Conformation-dependent charge transport through short peptides.

We report on charge transport across single short peptides using the Mechanically Controlled Break Junction (MCBJ) method. We record thousands of electron transport events across single-molecule junctions and with an unsupervised machine learning algorithm, we identify several classes of traces with multifarious conductance values that may correspond to different peptide conformations. Data analysis shows that very short peptides, which are more rigid, show conductance plateaus at low conductance values of about 10G and below, with G being the conductance quantum, whereas slightly longer, more flexible peptides also show plateaus at higher values.

Unravelling the conductance path through single-porphyrin junctions.

Porphyrin derivatives are key components in natural machinery enabling us to store sunlight as chemical energy. In spite of their prominent role in cascades separating electrical charges and their potential as sensitizers in molecular devices, reports concerning their electronic transport characteristics are inconsistent. Here we report a systematic investigation of electronic transport paths through single porphyrin junctions.

Mechanical Fixation by Porphyrin Connection: Synthesis and Transport Studies of a Bicyclic Dimer.

The bowl-shaped, 3-fold interlinked porphyrin dimer was obtained in respectable yields during macrocyclization attempts. Its bicyclic structure, consisting of a macrocycle made of a pair of acetylene interlinked tetraphenylporphyrins which are additionally linked by a C-C bond interlinking two pyrrole subunits, has been confirmed spectroscopically (2D-NMR, UV/vis, HR-MALDI-ToF MS). Late-stage functionalization provided the structural analogue with acetyl-protected terminal thiol anchor groups enabling single molecule transport investigations in a mechanically controlled break junction experiment.

Mechanically controlled quantum interference in graphene break junctions.

The ability to detect and distinguish quantum interference signatures is important for both fundamental research and for the realization of devices such as electron resonators, interferometers and interference-based spin filters. Consistent with the principles of subwavelength optics, the wave nature of electrons can give rise to various types of interference effects, such as Fabry-Pérot resonances, Fano resonances and the Aharonov-Bohm effect. Quantum interference conductance oscillations have, indeed, been predicted for multiwall carbon nanotube shuttles and telescopes, and arise from atomic-scale displacements between the inner and outer tubes.

Large Conductance Variations in a Mechanosensitive Single-Molecule Junction.

An appealing feature of molecular electronics is the possibility of inducing changes in the orbital structure through external stimuli. This can provide functionality on the single-molecule level that can be employed for sensing or switching purposes if the associated conductance changes are sizable upon application of the stimuli. Here, we show that the room-temperature conductance of a spring-like molecule can be mechanically controlled up to an order of magnitude by compressing or elongating it.

Quantum Transport through a Single Conjugated Rigid Molecule, a Mechanical Break Junction Study.

This Account provides an overview of our recent efforts to unravel charge transport characteristics of a metal-molecule-metal junction containing an individual π-conjugated molecule. The model system of our choice is an oligo(phenylene-ethynylene) consisting of three rings, in short OPE3, which represents a paradigmatic model system for molecular-scale electronics. Members of the OPE family are among the most studied in the field thanks to their simple and rigid structure, the possibility of chemically functionalizing them, and their clear transport characteristics.