Photoelectrochemical analysis of Pb²⁺ based on Au@PTCA Schottky junction with Pb²⁺-G quadruplex structure

Herein, a novel photoelectrochemical (PEC) aptasensor using gold nanoparticles@3,4,9,10-perylene tetracarboxylic (Au@PTCA) Schottky junction as the effective optoelectronic material and lead ion (Pb²⁺)-G quadruplex structure as the efficient quencher was constructed for the detection of Pb²⁺ with high sensitivity and excellent selectivity. Au@PTCA Schottky junction, which was proposed by the in situ reduction of Au NPs on the PTCA surface, exhibited a strong unidirectional conductivity, which could generate a significantly enhanced PEC signal compared with the pure PTCA. The Pb²⁺-G quadruplex structure with a large spatial hindrance effect was formed when the target Pb²⁺ was present owing to the occurrence of the specific recognition between Pb²⁺ and its aptamer S1. The formation of a Pb²⁺-G quadruplex structure effectively quenched the initial signal generated by the Au@PTCA Schottky junction, which was derived from restricted electron transport and light transmission. The obtained prominently decreased PEC signal could achieve the quantitative detection of Pb²⁺ from 0.5 pM to 500 nM, with a low detection limit of 0.17 pM. The preparation time of this PEC aptasensor was 13 h, and the time for PEC measurement depended on the illumination time, which switched off-on-off for 10 s-20 s-10 s. The study proposed here with high sensitivity and excellent selectivity for Pb²⁺ analysis offered a novel and reliable tool for environmental monitoring related to heavy metal ions.