Synthesis of nickel and cobalt oxide nanoparticles by pulsed underwater spark discharges

Electrical discharges in liquids are considered an efficient and ecological technique of nanoparticle synthesis via controlled erosion of electrodes. Herein, we use spark discharges between Co-Co, Ni-Ni, Co-Ni, or Ni-Co electrodes immersed in distilled water to synthesize Co and/or Ni nanoparticles, as well as their oxides. When mixed electrodes are used (Co-Ni or Ni-Co), both Co and Ni nanoparticles are produced, and the major species is dictated by the nature of the anode pin. The characteristics of nanoparticles synthesized under varying conditions of pulse width (100 and 500ns) and voltage amplitude (5 and 20kV) are analyzed by transmission electron microscopy. Within the investigated discharge conditions, it is not possible to produce Co-Ni nanoalloys; however, core-shell nanoparticles are observed among the Ni and Co nanoparticles. Finally, the direct optical bandgaps of the nanomaterials are determined using UV-visible absorption spectroscopy.

Automated summary

Electrical discharges in liquids are considered an efficient method for nanoparticle synthesis through controlled electrode erosion. This study used spark discharges between various electrodes in distilled water to synthesize Co and Ni nanoparticles and their oxides. Analysis of the nanoparticles synthesized under different pulse width and voltage amplitude conditions revealed the inability to produce Co-Ni nanoalloys, but the presence of core-shell nanoparticles among Ni and Co nanoparticles.