Investigation of the interaction between a sulfonated azo dye (AO7) and a TiO2 surface

The adsorption of an azo dye, Acid Orange 7 (AO7), on a TiO2 surface was studied using FT–IR spectroscopy and adsorption isotherm parameters. The major FT–IR bands of the dye have been assigned in the range 1000–1900 cm−1. Within the AO7–TiO2 complex, the dye appears to exist in its hydrazone form. The interaction of AO7 with the TiO2 surface is strong, leading to a surface inner-sphere-type complex. The dye is linked to three TiIV surface metallic cations through two oxygen atoms from the sulfonate group and the oxygen atom of the carbonyl group of the hydrazone tautomer.