[1] Dalian Univ Technol, State Key Lab Fine Chem, Dalian 116024, Peoples R China
[2] Nanyang Technol Univ, Sch Mat Sci & Engn, Singapore 639798, Singapore
[3] Nanyang Technol Univ, Sch Phys & Math Sci, Div Phys & Appl Phys, Singapore 637371, Singapore