Here, we report on microemulsion synthesis of nitrogen (N) doped TiO2 quantum dots (QDs) with improved visible-light response. XRD, FTIR, XPS, EDX and Raman spectroscopy confirms that N was doped successfully in TiO2 lattice. SEM and TEM study confirms spherical morphology of N-doped TiO2 QDs. N-doped TiO2 sample exhibit a narrower band gap and stronger visible light absorption as compared to pure TiO2. The assistance of the N enhances the photocatalytic activity in the visible light region by promoting the separation of the photo generated electrons and holes to accelerate the transmission of photocurrent carrier. Photocatalytic activity study evaluated for the degradation of acifluorfen herbicide under visible-light irradiation, demonstrated that N-doped TiO2 sample is more active than pure and commercial TiO2. The high visible-light photocatalytic activity is attributed to the anatase crystalline phase, small crystallite size, strong visible light absorption capacity and superior electron-hole charge carrier’s separation efficiency. The photoluminescence (PL) study was employed to test hydroxyl (•OH) radicals, which show that N-doped TiO2 helps to produce •OH radicals and favors to enhance its photocatalytic activity. N doped TiO2 quantum dots prepared in this work exhibit better photocatalytic activity and hence having a potential to use as a photocatalyst for the degradation of harmful organic chemicals, dyes and drugs coming out from industries and will help to keep environment clean and safe. Copyright © 2016 VBRI Press.