Electronic components based on graphene could render our current silicon-based electronics obsolete. Graphene, a more recently discovered form of carbon, consists of two-dimensional sheets of aromatic six-membered carbon rings in a honeycomb arrangement.
In contrast to extended graphene layers, narrow graphene nanoribbons have semiconducting properties and could thus be candidates for electronic applications. Klaus Müllen and a team from the Max Planck Institute for Polymer Research in Mainz have now introduced a new method for the synthesis of long, narrow graphene ribbons with defined dimensions in the journal Angewandte Chemie.
Previously, graphene ribbons were mainly cut out of larger graphene sheets or were obtained by slitting open carbon nanotubes lengthwise. However, with these methods it is impossible to produce ribbons that have a precisely established ratio of width to length as well as defined edges. These details are important because they determine the electronic properties of the ribbons. The search has thus been on for a method that allows controlled production of very narrow graphene ribbons—an extremely difficult challenge. The German researchers working with Müllen are now well on the way to overcome it. They are not starting with large structures to cut up (top-down); instead they are building their ribbons from smaller components (bottom-up).
The building blocks selected by Müllen and his team are long chains of aromatic six-membered carbon rings called polyphenlyenes. In contrast to previous approaches, they did not produce straight chains; instead they made them with a flexible, zigzagging, bent backbone. Furthermore, they attached hydrocarbon side-chains to the backbone to increase the solubility in organic solvents, which allows the compounds to be synthesized and processed in solution.
The next step is a reaction that splits off hydrogen (dehydrogenation). This causes a ring-closing reaction in each pointy tip of the zigzag, forming a new aromatic six-membered carbon ring that shares a side with three neighboring rings—the chain transforms in to a narrow ribbon.
In this way, the team was able to produce a series of different nanoribbons with lengths reaching over 40 nm. The width of the ribbon was defined by the size of the “points” of the polyphenylene precursor. The resulting ribbons are free of defects and soluble in common organic solvents.
“We have been the first to demonstrate that structural perfection can be achieved by the classical bottom-up synthesis of defined graphene nanoribbons,” says Müllen. “The solubility of the ribbons is an important requirement for the large-scale production of electronic components.”
Author: Klaus Müllen, Max-Planck-Institut für Polymerforschung, Mainz (Germany), http://www.mpip-mainz.mpg.de/groups/muellen/director
Title: Graphene Nanoribbons by Chemists: Nanometer-Sized, Soluble, and Defect-Free
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201006593
Klaus Müllen | Angewandte Chemie
A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences