1. a Institute of Chemistry, Academia Sinica , Nankang, Taipei, 11529, Taiwan, P. R. China
2. b Department of Physical and Macromolecular Chemistry, School of Science , Charles University , CZ-128 43 Prague 2, Czech Republic
3. c Center for Condensed Matter Sciences , National Taiwan University , Taipei, 10764, Taiwan, P. R. China
4. d Department of Chemistry , University of Massachusetts Lowell , Lowell, MA, 01854, U.S.A.
5. e Department of Chemistry , University of Arizona , Tucson, AZ, 85721-0041, U.S.A.