The Preparation Of Fluorescent Molecules And The Detection For Aniline

Aniline and its derivatives are the priority pollutants in the environment, they are high toxic and even very low dosage can be poisonous. With the development of fine chemicals, the demand of chemicals on aniline showed a rising trend, which made it urgent to establish a simple, rapid and effective detection method for aniline. Fluorescence sensing is a new detection method. With some specific fluorescent compounds as sensing media, it is characteristic of sensitivity, selectivity, quick and simple. Therefore, it has become a research hotspot in recent years.Fluorescent sensors depend on particular materials which are usually organic molecules. Organic molecules can be easily designed and functionalized. Their chemical structure can be easily tailored to meet the sensing demand. Many conjugated polymers are conductive and light emitting, easy for optoelectronic integration, and ready to form large area of film via a simple spin-coating. Novel fluorescent compounds could be readily realized via rational molecular design and organic synthesis resulting from the structural diversity and facile tailoring of organic molecules.TPA is a very important organic building unit, with three dimensional propeller-type architecture, higher glass transition temperature, which is widely used as hole transport material and luminescent material. Combined with other conjugated moieties, amorphous materials can be formed. Benzothiadiazole is a strong electron withdrawing unit. Its derivatives usually have better optical and thermal stability. Pyridyl group can form hydrogen bond with hydrogen donating analyte. In this article, with TPA as the electron donor and benzozhiadiazole as the electron acceptor, we built one, two and three branched fluorescent compounds named TPA1BP TPA2BP and TPA3BP according to the number of the branches.They were synthesized via Suzuki-miyaura reaction. Their structures were characterized by the MS and NMR spectra. Their potophysical properties both in their solution and film state were investigated by UV-vis and fluorescence spectrometer. Their cyclicvoltammetry (CV) curves were determined to obtain their HOMO-LUMO level and band gap. SEM images were used for surveying their self-aggregation in the film state. Their sensing behaviors to aniline were systemically studied by fluorescence spectrometer. In the film state, all of them could response to aniline vapor. But the sensitivity of TPA1BP (quenching rate is 48% in 40 s and rised to 70% in 300 s) is much better than TPA2BP and TPA3BP because of the self-aggregation effect in TPA2BP and TPA3BP film.To improve the permeability and the ratio of area-to-volume of the film, TPA2BP and TPA3BP were coated on the electrospun nanofibre mat, the sensing performance were improved greatly. The quenching efficiency of TPA2BP and TPA3BP nanofiber films were improved from 28% to 50% and from 25% to 60% after exposure to aniline vapor in 50 s, respectively.We also studied the detection selectivity of TPA1BP to amines including aniline, benzylamine, hexylamine, cyclohexylamine, triethylamine, and p-nitroamine, and found that TPA1BP show very good selectivity to aniline among these amines. The detection mechanism were concluded via the energy level diagram. The response of TPA1BP to benzene and its derivatives was also surveyed (such as toluene,2-chlorotoluene, bromobenzene, o-dichlorobenzene), and halides (such as trichloroethylene, tribromethane, ethylene chloride, diiodomethane), the results showed that the former enhanced the fluorescence and the latter quenched.