1. Department of Chemistry, City University of Hong Kong, Kowloon 999077, Hong Kong
2. Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
3. Department of Materials Science and Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong
4. Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195-2120, United States