Recent Advances in Colorimetric and Fluorescent Chemosensors for Ionic Species: Design, Principle and Optical Signalling Mechanism

Development of chemosensors for the biologically and chemically important ionic species has been an active area of research of supramolecular chemistry and received great attention because of their high sensitivity, selectivity, rapid response time and versatility. Moreover, exploration of new sensing mechanisms of interaction between recognition and signal reporting unit is of current interest. This minireview provides a detailed overview about the recent advances and developments in the field of colorimetric and fluorescent chemosensors, summarized types of optical chemosensors with their design principles and discuss various sensing mechanisms and photophysical processes like metal‐ligand charge transfer (MLCT), ligand‐metal charge transfer (LMCT), photoinduced electron transfer (PET), intramolecular charge transfer (ICT), paramagnetic fluorescence quenching, fluorescence resonance energy transfer (FRET), excited state intramolecular proton transfer (ESIPT), excimer/ exciplex formation that emerged in the past few years. Moreover, the mechanism of action of cation and anion chemosensors also summarizes in this review. This minireview summarizes recent advances in the design of fluorescent and colorimetric chemosensors, particularly small organic molecules for sensing of cations and anions. It includes general principle, working mechanism and challenges that met to find out the best solution for the detection of ions in different biological samples.