1. Department of Physics, Faculty of Science, University of Putra Malaysia, Serdang, Selangor 43300, Malaysia
2. Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
3. The Alan G MacDiarmid NanoTech Institute, The University of Texas at Dallas, Richardson, Texas 75080-3021, United States
4. Centre for Toxicology, Department of Biochemistry and Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom