Synthesis and characterisation of carboxylate-terminated silica nanohybrid powders and thin films

Novel organic-inorganic hybrid materials, in the form of bulk materials (powders) and thin films, exhibiting carboxylate functionality have been prepared by sol-gel co-condensation of 11-(triethoxysilyl)methylundecanoate with tetraethoxysilane (TEOS), followed by chemical treatment with AlI3 to convert the ester moieties into terminal carboxylic acid sites. Uniform nanostructured thin films were prepared by spin-coating on silicon wafers. Both powders and thin films were used to study the uptake behaviour of lanthanide cations, such as Eu3+ or La3+ from aqueous solutions. It has been shown that the uptake capacity (mg g-1) of the films is 3-4 times higher than that of bulk (powder) materials. This has been attributed to the larger number of accessible COO- groups in the thin film form compared with the bulk material.