One-dimensional wire-based hierarchies facilitate the complex and discretized transport of electrical and thermal energy, enabling such advanced structures as computer motherboards and composite thermal interfaces. Nanoscale miniaturization of the wire has become increasingly sophisticated in recent years with regards to synthesis; however, the ability to arrange and manufacture these small-scale materials to fully exploit their novel properties has been quickly outpaced. The purpose of this investigation is the establishment of a synthesis technique for a core/shell nanowire structure which can pass through this bottleneck via directed matrix assembly. A gold-nickel-gold nanowire structure was utilized as the core, synthesized via electrochemical deposition into an anodic aluminum oxide template; the nickel segment was chosen to act as a magnetic vehicle for assembly, while the surrounding gold tips were employed in the deposition of the shell structure. Tip-selective deposition of the shell was achieved by exposing the wires to one of various carboxylic acid structures, establishing a chemisorbed nickel-protective monolayer. Next, the protected wires were dispersed in an aqueous reaction vessel with excess sodium borohydride reducing agent. Dropwise addition of tin sulfate and sodium dodecyl sulfate solution to the vessel resulted in the formation of tin seeds which deposited along the gold tips of the nanowires; this deposition was observed qualitatively by monitoring the color of the reaction solution. After this seeding phase, excess tin solution was added to promote growth, resulting in a “dumbbell” shape nanowire with tin deposited on both gold tips; when arranged magnetically, these soldered tips will enable melting in the formation of a permanent joint. This work establishes an effective and scalable method for site-specific nanowire functionalization while simultaneously addressing miniaturization-associated assembly issues in its desired application.

Site-selective solder deposition on multi-segment nanowires for nanowire joining and bonding

256th National Meeting (2018)

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