Hongyu Chen1, Pingping Yu1, Zhenzhong Zhang2, Feng Teng1, Lingxia Zheng1, Kai Hu1, Xiaosheng Fang1
1Department of Materials Science, Fudan University Shanghai, 200433, P. R. China
2State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, P. R. China