Halochromic Chemosensor From Poly(acrylonitrile)/Phenolphthalein Nanofibers as pH Sensor

In this paper, poly(acrylonitrile-co-vinyl acetate) (PAN) and PAN/phenolphthalein (PAN/ph) solutions prepared in N, N-dimethylformamide with a different amount of polymer and dye content were electrospun. The electrospinning parameters, such as polymer concentration, feeding rate, applied voltage, and distance between tip and collector, were varied in order to study their effect on the nanofibers diameter. In general, addition of this additive to PAN solution resulted in nanofibers with lower diameter compared with raw PAN. For instance, the diameter of PAN/ph nanofibers produced under the same conditions as PAN was $\sim 194$ nm, whereas that of PAN was $\sim 299$ nm. Nanofibers prepared from PAN/ph showed halochromic behavior and were used as pH sensitive sensor. Nanofibers prepared under different conditions were analyzed by Fourier transform infrared spectroscopy, $^{13}\text{C}$ nuclear magnetic resonance spectroscopy, and ultraviolet-visible spectroscopy (UV-vis) spectrophotometer. Thermal properties of these halochromic sensors were investigated by differential scanning calorimetry. The existence of any interaction between PAN and phenolphthalein was investigated. Reversibility and reusability of these sensors were acceptable even after in eight months and using them for more than 200 times. The results show that these halochromic nanosensor could be a promising choice for using in hazardous places.