Metal organic framework-derived CuO/Cu2O polyhedron-CdS quantum dots double Z-scheme heterostructure for cathodic photoelectrochemical detection of Hg2+ in food and environment

Abstract

This study employed an innovative copper oxide/cuprous oxide (CuO/Cu₂O) polyhedron‑cadmium sulphide quantum dots (CdS QDs) double Z-scheme heterostructure as a matrix for the cathodic PEC determination of mercury ions (Hg²⁺). First, the CuO/Cu₂O polyhedral composite was prepared by calcining a copper-based metal organic framework (Cu-MOF). Subsequently, the amino-modified CuO/Cu₂O was integrated with mercaptopropionic acid (MPA)-capped CdS QDs to form a CuO/Cu₂O polyhedron-CdS QDs double Z-scheme heterostructure, producing a strong cathodic photocurrent. Importantly, this heterostructure exhibited a specifically reduced photocurrent for Hg²⁺ when using CdS QDs as Hg²⁺-recognition probe. This was attributed to the extreme destruction of the double Z-scheme heterostructure and the in situ formation of the CuO/Cu₂O-CdS/HgS heterostructure. Besides, p-type HgS competed with the matrix for electron acceptors, further decreasing the photocurrent. Consequently, Hg²⁺ was sensitively assayed, with a low detection limit (0.11 pM). The as-prepared PEC sensor was also used to analyse Hg²⁺ in food and the environment.

Keywords: Cadmium sulfide quantum dots; Double Z-scheme heterostructure; Mercury ion; Metal organic framework-derived porous copper oxide/cuprous oxide polyhedron composite; Photoelectrochemical sensor; Recognition-biomolecule-free.