Galvanic preparation of nano-Cu@Ag from reverse micelles for conductive inks

Abstract

A straightforward method for synthesizing copper-silver core-shell (Cu@Ag) nanoparticles (NPs) is presented, utilizing reverse micelles (RMs) and a two-step galvanic reaction to produce highly stable conductive materials. Para-n-dodecylbenzene sulfonic acid was employed as a functional surfactant, enabling the formation of reverse micelles in toluene by neutralizing Cu(II) and Ag(I) oxides, thus providing a controlled nano-reactor environment. During co-reduction with sodium borohydride (NaBH₄), the simultaneous reduction of Cu(II) and Ag(I) yielded a bimetallic Cu-Ag NP mixture rather than the intended Cu@Ag core-shell configuration. In contrast, the two-step approach successfully produced Cu@Ag core-shell NPs, achieved by first forming Cu NPs followed by Ag deposition via galvanic replacement.

The synthesized Cu@Ag NPs exhibit low electrical resistivity comparable to pure Cu post-sintering. Scanning electron microscopy (SEM) and resistivity assessments further demonstrated effective particle sintering and percolation, confirming their capability to establish stable conductive pathways below 200 °C.