الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The adoption of chlorine in drinking water disinfection with the determination of residual chlorine in the form of hypochlorite ion (ClO-) is a widespread demand. Several sensors including colorimetric, fluorometric, and electrochemical methods are currently in use, but detection limits and ease of application remain a challenge. In this work, new cyanine derivatives are applied as ClO- sensors. They were prepared by solvent-free microwave synthesis. The sensors are highly sensitive and selective to ClO-, exhibiting a noticeable color change that is visible to the naked eye. Additionally, the sensors can detect ClO- without interference from other potential water pollutants, with low limits of detection (LOD) values of 13.92 ppm, 0.127 ppm, 7.43 ppb, and 0.917 ppb based on absorption spectroscopy. Upon using fluorometric methods, the sensors’ (LOD) values are pushed down to 1.71 nM, 2.46 nM, 0.025 ppb and 0.598 ppb for sensors I, II, III, and IV, respectively. The sensors can be loaded on paper strips for field and domestic detection of ClO- in tap water and water treatment installations. Upon using the quartz crystal microbalance (QCM) technique, these sensors showed strong detection sensitivity to ClO-, with detection limits of 0.06, 0.045, 0.256 and 0.09 ppm for sensors I, II, III, and IV, respectively. Quantum chemical studies using Density Functional Theory (DFT) calculations, Natural Bond Orbital (NBO) analysis, Molecular Electrostatic Potential (MESP), and Time-Dependent Density Functional Theory (TD-DFT) supported the findings of cyanine loss of electrons giving radical cations. The sensing mechanism is rationalized in terms of radical cation formation upon ClO- oxidation of cyanine sensors. Further investigation of using a cyanine sensor as a new fluorescent DNA stain was performed. A substantial increase in fluorescence quantum yield was obtained upon cyanine uptake in DNA groves with subsequent rigidity imposed by DNA as a restricted medium.