Ultrathin Epitaxial Cu@Au Core–Shell Nanowires for Stable Transparent Conductors

Abstract

Copper nanowire networks are considered a promising alternative to indium tin oxide as transparent conductors. The fast degradation of copper in ambient conditions, however, largely overshadows their practical applications. Here, we develop the synthesis of ultrathin Cu@Au core-shell nanowires using trioctylphosphine as a strong binding ligand to prevent galvanic replacement reactions. The epitaxial overgrowth of a gold shell with a few atomic layers on the surface of copper nanowires can greatly enhance their resistance to heat (80 °C), humidity (80%) and air for at least 700 h, while their optical and electrical performance remained similar to the original high-performance copper (e.g., sheet resistance 35 Ω sq at transmittance of ∼89% with a haze factor <3%). The precise engineering of core-shell nanostructures demonstrated in this study offers huge potential to further explore the applications of copper nanowires in flexible and stretchable electronic and optoelectronic devices.

Printing Conductive Nanomaterials for Flexible and Stretchable Electronics: A Review of Materials, Processes, and Applications

“…To reduce the corrosion/oxidation of CuNWs in air, a passivation layer of carbon and metal (e.g., Ni, Ag, Au, and Pt) has been introduced during the CuNW synthesis process …”

Ligand‐Guided Growth of Alloyed Shells on Intermetallic Seeds as a Route toward Multimetallic Nanocatalysts with Shape‐Control

“…The selection of capping agents has been driven largely by empirical trends observed from the syntheses of monometallic NPs but translating this insight to multimetallic systems has been challenging on account of each compositional variant having different surface‐adsorbate interactions potentially. Moreover, capping agents can have secondary effects during nanoparticle syntheses ( e. g., changing the coordination environment of metal precursors) that become less predictable in multimetallic NP syntheses . Thus, understanding the mechanisms that govern the formation of shape‐controlled multimetallic NPs and controlling them through synthesis are important, especially for the field of nanocatalysis …”

Nanowire Genome: A Magic Toolbox for 1D Nanostructures

“…The phosphine ligand in TOP played important roles in reducing both the reduction potential and the reduction rate of the gold precursor, which shifted the growth mechanism into a galvanic‐replacement‐free pathway. The optical and electrical performance of the TCFs fabricated by Cu–Au NWs remained similar to those of the original Cu NWs (a sheet resistance of 35 Ω sq −1 at a transmittance of ≈89% with a haze factor <3%) …”

“…By replacing AgNO 3 with HAuCl 4 or K 2 PtCl 6 in water, this versatile synthetic strategy could be extended to the formation of Cu–Au (Figure g) and Cu–Pt core–shell NWs or NTs, respectively . With a similar strategy, Yang and his co‐workers adopted trioctylphosphine (TOP) as a strong binding ligand to prevent the galvanic replacement between Au(III) and Cu, which resulted in a gold shell with a few atomic layers (1–2 nm) on the surface of Cu NWs (Figure h) . The phosphine ligand in TOP played important roles in reducing both the reduction potential and the reduction rate of the gold precursor, which shifted the growth mechanism into a galvanic‐replacement‐free pathway.…”