1. School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
2. Division of Advanced Materials, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
3. Department of Physics, National University of Singapore, Singapore 117551, Singapore
4. Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China
5. Hong Kong Branch of National Precious Metals Material Engineering Research Center (NPMM), City University of Hong Kong, Hong Kong, Hong Kong, China
6. Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, China
7. CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno
Plaza, Singapore, 637553, Singapore