1. School of Advanced Materials and Nanotechnology, Xidian University, Xi'an 710126, P. R. China
2. Nanomaterials Group, Institute of System, Information Technologies and Nanotechnologies (ISIT), Fukuoka Industry-Academia Symphonicity (FiaS), 4-1 Kyudaishinmachi, Nishi-ku, Fukuoka 819-0388, Japan
3. School of Mechanical Engineering, Chengdu University, Chengdu 610106, P. R. China