Solution-Processable Oxidation-Resistant Copper Nanowires Decorated with Alkyl Ligands

Alkyl ligands with an amine or thiol headgroup have been chosen to investigate their effectiveness in preventing copper nanowire (Cu NW) oxidation in hydrothermal and hygrothermal environments. Ligand desorption has been found to be the key reason for Cu NWs to oxidize in a wet environment. Alkylamines interact with Cu NWs through weak coordination bonding, which would desorb easily, rendering Cu NWs prone to oxidation. Adding excess alkylamines in the aqueous solution can suppress the Cu NW oxidation, and keep the Cu NWs oxidation-free upon solution processing and long-term storage. In contrast, alkylthiols can strongly bind on Cu NW surfaces through thiolate bonding, which provides better oxidation protection than alkylamines even in hydrothermal and hygrothermal environments. Furthermore, it has been found that for the alkyl chains containing 12 carbons or longer, the alkyl chain length would have little effect on the oxidation-resistant properties of Cu NWs when the ligands are strongly bound to Cu NW surfaces. In addition to oxidation resistance, a shorter alkyl chain length is found to favor current transport between Cu NWs for potential applications in transparent flexible electronics and autonomous vehicles.