1. School
of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
2. Department
of Chemistry and the Institute for Lasers, Photonics, and Biophotonics, University at Buffalo, State University of New York, Buffalo, New York 14260, United States
3. Department
of Chemistry, Korea University, Seoul 136-701, Korea
4. Laboratory
of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892-2281, United States