1. Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Republic of Singapore
2. School of Food Science and Pharmaceutical Engineering Nanjing Normal University 1 Wenyuan Road Nanjing 210023 P. R. China
3. Joint School of National University of Singapore and Tianjin University International Campus of Tianjin University Binhai New City, Fuzhou 350207 China