An easy-to-apply fluorescent sensor for ClO − determination using merocyanine 540 in aqueous medium

Merocyanine 540 dye (MC 540) has been demonstrated as a ‘turn-off’ fluorescent probe to detect hypochlorite ions (ClO − ) in an aqueous medium. MC 540 was separately investigated by fluorescence and absorption spectroscopy in the presence of various analytes, including cations and anions. It was revealed that the fluorescence intensity of MC 540 was effectively quenched with only ClO − ions without being affected by the other twenty-five analytes. This was also observed with the naked eye, and the color of MC 540 changed from pink to colorless in the presence of only ClO − ions. Moreover, fluorescence interference experiments were performed for ClO − . MC 540 was found to detect ClO − independently of other analytes. The interaction ratio between MC 540 and ClO − was determined as 4:1, and the binding constant (K a ) was calculated as 28.38 M −4 for MC 540. The detection limit (LOD) of ClO − was determined to be 6.83 nM. The presented method was reliably applied to drinking, natural spring, and tap water samples. Thus, it has been proven that the MC 540 can be used as a sensitive, selective, color-changeable, and easy-to-apply ‘turn-off’ fluorescence sensor to detect ClO − in a specific concentration range. Graphical abstract