Ethylenediamine-Enhanced Oxidation Resistivity of a Copper Surface during Water-Based Copper Nanowire Synthesis

Copper nanowires (Cu NWs) are promising materials for transparent electrode applications. However, their growth mechanism during water-based synthesis remains unclear. The steric hindrance of a surfactant, which has been considered in previous studies, is insufficient to explain the suppression of Cu oxide formation during water-based synthesis. In this paper, we suggest that ethylenediamine (EDA, C2H4(NH2)2), which is commonly used as a structure-directing agent (SDA), may play an important role as an oxidation inhibitor in water-based synthesis of Cu NWs. High-resolution transmission electron microscopy (HR-TEM) analysis indicated that the Cu NWs grow from icosahedral seeds. Additionally, energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) suggested that EDA affects the oxidation state of the as-prepared Cu NW surface. Finally, density functional theory (DFT) calculations revealed that the adsorption of EDA effectively hinders the adsorption of oxidizing species and prevents the oxidation of the Cu seeds. This effect is attributed to a filling of the antibonding states and an increase in the electrostatic repulsion between the Cu seeds and the oxidizing species.