1. Department of Materials Science and Engineering; Department of Chemistry; University of North Texas; Denton TX 76203 USA
2. International Research Center for Renewable Energy; State key Laboratory of Multiphase Flow in Power Engineering; Xi'an Jiaotong University; Xi'an Shaanxi 710049 P. R. China
3. Center of Advanced Science and Engineering for Carbon (Case4Carbon); Department of Macromolecular Science and Engineering; Case Western Reserve University; Cleveland OH 44106 USA
4. School of Materials Science and Engineering; Northwestern Polytechnical University; Xi'an Shaanxi 710072 P. R. China