基金This work is supported by National Natural Science Foundation of China (NSFC, No. 61340046), National High Technology Research and Development Program of China (863 Program, No. 2006AA04Z247), Scientific and Technical Innovation Commission of Shenzhen Municipality (JCYJ20130331144631730, JCYJ20130331144716089), Specialized Research Fund for the Doctoral Program of Higher Education (No. 20130001110011).