Studies On The Synthesis And Sensing Properties Of Carbazole Derivatives For Nitroaromatic Compounds

Nitroaromatic compounds are the main constituent of explosives, which have been real threat to people's lives and properties. So developing a fast detection of nitroaromatic compounds in atmosphere, soil, and solvent has attracted great attention. At present, many analytical methods have been developped to monitoring nitroaromatic compounds, such as X-ray mass spectrometry, fluorescence method and so on. Fluorescent method attracts more and more attention because of its high selectivity, high sensitivity, quick response and facility. At present, the researches on nitroaromatic sensor materials were mainly focus on the polymer material. The fluorescent properties changed because of charge transport, which due to the strong electron-drawing group, nitro group, when the polymer faces nitroaromatic molecules. By this change, we can detect the nitroaromatic compound. But, using polymer as fluorescent sensor has many disadvantages. It is difficult for nitroaromatic compound to diffuse in polymer, which can slower the response. In order to solve this problem, we designed and synthesized single-molecular fluorescent sensor materials to detect nitroaromatic compounds, based on other studies and report and past work of our group.In this paper, two series of fluorescent compounds were synthesized. Their optical properties were studied. Their fluorescence quenching properties faced different nitroaromatics were researched.First, we synthesized two series of fluorescent compound containing carbazole groups, as fluorescence sensor, through Wittig reaction and Heck reaction. The compounds are CB-1, CB-2, CB-3, CZ-1 and CZ-3.Second, the optical properties of these compounds in different solvents were studied. The absorption spectra of all compounds have nothing to do with the solvent polarity. However, with the increasing of solvent polarity, the emission wavelengths appear red-shift, and the fluorescence intensity become lower. Especially to deserve to be mentioned, in ethanol, the fluorescence of CZ-1 and CZ-3 were totally quenched, which is probably due to hydrogen bonding of ethanol to the fluorescent groups. In the two series of compounds, the emission wavelength and fluorescence intensity both increase with the increase of carbazole groups.Third, the fluorescence quenching properties of all compounds to nitromethane. toluene, 1-methyl-4-nitrobenzene,4-nitrophenol,1-methyl-2,4-dinitrobenzene 2-nitrophenol, and picric acid were studied. We got the conclusions are as follows:As fluorescence sensor materials for nitroaromatic compounds, they all showed good selectivity. Nitromethane and toluene had little impact on the fluorescence spectra. With the increase of carbazole groups, the fluorescent quenching constant decreased. Among all the quenchers,2-nitrophenol has the biggest fluorescent quenching constant. We got a very low detection limit of 10-6 g/cm3, when we use CB-1,CZ-1 as fluorescent sensor to detect 2-nitrophenol.