Colorimetric detection of Hg²⁺ using a mixture of an anionic azo dye and a cationic polyelectrolyte in aqueous solution

Abstract

We investigated a colorimetric chemosensor for Hg2+ based on a mixture of xylidyl blue I as an anionic organic dye and poly(diallyldimethylammonium chloride) as a cationic polyelectrolyte in an aqueous solution at pH 7.5. The addition of Hg2+ to the mixture induced a bathochromic shift in the absorption spectra with a distinct color change from red to green which was readily identifiable by the naked eye, whereas the other metal ions gave rise to insignificant color changes. By contrast, upon adding Hg2+ to xylidyl blue I alone, the solution underwent no significant change in color. Moreover, a stoichiometric ratio for the complex between xylidyl blue I and Hg2+ in the presence of poly(diallyldimethylammonium chloride) was determined to be 1:1 by the absorption titration curve and Job's plot. Thus, the mixture can be used as a selective naked‐eye colorimetric chemosensor for Hg2+ over other common metal ions. This study raises the possibility that the combination of an organic dye and an oppositely charged polyelectrolyte is a potential candidate for the easy construction of a new chemosensor system. © 2018 Society of Chemical Industry

Colorimetric detection of Mn(ii) based on a mixture of an anionic pyridylazo dye and a cationic polyelectrolyte in aqueous solution

“… 22,23 PDADMAC causes the aggregation of an anionic dye by electrostatic interactions between them PDADMAC and an anionic dye, and consequently the dye has the potential to exhibit a new colorimetric response and sensing properties 24,25 . Our previous reports stated that the combination of an anionic dye and PDADMAC had sensing properties which were different to the original anionic dye 26‐32 …”

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“…50,51 Our recent studies reported the mixture of an anionic dye and PDADMAC showed a selective colorimetric detection as distinct from the original dye. [52][53][54][55] PDADMAC is one of typical examples of cationic polyelectrolytes. Among polycations, PDADMAC was chosen due to high water solubility and many positive charges in the wide pH range besides commercial availability.…”

Colorimetric Co2+ sensor based on an anionic pyridylazo dye and a cationic polyelectrolyte in aqueous solution

“…Cationic PDADMAC can interact with anionic dyes to induce dye aggregate formation, and it has the potential to exhibit spectroscopic and sensing properties . Our previous studies reported that a mixture of an anionic dye and PDADMAC showed selective colorimetric detection distinct from the original dye …”

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