In this work PbS and PbS/CdS core-shell QDs, were synthesized via a simple UV-assisted approach. Prepared QDs were characterized by means of XRD, FTIR, SEM, TEM, UV-vis and PL analysis. Synthesized QDs indicated cubic phase with a spherical morphology and the mean particle size was obtained about 4 nm. PbS QDs showed an emission with a peak at about 850 not which it was tunable with the UV-illumination time. CdS shell growth resulted in the shift of the XRD pattern peaks to the higher angles, blue shift of the PL peak and considerably enhancement of the PL intensity. PbS QDs indicated strong photocatalyst activity for Methylene blue (MB) photo-degradation which it was increased significantly after CdS shell growth.