1. Department of Materials Science and Engineering, A. J. Drexel Nanomaterials Institute, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
2. Sino-Russian International Joint Laboratory for Clean Energy and Energy Conversion Technology, College of Physics, Jilin University, Changchun 130012, P. R. China
3. International Center of Future Science, Jilin University, Changchun 130012, P. R. China