Nanomaterials are being applied in more and more fields within engineering and technology. One of the nanomaterial’s key benefits is that their properties differ from the bulk material of the same composition. The properties of nanoparticles, for example, can be easily altered by varying their size, shape, and chemical environment.
Copper nanoparticles (Cu-NPs) with sizes smaller than 31 nm were prepared by wet chemical reduction using copper sulfate solution, hydrazine, and a mixture of allylamine (AAm) and polyallylamine (PAAm) as stabilizing agents. The use of the AAm/PAAm mixture leads to the formation of Cu and CuO nanoparticles. The resulting nanostructures were characterized by XRD, TGA, and TEM. The average particle diameters were determined by the Debye-Scherrer equation. Analysis by TGA, TEM, GS-MS, and 1HNMR reveals that synthesized NPs with AAm presented a coating with similar characteristics to NPs with PAAm, suggesting that AAm underwent polymerization during the synthesis. The synthesis of NPs using AAm could be an excellent alternative to reduce production costs.
Nanoparticles have received much attention in the scientific community and industry due to their unique physicochemical properties attributed to their relatively small size and high surface-area-to-volume ratio. In particular, copper nanoparticles (Cu-NPs) are of great interest because of their distinctive catalytic, optical, thermal, magnetic, anti-microbial, electronic, and electrical conducting properties. They present a wide range of potential applications in nanotechnology, including catalysts, additives for lubricants, heat transfer nanofluids, manufacture of electronic and optical devices, conductive inks, materials for solar energy conversion, biosensors, anti-biofouling agents, and cancer cell treatments. Moreover, copper nanoparticles can be a promising candidate to replace expensive noble metal nanoparticles such as silver and gold.
The synthesis of high-performance copper nanostructures strongly depends on the method used, where a reasonable control over particle size, shape, and spatial distribution is of critical importance. Thus, the development of new low-cost and straightforward processes to enhance Cu-NPs properties is required in order to scale-up the production of Cu-NPs at an industrial level.
Among the methods employed for the preparation of nanosized copper particles, the chemical reduction of copper(II) salts in an aqueous solution are one of the most versatile routes because of its simplicity, solubility, inexpensive reagents, and short reaction times, allowing at the same time the possibility of controlling of Cu-NPs sizes and shapes. However, metallic copper is highly unstable as it can be easily oxidized under atmospheric conditions, generating Cu2O and/or CuO on the surface during and after preparation. Therefore, nanoparticles must be protected, adding surface-protecting stabilizing agents such as organic ligands, surfactants, or polymers that can form complexes with copper ions.
Copper nanoparticles can be manufactured using numerous methods. The electrodeposition method is considered by many as one of the most suitable and easiest. The electrolyte used for the process is an acidified aqueous solution of copper sulfate with specific additives.
Applications
The key applications of copper nanoparticles are listed below:
- Acts as an anti-biotic, anti-microbial, and anti-fungal agent when added to plastics, coatings, and textiles
- Copper diet supplements with efficient delivery characteristics
- High strength metals and alloys
- EMI shielding
- Heat sinks and highly thermal conductive materials
- The efficient catalyst for chemical reactions and for the synthesis of methanol and glycol
- As sintering additives and capacitor materials
- Conductive inks and pastes containing Cu nanoparticles can be used as a substitute for very expensive noble metals used in printed electronics, displays, and transmissive conductive thin film applications
- Superficial conductive coating processing of metal and non-ferrous metal
- Production of MLCC internal electrode and other electronic components in the electronic slurry for the miniaturization of microelectronic devices;
- As nanometal lubricant additives