Physicaland Mathematical Sciences, NTU) in providing their assistance with inductively coupled plasma (ICP) analyses.I also acknowledge the help of Miss Chow Shiau Kee (School of Mechanical and Aerospace Engineering, NTU) for her assistance in X-ray photoelectron spectroscopy (XPS) characterisations.I am grateful to Dr Stevin Snellius Pramana for his help and guidance in transmission electron microscope (TEM) measurements,