Synthesis of Copper(II) Oxide Nanoparticles by Anion-Exchange Resin-Assisted Precipitation and Production of Their Stable Hydrosols

Copper(II) oxide nanoparticles are promising materials for use in catalysis, biomedicine, and photovoltaics. They can also be used to prepare nanocomposites and hybrid nanoparticles. This paper presents a new one-pot method for preparing CuO nanoparticles without long-term washing and heat treatment. The proposed anion-exchange precipitation is a facile and fast process, and is easily reproducible under standard laboratory conditions. Anion-exchange precipitation of copper from copper chloride or copper sulfate solutions in the presence of the polysaccharide dextran-40 produces well-crystallized hydroxychloride Cu₂Cl(OH)₃ and hydroxysulfate Cu₄(SO₄)(OH)_6, respectively; from copper nitrate solutions, a poorly crystallized Cu(OH)₂ phase is formed. In the absence of polysaccharides, the product is copper oxide nanoparticles regardless of the anion in the precursor salt. The thus-prepared materials were used to prepare hydrosols. The hydrosols had high aggregation and sedimentation stability over a wide pH range (from 5 to 11) as shown by dynamic and electrophoretic light scattering. They were stable for more than three months at a concentration of 2 g/L (the average hydrodynamic diameter of the particles was 245 nm; the average ζ-potential was –31.1 mV). The optical and electronic properties of the prepared hydrosols imply that they could be of interest for use in photocatalysis and in optoelectronic devices.