[1] Nanyang Technol Univ, Sch Mat Sci & Engn, Singapore 639798, Singapore
[2] Nanyang Technol Univ, Sch Chem & Biomol Engn, Singapore 637819, Singapore
[3] Univ Oxford, Inorgan Chem Lab, Oxford OX1 3QR, England
[4] DSO Natl Labs, Singapore 118230, Singapore