A multidisciplinary UIUC team has made a significant advancement in the use of automated synthesis to find novel compounds for use in organic electronics. Technology that relies on an automated platform for rapid, large-scale chemical synthesis, which is a game-changer for organic electronics and other fields made the finding possible.
By quickly scanning through a library of molecules with precisely defined structures using automated synthesis, the team discovered a novel mechanism for high conductance through single-molecule characterization experiments. The research, which was recently published in Nature Communications, is the first significant accomplishment of the University of Illinois Urbana-Molecule Champaign’s Maker Lab, which is housed in the Beckman Institute for Advanced Science and Technology.
Charles M. Schroeder, the James Economy Professor in materials science & engineering and a professor of chemical & biomolecular engineering, led the tests that revealed the unexpectedly high conductivity.
The project’s objective was to identify novel compounds with high conductivity that would be useful in organic or molecular electronics applications. To determine how the side chains altered conductance, the team’s method involved methodically adding numerous distinct side chains to molecular backbones.
The project’s initial phase involved creating a sizable library of molecules to be studied in single-molecule electronics studies. The synthesis would have been a time-consuming, laborious procedure if it had been completed using traditional techniques.
The automated synthesis platform developed by the Molecule Maker Lab, which was created to support molecular discovery research that necessitates testing a huge number of potential compounds, allowed us to avoid that effort. Edward R. Jira, a Ph.D. student in chemical & biomolecular engineering who had a leading role in the project, explained the synthesis platform’s concept.
“What’s really powerful… is that it leverages a building-block-based strategy where all of the chemical functionality that we’re interested in is pre-encoded in building blocks that are bench-stable, and you can have a large library of them sitting on a shelf,” he said.
The building blocks are repeatedly coupled together as needed using the same type of reaction, and “because we have this diverse building block library that encodes a lot of different functionality, we can access a huge array of different structures for different applications,” according to the authors.
Semiconductor-metal interfaces are ubiquitous in electronic devices. The surprising find of a high conductance state induced by metallic interfaces can pave the way to new molecular design for highly efficient charge injection and collection across a wide range of electronic applications.
Ying Diao
As Schroeder put it, “Imagine snapping Legos together.”
Martin D. Burke, a co-author, expanded on the Lego-brick metaphor to illustrate why the synthesizer was crucial to the studies and why it wasn’t just because the initial molecular library was produced quickly.
“Because of the Lego-like approach for making these molecules, the team was able to understand why they are super-fast,” he explained.
“Using the ‘Legos,’ we could take the molecules apart piece by piece, swap in other ‘Lego’ bricks, and thereby methodically explore the structure/function interactions that lead to this ultrafast conductivity,” the researchers wrote after discovering the unexpectedly fast state.
The core of the conductivity discovery was described by Ph.D. student Jialing (Caroline) Li, a specialist in single-molecule electronics characterization who analyzed the molecules produced by the synthesizer.
“We observed that the side chains have a huge impact on how the molecule behaves and how this affects charge transport efficiency across the entire molecule,” she said.
The group specifically found that the conductance of molecular junctions with long alkyl side chains is unexpectedly high and concentration-dependent.
They also discovered the cause of the high conductivity: the lengthy alkyl side chains encourage surface adsorption, which in turn causes the molecules to planarize (effectively flatten out), allowing electrons to move through them more effectively.
Burke, a professor of chemistry and the May and Ving Lee Professor for Chemical Innovation, described the building-block method as a “one-two punch” because it transforms the platform into “a powerful engine for both discovering functions, and then understanding the function.”
For the field of organic electronics, conductivity discovery represents a significant advancement.
“Semiconductor-metal interfaces are ubiquitous in electronic devices. The surprising find of a high conductance state induced by metallic interfaces can pave the way to new molecular design for highly efficient charge injection and collection across a wide range of electronic applications,” said co-author Ying Diao, an I. C. Gunsalus Scholar, Dow Chemical Company Faculty Scholar, and associate professor of chemical & biomolecular engineering.
Schroeder outlined the several advantages of organic electronic materials. Using them eliminates the requirement for metals and other inorganic electronics, to start.
However, organic electronics also provide a lot more, including deformation and elastic qualities that can be crucial for some applications, such as implantable medical devices that could flex and bend in response to, for instance, the beating of the heart. Such organic gadgets might even be built to disintegrate inside the body once their purpose has been fulfilled.
Commercial items already contain some organic electronics. For instance, organic light-emitting diodes (OLED) are used in OLED TVs, smartwatches, and smartphone screens. It’s believed that organic solar cells will also be a commercial success in the near future.
However, due to a lack of important material discoveries like the one revealed recently by the UIUC team, progress in the field of organic electronics has only been made superficially.
Schroeder said that it’s significant to have proven that “we can design and synthesize large libraries for various applications.” The paper “showcases the fact that we successfully did it for a class of molecules for molecular electronics.” He admitted, “I didn’t expect to see something as interesting on this first study!”
Co-author Jeffrey S. Moore, who is a Stanley O. Ikenberry Endowed Chair, professor of chemistry, and Howard Hughes Medical Institute Professor, reflected on the work:
“Advancing basic science and technology by combining new facilities with a collaborative team is what makes the Beckman Institute so special. This discovery is the first of many that will come from the Molecule Maker Lab.”
According to Schroeder, the Molecule Maker Lab facilities, which also provide artificial intelligence capabilities for determining which molecules are likely to be worth making, will enable a new way of thinking about research in which “you can start thinking about designing based on a function instead of a structure.”
Whereas researchers today might start by saying, “I need to make this particular structure because I think it’s going to do something,” it will be possible to tell the system, “I want to get this ultimate function, and then let it help you figure out what structures you should make to get that function.”
The Molecule Maker Lab facilities will eventually be made available to researchers outside of UIUC. Burke stated that he wanted to see the Lab “become a global epicenter of democratized molecular innovation,” enabling those who are not experts in molecular synthesis to address crucial issues in science.
“I think this is the beginning of something really special,” Burke said. “The journey has begun.”
