Preparation and characterization of TiO2/SiO2-cationic hybrid nanoparticles for electrophoretic displays

The cationic hybrid nanoparticles (TiO2/SiO2-CHNPs) were researched on the basis of TiO2 nanoparticles (NPs), in order to further improve the performances of TiO2 electrophoretic particles. TiO2/SiO2-CHNPs were prepared via a series of steps including the preparation of SiO2 layer, silane coupling agent modification, synthesis of atom transfer radical polymerization initiator, preparation of polymer outer shell, and quaterization with methyl iodide. TiO2/SiO2-CHNPs were characterized by means of transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, dynamic light scattering, and micro-electrophoresis apparatus. The optical properties of TiO2/SiO2-CHNPs were measured by the formulation of electrophoretic dispersion. The results indicate that TiO2 NPs are truly encapsulated by silica and cationic polymer in turn. With the increase of SiO2 content from 0.1 to 0.2 (SiO2/TiO2, mol/mol), the zeta potential increases from +23.2 to +28.1 mV, the contrast ratio of white state to dark state changes from 36 to 40 and the response time shifts from 2.8 to 2.6 s, which indicates that the SiO2 content can significantly affect the electrophoretic properties of TiO2/SiO2-CHNPs.