1. Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education; Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics & Devices; School of Physics and Electronics; Hunan University; Changsha 410082 China
2. State Key Laboratory of Chemo/Biosensing and Chemometrics; Provincial Hunan Key Laboratory for Graphene Materials and Devices; College of Chemistry and Chemical Engineering; Hunan University; Changsha 410082 China
3. Clean Energy Automotive Engineering Center; Tongji University; Shanghai 201804 China
4. Department of Materials Science & Engineering; University of Washington; Seattle WA 98195 USA