1. Department
of Chemistry, Seoul National University, Seoul 151-747, Korea
2. Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
3. Display R&D Center, Samsung Display Co., Ltd., Yongin 446-711, Korea
4. Laboratory
of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, Building 50, Bethesda, Maryland 20892, United States