Affiliation: | 1. Low Dimensional Materials Research Centre, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia;2. The Chancellery Building, Multimedia University, Persiaran Multimedia, 63100 Cyberjaya, Selangor Darul Ehsan, Malaysia;3. Department of Chemistry, Faculty of Science, University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia |