Monodispersed CdSe and PbSe nanoparticles (NPs) as the building blocks could be applied to the allinorganic nanoparticle solar cells and quantum-dot based solar cells. In the present work, a low-cost preparation route to monodispersed CdSe NPs and PbSe NPs with the particle sizes less than their Bohr radii was present. CdSe NPs and PbSe NPs were synthesized with different preparation conditions, using non-toxic chemicals such as the soluble starch as the capping agent and sodium citrate as the chelating agent of metal ions in aqueous solutions. The effect of preparation conditions on the particle size (similar to 3-4 nm) of monodispersed cubic phase CdSe NPs, their optical absorption and photo-luminescent spectra were investigated by various measurements and discussed with Brus's effective mass model. Monodispersed cubic phase PbSe NPs with ca. 30-40 nm in size were also obtained, but the smaller sized (<10 nm) PbSe colloids could not be stabilized by this capping agent starch. Further modification need be done to prevent the smaller sized PbSe NPs from growing up. (C) 2012 Elsevier Ltd. All rights reserved.