1. School of Chemical and Biomedical Engineering; Nanyang Technological University; 62 Nanyang Drive Singapore 637459 Singapore
2. Beijing Synchrotron Radiation Facility (BSRF); Institute of High Energy Physics; Chinese Academy of Sciences; Beijing 100049 China
3. Department of Applied Physics; Faculty of Science; Tianjin University; Tianjin 300072 P. R. China