Synthesis And Fluorescence Sensory Properties Of Linear Carbazole-based Organogelators And Star-shaped Phenothiazine-based Fluorencent Probe Molecules

Organic conjugated molecules have attracted considerable attention in recentyears due to their potential applications in different fields, such as light-emittingdiodes, photovoltaic cells, optical power limiting, organic field-effect transistors, andso on. Fluorescence sensing based on organic π-conjugated molecules is one of thefirst choices among various methods used for detection because of its high sensitivity,quick response, low cost and easy sample preparation. It is well-known that theazoheterocyclic compounds, such as carbazole and phenothiazine derivatives possessexcellent optical and electrochemical properities. Therefore, they always could beacted as building blocks of fuctional materials for fluorescent detection. In this thesis,we mainly focus on the synthesis of5-membered azohetero fused ring compoundsand the investigations of their photophysical, electrochemical properties andfluorescence sensing. Some creative results have been obtained, and outlined below:(1) The simplest carbazole-based organogelator C1(9-hexadecyl-9H-carbazole)has been synthesized and can self-assemble into nanofibers in the gel phase directedby balanced π–π interactions. To extend the conjugation of the π gelator, we preparedlinear carbazole-based trimer C3and pentamer C5, which also exhibited gelationbehavior in some organic solvents upon ultrasound stimulation. It is found that thexerogel of C3emits strong blue light under UV irradiation. Notably, the emission ofC3in nanofiber-based films can be quenched upon exposure to vapors of TNT andDNT. The steady-state Stern–Volmer plots of C3in toluene revealed that thefluorescent quenching induced by aromatic nitro compounds is due to photoinducedelectron transfer. Therefore the emitting nanofibers fabricated from linear carbazoleby organogelation can be used as fluorescent sensors to detect explosives. (2) Two carbazole-based conjugated compounds TC3T and PC3P withterminal triphenylamine and phenothiazine have been synthesized and showedselective gelation behaviors in some organic solvents upon ultrasound stimulation.SEM and TEM images revealed that3D networks consisting of numerous nanofiberswere formed in the gels of TC3T and PC3P. It should be noted that the obtainedxerogels based on TC3T and PC3P emit strong blue and bluish green light,respectively, under UV irradiation. Upon exposed to the vapors of TNT and DNT,the emission of TC3T and PC3P in nanofibers-based films can be quenchedobviously. The steady-state Stern-Volmer plots reveal that the fluorescent quenchinginduced by aromatic nitro compounds is due to the photo-induced electron transfer.Therefore, the emitting nanofibers obtained from the organogelation of linearcarbazoles with terminal donors can be used as fluorescent sensors to detectexplosives.(3) A series of benzene, triphenyl benzene, and triazine cored, the samephenothiazine groups based star-shaped molecules P, TPP, TPT were synthesized,which could be used as fluorescence probing molecules for detection of DNT andTNT in toluene. It is found that all the molecules could emit strong fluorescence insolution, and the electrochemical behaviors of compounds P, TPP, and TPT shownthat all the molecules are the electron-rich systems. Stern-Volmer plots revealed thatthe star-shaped molecules P, TPP, TPT exhibited could be used as f fluorescentsensory materials for detection of explosives.