1. College of Chemistry, Chemical Engineering and Materials Science Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou 215123 China
2. Materials Sciences Division Lawrence Berkeley National Laboratory 1 Cyclotron Road Berkeley CA 94720 USA
3. Department of Physics City University of Hong Kong Kowloon China
4. School of Microelectronics University of Science and Technology of China Hefei Anhui 230026 China
5. Polymer Science and Engineering Department University of Massachusetts Amherst MA 01003 USA
6. Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical Technology Beijing 100029 China
7. Department of Physics and Astronomy Collaborative Innovation Center of IFSA (CICIFSA) Shanghai Jiaotong University Shanghai 200240 P. R. China
8. Advanced Institute for Materials Research (WPI-AIMR) Tohoku University 2-1-1 Katahira, Aoba Sendai 980-8577 Japan