Abstract. This work is focused on improvement on the photo-catalytic activity of a N-doped TiO2 (reference sample) by its grinding in solvent. Grinding the reference sample in solvent was performed by using a planetary mill at 200 rpm and 15 min grinding time with one of various solvents such as ethanol, ethyl acetate dehydrated (EAD), hexane and water. The ground samples were dried at 80 8…