Sensing in aqueous medium: mechanism and its application in the field of molecular recognition

In recent years, the field of molecular recognition has been extensively developed due to the need for efficient methods for the detection of various biologically and environmentally important analytes (metal ions, anions and biomolecules). A number of literature reports advocate the nano-molar detection of analytes. The major concern with most chemosensors is solubility in an aqueous medium. This critical review mainly focuses on the detection of analytes (metal ions, anions and biomolecules) in an aqueous medium. Various mechanisms, like a cation displacement assay, anion displacement assay, anion ligand exchange, aggregation-caused quenching (ACQ), aggregation-induced emission (AIE), hydrogen bonding mechanism and analyte-induced reaction mechanism are discussed. Based upon the mechanism, the relationship between the structure and properties are derived. Afterwards, a discussion on the current state-of-the-art in metal ions/anions/biomolecules sensing in an aqueous medium includes the design of ligand, preorganization in molecules, detection methods and applications. Finally, the future perspectives for detection in an aqueous medium in the field of molecular recognition are discussed.