* Corresponding authors

^a MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Department of Chemistry, School of Science, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, P. R. China
E-mail: zhougj@mail.xjtu.edu.cn
Fax: +86-29-8266 3914
Tel: +86-29-8266 3914

^b Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Faculty of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
E-mail: zhaoxinwu@mail.xjtu.edu.cn

^c Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, P. R. China
E-mail: wai-yeung.wong@polyu.edu.hk

^d Institute of Molecular Functional Materials and Department of Chemistry, Hong Kong Baptist University, Waterloo Road, Hong Kong, P. R. China