Synthesis of Surface-Functionalized Titania Particles with Organophosphorus Coupling Agents by Reactive Milling



We describe a top-down approach for the synthesis of metal oxide particles with simultaneous surface modification. Functionalized titania particles were obtained by reactive milling together with phenylphosphonic acid in a high-energy planetary ball mill. This process was accompanied by a tribochemical phase transition from the starting material anatase to the thermodynamically more stable rutile and a high-pressure modification of titania, which was influenced by the presence of the coupling agent. The obtained products were characterized by X-ray powder diffraction, IR and X-ray fluorescence spectroscopy, thermal and elemental analysis as well as by scanning electron microscopy. The analysis showed final particle sizes of 100 to 300 nm, depending on the milling time and speed (rpm). Furthermore, the prepared particles showed a high degree of surface coverage with organophosphorus coupling agent, up to 1.4 mmol per gram. Coordination of the coupling agent to the surface resulted in a stabilization of the high-pressure phase.