1. Institute of ChemistryMartin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
2. Department of Chemistry, Faculty of ScienceCairo University Giza Egypt
3. Department of Nonlinear Phenomena, Institute of PhysicsOtto von Guericke University Magdeburg Magdeburg Germany
4. State Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong University Xi'an 710049 P. R. China