Graphene Tech Digest - November 2016

Piping hot – atomic scale pipes

A group of researchers at the University of Manchester’s Graphene Research Institute have created atomic scale pipes. Usually when making graphene one would strip a layer from the graphite crystal, however, in this work the researchers focused on what was left – namely the graphite crystal. They found that there was an ultra-thin cavity inside the crystal. Similar cavities could be made inside various other types of materials allowing for the cavity to have any desired properties, e.g. porous or non-porous, smooth or rough, insulating or conductive, electrically charged or neutral. The voids in the crystal are use-adaptable with the potential to be used as either piping to transport liquids or gases, or as containers to store substances. As one would imagine in the through-the-mirror-world of nano objects the material acted in a strange but exciting way: water flowed through with minimal friction and at high speed, something that one would expect of a much larger tube. Radha Boya, postdoctoral researcher and research co-leader, said that this could have obvious uses in new filtration technology, desalination, and gas separation, although there are many other potential directions to explore.

Graphene ribbons could heal spinal cords

Having previously worked with graphene nanoribbons on projects such as de-icers for aeroplane wings, batteries and less permeable containers for natural gas storage, the team at Tour lab at Rice University are realising another use for nanoribbon – healing human spinal cords. In 2009 the team discovered a chemical process which ‘unzipped’ nanoribbons from multiwalled carbon nanotubes; through a process of immersion in a bath of potassium the nanotubes are turned inside-out, giving 100% yield of thin, long nanoribbon structures. Graphene nanoribbons are highly soluble in polyethylene glycol (PEG), a biologically compatible gel which is already widely used in the medical sector; and when they are primed with this they form an electrically active network that helps repair the severed ends of spinal cords. If this sounds too good to be true, it isn’t. Scientists at Konkuk University in South Korea, in cooperation with Tour Lab, restored functioning in a rodent with a severed spinal cord. Tour labs said that the material reliably allowed neuronal signals to cross the gap 24 hours after severing of the spinal cord, with almost full recovery after two weeks.

New method for wrinkling metal oxide using textured graphene

Textured metal-oxide films compared to non-textured metal oxide films have better performance when they are used as photocatalysts and battery electrodes. Wrinkled graphene-oxide will also perform better after being subjected to wrinkling and crumpling; it is better able to repel water, good for water-resistant coatings, and better able to conduct electricity. There was never a problem wrinkling graphene, but metal-oxides were a tougher bunch and wouldn’t crumple easily. Now, a team from Brown University have discovered that pre-textured graphene sheets can be put into an ionised metal oxide solution where particles are attracted into the space between the graphene sheets creating a sandwiched layer of textured metal-oxide. After this process is completed the graphene can be got rid of, leaving textured metal-oxide sheets.

Feeding silkworms graphene makes silk stronger

Silk has always been a great material, being both sensuously smooth and very strong. A recent experimental study by students at Tsinghua University in Beijing has resulted in graphene reinforced silk. The scientists fed the silkworms by coating mulberry leaves in carbon nanotubes which the silkworms ate. Some of the nanotubes came out predictably as excrement, what was left were incorporated into the silk the worm produced. The silk so produced is stronger – can with stand approximately 50 percent more stress than traditional silk – and better able to conduct electricity after being heat-treated at 1,050C.  

Ozone resistant graphene shows potential for use in nanoelectronics

A team of scientists at the National Research Nuclear University MEPhl in Russia have developed a technology to make graphene more resistant to ozonation (ozone is a gas composed of 3 oxygen atoms, when it degrades back to oxygen one oxygen atom is left over – this is called a free radical. It is highly reactive and consequently damaging.). Manufacturing methods in nanoelectronics currently require that graphene has a coating of polymerics (plastic) which is then evaporated – the reason for this is to apply an organic layer to a substrate, making it a process especially suited for electrochemical sensors. However, Ozone is commonly used in this process, damaging the graphite, and altering its properties. Graphene treated with MEPhl’s technique can withstand ten minutes of ozone without any noticeable degradation, compared to untreated graphene which can withstand only three minutes’ worth.

Tyres laced with graphene

Chinese tyre manufacturers are all jumping on the bandwagon of graphene-enhanced tyres. It started with Huagao and Sentury, and now Shandong Hengyu is entering the game. Shandong Hengyu reports that tyres laced with graphene show 25% less wear, and double the strength. According news sources road testing has been completed, and it is expected that marketing is to begin before Christmas. Hengyu gets its graphene from another Chinese company called Sixth Element Materials Technology that has recently opened sales offices in Europe, with the hope of increased trade with the Middle East and Africa. 

Borophene is the new kid on graphene’s patch

Graphene is a wonder material which has massive potential to change everything from tyres to mobile phones. Or is it really? According to researchers at Rice University, a new material could supersede graphene – borophene. Normal 3D boron is a non-metallic semiconductor which when stretched into 2D sheets starts to have some metallic properties.  Borophene, as they have named the 2D material, is a man-made material which looks like corrugated cardboard, possessing similar peaks and troughs which creates some interesting effects. Electricity flows more easily in one direction than another, for example. What’s more, borophene is believed to be the highest strength material scientists have yet come across, and it is incredibly flexible, opening up avenues of use for which inflexible graphene is not suited.

Graphene is a smashing solution to glass corrosion problem

Owing to its chemical inertness, thinness and transparency, graphene has recently been demonstrated to be a great material for protectively coating glass. Silicate glass will corrode causing it to become brittle and opaque. For medical, chemical and optical companies this is a problem. Researchers at the Institute for Basic Science have suggested that once graphene production is able to make larger and higher quality sheets then they believe it will become standard for manufacturers to apply this coating to not only glass but any substance which requires a protective coating. 

Graphene taking first steps towards becoming a superconductor

Everybody agrees that graphene has great potential, but there remains one area where graphene is causing scientists and engineers headaches: How to make graphene work as a semiconductor. In the past few weeks there have been two possible solutions – both coming from the Institute of Basic Science in South Korea. They made the surprising discovery that a current is created when a thin sheet of semiconducting MoS2 (Molybdenum Disulphide) is put between two graphene sheets, and a light then shone on it. They did further testing and found that this single layer configuration created more electrical current than multi-layered MoS2 devices. “This device is transparent, flexible and requires less power than silicon semiconductors”, said the professor, he also said that dependant on future experimental success this could “accelerate the development of 2D photoelectric devices.”

The scientists at the Institute of Basic Science in South Korea have also been trying to introduce hydrogen onto graphene through the ‘Birch-type reaction’, a solution of lithium dissolved in ammonia. The findings were that hydrogenation happens rapidly and evenly over single layer graphene but only from edges and slowly in multi-layer graphene. This process has been found to change the properties of the graphene, opening a bandgap (a gap separating the electron from joining an existing current) which is required for it to act as a semiconductor, making it possible to be used in electronics, photonics, optoelectronics, sensors and composites.



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