1. Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials Key Laboratory of Cluster Science Ministry of Education of China School of Chemistry and Chemical Engineering Beijing Institute of Technology Beijing 100081 P. R. China
2. Key Laboratory for Advanced Materials Processing Technology Ministry of Education of China State Key Laboratory of Tribology Department of Mechanical Engineering Tsinghua University Beijing 100084 P. R. China
3. College of Materials Sciences and Engineering Beijing University of Technology Beijing 100084 P. R. China
4. Department of Chemistry Tsinghua University Beijing 100084 P. R. China