Synthesis of Cu fine particles via a solid–liquid reduction method using copper oxide

Copper fine particles were synthesized dispersant-free via a solid-liquid reduction method using copper oxide (CuO) and water as starting materials.Hydrazine monohydrate (NHHO) was used as a reducing agent and water as a dispersion medium, enabling the formation of Cu particles without generating harmful counterions or organic residues.Even under a high precursor concentration of 0.5 M, the addition of acetic acid and microwave heating promoted the reduction reaction, leading to the formation of fine and uniform Cu particles with an average diameter of 170 nm while suppressing oxidation and aggregation.Fourier-transform infrared spectroscopy analysis confirmed the absence of hazardous byproducts, although a small amount of acetohydrazide formed as a minor side product.Consequently, the obtained particles could be collected with a high yield (90%) simply by vacuum drying, without any washing process.This method significantly simplifies the Cu particle synthesis by eliminating washing and waste treatment steps, and is expected to serve as a low-cost, sustainable, and high-throughput manufacturing approach applicable to conductive inks and electronic materials.