1. School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 Singapore
2. School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 Singapore
3. Institute of Sustainability for Chemical, Engineering and Environment (ISCE2), Agency of Science, Technology and Research (A*STAR), 1 Pesek Road, Singapore 627833, Singapore