1. Laboratory of Advanced Materials Fudan University Shanghai 200433 China
2. NRC Postdoctoral Associate at the Naval Research Laboratory Washington DC 20375 USA
3. Materials Science and Engineering Department University of California, Los Angeles Los Angeles CA 90095 USA
4. Department of Materials Science and Engineering College of Materials Xiamen University Xiamen 361005 China
5. School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore