1. Department
of Physics, East China University of Science and Technology, Meilong
Road 130, Shanghai 200237, China
2. Nano
and Molecular Systems Research Unit, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland
3. College
of Chemistry, Key Lab of Environment Friendly Chemistry and Application
in Ministry of Education, Xiangtan University, Yuhu District, Xiangtan 411105, China