A boronate hydrogel film containing organized two-component dyes as a multicolor fluorescent sensor for heavy metal ions in water

摘要

A multicolor fluorescent hydrogel sensor containing two types of fluorescent dyes with an amidoquinoline receptor unit and a rhodamine chromophore covalently incorporated into a polyvinyl alcohol-boronate matrix was prepared. Although the gel film exhibited red emission due to the rhodamine chromophore, the addition of a small amount of Zn~(~(2+)) ions induced a multicolor fluorescence response, which included white-light emission, of the film in water. The change in emission color is ascribed to fluorescence enhancement of the amidoquinoline moiety upon binding to Zn~(2+) ions with an association constant of (3.5 ± 0.2) x 10~5 M~(-1). In contrast, a negligible change in the emission color of the gel film was observed in the presence of Na~+, K~+, Mg~(2+), Ca~(2+), Fe~(3+), Co~(2+), Ni~(2+), Cu~(2+), Cd~(2+), Hg~(2+), Al~(3+), and Pb~(2+) ions. The selectivity of the gel film enabled visual detection of Zn~(2+) ions in tap water. Moreover, the film could be reused as a sensor strip after treatment with ethylenediaminetetraacetic acid.