Facile and green synthesis of stable aqueous dispersions of narrowly distributed copper nanoparticles

Copper nanoparticles (Cu NPs) without aggregation and oxidation in solvents are highly desired in the fields of antibiosis, electronics, lubrication, heat transfer, etc. Here, we facilely prepared ~3 nm Cu NPs with narrow size distribution in water at a low temperature of 45 °C under ambient atmosphere, using L-ascorbic acid and cetyltrimethylammonium bromide (CTAB) as a reductant and a capping agent, respectively. The size and shape of the Cu NPs can be controlled by changing the reaction time, molar ratio of L-ascorbic acid to copper chloride, and concentration of CTAB. In addition, the Cu NP aqueous dispersions showed good stability after one month of storage under ambient atmosphere because of their great resistance against aggregation and oxidation. This study opens a facile and green way to prepare stable Cu NP aqueous dispersions for their practical applications.