Colorimetric chemosensor based on a Ni2+ complex of a pyridylazo dye for detection of citrate in aqueous solution

Abstract We developed a colorimetric naked-eye chemosensor based on the complex between a pyridylazo dye and Ni2+ in a 2:1 stoichiometric ratio (BrPSAA2-Ni2+) for the selective detection of citrate in a pure aqueous solution via the indicator displacement assay. Upon the addition of citrate, BrPSAA2-Ni2+ exhibited a naked-eye detectable color change from red to orange over other anions including dicarboxylates with a blue shift in absorption spectra due to the regeneration of BrPSAA by the interaction of citrate with Ni2+. Furthermore, the citrate detection process was not significantly influenced by other coexisting anions. Therefore, BrPSAA2-Ni2+ can be utilized as a simple and practical colorimetric chemosensor for citrate with selectivity and fast response in aqueous solution.