1. Department of Physics and Materials
Science, City University of Hong Kong,
Kowloon, Hong Kong SAR, PRC
2. Department of Chemistry and
Biochemistry, University of California,
San Diego, 9500 Gilman Drive, La Jolla, CA 92039-0358, USA
3. School of Electronic Science and
Applied Physics, Hefei University of Technology, Hefei, 230009, Anhui, PRC