Sequential determination of cerium (IV) ion and ascorbic acid via a novel organic framework: A subtle interplay between intramolecular charge transfer (ICT) and aggregated-induced-emission (AIE)

Construction of systems with variable electron distribution is a relatively new method in design of responsive fluorophores. Herein, 4,4′,4″,4‴-(ethene-1,1,2,2-trayltetrakis (benzene-4,1-diyl))tetrakis(1-carboxymethyl-pyridin-1-ium)bromide ( LG556 ) is developed and its specific spectral behavior has been verified based on perturbation involving intramolecular charge transfer (ICT) via the connected electron donor and acceptor. In the presence of Ce 4+ ions, the fluorescence intensity of LG556 can be efficiently quenched due to the disassembly of LG556 nanoaggregates and inner filter effect (IFE). The sensitivity is dependent on the concentration of Ce 4+ with an excellent linear range 1–150 μM and a low detection limit of 0.62 μM. At this stage, the working principle behind the aggregated-induced-emission (AIE) has been employed and the difficulty lying in aggregate formation is overcome. The incorporated ascorbic acid causes the reduction of Ce 4+ to Ce 3+ and the re-assembly of LG556 has been realized. The detection limit has been evaluated to be 39.2 nM, which is lower than most of the reported results. Therefore, the “on-off-on” signal conversion leads to a reversible IMPLICATION logic gate and the molecular probe has been applied for the analysis of Ce 4+ and ascorbic acid in pure aqueous solution with satisfactory results.