1. Department of Chemistry, Beijing Normal University, Beijing City, China
2. Key Laboratory of Yunnan Provincial Higher Education Institutions for Organic Optoelectronic Materials and Devices, Kunming University, Kunming City, China
3. School of Physics and Technology, Kunming University, Kunming, China
4. Eberly School of Science, Pennsylvania State University Behrend, Erie, USA
5. Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA