Uncapped gold nanoparticles for the metallization of organic monolayers

Abstract

Deposition of the top-contact electrode to create large-area electrode | monolayer | electrode junctions represents a contemporary challenge to the integration of molecular electronic phenomena into device structures. Here, a top contact electrode is formed on top of an organic monolayer over a large area (cm2) by two simple, sequential self-assembly steps. Initial self-assembly of 4,4′-(1,4-phenylenebis(ethyne-2,1-diyl))dianiline onto gold-on-glass substrates gives high-quality monolayers. The exposed amine functionality is subsequently used to anchor uncapped gold nanoparticles deposited in a second self-assembly step. These uncapped gold nanoparticles are prepared by thermolysis of lipoic acid stabilized gold nanoclusters and contain gold oxide (≈9%) that provides stability in the absence of an organic capping ligand. This two-step procedure results in full coverage of the monolayer by the densely packed gold nanoparticles, which spontaneously condense to give a semi-continuous film. The electrical properties of these junctions are determined from I–V curves, revealing uniform electrical response and absence of metallic short-circuits or evidence of damage to the underlying molecular monolayer. These promising electrical characteristics suggest that the deposition of uncapped gold nanoparticles on suitably functionalized molecular monolayers provides a path for the fabrication of molecular electronic devices using simple methodologies.