Improving Energy Transfer Efficiency by Mimicking Photosynthetic Systems
A research team from the University of Groningen says that transporting energy through a single molecular nanowire is superior to transporting it through bundles.
In nature, the efficient long-range energy transport along supramolecular architectures of organic molecules is a key step for photosynthesis which converts sunlight into energy. Understanding these transport processes and being able to manipulate them for electrical transport is something that researchers have been trying to do for decades.
Building a well-defined system that mimics photosynthetic systems has proven difficult, however. Recent work by Richard Hildner, a physicist from the University of Groningen, and his colleagues has investigated energy transport in an artificial system made from nanofibers. Their findings have been published in the Journal of American Chemical Society.
An illustration (left) of the molecular building block for the fibers, comprised of (carbonylbridged triarylamine core (red), three amide moieties (blue and chiral bulky peripheries (grey). Image used courtesy of Richard Hildner, University of Groningen
Bundles of Nanofibers
“Natural photosynthetic systems have been optimized by billions of years of evolution. We have found this very difficult to copy in artificial systems,” said Hildner. However, he and his colleagues noticed that a system that they developed five years ago, which uses four micrometer-long fibers, was capable of transporting energy, but some sort of instability caused energy transport to get stuck in the middle of the fibers.
To try and improve the energy transport efficiency, Hildner and his team created bundles of nanofibers and used these instead. “This is the same idea as that which is used in normal electronics: very thin copper wires are bundled together to create a more robust cable,” he said. However, it transpired that these bundled nanofibers were worse at transporting energy than their single counterparts.
This, the team says, is down to something called coherence. When energy is put into the fibers’ molecules, it creates an excited state that is delocalized over several molecules. This means that it can move fast and efficiently across the fiber between molecules like a wave. Without coherence, energy is limited to a single molecule and must jump from one to the next—a slower method of transport. In nanofiber bundles, coherence is lost due to the compressed nature of the fibers and thus energy transport is dampened.
Optimizing Energy Transport in Molecular Fibers
Although the team’s work was technically a failure—their goal was to use these bundles to improve energy transfer efficiency—their findings still hold plenty of merit. They could now be used by other research teams as a way to calculate how to optimize transport in nanofibers.
And in doing so, we could begin to see the development of more efficient electronics that exhibit less electrical resistance, are more stable, and have more desirable properties engineered into them.