**Juan D. Cohen, Germán Alberto Sierra-Gallego and Jorge I. Tobón**

**Abstract:** Photocatalytic activity of Portland cement pastes blended with nanoparticles of titanium oxynitride (TiO2í*x*N*y*) was studied. Samples with different percentages of TiO2í*x*N*y* (0.0%, 0.5%, 1%, 3%) and TiO2 (1%, 3%) were evaluated in order to study their self-cleaning properties. The presence of nitrogen in the tetragonal structure of TiO2 was evidenced by X-ray diffraction (XRD) as a shift of the peaks in the 2ș axis. The samples were prepared with a water/cement ratio of 0.5 and a concentration of Rhodamine B of 0.5 g/L. After 65 h of curing time, the samples were irradiated with UV lamps to evaluate the reduction of the pigment. The color analysis was carried out using a Spectrometer UV/Vis measuring the coordinates CIE (Commission Internationale de l'Eclairage) *L*\*, *a*\*, *b*\*, and with special attention to the reddish tones (Rhodamine B color) which correspond to *a*\* values greater than zero. Additionally, samples with 0.5%, 1%, 3% of TiO2í*x*N*y* and 1%, 3% of TiO2 were evaluated under visible light with the purpose of determining the Rhodamine B abatement to wavelengths greater than 400 nm. The results have shown a similar behavior for both additions under UV light irradiation, with 3% being the addition with the highest photocatalytic efficiency obtained. However, TiO2í*x*N*y* showed activity under irradiation with visible light, unlike TiO2, which can only be activated under UV light.

Reprinted from *Coatings*. Cite as: Cohen, J.D.; Sierra-Gallego, G.; Tobón, J.I. Evaluation of Photocatalytic Properties of Portland Cement Blended with Titanium Oxynitride (TiO2í*x*N*y*) Nanoparticles. *Coatings* **2015**, *5*, 465-476.
