GNRs - Page 4

Researchers from the University of Nebraska-Lincoln, University of Illinois at Urbana-Champaign, and Russia’s Saratov State Technical University have shown that adding a graphene nanoribbons to gas sensors can significantly increase their sensitivity compared to traditional ones.

This rendering shows gas molecules widening the gaps between rows of the team's GNRs. This was proposed as a partial explanation to how the nano-ribbons grant sensors an unprecedented boost

The team integrated the nano-ribbons into the circuity of the gas sensor where it reportedly responded about 100 times more sensitively to molecules than did sensors featuring even the best performing carbon-based materials. With multiple sensors on a chip, we were able to demonstrate that we can differentiate between molecules that have nearly the same chemical nature, said the study author and associate professor of chemistry at the University of Nebraska. For example, we can tell methanol and ethanol apart. So these sensors based on graphene nano-ribbons can be not only sensitive but also selective.

Researchers from South Korea have created a graphene nanoribbon sensor which can measure high vacuum pressures.

The Researchers synthesized a mixture of graphene nanoribbons (of varying size and chemical composition) from a combination of multi-walled carbon nanotubes, sulphuric acid and phosphoric acid in a chemical exfoliation approach. The result was a mixture of several graphene nanoribbons which were separated and purified ready for device implementation and testing. The Researchers also synthesized graphene oxide through a modified Hummers’ method for use as a reference material.

Rice University scientists have developed highly efficient battery anodes using graphene and asphalt. To achieve this, the researchers mixed asphalt with conductive graphene nanoribbons and coated the composite with lithium metal through electrochemical deposition. The anodes showed exceptional stability after more than 500 charge-discharge cycles. A high-current density of 20 milliamps per square centimeter demonstrated the material’s promise for use in rapid charge and discharge devices that require high-power density.

SEM images show an anode of asphalt, graphene nanoribbons and lithium at left and the same material without lithium at right

The capacity of these batteries is enormous, but what is equally remarkable is that we can bring them from zero charge to full charge in five minutes, rather than the typical two hours or more needed with other batteries, Prof. James Tour said.

Researchers from Utrecht University, TU Delft and the Aalto University in Finland have shown that electronic components can be incorporated in single graphene wires (nanoribbons) with atomic precision. The result is a working electronic device that could be used in graphene-based electronic switches with extremely fast operational speeds.

The researchers state that their solution to using graphene in electronics is atomically precise; By selecting certain precursor substances (molecules), the team can code the structure of the electrical circuit with extreme accuracy. The switch is based on the principle of graphene nanoribbons. Previous research has shown that the ribbon’s electronic characteristics are dependent on its atomic width. A ribbon that is five atoms wide is an ordinary electric wire with extremely good conduction characteristics, but adding two atoms makes the ribbon a semiconductor. We are now able to seamlessly integrate a five-atom wide ribbon together with one that is seven atoms wide. That gives you a metal-semiconductor junction, which works as a diode, according to the team.

A team at the Department of Energy’s Oak Ridge National Laboratory and North Carolina State University has found a way to grow narrow ribbons of graphene without the use of metal substrates.

Narrow graphene ribbons can perform as a semiconductor if the ribbons are made with a specific edge shape, but to grow graphene nanoribbons with controlled width and edge structure from polymer precursors, is not a simple task. Previous researchers had used a metal substrate to catalyse a chemical reaction, but the metal substrate suppresses useful edge states and shrinks the desired band gap. The team in this work managed to grow graphene nanoribbons without a metal substrate. Instead, they injected charge carriers that promote a chemical reaction that converts a polymer precursor into a graphene nanoribbon.

Researchers from Rice University, led by the renowned Prof. James M. Tour, are attempting to repair spinal cord injuries with the help of TexasPEG, a water soluble graphene nanoribbon dispersion. In rodents, the method has been able to restore a completely paralyzed rat to a motility score of 19 out of 21, where 21 is a perfect score. If successful in humans as well, it may be applicable to new injuries, and potentially old injuries up to 30 years in the past - restoring function and sensation in both paraplegics and quadriplegics.

The team's novel approach acts as a directional scaffold for the neurons to grow along. It uses highly conductive graphene nanoribbons (GNR), which are long and thin. These graphene nanoribbons have been chemically modified to be water soluble (PEG-GNR), so they can disperse well between the existing neurons. Neurons then attach to these GNRs, and grow axons and dendrites along them until they re-connect with another neuron. These PEG-GNR are dissolved in PEG600 to form a solution that is topically administered to cuts in the spinal cord. This solution has been named TexasPEG by researchers in the field.

Researchers at the University of Illinois and the University of Nebraska-Lincoln have used graphene nanoribbons (GNRs) to create the electronic components used to carry out logic operations in computing. The team described this as "the first step toward integrating atomically precise graphene nanoribbons onto nonmetallic substrates".

The researchers explained that in most cases, GNRs are neither uniform nor narrow enough to exhibit the desired semiconductor properties. However, if the nanoribbons are made in a "bottom up approach, it is possible to create atomically precise nanoribbons with highly uniform electronic properties.

Researchers from Grenoble Alpes University in France have demonstrated (using atomistic calculations) that a lateral electric field can be used to tune the carrier mobility and change the spin polarization of the current driving through zigzag graphene ribbons.

The calculations predict a high variation of the carrier mobility, mean free path and spin polarization in the ZGNRs. It turns out that configurations with almost 100% spin-polarized current can be switched on and off. The researchers say that these effects can be nicely exploited in spintronics devices.

Researchers at Rice University have shown that combining graphene nanoribbons, made with a process developed at Rice University, and a common polymer to create a material called Texas-PEG could have potential of aiding in treating damaged spinal cords in people.

The customized GNRs are highly soluble in polyethylene glycol (PEG), a biocompatible polymer gel used in surgeries, pharmaceutical products and in other biological applications. When the biocompatible nanoribbons have their edges functionalized with PEG chains and are then further mixed with PEG, they form an electrically active network that can help the severed ends of a spinal cord reconnect (neurons tend to grow on graphene because it’s a conductive surface).

Researchers from the Israeli Technion University developed a novel and rapid method to optically visualize CNTs and graphene. The idea is that growing pNBA nanocrystals - which are optically visible on top of the CNTs or graphene sheets. This allows the crystals to be viewed by dark-field optical microscopy.

The pNBAs NCs can be easily removed - and the original material is not effected by this process. But it allows much easier study of graphene, and can also be used to aid production processes as it is a scalable, fast and cost-effective process. The video below shows how growing those NCs on carbon nanotubes makes the tubes visible.