Synthesis of copper and zinc nanostructures by discharges in liquid nitrogen

The peculiar behaviour of zinc depending on whether it is used pure or alloyed in Cu63Zn37 wire electrodes leads either to nanosheets or to nanoparticles when it is processed by nanosecond pulsed discharges in liquid nitrogen. Using one electrode of copper and one electrode of zinc gives core-shell Cu@Zn nanoparticles but no alloy for the smallest nanoparticles (typically below 20 nm). Once nitrogen is evaporated, their oxidization in air produces Cu2O@ZnO nanoparticles. If both electrodes are made of Cu63Zn37, then the smallest nanoparticles are made of Cu and Zn and oxidized next in air to give Cu2O and ZnO nanoparticles. No alloy is formed either. Time-resolved optical emission spectroscopy gives clues on the origin of such behaviours, explaining why no alloy is formed when electrodes are made of different materials.