Optical sensors for water and humidity and their further applications

Detection of trace quantities of water in laboratory and industrial processes is very crucial. Monitoring humidity is of vital importance in maintaining ambient atmosphere in places like hospitals, in climate sciences, automated devices, intelligent systems, etc. Development of optical detection systems for water and humidity entails real time progress in industrial processing and storage, human-machine interactions, clinical diagnosis and security solutions and many more. This review provides a comprehensive study of developments made in the field of optical sensing of water and humidity in the last decade. The compilation has been segmented into various sub-sections based on various molecular scaffolds. It covers a library of structural motifs containing anthracene, rhodamine, coumarin, bodipy, pyrene, naphthalene, naphthalimide, anthraquinone, tetraphenylethene, triphenylamine, thioxanthone, triarylmethane, etc. These have followed versatile mechanistic pathways like intramolecular charge transfer, photo-induced electron transfer, aggregation induced emission, solvatochromism, forster resonance energy transfer, hydrogen bonding interactions, reaction- based formation or cleavage of bonds, etc. to respond to presence of water in organic solvents or atmosphere by colorimetry or fluorimetry. All the reported probes have been dealt in a case by case manner with respect to their working mechanisms, advantages, limitations and applications. The detection limit and quantification limit values have been assembled to compare the efficacies of different probes. Real life applications of the sensors have been demonstrated, which shows that the scope of employing chemosensors in solving various real-time problems is huge and bright. It outlays concretely the opportunities and scope for future works. (C) 2021 Elsevier B.V. All rights reserved.