基金This project was supported by RGC-GRF Hong l(ong (766613, 14106145), the National Basic Research Program of China (2013CB531401), the National Natural Science Foundation of China (NSFC) (81201963, 81372600), the Shenzhen Municipal Science and Technology R&D fund (JCYJ20120619152326450), and the Shenzhen Virtual University Park Support Scheme to CUHK Shenzhen Research Institute.