1. State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 P. R. China
2. University of Science and Technology of China Hefei 230026 P. R. China
3. State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 P. R. China
4. Department of Physical Sciences MacEwan University Edmonton AB T5J4S2 Canada