Advanced naphthalimide-based supramolecular fluorescent self-assembly approach for Fe3+detection and applications

A facile low-molecular-weight gelator based on 1,8-naphthalimide derivative functionalized by 2-hydroxynaphthalene unit has been designed and synthesized. The gelator exhibited distinct fluorescence emission behavior in different organic solvents. Intriguingly, it could assemble into supramolecular solution aggregates and gel in DMF-H2O mixed solvents, as well as the gelation process showed fluorescence enhancement characteristic. The self-assembly mechanisms and structures of these states were thoroughly characterized by several technologies, and single crystal was proudly obtained to verify the self-assembly process. In addition, the solution aggregates and gel both showed superior selective and sensitive sensing property for Fe3+ with a fluorescence "turn-off" detection mechanism, and the detection limit was 7.58 x 10-8 M and 1.51 x 10-8 M, respectively. The sensing mechanism was thoroughly verified by spectral analysis and density functional theory (DFT) which was barely presented in the literatures. Furthermore, the solution aggregates were successfully applied in detecting Fe3+ in real water samples with satisfactory recoveries, as well as the gel-coated test strip could be used as a fluorescent display material.