2019 has been declared by UNESCO as the Year of the Periodic Table. To celebrate, we are releasing a series of blogs about our favourite elements and their importance to the chemical industry. Today’s blog is about one of the most abundant and most used elements, carbon!
Carbon could be called the element of life – it can be found in every living creature on Earth in a variety of different forms, from the backbone of your DNA, to the taste receptors in your tongue and the hormones controlling your hunger. Carbon-based chemistry surrounds us – in the air we breathe, in the food we eat and in the soil beneath our feet.
So, why is carbon so important to life? Carbon’s chemistry allows it to form large, intricate 3D structures, which are the basis of its interaction in biology – like jigsaw pieces that come together to build a tree, an elephant or a human being.
The study of carbon-based chemistry, or organic chemistry, has allowed us to better understand our living world and the interactions that occur, leading to development of better tasting food, higher yielding crops and more efficient medicines to improve our health.
In the early 19th century, chemist Justus von Liebig began synthesising organic, carbon-based molecules and said: ‘The production of all organic substances no longer belongs just to living organisms.’
Since then, hundreds of organic compounds for medicinal use have been synthesised – from adrenaline to ibuprofen – and hundreds of unique synthesis pathways have been described.
Organic chemistry – the study of carbon-based chemistry – has given us hundreds of modern medicines.
Carbon in materials
Atoms of carbon can make four bonds, each with another carbon attached, to arrange themselves into different molecular structures and form completely different substances. These molecular structures, known as allotropes, can result in vast differences in the end-result material.
For example, one allotrope, diamond, is the hardest and highest thermally conductive of any natural material, whereas another, graphite, is soft enough to be used in pencils, and is highly conductive of electricity.
Graphene is carbon allotrope that exists in thin, 2-dimensional layers, with the carbon atoms arranged in a honeycomb formation. Scientists had theorised its existence for years, but it was not isolated and characterised until 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester, UK. The pair won the 2010 Nobel Prize in Physics for their work.
The structure of carbon atoms in graphene.
Graphene is a highly conductive, flexible and transparent – this means it can be used in electronics, medical biotechnology, and a variety of other innovative solutions.
Another innovative material made from carbon is carbon fibre, which can then produce carbon-fibre reinforced polymer (CFRP). CFRP is a polymer interwoven with fibres of carbon, which is 5-10μm in diameter. The mixture of these two materials gives an extremely strong but lightweight material, useful in building products from aerospace and automotive, to sports equipment and technology.
Fueling the world
The name carbon comes from the Latin carbo meaning coal, and until recently most of our energy was generated by the consumption of carbon through the burning of naturally occurring carbon-based fuels, or fossil fuels. When these fuels, such as coal, natural gas and oil, are burnt, the combustion reaction generates carbon dioxide (CO2).
CO2, produced by burning fossil fuels, is thought to be a contributor to climate change. Image: Pixabay
High production of the by-product CO2, and its release into the atmosphere, is considered to have a negative environmental impact and is thought to contribute to global warming and climate change. Fossil fuels are not a renewable resource and supplies are expected to diminish in the next 50-100 years.
Consequently, there has been a movement towards more renewable energy, from wind, solar and hydropower, driving a move towards a low-carbon economy. These energy sources are generally considered to be better for the environment, with lower amounts of CO2 being produced.
Chemical engineer Jennifer Wilcox previews some amazing technology to scrub carbon from the air, using chemical reactions that capture and reuse CO2. Video: TED
In this strive for a low-carbon economy, new technology is being used that prevents the release of CO2 into the atmosphere in the first place. Carbon capture and storage (CCS) takes waste CO2 from large-scale industrial processes and transports it to a storage facility. This CCS technology is one of the only proven, effective methods of decarbonisation currently available.
2D materials have a thickness of just one molecule, which makes them especially promising for use in quantum computing, as electrons are restricted by movement across two dimensions, as the wavelength of the electron is longer than the thickness of the material.
The most well known of these new materials is graphene – a single layer or carbon – which since its Nobel prize-winning synthesis in 2004 has been posited as a game-changer in applications ranging from tissue engineering and water filtration to energy generation and organic electronics.
Now, an international team at DTU led by Assistant Professor Kasper Steen Pedersen has synthesised a novel nanomaterial with electrical and magnetic properties that the researchers claim make it suitable for future quantum computers and other applications in electronics.
Since graphene’s discovery, hundreds of new 2D materials have been synthesised, but the new material, published in Nature Chemistry, is based on a different concept. While the other 2D material candidates are all inorganic, chromium-chloride-pyrazine (chemical formula CrCl2(pyrazine)2) is an organic-inorganic hybrid material.
Water scarcity is a truly global problem, affecting each continent and a total of 2.8bn people across the world. By 2025, 15% of the global population will not have access to sufficient water resources.
Water usage is expected to grow by 40% in the coming 20 years as demand grows from industry and agriculture, driven by accelerating population growth and increased urbanisation.
Insufficient water supply affects the health of children disproportionally, as a decrease in food and nutrient intake can lead to problems with growth and an individual’s immune system.
