Effect of poly(N-vinyl-pyrrolidone) on electrochemical production of Cu nanoparticles

Cu nanoparticles were synthesized via electrochemical deposition and the effect of the addition of poly(N-vinyl-pyrrolidone) (PVP) and pH on the properties of the nanoparticles was investigated. The Cu nanoparticles were prepared from an electrolyte containing copper acetate (pH 5.50) or copper sulfate (pH 4.14) by collecting the dispersed particles in the solution after electrochemical reduction. With the use of the acetate bath, formation of Cu₂O at -0.2 and -1.5 V vs. Ag/AgCl was confirmed. On the other hand, Cu₂O formation was not observed with the sulfate bath due to the lower pH, and the Cu nanoparticles could not be obtained at the potential of -1.5 V vs. Ag/AgCl. Surface enhanced Raman spectroscopy with plasmon sensors was used to investigate the transformations of PVP during electrolysis under the different conditions when Cu particles were and were not formed. For the dispersed nanoparticles in the electrolyte, it was observed that the C=O and C-N peaks of PVP also exhibited a red-shift. It was thus confirmed that PVP was coordinated to both the cathode electrode and dispersed nanoparticles in the electrolyte upon electrochemical reduction.