Fluorescence Response Investigation Of Aromatic Group Silane Derivatives In Detecting Of Nitro-aromatics

In this paper, on the basis of fluoranthene with excellent fluorescence properties, two diphenylfluoranthene groups were incorporated into a silicon atom, thus forming a special rigid tetrahedral structure. As a result, diphenylfluoranthene and the silicon-cored diphenylfluoranthene derivatives were designed and synthesized by convenient ways. It is expected that the fluoranthene derivatives with silicon as the core not only retain the excellent fluorescent properties, but also improve the response in detecting of nitro-aromatics. The structures of the obtained diphenylfluoranthene and silicon-cored diphenylfluoranthene derivatives were characterized and analyzed by NMR spectrometer, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, elemental analyses. What’s more, their thermodynamic properties were studied by thermogravimetric analysis and differential scanning calorimetry. The results show that, the silicon-cored diphenylfluoranthene derivative has a higher glass transition temperature and better thermal stability compared with diphenylfluoranthene.The fluorescence response of the fluoranthene derivative in detecting of nitrobenzene and m-dinitrobenzene in THF solution was investigated. It was found that their Stern-Volmer cures are upward and sensitive to the presence of nitro-aromatics. What’s more, compared with diphenylfluoranthene, the silicon-cored diphenylfluoranthene derivative shows lower detection limit, higher sensitivity, and higher quenching efficiency in detecting of nitrobenzene and m-dinitrobenzene. This reason may be mainly attributed to the special tetrahedral structure of the silicon-cored diphenylfluoranthene derivative, with the non-planar state, reducing the intermolecular π-π interaction. Then two kinds of fluoranthene derivatives in the solid film state were studied by exposing the nitrobenzene vapor at diffident time. When the thin film of silicon-cored diphenylfluoranthene derivative was exposed to saturated nitrobenzene vapor for 120s, the fluorescence was completely quenched. However, the fluorescence of diphenylfluoranthene thin film, which was exposed to saturated nitrobenzene vapor for the same time, was still observed. At the same time, the silicon-core structure also improves the thermodynamic properties of fluorescent molecules, so it will have great application potential in the field of OLED.Based fluorescence response of the above fluoranthene derivative in improving detection capability of nitrobenzene and m-dinitrobenzene, we further designed and synthesized tetraphenylbenzene with complex topology and silicon-core tetraphenylbenzene derivative. Compared with the planar conjugated molecules, aryl substituents on benzene ring are not constrained by additional bonds in the plane of the aromatic core, and thus they exhibit twised angles with the plane of central benzene ring. What’s more, these non-planar topologies could efficiently limit conjugation and inhibit extensive aromatic π-π interaction. At the same time, it will be propitious to control their fluorescent properties.The thermodynamic properties of tetraphenylbenzene and silicon-core tetraphenylbenzene derivative were studied by thermogravimetric analysis and differential scanning calorimetry. Their fluorescence response was investigated in detecting of nitrobenzene and picric acid. It is found that the Stern-Volmer plot is linear at lower concentrations of nitro-aromatics. At higher concentrations, the plot was found to be a hyperbolic curve. In addition, according to the overlap of the absorption spectrum of nitro-aromatics and fluorescence spectrum of multi-phenyl derivatives, the quenching mechanism was discussed. The results indicate that the silicon-core structures improve ability of detecting nitro-aromatics.