Linear Oligocarbazole-Based Organogelators: Synthesis and Fluorescent Probing of Explosives

The simplest carbazole-based organogelator C1 (9-hexadecyl- 9H-carbazole) has been synthesized and can self-assemble into nanofibers in the gel phase directed by balanced pi-pi interactions. To extend the conjugation of the pi gelator, we prepared linear carbazole-based trimer C3 and pentamer C5, which also exhibited gelation behavior in some organic solvents upon ultrasound stimulation. It is found that the xerogel of C3 emits strong blue light under UV irradiation. Notably, the emission of C3 in nanofiber-based films can be quenched upon exposure to vapors of TNT and DNT. The steady-state Stern-Volmer plots of C3 in toluene revealed that the fluorescent quenching induced by aromatic nitro compounds is due to photoinduced electron transfer. Therefore the emitting nanofibers fabricated from linear carbazole by organogelation can be used as fluorescent sensors to detect explosives.