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Graphene enables a more robust electrical system

Posted By Graphene Council, Monday, April 27, 2020
The use of more renewable energy sources in Europe will rely on the smart electric grids, able to distribute and store energy matching production and demand. Circuit breakers are safety-critical components of electric grids, associated with very high and recurring maintenance costs. By adding graphene to the circuit breakers, the electrical system will become more robust and reduce the costs of maintenance drastically.

Low voltage circuit breakers, common in domestic and industrial applications, need grease to function properly. The grease is applied to all circuit breakers during manufacturing. The problem is that the grease stiffens and dries out with age and has a narrow temperature range. This leads to a metal-to-metal wear that must be serviced at high maintenance costs, and to an increased risk of circuit breaker failure. Lack of lubrication is the number one problem that test technicians find when servicing circuit breakers in the field. 

Self-lubrication properties enables maintenance free operation
Graphene is a material with self-lubricating properties; the Swedish company ABB, partner of the Graphene Flagship research program, has recently demonstrated that multifunctional graphene-metal composite coatings could improve the tribological (interactive surfaces in relative motion) performance of metal contacts. ABB will thus lead a new project, starting in April 2020, with the aim to take such graphene-based composites to commercial applications.

The project, named “Circuitbreakers” is one of eleven selected Spearhead projects funded by the Graphene Flagship, Europe’s biggest initiative on graphene research, involving more than 140 universities and industries located in 21 countries. Chalmers University of Technology is the coordinator of the Graphene Flagship.
 
Prototype for industrial use
All spearheads will start in April 2020, building on previous scientific work performed in the Graphene Flagship in last years. The aim of the Circuitbreakers project is to develop a fully functional and tested prototype ready for industrial implementation in just three years. This new generation of circuit breakers will be self-lubricant and have a wider temperature range than existing circuit breaker options. This will enable maintenance-free operation, which will save business huge costs and reduce the risk on any undesired outage of the electrical system due to circuit breaker failure.

Extensive experience of graphene- and graphene-based composites
Prof. Vincenzo Palermo and Dr. Jinhua Sun from the Department of Industrial and Materials Science, Chalmers University of Technology will support ABB in the spearhead project providing new solutions to process graphene in coatings, to fabricate graphene-enhanced circuit breaker prototypes for practical application in the industrial scale. The research group has more than ten years of research experience in graphene and graphene-based composites. Their knowledge on characterization and processing of graphene-based materials will help industrial partners to select the appropriate graphene raw materials.

Prof. Palermo and Dr. Sun will help work on developing new chemical procedures and industrial applicable processing methods to coat graphene on the major component of circuit breakers. In addition, the advanced characterization techniques available at Chalmers Materials Analysis Laboratory (CMAL) will be important to evaluate the added value of graphene on the performance of circuit breaker.

Tags:  ABB  Chalmers University of Technology  energy  Graphene  Graphene Flagship  Jinhua Sun  Vincenzo Palermo 

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​Graphene cleans water more effectively

Posted By Graphene Council, Friday, March 27, 2020

Billions of cubic meters of water are consumed each year. However, lots of the water resources such as rivers, lakes and groundwater are continuously contaminated by discharges of chemicals from industries and urban area. It’s an expensive and demanding process to remove all the increasingly present contaminants, pesticides, pharmaceuticals, perfluorinated compounds, heavy metals and pathogens. Graphil is a project that aims to create a market prototype for a new and improved way to purify water, using graphene.

Graphene enhanced filters for water purification (GRAPHIL) is one of eleven selected spearhead projects funded by The Graphene Flagship, Europe’s biggest initiative on graphene research, involving more than 140 universities and industries located in 21 countries. Chalmers is the coordinator of the Graphene Flagship.

The purpose of the spearhead projects which will start in April 2020, building on previous scientific work, is to take graphene-enabled prototypes to commercial applications. Planned to end in 2023, the project aims to produce a compact filter that can be connected directly onto a household sink or used as a portable water purifying device, to ensure all households have access to safe drinking water.

"This is a brand-new research line for Chalmers in the Graphene flagship, and it will be a strategic one. The purification of water is a key societal challenge for both rich and poor countries and will become more and more important in the next future. In Graphil, hopefully we will use our knowledge of graphene chemistry to produce a new generation of water purification system via interface engineering of graphene-polysulfone nanocomposites," says Vincenzo Palermo, professor at the Department of industrial and materials science.
 
