With regard to the recent research on Ag–Cu ink and also for conductive pattern by the ink-jet printing technique, Woo et al. In our earlier studies, we demonstrated that the similar ink made from silver colloids was capable of directly writing for conductive lines on the substrate by an ink-jet printer or a plotter. Moreover, the colloids can be further purified and concentrated to be an ink. dextrose, is also capable of producing silver–copper bimetallic nanoparticles. Yet, in the presence of silver, we will demonstrate that a mild reductant, i.e. Strong reducing agents, such as hydrazine, sodium borohydride, and sodium hypophosphite were often used to synthesize copper nanoparticles. During the process, the pH of the solution was adjusted by NaOH and urea, and the particle's size was controlled by polyvinyl pyrrolidone (PVP). In terms of the standard chemical potentials of these two metals listed in Table 1, silver has a much larger chemical potential than copper, thus silver particles as the core were firstly prepared in the colloids and followed by the addition of a copper precursor to obtain the final silver–copper particles.
In this work, silver–copper particles were prepared via chemical reduction in a two-stage process. Besides, they did not discuss whether the core–shell structure would be still stable upon heating, on account of the inter-diffusion of silver and copper. But unfortunately, in both of the above systems the metallic contents of particles were based on the precursor ratio rather than by carrying out the quantitative analysis of the final products. Normally, for a chemically potential reason, the weak reducing agent may not be able to convert all ions into particles, thus the real ratio may deviate from the original calculation. used a microwave-assisted method to produce silver-core copper-shell nanoparticles by alcohol reduction. used commercial copper powder and silver nitrate as precursors with the addition of sodium potassium tartrate as a reducing agent to synthesize copper-core silver-shell structure particles Nakamura et al. The alternative approaches of using reductant with a weaker reducing ability revealed in the references such as those of Xu et al. Hydrazine hydrate as known has a powerful reducing ability but has great toxicity, so this case in serious is not an appropriate route to obtain Ag–Cu colloids.
prepared the copper–silver core–shell nanoparticles by first synthesizing the copper colloids by hydrazine hydrate as a reductant in the presence of polyacrylic acid sodium salt as a polymeric stabilizer, and then adding silver salt to chemically substitute copper on the surface of the particle to form a core–shell structure. Others had tried to synthesize these particles by chemical methods. Some researchers had tried to incorporate these two elements into a film by processes such as sputtering, ion implantation or electrical plating. Hence nanoparticles of copper incorporated with silver in the form of a core–shell structure or a composite is expected to be a potentially conductive material in terms of issues of both cost and utility. However, the main obstacle for using copper nanoparticles is their spontaneous oxidation at ambient conditions. Recently, copper nanoparticles have been tried as a low-cost replacement for silver and gold nanoparticles which are currently used in the conductive interface materials. Various techniques have been used to prepare binary particles containing palladium (Pd) for their strongly catalytic properties, Au–Ag bimetallic particles for their unique optical behavior, and Ag–Cu particles for their electrical properties. Nanoparticles of several elements including gold, palladium, silver, ,, and copper, have been well-studied due to their potential applications as catalysts and conducting materials in the optoelectronic or semiconductor fields.īimetallic materials generally show distinct properties from the corresponding monometallic materials. Metallic nanoparticles have been widely investigated in recent years because they possess interesting properties that differ significantly from those of bulk materials.