructure and the specificity of aptamer. The CdSe QDs-capped cDNA, as a signal enhancement element, could hybridize with the aptamer on the sensing platform to generate a CdSe/CdS/ZnO dual co-sensitized structure, realizing a great enhancement in photocurrent response. In the presence of Pb 2+ , the aptamer on the sensing interface specifically bound with the Pb 2+ to form G-quadruplex structures, which greatly inhibit the hybridization between aptamer and CdSe QDs-cDNA, leading to a decrement of the photocurrent signal. As the concentration of Pb 2+ increased, the photocurrent response showed a diminishing tendency. Under the optimized conditions, the fabricated PEC aptasensor exhibited a linear response between photocurrent variation and the logarithm of Pb 2+ concentration in the scope of 1.0 × 10 −9  M to 1.0 × 10 −5  M with a detection limit of 3.4 × 10 −10  M. Moreover, the aptasensor has been applied in the determination of Pb 2+ in environmental water samples with the good selectivity .