Anodic dissolution of titanium in acetonitrile to Ti(IV) perchlorate and subsequent reductive electrodeposition of amorphous TiO2 films

Anodization of titanium electrodes in acetonitrile + 0.1 M Bu4NClO4 or LiCl O4 produces solutions of Ti(IV) as the titanyl ion. Subsequent reduction of the anodized solution produces films of amorphous TiO2 on the electrode su rface. The oxide films are characterized by cyclic voltammetry, electrochem ical quartz crystal microbalance, X-ray diffraction, and ultraviolet-visibl e (UV-vis) spectroscopy. The UV-vis spectrum of the TiO2 layer displays an absorption with optical gap (3.5 eV) characteristic of amorphous TiO2 with a quantized size effect due to the nanometer size of the particles. The fil ms are reversibly reduced in acetonitrile + LiClO4 in a redox process at E- 0 = -2.05 V vs. Ag/Ag+ to the lithium-intercalated oxide. Heating the films at 500 degrees C converts them into the crystalline anatase form. The TiO2 films are capable of forming stable monolayers of carboxyl- and dicarboxyl ferrocenes only when amorphous and freshly prepared. (C) 1999 The Electroch emical Society. S0013-4651(98)04-013-0. All rights reserved.