Green synthesis of Cu2O/Cu nanoparticles and conversion to Cu microparticles in one-bath reaction method for improved electrical conductivity

Sandra Sampaio and Julio C Viana

Abstract

This work aims at investigating the conversion of Cu₂O/Cu nanoparticles, prepared by green synthesis using artichoke extract, with ascorbic acid (AA) in one-bath process: a totally green method for production of pure Cu particles. Different pH values of the solution were studied to assess the conversion to Cu phase particles. It was found that by using the optimum synthesis conditions for the production of Cu₂O/Cu nanoparticles and adding at the end of the synthesis AA, the conversion of Cu₂O phase to pure Cu phase was possible when the pH of the solution was 8 or 10, but not when it was 12. The size of particles increased from nano to micron-sized after adding AA and multi-shaped particles with spherical, triangular, cubical and rod like shapes were formed, depending upon the pH of the synthesis solution. The electrical resistivity of the obtained pure Cu microparticles was studied after low-temperature sintering at different times and after preparing compact powder discs. After sintering for 30 min at 180 °C, discs showed resistivity of 2.9 × 10^–3 Ωcm and after sintering for 60 min at 180 °C the resistivity lowered to 5.1 × 10^–4 Ωcm. It can be concluded that the low resistivity of powder discs mainly depended on the size of Cu particles and sintering time, when using a fixed sintering temperature. The present synthesis of pure Cu phase microparticles is simple, convenient, environmentally friendly, cost-effective, it does not use inert gases, it is performed in aqueous media and the produced Cu particles are suitable for low electrical resistivity applications.