1. Ecole Nationale Supérieure de Chimie de Paris (Chimie ParisTech), Laboratoire de Chimie de la Matière Condensée de Paris (UMR 7574 CNRS), 11 Rue P&M Curie, 75231 Paris Cedex 05, France
2. Department of Physics, Goa University, Taleigao Plateau, Goa 403 206, India
3. Luminescence Materials Research group, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands