1. Research Centre for Crystalline Materials, School of Science and Technology, Sunway University, Bandar Sunway 47500, Selangor Darul Ehsan, Malaysia
2. Research Centre for Crystalline Materials, School of Science and Technology, Sunway University, Bandar Sunway 47500, Selangor Darul Ehsan, Malaysia, e-mail: edwardt@sunway.edu.my