1. Department
of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
2. Department
of Chemistry, Rice University, Houston, Texas 77005, United States
3. Department
of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
4. School
of Physical Science and Technology, Lanzhou University, Lanzhou, Gansu 730000, P. R. China
5. Department
of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, United States