Effect of Sodium Hydroxide on the Particle Diameter of Copper Nanoparticles Synthesized by Liquid Phase Method Using Sodium Borohydride

Abstract

The effect of NaOH on the synthesis of Cu nanoparticles was evaluated. For synthesis, the reducing agent used was NaBH₄, the polymer protective agent was PVP, and the source of copper was Cu(OH)₂. The highest generation of hydrogen as a reaction by-product occurred after 59 min of reaction when NaOH was added; this was an increase from 43 min for the case where NaOH was not added. The proportion of the volume of Cu nanoparticles 20 nm or more in diameter to the total volume changed from 0.7% to 73.9%.

These results are believed to be due to the fact that the pH increased when Cu(OH)₂ was stabilized, so that the degree of supersaturation at the time of nucleation declined and a small amount of nuclei was generated. In addition, because the retention time of NaBH₄ as a parent agent became longer, it is thought that copper was precipitated around the large particles grown from the plurality of the nuclei; the particles subsequently became enlarged. From this, the possibility of pH adjustment using NaOH was demonstrated, and as a result, the diameter of the Cu nanoparticles could be intentionally controlled.