1. School of Chemistry and Physics, University of Kwazulu-Natal , Private Bag X01 , Scottsville, Pietermaritzburg , 3209 , South Africa
2. Center of Physical Chemical Methods of Research and Analysis, Al-Farabi Kazakh National University , 71 Al-Farabi Ave. , Almaty 050040 , Kazakhstan
3. School of Education, Durban University of Technology , P O Box 101112 , Scottsville, Pietermaritzburg , 3209 , South Africa