The synthesis and spectroscopic characterizations of size-controlled Cu and Cu2O nanoparticles forming self-assembled 2D superlattices with hexagonal packing are described. The scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) were used to characterize the octanethiol-protected copper nanoparticles. Analysis of XPS confirms the formation of oxidized copper nanoparticles. Conductivity of copper metal film (0.1 mm) on the Si wafer can be improved simply by thermal annealing of copper monolayer protected clusters (MPCs) film (4.8 +/- 0.5 x 10(2) mu Omega cm) under air at 300 degrees C for 1 h, and then for another 5 h under a protective atmosphere of 90% N-2-10% H-2. (c) 2008 Elsevier B. V. All rights reserved.