The spectra of the pristine PAN membrane (Figure ) featured the main characteristic peaks of nitriles (at 2240 cm -1 ) and of alkanes (2925 and 1450 cm -1 ). However, it also features a broad band in the 3200-3500 cm -1 region as well as additional peaks at 1730 and 1230 cm -1 , which suggest the presence of some impurities (such as hydroxyl or carbonyls functions) at the surface of the PAN membrane.