1. Nanoscale Science and Technology Laboratory, Institute for Advanced Study, Nanchang University, Jiangxi 330031, P. R. China
2. School of Physics and Materials, Nanchang University, Jiangxi 330031, P. R. China
3. College of Ecology and Resources Engineering, Fujian Provincial Key Laboratory of Eco-Industrial Green Technology, Wuyi University, Fujian 354300, P. R. China