1Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
2School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
3School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 639798, Singapore
4Ding Yuan Tang, School of Electrical and Electronic Engineering Nanyang Technological University Singapore 639798 (Singapore).
5Kian Ping Loh, Department of Chemistry National University of Singapore 3 Science Drive 3, Singapore 117543 (Singapore).