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Khattab, Tawfik A.; Rehan, Mohamed; Aly, Sherif Abdelmoez; Hamouda, Tamer; Haggag, Karima M.; Klapötke, Thomas M. (2017): Fabrication of PAN-TCF-hydrazone nanofibers by solution blowing spinning technique: Naked-eye colorimetric sensor. In: Journal of Environmental Chemical Engineering, Vol. 5, No. 3: pp. 2515-2523
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A robust and reusable solid state colorimetric sensor for alkaline vapors and aqueous media is developed by embedding a novel tricyanofuran-hydrazone (TCF-H) pH-sensory disperse dye bearing a hydrazone recognition moiety into a polyacrylonitrile (PAN) matrix. UV/vis absorption and fluorescence spectra exhibit solvatochromism and reversible color change of the TCF-H colorant solution in acetonitrile under acid-base conditions. The solution blowing spinning technique is employed to develop the PAN-TCF-H nanofibrous colorimetric sensor. The approach adopted in the present study is based on entrapping TCF-H sensor within the polyacrylonitrile nanofibrous matrix that can afford simple numerical results for the pH of alkaline vapors and aqueous media. The vapochromic nanofibers provide an instant color change signal from light pink to blue upon exposure to alkaline vapors or aqueous media as indicated by the coloration measurements. Moreover, the nanofibers film sensor display fast response time (instant color change), concentration detection limit as low as 4.08 ppb for alkaline fluids, and very good reversibility. Recognition of alkaline vapors occurs via proton transfer of the hydrazone moiety to the base and is assisted by the strong electron withdrawing TCF moiety. The morphological properties of the nanofibrous sensor are determined by scanning electron microscopy, which showed that nanofibers with an average diameter range of 178-214 nm formed a nonwoven mat.