1. Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Energy School of Materials & Energy Southwest University Chongqing 400715 P.R. China
2. State Key Laboratory for Artificial Microstructure and Mesoscopic Physics Department of Physics Peking University Beijing 100871 P. R. China
3. Key Laboratory of Luminescence Analysis and Molecular Sensing Ministry of Education School of Chemistry and Chemical Engineering Southwest University Chongqing 400715 P. R. China