Nitrogen-doped TiO2 nanoparticles (N-TiO2 NPs) with anatase phase were synthesized by sol gel method using a single precursor containing titanium (IV) terbutoxide, glacial acetic acid, sodium dodecyl sulphate, ammonia, and urea. X-ray diffraction (XRD) reveals the nanocrystalline nature with anatase phase of all the samples. The particle size of all samples was found in the range of 5-12 nm using transmission electron microscopy (TEM). UV-visible absorption measurements examined that the optical band gap of the doped samples decrease with increase in dopant concentration from 0.0 to 7.0 mol%. Field-emission scanning electron microscopy (FESEM) with energy dispersive atomic X-ray (EDAX) spectroscopy was employed to analyse the morphology and chemical composition of these N-TiO2 NPs. The photocatalytic activity of bare/doped TiO2 samples was demonstrated for the degradation of Rhodamine B (RhB) dye tinder direct sunlight irradiation. The photocatalytic degradation was monitored by measuring the kinetic parameters based on UV-visible spectroscopy as well as the chemical oxygen demand (COD) during the course of the reaction. The effect of dye concentration and pH of the solution on the photocatalytic degradation reaction in the presence of colloidal bare/doped TiO2 were also studied. The N-TiO2 catalyst, with a nitrogen concentration of 7.0 mol%, showed the highest activity for photocatalytic mineralization of dye at acidic or alkaline medium than neutral condition under solar light irradiation directly. (C) 2016 Elsevier B.V. All rights reserved.