1. Department of Inorganic, Physical and Materials Chemistry and NIS Centre of Excellence, Università di Torino, Via P. Giuria 7, 10125 Torino, Italy, INSTM Centro di Riferimento, Department of Hydrocarbon Process Chemistry, SINTEF Materials and Chemistry, P.O. Box 124, Blindern, 031 Oslo, Norway, Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, Postboks 1033, Blindern N-0315, Oslo, Norway, and ESRF, 6 rue Jules Horowitz, BP220, F-38043, Grenoble CEDEX, France