A common strategy for the surface modification of nano TiO2 and other metal oxide nanoparticles is based on anchor groups using chelating ligands that can carry additional functionalities. This would allow the exploration of further applications of these materials. In the present work, we report the modification of TiO2 nanoparticles from nano TiO2 (Degussa P-25) dispersion in distilled water in the presence of 2-aminoethyl dihydrogen phosphate, followed by removing the excess of the capping agent through washing with water. The surface functionalization and the kind of surface interaction were analyzed applying different characterization methods like CHN elemental analysis, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), attenuated total reflectance (ATR-FTIR), X-ray powder diffraction (XRD) and 1H, 13C, 31P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), confirming the presence of modifying agent on the surface. In the study of modified nano TiO2 by MAS NMR spectroscopy, a distinct downfield shift for 31P signal has been seen comparing to the pure cappping agent due to P-O-Ti bond formation. The phosphate groups interact with the surface via quite strong covalent interaction, while according the analyses results, the surface amine groups remained uncoordinated.
Keywords
nano TiO2; surface modification; solid state 31P MAS NMR