A shortage of water can lead to communities relying on poorly sanitised water, allowing infections that can cause diarrhoea and intestinal parasites. Both can be deadly in areas without access to quality healthcare.
A family in Somalia collects their daily water allowance. Image: Oxfam International/Flickr
But it is not only a scarcity of clean drinking water that presents a global health challenge – the agriculture industry relies on an increasing supply of fresh water for food production. It is estimated that the number of crops such as wheat, rice, and maize will decrease by 43% by the end of the 21st century.
Agriculture accounts for 70% of the world’s water use, and is constantly competing with domestic and industrial uses for an already dwindling water supply. The World Wide Fund for Nature claims that many countries, such as the US, China, and India, have already reached their renewable water resource limits.
Agriculture is responsible for 70% of the world’s water usage.
The most popular current desalination methods – the process by which salt and minerals are removed from water – are thermal and membrane desalination. Both are energy-intensive and often not cost-efficient for developing countries, which are the most likely to struggle with poor water sanitation and shortages.
As a result, both the healthcare and agricultural industries are desperately searching for a solution.
A graphene-oxide membrane is at the forefront of new water filtration techniques. Image: University of Manchester
In Manchester, UK, the development of graphene – a material comprised of a single-layer of carbon in a honeycomb structure – is revolutionising modern membrane desalination and water filtration techniques.
An ultra-thin graphene-oxide membrane developed at the University of Manchester is not only able to separate water and salt – proving to be completely impermeable to all solvents but water – but other compounds as well.
A reverse osmosis desalination plant. Image: James Grellier/Wikimedia Commons
The technology – called organic solvent nanofiltration – separates organic compounds by charge and can differentiate solvents by the nanometre. The group tested the membranes using alcohol, such as whisky and cognac, and various dyes with successful results.
‘The developed membranes are not only useful for filtering alcohol, but the precise sieve size and high flux open new opportunities to separate molecules from different organic solvents for chemical and pharmaceutical industries,’ said Rahul Nair, team leader at the National Graphene Institute and Professor of Chemical Engineering and Analytical Science at the University of Manchester.
‘This development is particularly important because most of the existing polymer-based membranes are unstable in organic solvents, whereas the developed graphene-oxide membrane is highly stable.’
Graphene: Membranes and their practical applications. Video: The University of Manchester - The home of graphene
The graphene-oxide membrane is made up of sheets that are stacked in a way that creates pinholes connected by graphene nanochannels. The structure forms an atomic-scale sieve allowing the flow of solvents through the membrane.
Not only is the technology able to filter smaller molecules than existing filtration techniques – it also improves filtration efficiency by increasing the solvent flow rate.
‘Chemical separation is all about energy, with various chemical separation processes consuming about half of industrial energy usage,’ said Prof Nair. ‘Any new efficient separation process will minimise the consumption of energy, which is in high demand now.’
The Concorde was the first commercial supersonic aircraft to have been built. Image: Wikimedia Commons
In 2011, a chance encounter under the wings of Concorde at Duxford Air Museum, Cambridge, with Trinity College Dublin Professor Johnny Coleman, would set in motion a series of events that would lead, six years later, to the development of a 20t/year graphene manufacturing plant.
As soon as we got talking, I was impressed by Johnny’s practical, non-nonsense approach to solving the scalability issue with graphene production.
Coleman is a physicist, not a chemist, and believed that the solution lay in mechanical techniques. Following the conference, Thomas Swan agreed to fund his group for four years to develop a scalable process for the manufacture of graphene.
Just a nanometer thick, graphene consists of a single layer of carbon atoms joined in a hexagonal lattice. Image: Pixabay
Coleman and his team initially considered sonication – when sound waves are applied to a sample to agitate its particles – but quickly ruled it out due to its lack of scalability. He then sent one of his researchers out to the shops to buy a kitchen blender. They threw together some graphite, water, and a squirt of washing-up liquid into the blender, switched it on, and went for a cup of coffee.
When they later analysed the ‘grey soup’ they had created, they found they had successfully made few-layer graphene platelets. The group then spent months optimising the technique and worked closely with Thomas Swan scientists to transfer the process back to Thomas Swan’s manufacturing HQ in Consett, Ireland.
Graphene is 300 times stronger than steel.
The plant can make up to 20t/year of high quality graphene. It uses a high sheer continuous process to exfoliate graphite flakes into few-layer graphene platelets in an aqueous dispersion.
The dispersion is stabilised by adding various surfactants before separating out the graphene using continuous cross-flow filtration devices developed with the support of the UK’s Centre for Process Innovation (CPI), part of the High Value Manufacturing Catapult – a government initiative focused on fostering innovation and economic growth in specific research areas.
Using sticky tape, scientists pulled off graphene sheets from a block of graphite. Image: Pixabay
This de-risking of process development using a Catapult is a classic example of effective government intervention to support innovative SMEs. CPI not only showed us it worked, but also optimised the technique for us.
The company quickly realised that selling graphene in a powder form with no application data was not going to work. Instead, we developed a range of performance data to assist the sales team by highlighting what graphene can do if adopted into a range of applications.
