a
Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa
b
Department of Physics, University of the Western Cape, Cape Town, South Africa
c
Energy Materials, Materials Science and Manufacturing, Council for Scientific & Industrial Research (CSIR), Pretoria 0001, South Africa
E-mail: kozoemena@csir.co.za
;
Fax: +27 12 841 2135
;
Tel: +27 12 841 3664