Synthesis of photofunctional titania nanosheets by electrophoretic deposition

This work presents the first investigation of an effective methodology for the synthesis of transparent and durable thin films with a high regularity along the c-axis using titania nanosheets (TN) on electrodes. This technique, an electrophoretic deposition method (EPD), was found to be applicable for the preparation of TN thin films deposited on ITO electrodes, a promising nanomaterial for the design of UV-visible light-sensitive energy conversion systems. The deposition of TN was found to be significantly affected by the concentrations, viscosity, and pH values of the aqueous TN solutions. Using quartz crystal analysis (QCA), the optimal deposition conditions for the most adhesive amounts of TN were established, and the delicate balance between the TN solution viscosity and surface charges of the TN layers that govern the amount of TN deposited on the substrate was discerned. Moreover, the deposited thin films were greatly improved by the addition of poly(vinyl alcohol) (PVA) into the solutions, initiating an increase in the deposition weight and optical transmittance, thus leading to firm adhesion onto the substrate. Methyl viologen (MV2+) was intercalated into the TN layers and irradiated with UV light shorter than the end absorption of TN, leading to a blue coloring for the TN/MV2+ thin films attributed to the formation of reduction products from MV2+ and clearly indicating photocatalytic reactivity.