Development of a New Fluoride Colorimetric Sensor Based on Anti-aggregation of Modified Silver Nanoparticles

In this study, aggregated silver nanoparticles were prepared using sulphanilic acid and catechol as a collection of stabilizing-reducing system. Preliminary studies showed that catechol (CAT) is readily oxidized by silver ions followed by sulphanilic acid (SA) nucleophilic attack. The resulting catechol derivative aggregates silver nanoparticles (Ag-NPs). The resulting product was characterized by different characterization techniques including UV–VIS spectrometry and transmission electron microscope (TEM). The SA-CAT induced aggregated Ag-NPs were used to develop a fast and ready to use colorimetric detection method for fluoride ion in water. In the presence of fluoride ions, the color of aggregated Ag-NPs solution change from brown to yellow with an absorbance decrease at 508 nm and an increase at 397 nm. Under the optimized conditions, the ratio of the absorbance intensity at 508 nm and 397 nm (A397/A508) was proportional to the fluoride ion concentration in the range of 1-40 µM with a detection limit of 0.2 µM. The proposed new method was successfully used for the determination of fluoride concentration in the local spring water samples.