1. Department of Physics, Government Post Graduate Jahanzeb College Saidu Sharif, Swat 19130, Khyber Paktunkhwa, Pakistan
2. Department of Chemistry, College of Science, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia
3. College of Materials Science and Engineering, Jilin University, Changchun 130012, China