Colorimetric Probe for Mn2+ Using a Mixture of an Anionic Dye and a Cationic Polyelectrolyte in an Aqueous Solution.

Abstract

A novel colorimetric probe for Mn2+ was easily prepared by mixing negatively charged alizarin complexone (ALC) with positively charged poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl]urea] (PQ-2) in aqueous solutions at pH 6.0. Upon adding Mn2+ to ALC alone, the solution underwent no distinct color change, while the mixture displayed selective detection of Mn2+ over different physiological and environmentally significant metal ions by an efficient naked-eye color change from red to purple. The detection of Mn2+ by the mixture was achieved from the electrostatic interactions between ALC and PQ-2. The quantitative determination of Mn2+ was obtained by spectrophotometric measurement and naked-eye observation. This sensing strategy can be an attractive approach for the development of new colorimetric probes due to the advantages such as no organic synthesis, facile fabrication, and simple visual detection.