1. Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, 117543 Singapore
2. Solar Energy Research Institute of Singapore, National University of Singapore, 7 Engineering Drive 1, 117574 Singapore
3. Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, 138634 Singapore
4. National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani, 12120 Thailand