[1] Univ Sidi Mohamed Ben Abdellah, Fac Sci Dhar el Mahraz, Solid State Phys Lab, Res Grp Polymers & Nanomat, Atlas Fez 30000, Morocco
[2] iThemba LABS Natl Res Fdn South Africa, ZA-7129 Somerset West, Western Cape Pr, South Africa
[3] Univ S Africa, Coll Grad Studies, UNESCO UNISA Africa Chair Nanosci Nanotechnol, ZA-0001 Pretoria, South Africa