# Fabrication and Characterization of Modified Graphene Oxide/PAN Hybrid Nanofiber Membrane
## 3 Results  
### Characterization of Synthesized Graphene Oxide (GO)  
The SEM image (Figure 1a) indicates that GO is few micro-meters in length and width. Figure 1b shows the AFM image of GO, and the line scan conducted on this sample. Figure 1c shows the height profile of the line scan. The thickness of the synthesized GO is approximately 0.9-1 nm. It is reported that the thickness of perfect single layer of GO was about 0.8 nm. Therefore, we can infer that this synthesized GO is almost a single layer. FT-IR spectra is recognized as an important tool for characterization of functional group in GO, so FT-IR test was performed and the spectra is shown in Figure 2. Among the salient features observed are the bands at 1740 cm\({}^{-1}\), 1630 cm\({}^{-1}\), 1226 cm\({}^{-1}\), and 1040 cm\({}^{-1}\), corresponding to the stretching modes of C=O, -C=C, C-O, and C-O-C groups in GO, respectively [32; 33]. As shown in Figure 3, the Raman spectrum of synthesized GO displays a D-band at 1353 cm\({}^{-1}\) and a broad G-band at 1587 cm\({}^{-1}\), which were the typical spectra of GO [34]. [PERSON] et al. Figure 1: (**a**) field emission scanning electron microscopy (FESEM) image of graphene oxide (GO), (**b**) atomic force microscopy (AFM) image of GO, and (**c**) height profile of GO. Figure 2: Fourier-transform infrared spectroscopy (FT-IR) of synthesized graphene oxide (GO). reported that the G-band and D-band represented different carbon networks. The G-band was due to the characteristics of all sp2-hybridized carbon networks, resulting in the first-order scattering in the Brillouin zone center, while the D-band, caused by the attachment of oxygen groups on the carbon basal plane, showed the structural imperfections [35]. Characterization of Graphene Oxide Modified by Polydiallyldimethylammonium Chloride/Polyacrylonitrile (GP/PAN) Hybrid Nanofiber Membranes  
Figures 4 and 5 show the digital photos and the SEM images of representative PAN and a series of GP/PAN hybrid nanofiber membranes, respectively. It can be easily observed that the more GP content in the PAN, the darker the color that was obtained [30]. Based on our previous research, the loading amount of bare GO into PAN nanofiber membranes by electrospinning generally reached up to 0.4 wt.% with respect to the polymer concentration, due to the limited dispersity of GO in a polymer precursor solution [26]. Only through the process of simple surface modification, the modified GO (GP) nanofiller was reliably added up to 1.0 wt.% under the same electrospinning conditions. This modification involved the electrostatic interactions between PDDA and GO, which greatly improved the dispersity of GO in polymer precursor solution as well as reliable electrospinning of nanofibers without a needle blocking problem. Meanwhile, as the amount of GP increased, the average diameter of nanofibers increased from 0.563 \(\upmu\)m to 0.618 \(\upmu\)m. This is reasonable, since as the amount of GP increases in the polymer solution, the viscosity of the final precursor solution increases due to the low amount of solvent, resulting in thicker nanofibers. However, we think that this can only happen if GP is dispersed homogeneously in the polymer solution. Otherwise, the viscosity of the GP polymer solution will not increase consistently. The pore size and thickness of the nanofiber membranes were examined (Table 2). The PAN nanofiber membrane possessed an average pore size of 213.3 nm and a thickness of 77 \(\upmu\)m. The hybrid nanofiber membranes gradually increased the pore size and the thickness with the increase of the GP content. These results demonstrate our previous research results once more, i.e., as the diameter of nanofibers increases, the pore size and thickness also increase [26]. Figure 3: Raman spectra of synthesized graphene oxide (GO). To confirm the successful composite of GP into the nanofibers, the FT-IR of GP/PAN nanofibers were measured (Figure 6). It was easily recognized that GP was successfully added, due to the fact that GP was successfully added to the