1. Nanostructured & Nanotechnology Division, Advanced Materials Department, Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87 Helwan, Cairo 11421, Egypt
2. Photocatalysis and Nanotechnology Unit, Institut für Technische Chemie, Leibniz Universität Hannover, Callinstrasse 3, 30167 Hannover, Germany