Ultrasensitive “signal-on” photoelectrochemical aptasensor based on self-assembled Cu3(BTC)2/TiO2 interface for trace Pb2+ monitoring in real water samples

First application of Cu 3 (BTC) 2 -based composite as a photoelectrochemical platform for trace-level lead ion detection. • Synergistic integration of DNAzyme amplification and exciton-plasmon interaction for enhanced sensitivity. • A Weighted Least Squares (WLS)-based calibration framework to minimize matrix effects, ensuring reproducible and reliable outcomes. The accurate monitoring of lead ions (Pb 2+ ) in complex environmental matrices demands ultrasensitive and robust sensing technologies. Herein, we engineer a DNAzyme-driven “signal-on” photoelectrochemical (PEC) aptasensor based on a precisely controlled layer-by-layer self-assembled TiO 2 /Cu 3 (BTC) 2 hierarchical architecture. By exploiting the spatial precision of this architecture, we position Au nanoparticles (AuNPs) in optimal proximity to the Cu 3 (BTC) 2 framework to facilitate efficient exciton-plasmon interaction (EPI)-mediated photocurrent quenching. Target Pb 2+ triggers the specific cleavage of substrate DNA (sDNA), detaching the Au/PAMAM-hairpin DNA conjugates, thereby restoring the photocurrent proportionally to Pb 2+ concentration. This self-assembled platform achieves exceptional sensitivity with a broad linear range (10 −12 to 10 −6  mol/L) and an ultralow detection limit of 0.97 pM. Crucially, to mitigate heteroscedasticity and matrix interference, a weighted least squares (WLS) calibration model is integrated, which assigns higher statistical weights to low-concentration measurements, significantly enhancing quantitative reliability. The sensor demonstrates satisfactory recoveries in real water samples, establishing a standardized and robust paradigm for trace heavy metal monitoring. This study develops a DNAzyme-driven signal-on PEC aptasensor for trace Pb 2+ detection. A novel Cu 3 (BTC) 2 composite serves as the first PEC substrate for this application. It enhances charge separation efficiency. The sensor synergistically integrates exciton-plasmon interaction with DNAzyme amplification for dual signal enhancement. A WLS-based calibration framework is also incorporated. It standardizes signal processing, mitigates matrix effects, and ensures reproducible quantification in real water samples. Download: Download high-res image (109KB) Download: Download full-size image