[1] Univ Nigeria, Dept Phys & Astron, Nsukka, Nigeria
[2] Quaid I Azam Univ Campus, Natl Ctr Phys, Islamabad 44000, Pakistan
[3] Univ South Africa, Coll Grad Studies, UNESCO UNISA Africa Chair Nanosci Nanotechnol, Pretoria, South Africa
[4] Natl Res Fdn, iThemba LABS, Nanosci African Network NANOAFNET, Somerset West, Western Cape Pr, South Africa
[5] Univ Nigeria, Dept Pharmaceut, Nsukka, Nigeria
[6] Northwestern Polytech Univ, NPU NCP Joint Int Res Ctr Adv Nanomat & Defects E, Xian 710072, Peoples R China
[7] Northwestern Polytech Univ, Sch Mat Sci & Engn, Xian 710072, Peoples R China
[8] Coal City Univ, Fac Nat & Appl Sci, Dept Phys, Enugu, Nigeria