1. Jiangsu Key Laboratory for Nanotechnology, National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
2. Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology, Center on Nanoenergy Research, Novel Battery Materials Research Center of Engineering Technology, School of Physics Science and Technology, Guangxi University, Nanning 530004, P. R. China
3. Center for Advanced Marine Materials and Smart Sensors, Minjiang University, Fuzhou 350108, P. R. China