1. Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
2. Beijing Institute of Technology Chongqing Innovation Center, Chongqing 401120, P. R. China
3. Yangtze Delta Region Academy of Beijing Institute of Technology, Jiaxing 314000, P. R. China
4. Department of Chemistry, Purdue University, 560 Oval Drive,
P.O. Box 68, West Lafayette, Indiana 47907, United States