1. Graphene Research Center, KAIST Institute for the NanoCentury, Division of Ocean Systems Engineering, School of Mechanical, Aerospace and Systems Engineering, Korea Advanced Institute of Science and Technology, 335 Gwahak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
2. SKKU Advanced Institute of Nanoscience and Technology, School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangangu, Suwon, 440-746, Republic of Korea
3. Department of Chemistry, Inha University, 100 Inha-ro, Nam-gu, Incheon 402-751, Republic of Korea