[1] Natl Univ Singapore, Healthcare & Energy Mat Lab, Nanosci & Nanotechnol Initiat, Singapore 117576, Singapore
[2] Natl Univ Singapore, NUS Grad Sch Integrat Sci & Engn, Singapore 117456, Singapore
[3] Inst Mat Res & Engn, Singapore 117602, Singapore
[4] King Saud Univ, Riyadh 11451, Saudi Arabia