Design, Synthesis And Properties Research Of Fluorescent TNT Sensor Based On Carbazole

Explosives detection is a significant research which is important for the field ofecological environment, homeland security, military and so on. Particularly,2,4,6-trinitrotoluene (TNT) is considered as main detect object. Substitution of threeelectron-withdrawing nitro groups on the aromatic ring, thereby making TNT goodelectron acceptors. The mechanism of fluorescent sensor is electron-transfer fromdonor to accepter (TNT) which leads fluorescence quenching.Conjugated polymer has drawn the center of attention for its amplifyingfluorescent effect which can realize rapid explosives detection. For the conjugatedstructure in mainchain can enhance its delocalized π*excited states. When the excitedelectron transfers from its unite in conjugated polymer to TNT, the fluorescence ofwhole polymer would be all quenched.Based on the mechanism of fluorescent TNT detection, we have designed andsynthesized a series of carbazole contained compounds in order to improve donorability and controlled the aggregation in solid state. It is demonstrate that thesefluorescent films fabricated by carbazole compounds can detect TNT in both vaporand aqueous medium rapidly. The research is composed of three parts.1, In order to improve donor ability, we have designed and synthesized a novelpolycarbazole (PCz) with the superior electron donor ability of carbazole. And thePCz spin-coating film displayed high sensitive to TNT vapor which fluorescencequenched73.0%in60s. Compared with the alkyl group in sidechain, the large rigidsidechain not only prevents π-stacking of polymers and reduces the interactionsbetween polymers, which contributes to the high fluorescence efficiency, but alsogenerates efficient pathway and benefit the diffusion of explosives. Meanwhile, PCzfilm has displayed high fluorescent stability, selectivity and reversible.2, In order to control the aggregation to generate cavities, electropolymerization(EP) films are first used to detect TNT with the electro-activity of carbazole. Three EP films (TCPC, OCPC and OCz) have been demonstrated to be sensitive to TNT.This performance is mainly due to the intrinsic cross-linking network which isgenerated by oxidation coupling reaction of carbazole in electropolymerization. Thecross-linking network could not only enlarge the contact area between the EP filmsand TNT, but also generate cavities to benefit remarkably the TNT penetration.Furthermore, we have analyzed the relationship between molecular structure andTNT which influence their donor-accepter process by density functional theory.3, Combined the results of part1and part2, we have designed and synthesized anew polycarbazole (PFPCz) which EP film displayed good sensitive to TNT by bothcarbazole’s donor ability and electro-activity. It is contained carbazole as TNTrecognition unit in mainchain, and carbazole in sidechain for its electroactivity.Besides the carbazole, large rigid group is also in sidechain that can prevent stackingof polymers and reduces the interactions between polymers. Meanwhile, the largerigid sidechain is benefit for controlling its aggregation in its electropolymerization.The PFPCz EP film displayed higher sensitivity towards TNT in aqueous mediumthan EP film.