Chemically Tapered Multimode Optical Fiber Probe for Fluoride Detection Based on Fluorescence Quenching of Curcumin

This paper reports a simple fluorescence-based tapered fiber optic probe for fluoride ion having a detection range of 2.08 × 10^-6-2.005 × 10^-4 M. The performance of the tapered probe is evaluated with respect to the probes that consist of combinations of bare uncladded multimode optical fibers. The effect of fluorescence quenching of a natural dye curcumin in the presence of fluoride ion is used in the implementation of the probes. The probe effectively uses multiple mechanisms for the excitation and collection of fluorescence from the medium enabling higher sensitivity compared with conventional spectrophotometry especially at very low concentrations of fluoride.