# Fabrication and Characterization of Modified Graphene Oxide/PAN Hybrid Nanofiber Membrane
## 1 Introduction  
Nanofibers, which are important nanomaterials, have attracted increasing attention over the last two decades. A nanofiber generally refers to a fiber having a diameter less than 100 nm. However, fibers with diameters less than 1000 nm (micro-) can also be defined as nanofibers in the fiber industry field [1; 2]. Many researches on the fabrication and application of nanofibers have attracted great interest from both academia and industry. The general fabricating methods of nanofibers are electrospinningning, self-assembly, phase separation, melting blown, and nanoporous template. Among these methods, electrospinningning is the most promising method for producing continuous nanofibers on a large scale, and the fiber diameter can be easily adjusted. Also, electrospinningning is a relatively simple and fast process to produce nanofibers [3; 4; 5; 6]. A number of organic polymers, including natural and biomaterial polymers, have been successfully spun into nanofibers using electrospinningning. Electrospun nanofibers have many applications due to their excellent properties, such as very small pores, large surface area, and higher porosity compared with regular fibers, which are produced by conventional melt and wet spinning processes [7; 8; 9]. Until now, nanofibers have been widely reported and applied in various fields, such as filtrations, wound dressings, tissue engineering scaffolds, protective clothing, electronics, sensors, energy storage, and drug delivery materials. Other new applications have been continuously explored for these nanofibers [10; 11; 12].  
Recent researches have shown that polyacrylonitrile (PAN) was generally chosen to prepare nanofiber membranes and used as a water treatment membrane or Li-ion battery (LIB) separator [14; 15]. Firstly, PAN is one of the most extensively used polymers in electrospinning because of its excellent properties [16; 17]. Furthermore, electrospun PAN nanofibers possess a variety of advantages, including thermal stability, resistance to most solvents, high strength, and so on [18; 19]. In addition, in order to further improve the hydrophilicity and other properties of PAN nanofibers, some nanofillers such as nanosized TiO\({}_{2}\), ZnO, graphene oxide (GO), etc. have been added to the polymer solution to prepare hybrid nanofibers [20; 21; 22]. Instead, GO contains several oxygen-containing groups, such as epoxy and hydroxyl groups at basal plane and carbonyl and carboxylic groups at the edge. As a result, GO has higher amphiphilicity and reactivity than other nano-materials, thus making it a more suitable nanofiller for improving the properties of hybrid nanofiber membranes than other nanomaterials [23; 24; 25]. Recently, it has been found that adding GO nanofillers can greatly enhance the mechanical properties of hybrid nanofiber membranes. However, due to the limitation of dispersibility in the polymer precursor solutions, uniform distribution of excess GO nanofillers over 0.4 wt.% into nanofibers is still challenging [26]. Therefore, improving the dispersibility of GO in polymer precursor solution has become a hot topic in recent research [27; 25; 28; 29].  
In this report, GO was firstly prepared from flake graphite using an improved Hummer's method. We also modified the surface of GO with a simple method in order to improve its dispersibility. This modified GO was mixed with a PAN polymer solution to form a homogeneous precursor solution. The final precursor solution was then fabricated as the hybrid nanofiber membranes via the electrospinning process. The resulting nanofiber membranes were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), contact angle, thermogravimetric analysis (TGA), and mechanical property.