1. Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
2. Department of Chemistry, Faculty of Science, Beni-Suef University, Salah Salem Str., 62511 Beni-Suef, Egypt
3. Lumileds Phosphor Center Aachen, Lumileds Germany GmbH, Philipsstraße 8, 52068 Aachen, Germany
4. Department of Chemistry, University of Munich (LMU), Butenandtstraße 5-13, 81377 München, Germany