Graphene enhanced filters outperforms other water purification techniques
Most of the water purification processes today are based on several different techniques. These are adsorption on granular activated carbon that removes organic contaminants, membrane filtration that removes for example, bacteria or large pollutants, and reverse osmosis. Reverse osmosis is the only technique today that can remove organic or inorganic emerging concern contaminants with high efficiency. Reverse osmosis has however high electrical and chemical costs both from the operation and the maintenance of the system.
 
Many existing contaminants present in Europe’s water sources, including pharmaceuticals, personal care products, pesticides and surfactants, are also resistant to conventional purification technologies. Consequently, the number of cases of contamination of ground and even drinking water is rapidly increasing throughout the world, and it is matter of great environmental concern due to their potential effect on the human health and ecosystem.
 
Graphil is instead proposing to use graphene related material polymer composites. Thanks to the unique properties of graphene, the composite material favours the absorption of organic molecules. Its properties also allow the material to bind ions and metals, thus reducing the number of inorganic contaminants in water. Furthermore, unlike typical reverse osmosis, granular activated carbon and microfiltration train systems, the graphene system will provide a much simpler set up for users.

Graphil will not just replace all the old techniques, but significantly out-perform them both in efficiency and cost. The filter works as a simple microfiltration membrane, and this simplicity requires lower operation pressures, amounting in reduced water loss and lower maintenance costs for end users.
 
Upscaling the technique for industrial use
Chalmers has, in collaboration with other partners of the Graphene Flagship, investigated during the last years the fundamental structure-property relationships of graphene related material and polysulfones composition in water purification. A filter has then been successfully developed and validated in an industrial environment by the National Research Council of Italy (CNR) and the water filtration supplier Medica.

Now the task is to integrate the results and prove that the production can be upscaled in a complete system for commercial use.

Prof. Vincenzo Palermo and Dr. Zhenyuan Xia from the department of Industrial and Materials Science, Chalmers will support Graphil with advanced facilities for chemical, structural and mechanical characterization and processing of graphene oriented-polymer composite on the Kg scale. Chalmers’ role in the project will be to perform chemical functionalization of the graphene oxide and of the polymer fibers used in the filters, to enhance their compatibility and their performance in capturing organic contaminants.

"We are very excited to begin this new activity in collaboration with partners from United Kingdom, France and Italy, and I hope that my previous ten years’ international working experience in Italy and Sweden will help us to better fulfil this project," says Zhenyuan Xia, researcher at the Department of industrial and materials science.
 
 
Partners
Graphil is a multidisciplinary project that consists of both academic and industry partners. The academic partners include Chalmers, the National Research Council of Italy (CNR) and the University of Manchester. The industrial partners are Icon Lifesaver, Medica SpA and Polymem S.A – all European industry leaders in the water purification sector. The aim is to have a working filter prototype that can be commercialized by the industry for household water treatment and portable water purification.
 
Funding
The Graphene Flagship is one of the largest research projects funded by the European Commission. With a budget of €1 billion over 10 years, it represents a new form of joint, coordinated research, forming Europe's biggest ever research initiative. The Flagship is tasked with bringing together academic and industrial researchers to take graphene from academic laboratories into European society, thus generating economic growth, new jobs and new opportunities.
 
The total budget of the spearhead project GRAPHIL will be 4.88 million EURO and it will start from April 2020 with a total period of 3 years.

Tags:  Chalmers University of Technology  Graphene  Graphene Flagship  GRAPHIL  nanocomposites  Vincenzo Palermo  water purification  Zhenyuan Xia 

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Graphite nanoplatelets on medical devices kill bacteria and prevent infections

Posted By Graphene Council, Friday, March 27, 2020
Graphite nanoplatelets integrated into plastic medical surfaces can prevent infections, killing 99.99 per cent of bacteria which try to attach -- a cheap and viable potential solution to a problem which affects millions, costs huge amounts of time and money, and accelerates antibiotic resistance. This is according to research from Chalmers University of Technology, Sweden, in the journal Small.

Every year, over four million people in Europe are affected by infections contracted during health-care procedures, according to the European Centre for Disease Prevention and Control (ECDC). Many of these are bacterial infections which develop around medical devices and implants within the body, such as catheters, hip and knee prostheses or dental implants. In worst cases implants need to be removed.

Bacterial infections like this can cause great suffering for patients, and cost healthcare services huge amounts of time and money. Additionally, large amounts of antibiotics are currently used to treat and prevent such infections, costing more money, and accelerating the development of antibiotic resistance.

