[1] City Univ Hong Kong, COSDAF, Hong Kong, Hong Kong, Peoples R China
[2] City Univ Hong Kong, Dept Phys & Mat Sci, Hong Kong, Hong Kong, Peoples R China
[3] Chinese Acad Sci, Tech Inst Phys & Chem, Nanorgan Photoelect Lab, Beijing 100101, Peoples R China
[4] City Univ Hong Kong, Dept Biol & Chem, Kowloon, Hong Kong, Peoples R China