1. Youssef Jameel Science and Technology Research Center, The American University in Cairo, P.O. Box 74, New Cairo 11835, Egypt
2. Madirel, Centre de St Jerome, CNRS-Universite de Provence, 13397 Marseille Cedex 20, France
3. Department of Chemistry, American University in Cairo, P.O. Box 74, New Cairo 11835, Egypt