Transmission electron microscopy (TEM) was taken at a Zeiss CEM902 electron microscope (Zeiss, Oberkochen, Germany) and a JEOL JEM-2200FS electron microscope. Samples were dissolved in THF. The solution was dropped on a carbon coated copper grid (mesh 200, Science Services, Munich). Electron acceleration voltage was set to 80 kV (CEM902) and 200 kV (JEOL 2200FS). For the Zeiss CEM902 micrographs were taken with a MegaView III / iTEM image acquiring and processing system from Olympus Soft Imaging Systems (OSIS, Münster, Germany) and an Orius 830 SC200W / DigitalMicrograph GMS 2.3 system from Gatan (Munich, Germany). For the JEOL JEM-2200FS micrographs were taken with an OneView 1095 / DigitalMicrograph GMS 3.2 system from Gatan (Munich, Germany). Both microscopes are Energy-Filtering TEMs (EFTEM). All micrographs were acquired in near focus bright field mode and zero-loss filtered. For the Zeiss CEM902 an objective aperture of 60µm and in case of the JEOL JEM-2200FS an objective aperture of 120µm were used. Particles size measurements were done with "ImageJ" image processing software developed by Wayne Rasband (National Institutes of Health, USA).