The potential of graphene can be commercialised using composites. Video: The University of Manchester – The home of graphene
We also moved to make the product available in ‘industry friendly’ forms such as epoxy resin dispersions or polymer masterbatches. This move, slightly downstream from the raw material, has recently led to Thomas Swan announcing its intention to expand its range of formulated graphene materials, with a prototype product focusing on the manufacture of a carbon fibre composite.
Our application data shows that graphene has significant benefits as an industrial additive. Presenting this data to composite-using downstream customers is starting to open doors and create supply chain partnerships to get a raw material all the way to a fully integrated application.
Andre Geim and Kostya Novoselov won the 2010 Nobel Prize in Physics for their discovery of graphene. Image: Wikimedia Commons
The move downstream, to develop useable forms of graphene, is common in the industry, with most graphene suppliers now making their products available as an ink, dispersion or masterbatch. Thomas Swan’s experience with single-wall carbon nanotubes has made us aware of the need to take more control of graphene application development to ensure rapid market adoption.
Graphene applications drawing most interest include composites, conductive inks, battery materials, and resistive heating panels, although much of this demand is to satisfy commercial R&D rather than full commercial production.
Graphene science | Mikael Fogelström | TEDxGöteborg. Video: TEDx Talks
Thanks to innovations like our continuous high sheer manufacturing process, Thomas Swan believes that graphene is about to become very easy to make. Before it can be considered a commodity, however, it will also need to deliver real value in downstream applications. Therefore, the company is also increasing its efforts to understand market driven demand and application development.
As the initial hype over the ‘wonder’ material graphene starts to wane, progress is being made to develop scalable manufacturing techniques and to ensure graphene delivers some much-promised benefits to downstream applications.
What is paralysis? Video: Doctors’ Circle
Patients suffering from paralysis can at last look forward to a time when their condition is cured, and they can walk, run or move their damaged limbs again, as recent advancements show the possibility of reversal.
‘The environment has never been better for exploring ways to restore neurological function, including paralysis – in fact, there has been a dramatic escalation of the entire research spectrum aimed at functional neurorestoration,’ says Charles Liu, Director of the University of Southern California Neurorestoration Center.
Paralysis comes in many forms: the paralysis of one limb (monoplegia), one side of the body (hemiplegia), below the waist (paraplegia), and all four limbs below the neck (tetraplegia, or also referred to as quadriplegia).
There are many classifications of paralysis. It can be localised or generalised, and can affect most areas of the body. Image: Pixabay
In an able-bodied person, the brain sends a signal as an electrical impulse, known as an action potential, down the spinal cord to the peripheral nerves, which instruct the muscles to contract and move, whereupon sensors in the muscles and skin send signals back to the brain.
In most paralysis cases, the condition occurs as a result of damage to nerves rather than an injury to the affected area. Strokes are the most common cause of paralysis, followed by spinal cord injuries. Multiple sclerosis, cerebral palsy, polio, head injuries and several other rare diseases can also cause paralysis.
‘Long term, we hope to cure paralysis and make the injured walk,’ explains William Sikkema, a graduate student at Rice University, Houston. The challenge is not only to repair cells but to restore connectivity, too. In collaboration with researchers at Konkuk University in South Korea, the team has already made a paralysed rat walk again.
The addition of graphene nanoribbons restored motor and sensory neuronal signals across the previous nerve gap after 24 hours, with almost perfect motor control recovery after a period of healing. ‘Two weeks later, the rat could walk without losing balance, stand up on his hind limbs and use his forelimbs to feed himself with pellets. No recovery was observed in controls,’ the team reported.
‘After a neuron is cut, it doesn’t know where to grow. So, it either doesn’t grow, or grows in the wrong direction,’ says Sikkema. ‘Our graphene nanoribbons act as a scaffolding track, and it tells the neurons where to grow.’
Rats are a common animal model in paralysis studies, as they share similar structure and functions with humans. Image: Pexels
Spinal cord stimulation
Electrical stimulation of the spinal cord could also provide a big breakthrough, says Chet Moritz, Co-Director of the Center for Sensorimotor Neural Engineering at the University of Washington, US.
‘We’re seeing some really impressive results with spinal cord stimulation where people with complete paralysis, who have been unable to function, have regained control of their limbs. We didn’t expect this. It’s the most exciting thing we’ve seen in the last 20 years,’ he says.
Last year, a team led by Grégoire Courtine at the Swiss Federal Institute of Technology inserted an implant in the brains of paralysed monkeys and another over the spinal cord below the injury. The brain-spine interface worked by capturing leg-moving brain signals, decoded by a computer and sent – bypassing the damaged region – to the second implant, which delivered the signals as electrical impulses to the nerves, causing the leg to move.
Grégoire Courtine talks about his pioneering work on paralysis using electrical stimulation. Video: TED
Within six days, the monkeys had regained the use of their lower limbs and improved even more over time. The success of the experiment has led Courtine to launch a human trial of a spinal implant system.
We may be a long way still from restoring full function, as prior to paralysis, but Moritz is optimistic. Even a modest change, such as the movement of a single finger, can have a dramatic effect on quality of life and independence. ‘In five years, we’ve had dramatic improvement in function,’ he says. ‘It’s an exciting trajectory with tremendous potential.’