Environmentally friendly synthesis and formation mechanism of copper nanowires with controlled aspect ratios from aqueous solution with ascorbic acid

Copper (Cu) nanowires (NWs) were synthesized by the reduction of Cu-chloride complexes using ascorbic acid (AA) as a mild reducing agent, polyvinylpyrrolidone (PVP) as a capping agent, and NaCl as an additive under atmospheric conditions at 80 °C. Surface analyses revealed that both Cl ions and PVP were required for the synthesis of Cu NWs. Together, the Cl ions and PVP capped the Cu (1 0 0) side faces, leading to anisotropic growth of Cu NWs along the [1 1 0] direction. To obtain Cu NWs with high aspect ratios, we evaluated the synthetic mechanism under different reaction conditions. The results indicated that the presence of dissolved oxygen (DO) was the dominant factor affecting aspect ratio of Cu NWs. DO and hydrogen peroxide resulting from the reaction between DO and AA oxidized the surfaces of the growing Cu NWs, preventing further growth. Decreasing the amount of oxides on the Cu NW surfaces and removing DO increased the aspect ratios of the Cu NWs. The results indicated that DO should be removed from the reaction solution to obtain high-aspect-ratio Cu NWs in aqueous solutions containing AA.