Size-controlled chemical reduction synthesis of nanostructured Cu was studied in the presence of a single modifier such as polyethylene glycols, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or a mixture of two different types of modifiers. The Cu nanoparticles were characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction and Fourier transform infrared spectroscopy. The average particle size and particle size distribution of the nanostructured Cu depend upon the type of modifiers and the modifier effect follows the order: PEG-2000 > SDBS > PEG-600 > SDS > PEG-6000. The experimental results indicate that due to the existence of a synergistic action, a mixture of two types of modifiers has a significant effect on the particle size and the size distribution of Cu nanoparticles. (c) 2006 Elsevier B.V. All rights reserved.