Illustration of a cycloparaphenylene, or nanohoop, that has been doped with nitrogen atoms. Research in the University of Oregon lab of Ramesh Jasti has shown the combination of nitrogen and carbon atoms extends the potential efficiency and capabilities of such structures. Credit: Courtesy of Ramesh Jasti
While application is down the road, these tiny organic circular structures could be used in solar cells, light-emitting diodes and medical diagnostics. When scientists began making tiny organic circular structures using carbon atoms, the idea was to improve carbon nanotubes for use in electronics or optical devices. Now they believe this technique might roll solo. Researchers now show that these cycloparaphenylenes can be made using a variety of atoms, not just those from carbon.
These barely one-nanometer nanohoops offer a new class of structures -sized between those made with long-chained polymers and small, low-weight molecules – for use in energy or light devices. “These structures add to the toolbox and provide a new way to make organic electronic materials,” Jasti said. “Cyclic compounds can behave like they are hundreds of units long, like polymers, but be only 6 to 8 units around. We show that by adding non-carbon atoms, we are able to move the optical and electronic properties around.”
Nanohoops help solve challenges related to materials with controllable band gaps – the energies that lie between valance and conduction bands and is vital for designing organic semiconductors. Currently long materials such as those based on polymers work best. “If you can control the band gap, then you can control the color of light that is emitted, for example,” Jasti said. “In an electronic device, you also need to match the energy levels to the electrodes. In photovoltaics, the sunlight you want to capture has to match that gap to increase efficiency and enhance the ability to line up various components in optimal ways. These things all rely on the energy levels of the molecules. We found that the smaller we make nanohoops, the smaller the gap.”
To prove their approach could work, Darzi synthesized a variety of nanohoops using both carbon and nitrogen atoms to explore their behavior. “What we show is that the charged nitrogen makes a nanohoop an acceptor of electrons, and the other part becomes a donator of electrons,” Jasti said.
“The addition of other elements like nitrogen gives us another way to manipulate the energy levels, in addition to the nanohoop size. We’ve now shown that the nanohoop properties can be easily manipulated and, therefore, these molecules represent a new class of organic semiconductors – similar to conductive polymers that won the Nobel Prize in 2000,” he said. “With nanohoops, you can bind other things in the middle of the hoop, essentially doping them to change properties or perhaps sense an analyte that allows on-off switching.” http://around.uoregon.edu/content/new-oregon-approach-nanohoops-could-energize-future-devices
Recent Comments