Wancheng Zhu*, Xili Cui, Xiaofei Liu, Liyun Zhang, Jia-Qi Huang, Xianglan Piao and Qiang Zhang*
* Corresponding authors: Wancheng Zhu zhuwancheng@tsinghua.org.cn - Qiang Zhang zhang-qiang@mails.tsinghua.edu.cn
Nanoscale Research Letters 2013, 8:2 doi:10.1186/1556-276X-8-2