1. School of Materials Science and Engineering; Nanyang Technological University; 639798 Singapore
2. Institute of Biomedical and Health Engineering; Shenzhen Institute of Advanced Technology; Chinese Academy of Sciences; Shenzhen University Town; 1068 Xueyuan Avenue Shenzhen 518055 P. R. China
3. State Key Laboratory of Urban Water Resource and Environment; School of Municipal and Environmental Engineering; Harbin Institute of Technology; Harbin 150090 P. R. China