1. Engineering Research Center in Biomaterials, Sichuan University, Chengdu, Sichuan 610065, P. R. China
2. ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Melbourne, Parkville, VIC 3010, Australia
3. College of Biomedical Engineering, Sichuan University, Chengdu, Sichuan 610065, P. R. China
4. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, Sichuan 610065, P. R. China