Spontaneous Assembly of Extremely Long, Horizontally-Aligned, Conductive Gold Micro-Wires in a Langmuir Monolayer Template

"Bottom-up" technologies are based upon the premise that organized systems - from the nano-scale up to the macro-scale - can be assembled spontaneously from basic building blocks in solution. We demonstrate a simple strategy for the generation of extremely long (up to several centimeters), horizontally-aligned gold micro-wires, produced through a surfactant monolayer template deposited from gold thiocyanate [Au(SCN)₄^-] aqueous solution. Specifically, we show that the surfactant, octyl-maleimide (OM), spontaneously forms oriented micro-wires at the air/water interface, which constitute a template for deposition of metallic gold through binding and crystallization of the soluble gold complex. The Au micro-wires can be subsequently transferred onto solid substrates, and following plasma treatment and gold enhancement exhibit excellent conductivity even at electrode spacings of several centimeters. Importantly, the micro-wire alignment determines the direction of electrical current, demonstrating that long-range ordering of the micro-wires can be accomplished, significantly affecting the physical properties of the system. The new approach is simple, robust, and can be readily exploited for bottom-up fabrication of micro-wire assemblies and transparent conductive electrodes. A new "bottom-up" method for fabricating long, aligned Au micro-wires is described. The approach is based upon a single-step reaction between soluble Au-thiocyanate and surfactant monolayer "template" assembled at the air/water interface. Films comprising the aligned Au micro-wires can be transferred onto solid substrates and exhibit excellent optical transparency and electrical conductivity.