1. School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
2. Nanyang Environment & Water Research Institute (Environmental Chemistry and Materials Centre), Interdisciplinary Graduate Program, Nanyang Technological University, Singapore
3. The University of Sydney, Sydney Nano Institute, Faculty of Medicine and Health, Sydney Pharmacy School, Sydney, New South Wales 2006, Australia
4. Skin Research Institute of Singapore, Biomedical Science Institutes, Immunos, 8A Biomedical Grove, Singapore 138648, Singapore
5. Department of Environmental Health, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Boston, Massachusetts 02115, United States