1. School of Environment and Energy Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling South China University of Technology Guangzhou 510000 P. R. China
2. Siyuan Laboratory Guangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy Materials Department of Physics Jinan University Guangzhou Guangdong 510632 P. R. China
3. Department of Physics The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong 999077 P. R. China