1. School of Chemical and Biomedical EngineeringNanyang Technological University 62 Nanyang, Drive Singapore 637459 Singapore
2. Department of Applied PhysicsTianjin Key Laboratory of Low Dimensional Materials Physics and Preparing TechnologyFaculty of ScienceTianjin University Tianjin 300072 China
3. Beijing Synchrotron Radiation Facility (BSRF)Institute of High Energy PhysicsChinese Academy of Sciences Beijing 100049 China