Colorimetric Chemosensor for Hg²⁺ Based on Nuclear Fast Red and a Cationic Polyelectrolyte in Aqueous Solution

We have developed a colorimetric chemosensor based on an anionic organic dye, commercially available nuclear fast red (NFR) and a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC) for detection of Hg²⁺ in aqueous solution at physiological conditions. Upon addition of Hg²⁺, a bathchromic shift in the absorption was observed concomitantly with color change from pink to reddish violet which was easily detectable by the naked eye, while such a change was not observed for NFR alone, indicating that PDADMAC played an important role in detecting Hg²⁺. This investigation can propose the simple and valuable construction method for a novel chemosensor by mixture of a water-soluble organic dye and an oppositely charged polyelectrolyte.