Regulation of fluorescence, morphology, surface wettability and function of naphthalimide-based self-assembly system by metal coordination

Three naphthalimide-based supramolecular gelators (N1, N2 and N3) that contained one, two, or three naphthalimide groups, respectively, were designed and synthesized, and the self-assembly processes of the three gelators were studied using different technique. Their self-assembly behavior could be regulated through the number of terminal branches. More importantly, their self-assembled structure, fluorescence behavior and surface wettability and function could be regulated through metal coordination, and helical nanofibers could be formed by gel N2 with Cd2+, Co2+, Eu3+, Tb3+, Mn2+, Ni2+ and Hg2+. The fluorescence emission intensities of these gels could change with different degrees under the addition of different metal ions, and a super-hydrophilic surface could be obtained from xerogel N3 in the presence of Co2+, Eu3+, Mn2+ and Tb3+. Specifically, gelator N3 could selectively and sensitively respond to Fe2+ in the solution and gel state with a response time of 0.5 s and a low limit of detection of 1.84 nM. This work provided a new regulation method for the supramolecular selfassembly process.