Enhanced oxidation-resistant Cu-Ni core-shell nanowires: Controllable one-pot synthesis and solution processing to transparent flexible heaters

Coating nickel onto copper nanowires (Cu NWs) by one-pot synthesis is an efficient approach to improving the oxidation resistance of the nanowires. Because Ni is much less conductive than Cu, it is of great importance to understand the relationship between the thickness of the Ni coating layer and the properties of NWs. Here we demonstrate one-pot synthesis of Cu-Ni core-shell NWs with a tunable Ni thickness by simply varying the Cu and Ni mole ratio in the precursor. We have observed that an increase in Ni thickness decreases the aspect ratio, surface smoothness and network conductivity of the resulting NWs. However, Cu-Ni NWs with a thicker Ni layer display higher oxidation temperature. The optimal Cu-Ni NWs, which were prepared using a Cu²⁺/Ni²⁺ molar ratio of 1/1, have a Ni-layer thickness of about 10 nm and the onset oxidation temperature of 270 °C. The derived transparent conductive films present a transmittance of 76% and a sheet resistance of 300 Ω sq^-1. The flexible heater constructed from such high quality Cu-Ni NW films demonstrates effective performance in heating and defrosting.