1. Institute of Physics, Martin Luther University Halle-Wittenberg, von Danckelmann Platz 3, D-06099 Halle/S., Germany, Biomedical Materials Group, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Heinrich-Damerow-Strasse 4, 06120 Halle (Saale), Germany, and National Research Centre, El Buhoth Street, 12311 Cairo, Egypt