Photoelectrochemical sensor for detection Hg2+ based on in situ generated MOFs-like structures

Trace analysis of mercury ions (Hg2+) is of great significance to human health and environmental protection. In this work, a novel photoelectrochemical (PEC) biosensor was developed for the ultrasensitive detection of Hg2+ based on the MOFs-like composite/CdS quantum dots (QDs) as photoactive substrate materials. The MOFs-like composite in situ formed by hydrophobically modified alginate (HMA) with europium ion (Eu3+) not only offered a friendly platform for bioconjugation but also resulted in enhancing sensor photocurrent response. Furthermore, the immobilized thymidine-rich probe DNA on the MOFs-like composite surface was bent to produce a T-Hg2+-T structure in the presence of Hg2+, resulting in enlarged steric hindrance on the electrode surface and decreased the proposed biosensor PEC response. This proposed photoelectrochemical sensing system displayed selective detection of Hg2+ with a linear range from 0.1 pM to 1.0 μM with a detection limit of 0.067 pM. The utilization of semiconductor quantum dots as light-harvesting components and the MOFs-like composite as sensitizers broadens the possible design ideas for photoelectrochemical sensing systems.