1. Department of Physics; East China University of Science and Technology; Shanghai 200237 China
2. Liquid Crystal Institute and Chemical Physics Interdisciplinary Program; Kent State University; Kent OH 44242 USA
3. Shanghai Key Laboratory of Functional Materials Chemistry; East China University of Science and Technology; Shanghai 200237 China
4. National Laboratory of Solid State Microstructures; Collaborative Innovation Center of Advanced Microstructures and Colleague of Engineering and Applied Sciences; Nanjing University; Nanjing 210093 China