Synthesis of Cu@ZnO core-shell nanocomposite through digestive ripening of Cu and Zn nanoparticles

The synthesis of colloids of copper and zinc nanoparticles by solvated metal atom dispersion (SMAD) is described. The as-prepared colloids with a large size distribution of the particles are-transformed into colloidal nanoparticles of a narrow size distribution by the digestive ripening process which involves refluxing the colloid at or near the boiling point of the solvent in the presence of a passivating ligand. The copper nanoparticles of 2.1 +/- 0.3 nm and zinc nanoparticles of 3.9 +/- 0.3 nm diameters have thus been obtained. Digestive ripening of the as-prepared copper and zinc colloids together in the presence of a passivating agent gave Cu@ZnO core-shell nanoparticles, with an average diameter of 3.0 +/- 0.7 nm. Particles synthesized in this manner were characterized by UV-visible spectroscopy, high-resolution electron microscopy, energy-filtered electron microscopy, and powder X-ray diffraction methods which confirm the core-shell structure.