1. Departments of Chemistry and Chemical and Biomolecular Engineering National University of Singapore Singapore 119077 Singapore
2. Institute for Functional Intelligent Materials National University of Singapore Singapore 117544 Singapore
3. Singapore Centre for Environmental Life Sciences Engineering Nanyang Technological University Singapore 639798 Singapore
4. Department of Radiation Science and Technology Delft University of Technology Delft 2629 JB The Netherlands
5. Department of Chemistry and Biochemistry University of California Santa Barbara CA USA