A series of D-π-A- type dyes based on pyrimidines, bearing various thiophene linkers, have been studied as sensing fluorophores. Fluorescence studies have demonstrated that the emission of all derivatives is sensitive to the presence of nitroaromatic explosives, such as 2,4,6-trinitrophenol (PA), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT), in their acetonitrile solutions. The detection limits of fluorophores to PA, TNT, and DNT proved to be in the range from 5.83 × 10(-6) to 2.38 × 10(-7) mol/L, 1.70 × 10(-4) to 8.40 × 10(-6) mol/L, and 8.39 × 10(-5) to 6.87 × 10(-6) mol/L, respectively. The theoretical investigation into the quenching mechanism in the presence of fluorophore has been performed. All compounds have shown a good efficiency as sensor materials when tested as elements of the original device «Nitroscan» for detecting nitro-containing explosives in vapor phase (Plant "Promautomatika", Ekaterinburg, Russia). Graphical Abstract ᅟ.

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Five random copolymers comprising styrene and styrene with pendant fluorophore moieties, namely pyrene, naphthalene, phenanthrene, and triphenylamine, in molar ratios of 10:1, were synthesized and employed as fluorescent sensors. Their photophysical properties were investigated using absorption and emission spectral analyses in dichloromethane solution and in solid state. All copolymers possessed relative quantum yields up to 0.3 in solution and absolute quantum yields up to 0.93 in solid state, depending on their fluorophore components. Fluorescence studies showed that the emission of these copolymers is highly sensitive towards various nitroaromatic compounds, both in solution and in the vapor phase. The detection limits of these fluorophores for nitroaromatic compounds in dichloromethane solution proved to be in the range of 10−6 to 10−7 mol/L. The sensor materials for new hand-made sniffers based on these fluorophores were prepared by electrospinning and applied for the reliable detection of nitrobenzene vapors at 1 ppm in less than 5 min.

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A number of D-π-A-π-D type dyes based on pyrimidines, bearing various electron-donating carbazole and triphenylamine fragments, have been studied as sensing fluorophores. Fluorescence studies demonstrated that the emission of all derivatives in acetonitrile is sensitive to the presence of a number of nitroaromatic benzenoids, including explosives such as 2,4-dinitroanisole, picric acid, styphnic acid, 1,3,5-triethoxy-2,4,6-trinitrobenzene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene. Detection limits of fluorophores for the explosive compounds were in the range from 2 mM to 29 μM. A selective fluorescence quenching response, including a sharp color change under UV, especially for the trinitrophenolics, makes these fluorophores promising fluorescence sensory materials for nitroaromatic explosives.

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