1. Beijing Institute of Nanoenergy and NanosystemsChinese Academy of Sciences Beijing 100083 P. R. China
2. School of Nanoscience and TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
3. National Center for Nanoscience and Technology (NCNST) Beijing 100190 P. R. China
4. Beijing Advanced Innovation Center for Intelligent Robots and SystemsSchool of Mechatronical EngineeringBeijing Institute of Technology Beijing 100081 China
5. School of Advanced Materials and NanotechnologyXidian University Xi'an 710126 China
6. School of Physics and ElectronicsCentral South University Changsha 410083 China
7. Center on Nanoenergy ResearchSchool of Physical Science and TechnologyGuangxi University Nanning 530004 China