The purposes of this research were to study the effects of two modified photocatalysts, Nafion-coated TiO2 and fluorinated TiO2, and photocatalytic degradation of Victoria Blue R in aqueous solution. Photocatalytic degradation of Victoria Blue R was accelerated by the modified photocatalysts. Bulk and surface characterizations of the resulting powders were carried out. Attachment of the anions to the TiO2 surface using the Nafion-coated-TiO2 possibly results in increased adsorption of the cationic dye, and the degradation rate is larger for the cationic dye. It was found that Victoria Blue R on the two illuminated TiO2 surfaces underwent very different changes. To obtain a better understanding on the mechanistic details of this modified-TiO2-assisted photodegradation of the Victoria Blue R dye with UV irradiation, a large number of intermediates of the process were separated, identified, and characterized by a high-performance liquid chtomatography-mass spectrometry technique. Several probable photodegradation pathways were proposed and discussed. (C) 2009 Elsevier B.V. All rights reserved.