Chemical modification of nanometric TiO <inf>2</inf> particles by anchoring functional silane molecules in supercritical CO <inf>2</inf>

Supercritical carbon dioxide (scCO 2 ) was used as a green solvent for the grafting of complex functional organosilanes containing nitrogen moieties on titanium dioxide (TiO 2 ) nanoparticles using two strategies. The first strategy involved the preparation of two functional silanes, 4-nitrophenyl-(3-(trimethoxysilyl)-propyl)methanimine (NPTMS) and 4-(((3-(trimethoxysilyl)propyl)imino)methyl)-benzaldehyde (FPTMS) and further deposited under anhydrous conditions and scCO 2 onto the TiO 2 surface. The second strategy involved the scCO 2 anhydrous deposition of bifunctional commercial silanes on the TiO 2 surface . Two structures were synthesized. The first consisted in grafted TiO 2 nanoparticles prepared by addition of the ligand, ((1R,2R)-N-(pyridin-2-ylmethyl)-2-(((E)-pyridin-2-ylmethylene) amino)-cyclohexan-1-amine (L Py-red ), and designated as Ti-Cl-L Py-red . The second structure was synthesized by the reaction of (1,2)-diaminocylohexane (Dac), through the reactive site of 3-(Trimethoxysilyl) propyl methacrylate (MPTMS) previously deposited on the TiO 2 surface and designated as Ti-MP-Dac. The synthesized silanes were characterized by ATR-FT and NMR spectroscopies and mass spectrometry. ATR-FT spectroscopy confirmed the presence of the silanes on the surface of the hybrid nanoparticles. Thermogravimetic analysis was used to estimate the loading of the silane grafted through both hydrogen and covalent bonding on the TiO 2 surface. Further characterization of the solid samples was done by N 2 adsorption-desorption and UV-vis diffuse reflectance. © 2014 Elsevier B.V. All rights reserved.