"The purpose of our research is to develop antibacterial surfaces which can reduce the number of infections and subsequent need for antibiotics, and to which bacteria cannot develop resistance. We have now shown that tailored surfaces formed of a mixture of polyethylene and graphite nanoplatelets can kill 99.99 per cent of bacteria which try to attach to the surface," says Santosh Pandit, postdoctoral researcher in the research group of Professor Ivan Mijakovic at the Division of Systems Biology, Department of Biology and Biotechnology, Chalmers University of Technology.

Infections on implants are caused by bacteria that travel around in the body in fluids such as blood, in search of a surface to attach to. When they land on a suitable surface, they start to multiply and form a biofilm -- a bacterial coating.

Previous studies from the Chalmers researchers showed how vertical flakes of graphene, placed on the surface of an implant, could form a protective coating, making it impossible for bacteria to attach -- like spikes on buildings designed to prevent birds from nesting. The graphene flakes damage the cell membrane, killing the bacteria. But producing these graphene flakes is expensive, and currently not feasible for large-scale production.

"But now, we have achieved the same outstanding antibacterial effects, but using relatively inexpensive graphite nanoplatelets, mixed with a very versatile polymer. The polymer, or plastic, is not inherently compatible with the graphite nanoplatelets, but with standard plastic manufacturing techniques, we succeeded in tailoring the microstructure of the material, with rather high filler loadings, to achieve the desired effect. And now it has great potential for a number of biomedical applications," says Roland Kádár, Associate Professor at the Department of Industrial and Materials Science at Chalmers.

The nanoplatelets on the surface of the implants prevent bacterial infection but, crucially, without damaging healthy human cells. Human cells are around 25 times larger than bacteria, so while the graphite nanoplatelets slice apart and kill bacteria, they barely scratch a human cell.

"In addition to reducing patients' suffering and the need for antibiotics, implants like these could lead to less requirement for subsequent work, since they could remain in the body for much longer than those used today," says Santosh Pandit. "Our research could also contribute to reducing the enormous costs that such infections cause health care services worldwide."

In the study, the researchers experimented with different concentrations of graphite nanoplatelets and the plastic material. A composition of around 15-20 per cent graphite nanoplatelets had the greatest antibacterial effect -- providing that the morphology is highly structured.

"As in the previous study, the decisive factor is orienting and distributing the graphite nanoplatelets correctly. They have to be very precisely ordered to achieve maximum effect," says Roland Kádár.

Tags:  Chalmers University of Technology  Graphene  Graphite  Healthcare  Ivan Mijakovic  Medical Devices  nanoplatelets  Roland Kádár  Santosh Pandit 

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Graphite nanoplatelets on medical devices kill bacteria and prevent infections

Posted By Graphene Council, Friday, March 27, 2020
Graphite nanoplatelets integrated into plastic medical surfaces can prevent infections, killing 99.99 per cent of bacteria which try to attach - a cheap and viable potential solution to a problem which affects millions, costs huge amounts of time and money, and accelerates antibiotic resistance. This is according to research from Chalmers University of Technology, Sweden, in the journal Small.

Every year, over four million people in Europe are affected by infections contracted during health-care procedures, according to the European Centre for Disease Prevention and Control (ECDC). Many of these are bacterial infections which develop around medical devices and implants within the body, such as catheters, hip and knee prostheses or dental implants. In worst cases implants need to be removed.

Bacterial infections like this can cause great suffering for patients, and cost healthcare services huge amounts of time and money. Additionally, large amounts of antibiotics are currently used to treat and prevent such infections, costing more money, and accelerating the development of antibiotic resistance.

"The purpose of our research is to develop antibacterial surfaces which can reduce the number of infections and subsequent need for antibiotics, and to which bacteria cannot develop resistance. We have now shown that tailored surfaces formed of a mixture of polyethylene and graphite nanoplatelets can kill 99.99 per cent of bacteria which try to attach to the surface," says Santosh Pandit, postdoctoral researcher in the research group of Professor Ivan Mijakovic at the Division of Systems Biology, Department of Biology and Biotechnology, Chalmers University of Technology.

Infections on implants are caused by bacteria that travel around in the body in fluids such as blood, in search of a surface to attach to. When they land on a suitable surface, they start to multiply and form a biofilm - a bacterial coating.

Previous studies from the Chalmers researchers showed how vertical flakes of graphene, placed on the surface of an implant, could form a protective coating, making it impossible for bacteria to attach - like spikes on buildings designed to prevent birds from nesting. The graphene flakes damage the cell membrane, killing the bacteria. But producing these graphene flakes is expensive, and currently not feasible for large-scale production.

