1. Department of Chemistry, UAE University, P.O. Box 15551, Al-Ain, UAE
2. Physics Department, Faculty of Science, Fayoum University, Fayoum 63514, Egypt
3. Center for Advanced Materials Research, Research Institute of Sciences and Engineering, University of Sharjah, P.O. Box 27272, Sharjah, UAE
4. Department of Applied Physics & Astronomy, University of Sharjah, P.O. Box 27272, Sharjah, UAE