Large-Scale and Galvanic Replacement Free Synthesis of Cu@Ag Core–Shell Nanowires for Flexible Electronics

Abstract

Copper nanowires (CuNWs) are considered a promising alternative to indium tin oxide due to their cost-effectiveness as well as high conductivity and transparency. However, the practical applications of copper-based conductors are greatly limited due to their rapid oxidation in atmosphere. Herein, a facile adsorption and decomposition process is developed for galvanic replacement free and large-scale synthesis of highly stable Cu@Ag core–shell nanowires. First, Ag-amine complex ([Ag­(NH2R)2]+) as silver source adsorbs on CuNWs surface, and Cu@Ag-amine complex core–shell structure is formed. After that, Ag-amine complex is easily decomposed to pure Ag shell through a simple thermal annealing under air. By adjusting the concentration of Ag-aminein CuNWs solution, Cu@Ag core–shell nanowires with different thickness of silver shell can be easily obtained. The obtained core–shell nanowires exhibit high stability for at least 500 h at high temperature (140 °C) and high humidity (85 °C, 85% RH) due to the protection of Ag shell. More importantly, the conductivity and transparency of Cu@Ag nanowires-based conductors is similar to that of pure CuNWs. The large-scale and facile synthesis of Cu@Ag core–shell nanowires provides a new method to prepare stable metallic core–shell nanowires.

Nanowire Genome: A Magic Toolbox for 1D Nanostructures

“…Clearly, the galvanic reaction quickly took place between Ag + and Cu NWs, which resulted in Ag nanosheets deposited onto Cu NWs (Figure d) . Moreover, the galvanic replacement of Cu by Ag + could be suppressed by adding a high concentration of the reducing agent (such as ascorbic acid) . The resultant Cu–Ag NWs showed an increased shell thickness of 14 nm with less etching of the Cu core (Figure e).…”

Copper nanomaterials and assemblies for soft electronics

“…To date, several reasonable strategies have been suggested to address the stability issue of copper nanomaterials. One is to introduce antioxidant alloyed encapsulation layers made of Au, Ag, Pt, Ni on the surface of individual Cu nanomaterials [34,70,[139][140][141]. The second approach is to immerse Cu nanomaterials in polymeric matrices or between two airtight layers such as PDMS, PU, poly(vinyl alcohol) (PVA) to improve the antioxidation ability [82,142].…”

“…Nobel metals, such as Au, Ag and Pt, can form effective protection layers to prevent Cu from oxidation [140,146]. Ag is especially favored due to the lower cost in comparison to Au and Pt [34,70,141], although it might be oxidized with long time exposure to air or be eroded in a more reactive environment [5]. There are several ways to uniformly coat Cu nanomaterials with an Ag layer [140].…”

“…Other less oxidizing Ag salts, such as Ag-amine complexes, have been shown to effectively create the coreshell structure without inducing the galvanic replacement reaction. Ag-amine complexes adsorbed onto the Cu surface would be decomposed into pure Ag after annealing at 140°C for 5 min [34]. In addition, Ag can be directly electroplated to the CuNWs networks in a roll-toroll continuous way.…”

Cu@Ag core–shell nanoparticle with multiple morphologies: a simple surfactant‐free synthesis and finite element simulation

“…There is a new approach to enhance the oxidation stability of Cu NPs by the formation of a Cu core-Ag shell (Cu@Ag) structure. Recently, Cu@Ag particles were prepared using organic solvent [1,2], a combination of electro-spinning and chemical reduction [3], galvanic replacement-free [4], NaOH assisted [5], epitaxial growth [6], and chemical dealloying [7] methods. Although Cu@Ag NPs were also prepared by using galvanic exchange [8], they have not been obtained using a surfactant-free and protective gas-free in the process [9][10][11][12][13][14][15][16][17].…”