Photoelectrochemical Pb²⁺ Analysis Based on the Effective Signal Quenching of CoPP toward Ag@PTCA Schottky Junction

In this work, a specific and sensitive photoelectrochemical (PEC) biosensor has been constructed for the lead ion (Pb²⁺) assay by applying a silver nanoparticles@3,4,9,10-perylene tetracarboxylic acid (Ag@PTCA) Schottky junction as the signal substrate and cobalt tetraphenyl porphyrin (CoPP) as the signal quencher integrated with nucleic acid double-amplification strategies. The strong unidirectional conductivity of the Shottky junction and the surface plasmon resonance (SPR) effect of Ag NPs significantly enhanced the charge separation capability within the Ag@PTCA Schottky junction, thus providing a robust signal substrate for this biosensor. CoPP embedded within the double-strand DNA structure acted as the effective quencher. The double-amplification strategies containing rolling circle amplification (RCA) and DNAzyme-assisted Pb²⁺ cycling reaction were exquisitely designed and applied for upgrading the detection characteristics of the biosensor. The experimental findings demonstrated that the PEC signal was progressively recovered as the Pb²⁺ concentration increased from 500 fM to 5 μM, and the detection limit was 166.7 fM under optimal conditions, thus endowing the biosensor with the benefits of strong specificity and high selectivity. This method provides promising opportunities for detecting various heavy-metal ions in the fields of environmental monitoring, biological analysis, and medical research under complex conditions.