A novel strategy for the construction of photoelectrochemical sensing platform based on multifunctional photosensitizer

A responsive organic probe based photoelectrochemical sensor for hydrazine detection

This study developed a new photoelectrochemical (PEC) sensor for the detection of the hydrazine (N2H4, HZ) based on a donor-π-bridge-acceptor (D-π-A) configuration organic photoactive dye (Dye-HZ). The dye was covalently immobilized on an FTO/TiO2 (FTO: fluorine-doped tin oxide) substrate, resulting in a photoanode FTO/TiO2/Dye-HZ that exhibits a specific PEC response to N2H4. Hydrazine reacts with the acetyl group in the Dye-HZ molecule, leading to its removal and the formation of a hydroxy group. The hydroxy group dissociates a hydrogen ion, forming a phenoxide anion with strong electron-donating characteristics. As a result, the dye molecule exhibits a strong intramolecular charge transfer effect, significantly enhancing absorbance and photoelectric response under visible light irradiation, leading to a remarkable increase in photocurrent and enabling highly sensitive detection of hydrazine. Furthermore, the PEC sensor demonstrates excellent selectivity and can be applied for the detection of hydrazine in real water samples. This study presents an innovative PEC sensing approach for hydrazine based on responsive photoactive molecules, providing new insights for PEC detection of other environmental pollutants.

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.

Target-Induced In Situ Formation of Organic Photosensitizer: A New Strategy for Photoelectrochemical Sensing

Small-molecule photosensitizers have great application prospects in photoelectrochemical (PEC) sensing due to their defined composition, diversified structure, and adjustable photophysical properties. Herein, we propose a new strategy for PEC analysis based on the target-induced in situ formation of the organic photosensitizer. Taking thiophenol (PhSH) as a model analyte, we designed and synthesized a 2,4-dinitrophenyl (DNP)-caged coumarin precursor (Dye-PhSH), which was then covalently coupled onto the TiO₂ nanoarray substrate to obtain the working photoanode. Due to the intramolecular photoinduced electron transfer process, Dye-PhSH has only a very weak photoelectric response. Upon reacting with the target, Dye-PhSH undergoes a tandem reaction of the detachment of the DNP moiety and the intramolecular cyclization process, which leads to a coumarin dye with a pronounced photoelectric effect, thus achieving a highly selective turn-on PEC response to PhSH. For the first time, this study was to construct a PEC sensor by exploiting specific organic reactions for the in situ generation of small molecule-based photoactive material. It can be anticipated that the proposed strategy will expand the paradigm of PEC sensing and holds great potential for detecting various other analytes.