Hidemichi Fujiwara

Formation of Rod Shape Secondary Aggregation of Copper Nanoparticles in Aqueous Solution of Sodium Borohydride with Stabilizing Polymer

Morphological variations of copper nanoparticles synthesized by the reduction of copper acetate with sodium borohydride in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) have been investigated. The results indicate that the specific rod shape secondary aggregation of copper nanoparticles are formed in the case that the oxygen is dissolved in the reacting solutions. Furthermore, it is also demonstrated that the copper nanorods with the aspect ratio of 2 - 20 and the average short axis length of 5 nm are synthesized in the weak oxidizing ambiance with a medium amount of PVP. The anomalous variations of copper nanoparticles are explained by the alignments of precursor copper ions and their reducing rates, which are modified by the density of resolved oxygen and the amount of PVP.