Amphiphilic perylene diimide-based fluorescent hemispherical aggregates as probes for metal ions

Abstract

The self-assembly behaviour of a newly synthesized amphiphilic core-positioned thioester appended with carboxylic acid functionalized perylene diimide derivative is studied in different organic solvents. Fluorescent J-type hemispherical aggregates are formed in THF solution. The effect of added metal ions on these fluorescent aggregates is evaluated using spectroscopic techniques, where we found these probes bind selectively to Fe3+ and Ba2+ ions. Two equivalents of Fe3+ ions bind cooperatively to one equivalent of perylene diimide derivative in the hemispherical aggregates with a binding constant of 1.4×107 M−1 and the limit of detection (LOD) was calculated to be 8.66×10-6 M. The positive cooperative binding effect of Fe3+ ions towards hemispherical aggregates equipped with perylene diimide derivatives leads to supramolecular polymerization. Ba2+ ions showed selectivity and sensitivity towards the fluorescent aggregates in THF by quenching the fluorescence intensity completely. The linear Stern-Volmer plot with a Stern-Volmer constant value of 502.6 M−1 signifies the heavy atom effect of Ba2+ ions, leading to fluorescence quenching. The morphological transformation of the fluorescent J-type hemispherical aggregates in the presence of Fe3+ and Ba2+ was studied in detail using electron microscopy.