Au NP-Decorated g-C₃N₄-Based Photoelectochemical Biosensor for Sensitive Mercury Ions Analysis

Herein, an efficient and feasible photoelectrochemical (PEC) biosensor based on gold nanoparticle-decorated graphitic-like carbon nitride (Au NPs@g-C₃N₄) with excellent photoelectric performance was designed for the highly sensitive detection of mercury ions (Hg²⁺) . The proposed Au NPs@g-C₃N₄ was first modified on the surface of the electrode, which possessed a remarkable photocurrent conversion efficiency and could produce a strong initial photocurrent. Then, the thymine-rich DNA (S1) was immobilized on the surface of the modified electrode via Au-N bonds. Subsequently, 1-hexanethiol (HT) was added to the resultant electrode to block nonspecific binding sites. Finally, the target Hg²⁺ was incubated on the surface of the modified glassy carbon electrode (GCE). In the presence of target Hg²⁺, the thymine-Hg²⁺-thymine (T-Hg²⁺-T) structure formed due to the selective capture capability of thymine base pairs toward Hg²⁺, resulting in the significantly decrease of the photocurrent. Thereafter, the proposed PEC biosensor was successfully used for sensitive Hg²⁺ detection, as it possessed a wide linear range from 1 pM to 1000 nM with a low detection limit of 0.33 pM. Importantly, this study demonstrates a new method of detecting Hg²⁺ and provides a promising platform for the detection of other heavy metal ions of interest.