A label-free photoelectrochemical biosensor with ultra-low-background noise for lead ion assay based on the Cu2O-CuO-TiO2 heterojunction

Abstract

Herein, a label-free and ultra-low-background-noise PEC biosensor was developed for lead ion (Pb²⁺) assay based on the Cu₂O-CuO-TiO₂ heterojunction. By calcination of cupric ion (Cu²⁺) doped-titanium based metal organic framework (MOF) material (NH₂-MIL-125), the Cu₂O-CuO-TiO₂ heterojunction was synthesized. With Pb²⁺, lots of DNA single strands (S1) could be released based on the Pb²⁺ assisted cyclic amplification strategy and hybridized with hairpin DNA (HP1) on the modified electrode. The exposed phosphate groups on S1 can adsorb Cu₂O-CuO-TiO₂ heterojunction, which results in a large cathode photocurrent. Due to the good photoelectric property of Cu₂O-CuO-TiO₂ and Pb²⁺-triggering cyclic amplification strategy, the constructed PEC biosensor achieves a wide linear detection range (10 fM - 1 μM) and a low detection limit (6.8 fM), which provides potential applications in ultrasensitive determination of Pb²⁺ in environmental water samples and organisms.

Keywords: Cu(2)O-CuO-TiO(2); Label free; Pb(2+) assay; Photoelectrochemical biosensor; Ultra-low-background noise.