Blog

Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors

The effectiveness of five different anchor groups for non‐covalent interfacing to graphene electrodes are compared in this recent paper in Advanced Functional Materials. A family of six molecules is tested in single‐molecule junctions: five consist of the same porphyrin core with different anchor groups, and the sixth is a reference molecule without anchor groups. The junction formation probability (JFP) has a strong dependence on the anchor group. Larger anchors give higher binding energies to the graphene surface, correlating with higher JFPs. The best anchor groups tested are 1,3,8‐tridodecyloxypyrene and 2,5,8,11,14‐pentadodecylhexa‐peri‐hexabenzocoronene, with JFPs of 36% and 38%, respectively. Many junctions are tested at 77 K for each molecule by measuring source‐drain current as a function of bias and gate voltages. For each compound, there is wide variation in the strength of the electronic coupling to the electrodes and in the location of Coulomb peaks. In most cases, this device‐to‐device variability makes it impossible to observe trends between the anchor and the charge‐transport characteristics. Tetrabenzofluorene anchors, which are not π‐conjugated with the porphyrin, exhibit different charge transport behavior to the other anchors tested, and they show multiple Coulomb peaks with characteristically small molecular electron‐addition energies of 0.3–0.7 eV, whereas the other compounds give single Coulomb peaks.

Challenges in fabricating graphene nanodevices for electronic DNA sequencing

Graphene-based electronic DNA sequencing techniques have received significant attention over the past decade and are hoped to provide a new generation of portable, low-cost devices capable of rapid and accurate DNA sequencing. However, these devices are yet to demonstrate DNA sequencing. This is partly due to complex fabrication requirements resulting in low device yields and limited throughput. In this paper, we review the challenging fabrication of graphene-based electronic DNA sequencing devices. We will place a particular focus on common fabrication challenges and look toward the development of high-throughput, high-yield fabrication of these devices.