1. School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore, College of Chemistry and Environment Science, Hebei University, Baoding, P. R. China, Pillar of Engineering Product Development, Singapore University of Technology and Design, 287 Ghim Moh Road, Singapore 279623, Singapore, and School of Chemical Biological and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore