An average diameter and morphology of the nanofibers were
observed by using scanning electron microscopy (SEM; S-4800,
Hitachi). More detailed microstructures were observed by transmission
electron microscopy (TEM; JEM-2100F, JEOL) under an accelerating
voltage of 120 kV. X-ray diffraction (XRD) analysis was
performed with a diffractive meter (D/Max-2500, Rigaku) using Cu
Kα radiation. Fourier transform infrared spectroscopy (FT-IR; Scimitar
1000, Varian) was utilized to identify organic functional groups within
the nanofibers. A surface area and a pore size distribution were also
evaluated from nitrogen sorption isotherms measured by an analyzer
(Tristar II, Micromeritics) at 77 K.