In a brand new Nature Communications research, Columbia Engineering researchers report that they’ve constructed extremely conductive, tunable single-molecule units during which the molecule is hooked up to leads through the use of direct metal-metal contacts. Their novel method makes use of mild to regulate the digital properties of the units and opens the door to broader use of metal-metal contacts that might facilitate electron transport throughout the single-molecule machine.
The problem
As units proceed to shrink, their digital elements should even be miniaturized. Single-molecule units, which use natural molecules as their conductive channels, have the potential to resolve the miniaturization and functionalization challenges confronted by conventional semiconductors. Such units provide the thrilling risk of being managed externally through the use of mild, however — till now — researchers haven’t been in a position to show this.
“With this work, we have unlocked a brand new dimension in molecular electronics, the place mild can be utilized to regulate how a molecule binds inside the hole between two metallic electrodes,” mentioned Latha Venkataraman, a pioneer in molecular electronics and Lawrence Gussman Professor of Utilized Physics and professor of chemistry at Columbia Engineering. “It is like flipping a change on the nanoscale, opening up all types of potentialities for designing smarter and extra environment friendly digital elements.”
The method
Venkataraman’s group has been finding out the elemental properties of single-molecule units for nearly 20 years, exploring the interaction of physics, chemistry, and engineering on the nanometer scale. Her underlying focus is on constructing single-molecule circuits, a molecule hooked up to 2 electrodes, with various performance, the place the circuit construction is outlined with atomic precision.
Her group, in addition to these creating practical units with graphene, a carbon-based two-dimensional materials, have recognized that making good electrical contacts between metallic electrodes and carbon methods is a serious problem. One answer could be to make use of organo-metallic molecules and devise strategies to interface electrical results in the metallic atoms inside the molecule. In the direction of this aim, they determined to discover the usage of organo-metallic iron-containing ferrocene molecules, that are additionally thought of to be tiny constructing blocks on this planet of nanotechnology. Similar to LEGO items may be stacked collectively to create complicated constructions, ferrocene molecules can be utilized as constructing blocks to assemble ultra-small digital units. The group used a molecule terminated by a ferrocene group comprising two carbon-based cyclopentadienyl rings that sandwich an iron atom. They then used mild to leverage the electrochemical properties of the ferrocene-based molecules to kind a direct bond between the ferrocene iron middle and the gold (Au) electrode when the molecule was in an oxidized state (i.e. when the iron atom had misplaced one electron). On this state, they found that ferrocene might bind to the gold electrodes used to attach the molecule to the exterior circuitry. Technically, oxidizing the ferrocene enabled the binding of a Au0 to an Fe3+ middle.
“By harnessing the light-induced oxidation, we discovered a solution to manipulate these tiny constructing blocks at room temperature, opening doorways to a future the place mild can be utilized to regulate the habits of digital units on the molecular stage,” mentioned the research’s lead creator Woojung Lee, who’s a PhD scholar in Venkararaman’s lab.
Potential influence
Venkataraman’s new method will allow her group to increase the varieties of molecular terminations (contact) chemistries they’ll use for creating single-molecule units. This research additionally exhibits the power to activate and off this contact through the use of mild to vary the oxidation state of the ferrocene, demonstrating a light-switchable ferrocene-based single-molecule machine. The sunshine-controlled units might pave the best way for the event of sensors and switches that reply to particular mild wavelengths, providing extra versatile and environment friendly elements for a variety of applied sciences.
The group
This work was a collaborative effort involving synthesis, measurements, and calculations. The synthesis was performed primarily at Columbia by Michael Inkpen, who was a post-doc within the Venkataraman group and is now an assistant professor on the College of Southern California. All of the measurements have been made by Woojung Lee, a graduate scholar within the Venkataraman group. The calculations have been carried out each by graduate college students within the Venkataraman group and by collaborators from the College of Regensburg in Germany.
What’s subsequent
The researchers at the moment are exploring the sensible purposes of light-controlled single-molecule units. This might embody optimizing machine efficiency, finding out their habits beneath completely different environmental circumstances, and refining further functionalities enabled by the metal-metal interface.
