Highly Sensitive Optical Sensor for Selective Detection of Fluoride Level in Drinking Water: Methodology to Fabrication of Prototype Device

Excess consumption of fluoride (F–) through drinking water and its detrimental effects on human health have been a serious global concern. Herein, we have developed a facile and highly sensitive spectroscopic technique for selective detection of F– in aqueous media using aluminum phthalocyanine chloride (AlPc-Cl) as a sensor. The absorbance and steady-state fluorescence intensity of AlPc-Cl has been found to decrease in the presence of F– which has been used as a marker for the determination of F– concentration in water. The structural change in AlPc-Cl after addition of F– has been thoroughly studied by using ¹⁹F nuclear magnetic resonance spectroscopy. Our detailed steady-state and time-resolved fluorescence studies reveal that the quenching mechanism is static in nature. The response of the sensor is found to be linear over the F– concentration regime from 0 to 6 ppm with a detection limit of 0.05 ppm. Additionally, it shows an excellent selectivity as well as an insignificant change in sensitivity, even in the presence of interfering iron and aluminum ions. Based on the detailed photophysical study, we have further developed a low cost and portable prototype device that shows an excellent sensitivity with the detection limit of 0.10 ppm.