Preparation and Luminescence Properties of in Situ Formed Lanthanide Complexes Covalently Grafted to a Silica Networkelectronic Supplementary Information (Esi) Available: Color Photograph of Organic-Inorganic Hybrid Materials Containing Eu3+ Ions and Tb3+ Ions. See Http://Www.rsc.org/Suppdata/Nj/B4/B401673D/