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

Abstract

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.