Low-temperature synthesis and electrophoretic deposition of shape-controlled titanium dioxide nanocrystals

Abstract

A comprehensive, low-temperature strategy for obtaining optimized, dense and nanostructured TiO₂ thin films is proposed. The nanocrystals of anatase-TiO₂ were prepared from highly reactive crystals of [Ti₈O₁₂(H₂O)₂₄]Cl₈, HCl, 7H₂O, a preferred titanium precursor for replacing alkoxides. Oleic acid and oleylamine were employed as capping ligands in order to control the shape and the size of TiO₂ nanocrystals during solvothermal treatment. Following an acid treatment, the ligands were removed from the surface of the nanocrystals, thereby enabling their re-dispersion in an ethanol-based charging solution. The stable transparent colloidal solutions were suitable for electrophoretic deposition of the nanocrystals (<15 nm in size) on conductive substrates. Transparent layers of TiO₂ nanocrystals, without post-annealing, were successfully prepared under low bias voltage (10 V) with thicknesses of up to 2 μm within a mere 10 min.