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

Abstract

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 TiO 2 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.

Photoinduced Electron Transfer Modulated Photoelectric Signal: Toward an Organic Small Molecule-Based Photoelectrochemical Platform for Formaldehyde Detection

“…Advanced photoelectrochemical (PEC) analysis has experienced a notable surge in momentum, owing primarily to its features of high sensitivity, low background, and distinct input–output signal separation. − Despite this progress, to design stable photoelectrodes, enrich signal transduction modes, and expand recognition elements are still ongoing goals for researchers. − PEC biosensors have functioned by incorporating autonomous recognition elements like DNA, aptamers, or antibodies on the surface of the photoelectrode to achieve specificity. − These recognition elements typically exhibit insulating properties and are susceptible to environmental conditions such as temperature, humidity, and pH value. Additionally, a multistep electrode assembly process may introduce unstable factors, e.g., photoactive material detachment or contamination, thereby compromising their stability and reproducibility.…”

Revisiting the Chemistry and Photophysics of 3‐(N‐Methylpyridinium‐4‐yl)Coumarins for Designing “Covalent‐Assembly” and “Molecular Disassembly” Fluorescent Probes**

“…This will enable to tune their physico‐chemical properties (especially water solubility), targeting ability, pharmacokinetics ( e. g ., introduction of a PEG linker) or to confer them release capabilities of a molecule of interest ( e. g ., a drug or a second reporter). Furthermore, pyridine N ‐quaternarization may be used to achieve covalent immobilization of such probes over functionalized solid surfaces aimed at creating “smart” material sensors [37b,c,52] . This will undoubtedly contribute to the popularization of “covalent‐assembly” strategy in the fields of biosensing, bioimaging and (photo)theranostics based on the use of “smart” photoactive organic molecules.…”

Recent Advances in Photoswitchable Fluorescent and Colorimetric Probes

“…Additionally, the study introduces a logic gate based on the 1O probe that utilizes the probe's color and fluorescence changes to perform logical operations, paving the way for the development of innovative biosensors. Thiol small molecules, including biothiols such as cysteine, homocysteine, and glutathione, as well as industrial thiophenols, are crucial for both biological systems and industrial applications [207][208][209][210][211][212]. Inside living organisms, these thiol compounds mainly act as antioxidants to maintain cellular redox balance and participate in various biochemical reactions; accurate detection of these compounds can help study cellular responses to disease and stress.…”