1. Department of Chemical Engineering, Faculty of Engineering, University of Nottingham Malaysia Campus, Broga Road, 43500, Semenyih, Selangor Darul Ehsan, Malaysia, School of Applied Physics, Faculty of Science & Technology (UKM), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan, Malaysia, Solid State Physics Research Laboratory, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia