Tag Archives: Roman Fasel

Graphene Flagship high points

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The European Union’s Graphene Flagship project has provided a series of highlights in place of an overview for the project’s ramp-up phase (in 2013 the Graphene Flagship was announced as one of two winners of a science competition, the other winner was the Human Brain Project, with two prizes of 1B Euros for each project). Here are the highlights from the April 19, 2016 Graphene Flagship press release,

Graphene and Neurons – the Best of Friends

Flagship researchers have shown that it is possible to interface untreated graphene with neuron cells whilst maintaining the integrity of these vital cells [1]. This result is a significant first step towards using graphene to produce better deep brain implants which can both harness and control the brain.

Graphene and Neurons
 

This paper emerged from the Graphene Flagship Work Package Health and Environment. Prof. Prato, the WP leader from the University of Trieste in Italy, commented that “We are currently involved in frontline research in graphene technology towards biomedical applications, exploring the interactions between graphene nano- and micro-sheets with the sophisticated signalling machinery of nerve cells. Our work is a first step in that direction.”

[1] Fabbro A., et al., Graphene-Based Interfaces do not Alter Target Nerve Cells. ACS Nano, 10 (1), 615 (2016).

Pressure Sensing with Graphene: Quite a Squeeze

The Graphene Flagship developed a small, robust, highly efficient squeeze film pressure sensor [2]. Pressure sensors are present in most mobile handsets and by replacing current sensor membranes with a graphene membrane they allow the sensor to decrease in size and significantly increase its responsiveness and lifetime.

Discussing this work which emerged from the Graphene Flagship Work Package Sensors is the paper’s lead author, Robin Dolleman from the Technical University of Delft in The Netherlands “After spending a year modelling various systems the idea of the squeeze-film pressure sensor was formed. Funding from the Graphene Flagship provided the opportunity to perform the experiments and we obtained very good results. We built a squeeze-film pressure sensor from 31 layers of graphene, which showed a 45 times higher response than silicon based devices, while reducing the area of the device by a factor of 25. Currently, our work is focused on obtaining similar results on monolayer graphene.”

 

[2] Dolleman R. J. et al., Graphene Squeeze-Film Pressure Sensors. Nano Lett., 16, 568 (2016)

Frictionless Graphene


Image caption: A graphene nanoribbon was anchored at the tip of a atomic force microscope and dragged over a gold surface. The observed friction force was extremely low.

Image caption: A graphene nanoribbon was anchored at the tip of a atomic force microscope and dragged over a gold surface. The observed friction force was extremely low.

Research done within the Graphene Flagship, has observed the onset of superlubricity in graphene nanoribbons sliding on a surface, unravelling the role played by ribbon size and elasticity [3]. This important finding opens up the development potential of nanographene frictionless coatings. This research lead by the Graphene Flagship Work Package Nanocomposites also involved researchers from Work Package Materials and Work Package Health and the Environment, a shining example of the inter-disciplinary, cross-collaborative approach to research undertaken within the Graphene Flagship. Discussing this further is the Work Package Nanocomposites Leader, Dr Vincenzo Palermo from CNR National Research Council, Italy “Strengthening the collaboration and interactions with other Flagship Work Packages created added value through a strong exchange of materials, samples and information”.

[3] Kawai S., et al., Superlubricity of graphene nanoribbons on gold surfaces. Science. 351, 6276, 957 (2016) 

​Graphene Paddles Forward

Work undertaken within the Graphene Flagship saw Spanish automotive interiors specialist, and Flagship partner, Grupo Antolin SA work in collaboration with Roman Kayaks to develop an innovative kayak that incorporates graphene into its thermoset polymeric matrices. The use of graphene and related materials results in a significant increase in both impact strength and stiffness, improving the resistance to breakage in critical areas of the boat. Pushing the graphene canoe well beyond the prototype demonstration bubble, Roman Kayaks chose to use the K-1 kayak in the Canoe Marathon World Championships held in September in Gyor, Hungary where the Graphene Canoe was really put through its paces.

Talking further about this collaboration from the Graphene Flagship Work Package Production is the WP leader, Dr Ken Teo from Aixtron Ltd., UK “In the Graphene Flagship project, Work Package Production works as a technology enabler for real-world applications. Here we show the worlds first K-1 kayak (5.2 meters long), using graphene related materials developed by Grupo Antolin. We are very happy to see that graphene is creating value beyond traditional industries.” 

​Graphene Production – a Kitchen Sink Approach

Researchers from the Graphene Flagship have devised a way of producing large quantities of graphene by separating graphite flakes in liquids with a rotating tool that works in much the same way as a kitchen blender [4]. This paves the way to mass production of high quality graphene at a low cost.

The method was produced within the Graphene Flagship Work Package Production and is talked about further here by the WP deputy leader, Prof. Jonathan Coleman from Trinity College Dublin, Ireland “This technique produced graphene at higher rates than most other methods, and produced sheets of 2D materials that will be useful in a range of applications, from printed electronics to energy generation.” 

[4] Paton K.R., et al., Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids. Nat. Mater. 13, 624 (2014).

Flexible Displays – Rolled Up in your Pocket

Working with researchers from the Graphene Flagship the Flagship partner, FlexEnable, demonstrated the world’s first flexible display with graphene incorporated into its pixel backplane. Combined with an electrophoretic imaging film, the result is a low-power, durable display suitable for use in many and varied environments.

Emerging from the Graphene Flagship Work Package Flexible Electronics this illustrates the power of collaboration.  Talking about this is the WP leader Dr Henrik Sandberg from the VTT Technical Research Centre of Finland Ltd., Finland “Here we show the power of collaboration. To deliver these flexible demonstrators and prototypes we have seen materials experts working together with components manufacturers and system integrators. These devices will have a potential impact in several emerging fields such as wearables and the Internet of Things.”

​Fibre-Optics Data Boost from Graphene

A team of researches from the Graphene Flagship have demonstrated high-performance photo detectors for infrared fibre-optic communication systems based on wafer-scale graphene [5]. This can increase the amount of information transferred whilst at the same time make the devises smaller and more cost effective.

Discussing this work which emerged from the Graphene Flagship Work Package Optoelectronics is the paper’s lead author, Daniel Schall from AMO, Germany “Graphene has outstanding properties when it comes to the mobility of its electric charge carriers, and this can increase the speed at which electronic devices operate.”

[5] Schall D., et al., 50 GBit/s Photodetectors Based on Wafer-Scale Graphene for Integrated Silicon Photonic Communication Systems. ACS Photonics. 1 (9), 781 (2014)

​Rechargeable Batteries with Graphene

A number of different research groups within the Graphene Flagship are working on rechargeable batteries. One group has developed a graphene-based rechargeable battery of the lithium-ion type used in portable electronic devices [6]. Graphene is incorporated into the battery anode in the form of a spreadable ink containing a suspension of graphene nanoflakes giving an increased energy efficiency of 20%. A second group of researchers have demonstrated a lithium-oxygen battery with high energy density, efficiency and stability [7]. They produced a device with over 90% efficiency that may be recharged more than 2,000 times. Their lithium-oxygen cell features a porous, ‘fluffy’ electrode made from graphene together with additives that alter the chemical reactions at work in the battery.

Graphene Flagship researchers show how the 2D material graphene can improve the energy capacity, efficiency and stability of lithium-oxygen batteries.

Both devices were developed in different groups within the Graphene Flagship Work Package Energy and speaking of the technology further is Prof. Clare Grey from Cambridge University, UK “What we’ve achieved is a significant advance for this technology, and suggests whole new areas for research – we haven’t solved all the problems inherent to this chemistry, but our results do show routes forward towards a practical device”.

[6] Liu T., et al. Cycling Li-O2 batteries via LiOH formation and decomposition. Science. 350, 6260, 530 (2015)

[7] Hassoun J., et al., An Advanced Lithium-Ion Battery Based on a Graphene Anode and a Lithium Iron Phosphate Cathode. Nano Lett., 14 (8), 4901 (2014)

​Graphene – What and Why?

Graphene is a two-dimensional material formed by a single atom-thick layer of carbon, with the carbon atoms arranged in a honeycomb-like lattice. This transparent, flexible material has a number of unique properties. For example, it is 100 times stronger than steel, and conducts electricity and heat with great efficiency.

A number of practical applications for graphene are currently being developed. These include flexible and wearable electronics and antennas, sensors, optoelectronics and data communication systems, medical and bioengineering technologies, filtration, super-strong composites, photovoltaics and energy storage.

Graphene and Beyond

The Graphene Flagship also covers other layered materials, as well as hybrids formed by combining graphene with these complementary materials, or with other materials and structures, ranging from polymers, to metals, cement, and traditional semiconductors such as silicon. Graphene is just the first of thousands of possible single layer materials. The Flagship plans to accelerate their journey from laboratory to factory floor.

Especially exciting is the possibility of stacking monolayers of different elements to create materials not found in nature, with properties tailored for specific applications. Such composite layered materials could be combined with other nanomaterials, such as metal nanoparticles, in order to further enhance their properties and uses.​

Graphene – the Fruit of European Scientific Excellence

Europe, North America and Asia are all active centres of graphene R&D, but Europe has special claim to be at the centre of this activity. The ground-breaking experiments on graphene recognised in the award of the 2010 Nobel Prize in Physics were conducted by European physicists, Andre Geim and Konstantin Novoselov, both at Manchester University. Since then, graphene research in Europe has continued apace, with major public funding for specialist centres, and the stimulation of academic-industrial partnerships devoted to graphene and related materials. It is European scientists and engineers who as part of the Graphene Flagship are closely coordinating research efforts, and accelerating the transfer of layered materials from the laboratory to factory floor.

For anyone who would like links to the published papers, you can check out an April 20, 2016 news item featuring the Graphene Flagship highlights on Nanowerk.

Bespoke (custom made) carbon nanotubes

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Researchers have found a way to create single-walled carbon nanotubes (SWCNTs) that  are consistent and, hopefully, designed for specific applications if I’m reading the research rightly, (I have an embedded video in a March 15, 2013 posting which illustrates some of the issues with producing carbon nanotubes.) Getting back to this latest research, it suggests that we could order SWCNTs-on-demand. An Aug. 14, 2014 news item on Azonano provides more insight,

In future, it will be possible to specifically equip carbon nanotubes with properties which they need for electronic applications, for example. Researchers at Empa in Dübendorf/Switzerland and the Max Planck Institute for Solid State Research in Stuttgart [Germany] have succeeded for the first time in growing single-walled carbon nanotubes (CNTs) with only a single, prespecified structure.

The nanotubes thereby have identical electronic properties. The decisive trick here: The team has taken up an idea which originated from the Stuttgart-based Max Planck researchers and produced the CNT from custom-made organic precursor molecules. The researchers started with these precursor molecules and have built up the nanotubes on a platinum surface, as they report in the latest issue of the scientific journal Nature. Such CNTs could be used in future, for instance, in ultra-sensitive light detectors and very tiny transistors.

An Aug. 13, 2014 Max Planck Institute press release, which originated the news item, provides more detail,

For 20 years, material scientists working on the development of carbon nanotubes for a range of applications have been battling a problem – now an elegant solution is at hand. With their unusual mechanical, thermal and electronic properties, the tiny tubes with their honeycomb lattice of graphitic carbon have become the embodiment of nanomaterials. They could be used to manufacture the next generation of electronic and electro-optical components so that they are even smaller and with even faster switching times than before. But to achieve this, the material scientists must specifically equip the nanotubes with desired properties, and these depend on their structure. The production methods used to date, however, always result in a mixture of different CNTs. The team from Empa  and the Max Planck Institute for Solid State Research has now remedied the situation with a new production path for single-walled nanotubes.

Carbon nanotubes with the best possible varietal purity are in demand

With a diameter of around one nanometre, single-walled CNTs (SWCNTs) are deemed to be quantum structures; very tiny structural differences, in the diameter, for example, or in the orientation of the atomic lattice, can dramatically change the electronic properties: one SWCNT can be a metal, while one with a slightly different structure is semi-conducting. Correspondingly great is the interest in reliable methods for producing SWCNTs with the best possible varietal purity. Researchers working with Martin Jansen, Director Emeritus at the Max Planck Institute for Solid State Research, have been pursuing suitable concepts for the synthesis for ten years. But it is only now that the surface physicists at Empa and the chemists at the Stuttgart-based Max Planck Institute have succeeded in implementing one of these ideas in the laboratory. The researchers allowed structurally identical SWCNTs to grow on a platinum surface in a self-organised process and were able to unambiguously define their electronic properties.

The Max Planck research team headed by Martin Jansen had the idea of starting with small precursor molecules to synthesise carbon nanotubes. They felt it should be possible to achieve controlled conversion of the precursor molecules into a cap which acts as the seed for a SWCNT and thus unambiguously specify the structure of the nanotube. With this concept, they approached the Empa team working with Roman Fasel, head of Empa’s «nanotech@surfaces» department and titular professor at the Department of Chemistry and Biochemistry of the University of Bern. This group has already been working for some time on how molecules on a surface can be converted or combined into complex nanostructures according to the principle of molecular self-organisation. “The challenge now consists in finding the right precursor molecule which would actually grow on a smooth surface,” says Roman Fasel. This was ultimately achieved by Andreas Mueller and Konstantin Amsharov from the Max Planck Institute in Stuttgart with the synthesis of a hydrocarbon molecule from a not-inconsiderable 150 atoms.

Molecular origami on the platinum surface

What exactly is the process in which the carbon nanotube forms? In the first step, the flat precursor molecule must – as is the case in origami – convert into a three-dimensional object, the seed. This takes place on a hot platinum surface with the aid of a catalytic reaction, whereby hydrogen atoms split off from the precursor molecule and form new carbon-carbon bonds at very specific positions. The seed folds up from the flat molecule: a tiny, domed shape with open rim, which sits on the platinum surface. This so-called end cap forms the top of the growing SWCNT.

In a second chemical process, further carbon atoms, which are formed during the catalytic decomposition of ethanol on the platinum surface, are taken up. They deposit on the open rim between end cap and platinum surface and lift the cap higher and higher; the tube slowly grows upwards. The atomic structure of the nanotube is determined solely by the shape of the seed. The researchers proved this by analysing the vibrational modes of the SWCNTs and taking measurements with the scanning tunnelling microscope. Further investigations at Empa showed that the SWCNTs produced were over 300 nanometres in length.

Different nanotubes are formed from suitable precursor molecules

The researchers have thus proved that they can unambiguously specify the growth and thus the structure of long SWCNTs using custom-made molecular seeds. The SWCNTs synthesised in this study can exist in two forms, which correspond to an object and its mirror image. By choosing the precursor molecule appropriately, the researchers were able to influence which of the two variants forms. Depending on how the honeycomb atomic lattice is derived from the original molecule – straight or oblique with respect to the CNT axis – it is also possible for helically wound tubes, i.e. with right- or left-handed rotation, and with non-mirror symmetry to form. And it is precisely this structure that then determines which electronic, thermo-electric and optical properties of the material. In principle, the researchers can therefore specifically produce materials with different properties through their choice of precursor molecule.

In further steps, Roman Fasel and his colleagues want to gain an even better understanding of how SWCNTs establish themselves on a surface. Even if well in excess of 100 million nanotubes per square centimetre already grow on the platinum surface, only a relatively small fraction of the seeds actually develop into «mature» nanotubes. The question remains as to which processes are responsible for this, and how the yield can be increased.

Here’s a link to and a citation for the paper,

Controlled synthesis of single-chirality carbon nanotubes by Juan Ramon Sanchez-Valencia, Thomas Dienel, Oliver Gröning, Ivan Shorubalko, Andreas Mueller, Martin Jansen, Konstantin Amsharov, Pascal Ruffieux, & Roman Fasel. Nature 512, 61–64 (07 August 2014) doi:10.1038/nature13607

Published online 06 August 2014

This paper is behind a paywall.