## 3 Results  
### TiO\({}_{2}\)/ZnO Nanofibers  
Figure 2 shows the FE-SEM images of TiO\({}_{2}\)/ZnO nanofibers fabricated by the electrospinning process at various applied voltages of 12 kV, 15 kV, and 18 kV. TiO\({}_{2}\)/ZnO nanofibers have a typical one-dimensional and clean microstructure without droplets. Increasing the voltage during the electrospinning process increased the charge density of the solution and nanofibers with a small diameter were obtained. When voltage exceeding the limit was applied, nanofibers were not formed and sprayed. If a lower voltage is used then surface tension is applied, and nanofibers in the form of nanofiber intermediate beads can be obtained instead of nanofibers of a constant diameter.  
The average diameters of TiO\({}_{2}\)/ZnO nanofibers with applied voltage was 1025 nm, 735 nm, and 694 nm, respectively. It reveals that the higher the voltage, the smaller the diameter. The diameters of TiO\({}_{2}\)/ZnO nanofibers with applied voltage are plotted in Figure 3.  
Figure 2: Field emission scanning electron microscope (FE-SEM) images of electrospinning TiO\({}_{2}\)/ZnO nanofibers: (**A**) 12 kV, (**B**) 15 kV, and (**C**) 18 kV.  
Figure 4 shows FE-SEM images of TiO\({}_{2}\)/ZnO nanofibers fabricated by the electrospinningning process at various inflow rates of 1.0 mL/h, 0.8 mL/h, and 0.6 mL/h. A one-dimensional nanofiber was observed in all TiO\({}_{2}\)/ZnO nanofibers. When the flow rate of the electrospinningning solution is fast, the size of the droplet that forms on the tip of the needle becomes large. Even when the solution is reached at the collector, the solvent in the solution may not be completely evaporated, and a nanofiber with a bead-shape or large diameter can be obtained.  
The average diameters of TiO\({}_{2}\)/ZnO nanofibers with an inflow rate were 1025 nm, 771 nm, and 728 nm, respectively. The average diameter of TiO\({}_{2}\)/ZnO nanofibers increased with inflow rate. The diameters of TiO\({}_{2}\)/ZnO nanofibers with an inflow rate are plotted in Figure 5.  
Figure 4: FE-SEM images of electrospinningning TiO\({}_{2}\)/ZnO nanofibers: (**A**) 1 mL/h, (**B**) 0.8 mL/h, and (**C**) 0.6 mL/h.  
Figure 3: Average diameters of TiO\({}_{2}\)/ZnO nanofibers with voltage.  
Figure 6 shows FE-SEM images of TiO2/ZnO nanofibers fabricated by the electrospinning process at various amounts of acetic acid--21 wt %, 28 wt %, and 35 wt %--in the precursor solution. All TiO2/ZnO nanofibers have nanofiber structural networks. As the amount of acetic acid in the electrospinning solution increases, the viscosity decreases, and the diameter of the nanofibers dramatically decreases. This reveals that the viscosity is the most important parameter for controlling the diameter in the electrospinning process.  
The average diameters of TiO2/ZnO nanofibers with an inflow rate were 1025 nm, 233 nm, and 189 nm, respectively and the average diameter dramatically decreased with the amount of acetic acid. The diameters of TiO2/ZnO nanofibers with different amounts of acetic acid are plotted in Figure 7.  
Figure 5: Average diameters of TiO2/ZnO nanofibers with inflow rate.  
Figure 6: FE-SEM images of electrospinning TiO2/ZnO nanofibers: (**A**) 21 wt %, (**B**) 28 wt %, and (**C**) 35 wt %.  
To observe the crystal phase of TiO\({}_{2}\)/ZnO nanofibers, XRD analysis was conducted. Figure 8 shows the XRD pattern of TiO\({}_{2}\)/ZnO nanofibers. The peaks of TiO\({}_{2}\) anatase, ZnO, Ti\({}_{2}\)O\({}_{3}\), and ZnTiO\({}_{3}\) were identified and the peak of ZnTiO\({}_{3}\) was obtained by the reaction of TiO\({}_{2}\) and ZnO.