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.
Highlights
Anchor groups fulfil a critical role in materials designed to assemble on surfaces.[1]
To probe the nature of the electronic coupling between the tetrapods and the gold surface, we conducted charge transport simulations in which BB was compared to a simple, unfunctionalised OPE2, which was held in the same geometry as the OPE2 backbone of BB when relaxed in a junction configuration (Figures 3a and 3b)
Our Conductive probe atomic force microscopy (cAFM) method results in slightly lower conductances for both SpP and SmP; a comparable deviation between cAFM and MCBJ has been observed previously.[21]. Such discrepancies may Tetrapodal anchor units for gold surfaces based on thiomethoxysubstituted carbazole have been developed
Summary
Anchor groups fulfil a critical role in materials designed to assemble on surfaces.[1]. Stronger molecule-probe interactions are possible in the former case as π-π overlap may occur between the head groups and graphene, which could enhance electronic coupling and increase conductance.
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