1. Department of Physics, City University of Hong Kong, Hong Kong 999077, P. R. China
2. Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, P. R China
3. X-Ray Science Division, Argonne National Laboratory, Argonne Illinois 60439, United States
4. Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, P. R. China
5. Department of Chemical and Biological Engineering, Hong Kong University of Science and Technology, Hong Kong 999077, P. R. China