<p><b>Excess consumption of fluoride
through drinking water and its detrimental effects on human health have been a serious
global concern. Therefore, frequent monitoring as well as quantitative
determination of fluoride ion (F<sup>-</sup>) concentration in aqueous media is
of vital importance. Herein, we have developed a facile</b> <b>and</b> <b>highly sensitive spectroscopic technique for selective detection of F<sup>-</sup>
in aqueous media using aluminium phthalocyanine chloride (AlPc-Cl) as a sensor.
The absorbance as well as steady-state fluorescence intensity of AlPc-Cl has
been found to decrease in presence of F<sup>-</sup> which has been used as a
marker for the determination of fluoride ion concentration in water. The
structural change in AlPc-Cl after addition of F<sup>-</sup> has been thoroughly
studied by using <sup>19</sup>F NMR (Nuclear Magnetic Resonance) spectroscopy. Our
detailed steady-state as well as time-resolved fluorescence studies reveal that
the quenching mechanism is static in nature due to ground state complexation in
between F<sup>-</sup> and AlPc-Cl molecules. The response of the sensor is
found to be linear over the F<sup>-</sup> concentration regime from 0 to 6 parts
per million (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 aluminium ions. Based on the detailed
photophysical study, we have further developed a low cost and portable
prototype device which shows an excellent sensitivity with the detection limit
of 0.10 ppm. This prototype device has a high prospect for real-time monitoring
of fluoride ion concentration especially in remote areas.</b></p>
Highly Sensitive Optical Sensor for Selective Detection of Fluoride Level in Drinking Water: Methodology to Fabrication of Prototype Device