Visual detection of fluoride based on supramolecular aggregates of perylene diimide in 100% aqueous media

A water-soluble perylene imide derivative (PDI-Glu) was synthesized and their supramolecular aggregates composed of PDI-Glu and Al³⁺ were prepared as a "turn on" fluorometric probe to monitor F^- in a purely aqueous system. Based on an "indicator displacement assay" (IDA) approach, the sensing performance and mechanism of PDI-Glu/Al³⁺ complex toward F^- were investigated by absorption and emission spectra. It was suggested that disassembly of PDI-Glu/Al³⁺ aggregates was promoted by addition of F^- through the competitive binding between Al³⁺ and F^-. The detection limit is 240 nmol/L. This method featured simple preparation, excellent water solubility, adjustable self-assembly performance, ease of observation and operation, and high selectivity and sensitivity. It was used for monitoring F^- in toothpaste and tap water samples with excellent accuracy and recovery. To the best of our knowledge, this is the first water-soluble perylene diimide-based probe for F^- detection in 100% aqueous media. We believe this work could not only extend the sensing scope of water-soluble perylene diimide, but also bring some useful information for the rapid detection of anionic analytes  in aqueous media. The disassembly of supramolecular aggregates of PDI-Glu/Al³⁺ along with significant fluorescence recovery enable a rapid and visual detection of F^- based on an "indicator displacement assay" strategy.