Dual-modal biosensor for mercuric ion detection based on Cu2O@Cu2S/D-TA COF heterojunction with excellent catalase-like, electrochemical and photoelectrochemical properties

Abstract

In this study, a dual-mode biosensor based on the heterojunction of Cu₂O@Cu₂S/D-TA COF was constructed for ultra-sensitive detection of Hg²⁺ using both photoelectrochemical and electrochemical approaches. Briefly, a 2D ultra-thin covalent organic framework film (D-TA COF film) with excellent photoelectrochemical signals was prepared on ITO surfaces through an in situ growth method. Subsequently, the probe H1 was immobilized onto the biosensor via Au-S bonds. In the presence of Hg²⁺, the formation of T-Hg²⁺-T complexes triggered hybridization chain reactions (HCR), leading to the attachment of abundant Cu₂O@Cu₂S probes onto the biosensor. As a p-type semiconductor, Cu₂O@Cu₂S could form a heterojunction with the underlying D-TA COF films. Meanwhile, it exhibited catalase-like activity, and the O₂ produced by its catalytic decomposition of H₂O₂ can interact with the D-TA COF films, thus achieving double amplification of the photocurrent signal. Benefiting from the excellent and inherent Cu²⁺/Cu⁺ redox pairs of Cu₂O@Cu₂S, satisfactory differential pulse voltammetry (DPV) signals were obtained. As expected, the dual-mode biosensor was realized with wider linear ranges and low detection limits. Additionally, the analytical performance for Hg²⁺ in real water samples was excellent. Briefly, this suggested approach offers a facile and highly efficient modality for monitoring heavy metal ions in aquatic environments.

Keywords: Catalase-like activity; Covalent organic framework; Electrochemical biosensor; Heterojunction; Photoelectrochemical biosensor.