Small-molecule fluorescent sensors (1-5) for the recognition of nitroaromatic compounds, such as 2,4-dinitrotoluene and the explosive TNT, were obtained by using a three-step dehydrohalogenation cycloaddition protocol. The interaction of the receptors and nitroaromatics was studied both in solution and in the solid state by using fluorescence spectroscopy and X-ray crystallography, respectively. It is shown that the iptycene receptors 1-5 provide a cavity suitable for binding nitroaromatic compounds in an edge-to-face mode, rather than simple ring-stacking interactions. The results obtained inspired us to develop an inexpensive, reliable and robust sensor for vapour detection of explosives. Polymer nanofibres are particularly suitable for the production of such TNT sensors as they accelerate the mass exchange between the polymer and the vapours of TNT. Quenching of the sensors took place within 1 min compared to 10 min for a glass-slide assay. Hence, the sensor performance can be improved by optimising the matrix material and morphology without resynthesising the sensor moieties.
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