1. Faculty of Engineering and Science, Western Norway University of Applied Sciences, P.O. Box 7030, 5020 Bergen, Norway
2. Clean Energy Research Laboratory, Department of Physics, University of Jaffna, Jaffna 40000, Sri Lanka
3. Department of Chemistry, University of Jaffna, Jaffna 40000, Sri Lanka
4. Department of Physics and Technology, University of Bergen, Allegaten 55, 5007 Bergen, Norway