Supramolecular fluorescent organogel bearing 1,8-naphthalimide residue for the detection of Fe3+ through the gel-gel transformation

Supramolecular gels with metal ion-responsiveness are an important kind of smart materials due to their potential application in environmental monitoring. In this study, a novel l-glutamine-contained 1,8-naphthalimide derivative (NDG) has been designed and synthesized as an organogelator. NDG could self-assemble into stable supramolecular organogels in different kind of solvents, and the gelation process showed bright blue aggregation-induced emission (AIE). The self-assembly behavior, morphology and structure of NDG gels were thoroughly studied by various techniques. Interestingly, the obtained NDG organogel exhibited a fluorescence ‘‘turn-off’’ response for Fe3+ and formed a stable metallogel NDG-Fe3+. The detection limit (LOD) of NDG in diluted solution and gel states for Fe3+ was calculated to be 30.8nM and 11.5nM, respectively, indicating high sensitivity. In addition, the blue fluorescence emission of the gel system was restored in the presence of ascorbic acid and then quenched again with oxygen, which showed reversible fluorescence sensing effect and employed as a logic gate at the molecular level. Furthermore, xerogel-based film of NDG emitted strong blue emission and could be utilized as paper-based chemosensor to detect Fe3+. And also, the NDG gel had potential application in fluorescence display material.