Stabilization of copper nanoparticles prepared by reduction from solutions of poly(acrylic acid) complexes with Cu2+ ions and poly(ethylene glycols)

Copper sols are prepared via the reduction of copper ions with hydrazine borane in dilute aqueous solutions of mixtures of the PAA-Cu²⁺ complex and poly(ethylene glycols) of various molecular masses at PEG: PAA = 0.25 base-mol/base-mol and PAA: Cu²⁺ = 10 base-mol/mol in the pH range 4.0–7.0. The stability of sols against oxidation (dissolution) or aggregation (enlargement) of metal nanoparticles is much higher than that of sols prepared in the absence of PEG. With an increase in the initial pH or a decrease in the molecular mass of PEG, the formed copper nanoparticles are much larger (no less than 20 nm in diameter) than copper nanoparticles occurring in the sol prepared in a solution of the PAA double complex with Cu²⁺ ions and high-molecular-mass PEG at a low initial pH (3–10 nm in diameter). Copper nanoparticles in sols prepared in solutions of complexes based on the high-molecular-mass PEG do not aggregate during exposure, thereby indicating the high stability of polymer screens on their surfaces.