A novel sulfur-incorporated naphthoquinone as a selective turn-on fluorescence chemical sensor for rapid detection of Ba2+ ion in semi-aqueous medium

A sulfur-functionalised analogue of the naturally available 1,4-naphthoquinone (N) has been synthesized and evaluated as a sensitive and highly selective fluorimetric sensor against the environmentally toxic barium (II) ion in a semi-aqueous medium. The host ligand exhibits a distinct enhancement in its native fluorescence in the presence of barium ions in ethanol/H2O (1:1, v/v). Its sensing activity was further corroborated by a minimum interference offered by a diverse array of other competing metal cations during the fluorimetric sensing of barium ions. The stoichiometry of N:Ba2+ ion system was calculated from the Benesi-Hildebrand plot to be 2:1 with a binding constant of 3.29 mM. The detection limit of the potential fluorescence probe N against aqueous barium ions was observed to be 4.22 mM. In conclusion we propose that sulfur-containing naphthoquinone act as a potential turn-on fluorescence sensor for the selective detection of toxic barium ions in semi-aqueous medium.