1. School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, P. R. China
2. Shannxi Engineering Laboratory for Graphene New Carbon Materials and Applications, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, P. R. China
3. Research Center for Carbon-Based Electronics, School of Electronics, Peking University, Beijing 100871, P. R. China
4. Department of Chemistry, Abdul Wali Khan University Mardan, Mardan 23200, Pakistan
5. School of Chemistry and Chemical Engineering, Ningxia Normal University, Guyuan 756000, P. R. China