1. Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea
2. School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul 151-742, Republic of Korea
3. Interdisciplinary Program for Bioengineering, Seoul National University, Seoul 151-742, Republic of Korea
4. Department of Physics, Inha University, Incheon, 402-751, Republic of Korea
5. School of Mechanical Engineering, Pusan National University, Busan 609-735, Republic of Korea