* Corresponding authors

^a Division of Metrology for Quality Life, Korea Research Institute of Standards and Science, Daejeon, Korea

^b Center for Biomolecular Nanotechnology, Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, Korea
E-mail: syjon@gist.ac.kr
Fax: +82 62 970 2504
Tel: +82 62 970 2484

^c Department of Biomedical Engineering, The Johns Hopkins University, Maryland 21218, USA

^d Electronics and Telecommunications Research Institute, Daejeon, Korea

^e Department of Chemistry, University of Incheon, Incheon, Korea
E-mail: kyuwon_kim@incheon.ac.kr
Fax: +82 32 770 8243
Tel: +82 32 770 8238