[1] Natl Univ Singapore, Dept Chem & Biomol Engn, Singapore 117576, Singapore
[2] Hong Kong Univ Sci & Technol, Dept Chem, Kowloon, Hong Kong, Peoples R China
[3] Inst Mat Res Engn, Singapore 117602, Singapore
[4] Nanjing Univ, Dept Mat Sci & Engn, Natl Lab Solid State Microstruct, Nanjing 210093, Jiangsu, Peoples R China