1. State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, School of Materials Science and Engineering, Northwestern Polytechnical University and Shaanxi Joint Laboratory of Graphene (NPU), Xi’an 710072, P. R. China
2. Chongqing Innovation Center, Northwestern Polytechnical University, Chongqing 401135, P. R. China
3. Materials Institute of Atomic and Molecular Science, Shaanxi University of Science and Technology, Xi’an 710021, P. R. China
4. Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, P. R. China
5. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China