1. Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
2. School of Physical Science and Technology, Lanzhou University, Lanzhou, Gansu 730000, P. R. China
3. State Key Laboratory of Mechanics and Control
of Mechanical Structures, Key Laboratory for Intelligent Nano Materials
and Devices of the Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
4. Department of Chemistry, Rice University, Houston, Texas 77005, United States
5. Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States