1. Technical Chemistry I, Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany
2. Center for Engineered Materials and Manufacturing, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
3. Department of Neurosurgery, Hannover Medical School, 30625 Hannover, Germany