1. Beijing Key Laboratory for Optical Materials and Photonic Devices Department of Chemistry Capital Normal University Beijing 100048 China
2. State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 P. R. China
3. Departments of Physics and Chemistry, Nanoscience Center University of Jyväskylä 40014 Jyväskylä Finland
4. Department of Physics School of Physical Science and Technology Ningbo University Ningbo 315211 China
5. University of Chinese Academy of Sciences Beijing 100049 China