Solvent-based ambient condition sol (SACS) process with N-methylpyrrolidone (NMP) as the solvent, is a post-treatment technique utilized to modify polymorphic titania nanoparticles prepared by a water-based ambient condition sol process. All samples were characterized by X-ray diffraction, N-2 physisorption, CHNS analysis, UV-vis absorption spectrophotometry, FT-IR, and TEM and compared to a commercial reference titania product, Degussa P25. Photocatalytic activity, evaluated by the degradation of methyl orange under ultraviolet (UV) and visible light (VL), showed that SACS, with NMP as the solvent, is a powerful treatment to enhance TiO2 photocatalytic activity by minimizing lattice hydroxyls and doping titania samples with nitrogen.