1. Herbert Gleiter Institute of Nanoscience, College of Materials Science and Engineering; Nanjing University of Science and Technology; No. 200 Xiaolingwei Nanjing, Jiangsu 210094 China
2. Department of Chemistry; National University of Singapore; 3 Science Drive 3 117543 Singapore
3. Department of Physics; National University of Singapore; 2 Science Drive 3 117542 Singapore
4. National University of Singapore (Suzhou) Research Institute; 377 Lin Quan Street, Suzhou Industrial Park Jiang Su 215123 China