Carbazole‐Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties

Abstract

As the field of molecular‐scale electronics matures and the prospect of devices incorporating molecular wires becomes more feasible, it is necessary to progress from the simple anchor groups used in fundamental conductance studies to more elaborate anchors designed with device stability in mind. This study presents a series of oligo(phenylene‐ethynylene) wires with one tetrapodal anchor and a phenyl or pyridyl head group. The new anchors are designed to bind strongly to gold surfaces without disrupting the conductance pathway of the wires. Conductive probe atomic force microscopy (cAFM) was used to determine the conductance of self‐assembled monolayers (SAMs) of the wires in Au–SAM–Pt and Au–SAM–graphene junctions, from which the conductance per molecule was derived. For tolane‐type wires, mean conductances per molecule of up to 10−4.37 G0 (Pt) and 10−3.78 G0 (graphene) were measured, despite limited electronic coupling to the Au electrode, demonstrating the potential of this approach. Computational studies of the surface binding geometry and transport properties rationalise and support the experimental results.

Hybrid Molecular-Junction Mapping Technique for Simultaneous Measurements of Single-Molecule Electronic Conductance and Its Corresponding Binding Geometry in a Tunneling Junction

“…Molecular electronics is an important branch of nanoscience and nanotechnology in researching single molecules for the development of a new generation of nanocircuits, wherein a comprehensive understanding of the electrical properties of a single molecule is a prerequisite. A number of different methods have been developed in the past decade to characterize single-molecule electronic conductance based on the techniques of scanning tunneling microscopy (STM), , conductive atomic force microscopy, , nanofabricated junctions, , and nanoparticle arrays. , The common strategy is to bridge a single molecule in a nanojunction between two metal electrodes and study the current passing though the molecule while applying a voltage. On the basis of whether the nanogap distance is actively changed during the course of measurements, these methods can be categorized into two types, break-junction and fixed-junction techniques…”