Surface Chemistry Determines Electron Storage Capabilities in Alcoholic Sols of Titanium Dioxide Nanoparticles. A Combined FTIR and Room Temperature EPR Investigation

YESICA DI IORIO; MATÍAS E. AGUIRRE; MARTA A. BRUSA; MARIA A. GRELA

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2012 vol. 116 p. 9646 - 9652

1932-7447

Electron accumulation in TiO2 ethanolic sols prepared by the HCl hydrolysis of a titanium alkoxide has been scrutinized by UV-Visible and EPR spectroscopy. Unexpectedly, Ti(III) centers, g = 1.9551, formed after controlled monochromatic irradiation of the sols could be detected at room temperature by EPR spectroscopy. The yield of the paramagnetic signal and the number of accumulated reducing species, detected in dark titration experiments, increase as the water to titanium molar ratio, h, used in the synthesis diminishes. A 3.8% Ti(III) production efficiency was estimated for h = 6.5. Bidentate ethoxide coordination to the titanium dioxide surface and the replacement of surface hydroxylic groups by chloride ions is directly inferred by FTIR and EPR spectroscopies. Both findings are proposed to account for the room temperature detection of the Ti(III) species, and the higher electron storage capacity of the colloids prepared with lower h values.