High-throughput and waste-reducing synthesis of dispersant-free Cu nanoparticles via CuO reduction

The size of nanoparticles synthesized by the liquid phase reduction method depends on the concentration of metal ions. Thus, it is difficult to synthesize fine nanoparticles with high concentration. However, by using solid raw materials and by controlling both solubility and nucleation, the synthesis of nanoparticles at high concentrations can be realized. The instantaneous high degree of nucleation would not necessitate the addition of dispersants. Cu nanoparticles were synthesized by reduction with N 2 H 4 ·H 2 O using CuO as a raw material whose dissolution was promoted with the addition of CH 3 COOH. Varying concentrations of CH 3 COOH, N 2 H 4 ·H 2 O, and CuO were used to investigate their effects. The synthesized material was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cu nanoparticles (raw material concentration of 4 M) were synthesized by a 10 min reduction. This concentration is 20 times higher than that of conventional chemical reduction methods. At a raw material concentration of 4 M, Cu nanoparticles were synthesized with a high yield (99.69 %). The average particle size of the synthesized sample was 121.9 nm, half the size of nanoparticles synthesized at 1 M concentration. Furthermore, this process suppresses the generation of harmful waste liquids and does not require further cleaning. The rate-determining step of the reaction in the solid-liquid reaction field was the dissolution process of the raw material particle surface, and due to the instantaneous high nucleation rate, it is a Waste-Reducing synthesis method that does not require a dispersant. • Dispersant-free synthesis of 83.6 nm Cu nanoparticles was established. • Nanoparticles synthesized in a short time (10 min) and at a high concentration (4 M). • The synthetic method requires no cleaning process. • This study will contribute to the industrial application of nanoparticles. • This study will contribute to SDGs as a clean nanoparticle synthesis method.