1. Department of Materials Science and Engineering and Center for Micro/Nano Science and Technology, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan, National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan, Department of Biomedical Engineering, Yuanpei University, No. 306, Yuanpei Street, Hsinchu 30015, Taiwan, and Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany