Reversible Formation of Molecular Junctions in 2D Nanoparticle Arrays

Abstract

ual junctions into functional electronic circuits remains a demanding task, requiring innovative approaches in fabrication philosophy and circuit structure. [12,13] We show here that an approach combining the self-assembly [14] and microcontact printing [15] of ligand-protected metallic nanoparticles, followed by an in situ ligand-exchange reaction, [16] allows the preparation of stable 2D networks of molecular junctions. [17] A significant decrease in resistance (up to three orders of magnitude) after the exchange of alkanethiol ligands with conjugated, double-ended organic wires (thiolated oligo(phenylene ethynylene), OPE) confirms a proper interlinking of neighboring nanoparticles. We also demonstrate that the formation of the molecular junctions is reversible, making nanoparticle networks a promising platform for the development of molecular electronic circuits. The flexibility of this approach lets us envisage the realization of more complex networks, for instance, by intermixing ensembles of bimodal nanoparticles [18] of different materials. Both experimental and theoretical evidence shows that the electronic properties of molecular junctions are not only dictated by the molecules contacted but also depend on the anchoring groups and the electrodes forming the junction. [3,11] The use of nanometer-sized metallic colloids as electrodes appears, therefore, as an elegant solution to build molecular junctions with well-defined geometry and electronic properties. Recent results on colloid dimers interlinked by a conjugated molecule demonstrate the validity of this approach. [19] The demonstration here of the fabrication of reversible 2D networks of hybrid metallic colloid organic-molecule junctions opens new possibilities for the realization of molecular circuits.