Development of Cyclic and Acyclic Fluorescent Chemosensors for Selective Detection of Ions and Biomolecules in Water

The intriguing effect of metal ions and biomolecules on various biological entities warrants developing selective and sensitive fluorescent chemosensors in water and other organic solvents. A review of comparable literature in related areas, including material chemistry, environmental science, and supramolecular chemistry, indicates that most of the research work is carried out in varying types of organic solvents. The existing chemosensor research explores the use of various organic solvents, including DMSO/H₂O, methanol, and DMF/HEPES systems, in photoinduced electron transfer (PET)-based chemosensors. DMSO and DMF are strong polar solvents resulting in strong fluorescence emission. Additionally, dichlorobenzene and chlorobenzene are employed to form selective gels with urea compounds, further improving the sensor's functionality and selectivity. Also, parallel investigations, when carried out in water as a solvent, revealed a decrease in the binding/ detection ability of the guest analytes since the polar molecules form strongly solvated (hydrated) moieties, whereas the non-polar molecules (or amphiphilic molecules) are found to form aggregations or self-assemblies. The present review attempts to analyze and characterize water-soluble fluorescent chemosensors (FCHs) into cyclic and acyclic entities as per their topological and structural architectures. In addition, various seminal examples of synthetic FCHs, included herein, provide an understanding of their rational designs, fundamental properties, supramolecular interactions, and emerging switchable properties in aqueous medium. Thus, the knowledge of the properties of these molecules with high affinity and selectivity would facilitate the synthesis of novel FCHs with potential future applications.