1. a Department of Chemistry , Quaid-i-Azam University , Islamabad , 45320 , Pakistan
2. b Department of Biochemistry, Faculty of Biological Sciences , Quaid-i-Azam University , Islamabad , Pakistan
3. c Institute of Physics , University of Neuchátel , Rue Emile-Argand 11, CH-2009 , Neuchátel , Switzerland