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

Abstract

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.