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)

Abstract 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 Ce4+ 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 Ce4+ 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 Ce4+ to Ce3+ 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 Ce4+ and ascorbic acid in pure aqueous solution with satisfactory results.