1. Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan
2. NanoElectrochemistry Laboratory, Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
3. Department of Physics, National Tsing-Hua University, Hsinchu 300, Taiwan
4. Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei 115, Taiwan