1. School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, P. R. China
2. The State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, School of Physics and Optoelectronics, South China University of Technology, Guangzhou 510640, P. R. China
3. The China-Germany Research Center for Photonic Materials and Devices, The State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, School of Materials Science and Technology, South China University of Technology, Guangzhou 510640, P. R. China
4. Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, Zhejiang 310058, P. R. China
5. Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA