High surface area TiO2 nanoparticles: impact of carboxylporphyrin sensitizers in the photocatalytic activity

TiO2 nanoparticles in anatase-brookite phases were synthesized, modified with (5,10,15,20-tetrakis(carboxyphenyl)porphyrinate)manganese(III) - [Mn-III(T4CPP)] and (5,10,15,20-tetrakis(carboxyphenyl))porphyrin H(2)T4CPP, and their photocatalytic activities were evaluated by the degradation of methylene blue dye. The prepared materials were characterized by XRD, Raman, gas adsorption, HRTEM-EDS, EELS, fluorescence spectroscopy, and XPS. These techniques provide direct evidence that crystalline TiO2 nanoparticles with high specific surface area were prepared from aqueous TiCl4 precursor and had their surfaces modified by porphyrins. Differences in textural properties between TiO2 samples modified with H(2)T4CPP and [Mn-III(T4CPP)] evidenced the role of the Mn-III and carboxyl groups in anchoring these molecules on the TiO2 surface. This molecular configuration was important for understanding the photocatalytic performance associated with the charge transfer between TiO2 and the sensitizers.