A fluorescent probe for the selective detection of sulfate ions in water

Abstract

A nicotinamide–anthracene conjugate based fluorescent probe 1 exhibits highly selective fluorescence enhancement at 535 nm only with sulfate in HEPES buffer–DMSO (9 : 1) at pH 7.4. The other anions viz. F⁻, Cl⁻, Br⁻, I⁻, AcO⁻, HSO₄⁻, H₂PO₄⁻, CN⁻, OH⁻, NO₃⁻, ClO₄⁻, SCN⁻, even if present in excess, do not interfere in the estimation of sulfate. The limit of detection for sulfate ions by probe 1 is 0.5 μM. Probe 1 can also be used to determine the sulfate ions in tap water using EDTA as a metal ion masking agent. Titration experiments and Job's plot reveal the formation of a 1 : 1 stoichiometric complex between the probe 1 and sulfate ions and DFT studies show the electron transfer from SO₄²⁻ to anthracene moiety responsible for the observed optical changes.