"But now, we have achieved the same outstanding antibacterial effects, but using relatively inexpensive graphite nanoplatelets, mixed with a very versatile polymer. The polymer, or plastic, is not inherently compatible with the graphite nanoplatelets, but with standard plastic manufacturing techniques, we succeeded in tailoring the microstructure of the material, with rather high filler loadings, to achieve the desired effect. And now it has great potential for a number of biomedical applications," says Roland Kádár, Associate Professor at the Department of Industrial and Materials Science at Chalmers.

The nanoplatelets on the surface of the implants prevent bacterial infection but, crucially, without damaging healthy human cells. Human cells are around 25 times larger than bacteria, so while the graphite nanoplatelets slice apart and kill bacteria, they barely scratch a human cell.

"In addition to reducing patients' suffering and the need for antibiotics, implants like these could lead to less requirement for subsequent work, since they could remain in the body for much longer than those used today," says Santosh Pandit. "Our research could also contribute to reducing the enormous costs that such infections cause health care services worldwide."

In the study, the researchers experimented with different concentrations of graphite nanoplatelets and the plastic material. A composition of around 15-20 per cent graphite nanoplatelets had the greatest antibacterial effect - providing that the morphology is highly structured.

"As in the previous study, the decisive factor is orienting and distributing the graphite nanoplatelets correctly. They have to be very precisely ordered to achieve maximum effect," says Roland Kádár.

Tags:  Chalmers University of Technology  Graphene  Graphite  Healthcare  Ivan Mijakovic  Medical Devices  nanoplatelets  Plastics  Roland Kádár  Santosh Pandit 

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Graphene gas sensors for real-time monitoring of air pollution

Posted By Graphene Council, Tuesday, January 7, 2020
Scientists at the National Physical Laboratory (NPL), working with partners from the Graphene Flagship, Chalmers University of Technology, the Advanced Institute of Technology, Royal Holloway University and Linköping University, have created a low-cost, low-energy consuming NO2 sensor that measures NO2 levels in real-time.

The World Health Organisation reported that 4.2 million deaths every year are a direct result of exposure to ambient air pollution such as NO2, SO2, NH3, CO2 and CO. One of the most dangerous pollutants, NO2 gas, is produced by burning fossil fuels e.g. in diesel engines. Significant portions of the population in large cities, specifically London, have been consistently exposed to NO2 levels above the legislated limit. Even at very low concentrations NO2 is toxic for humans, leading to breathing problems, asthma attacks and potentially causing childhood obesity and dementia.  

NPL and partners have developed a graphene-based NO2 detector that reports pollutant levels based on changes in its electrical resistance. The high sensitivity of graphene to the local environment has shown to be highly advantageous in sensing applications, where ultralow concentrations of absorbed molecules induce a significant response on the electronic properties of graphene. The unique electronic structure makes graphene the ‘ultimate’ sensing material for applications in environmental monitoring and air quality.  

NPL has developed and demonstrated the novel type of NO2 sensors based on different types of graphene. This low-cost and technologically simple solution uses simple chemiresistor approach and allows for measurements of the exceedingly low levels of NO2 e.g. below 10 ppb. 1 ppb is a concentration equal to a droplet of ink in 2 Olympic size swimming pools. According to the World Health Organisation’s guidelines the targeted level of NO2 pollution in cities is 21 ppb however, the typical average level in London is 30-40 ppb.    

There is a well-demonstrated global need for high sensitivity, low-cost, low-energy consumption miniaturised NO2 gas sensors to be deployed in a dense network and to be used to pinpoint and avoid high pollution hot spots. Such sensors operating in real-time can help to visualise pollution in urban areas with unprecedently high local resolution. 

Olga Kazakova, National Physical Laboratory (NPL) states: “Understanding the problem is the first step to solving the problem. If you only monitor certain junctions or roads for NO2 pollution, you do not get an accurate picture of the environment. In order to do this, a dense network must be set up to show the dynamically changing level of pollution through different times of day and year, so you can get to know the real level of critical exposure.” 

With the data provided by a dense network of graphene sensors, people could us an app to check how much NO2 pollution they might be exposed to on their planned route, and city councils could use this information to dynamically restrict and divert cars near schools and hospitals. This would enable governing bodies to adopt smart and flexible restrictive measures in specific areas recognised as being highly pollutive. 

Tags:  Chalmers University of Technology  environment  Graphene  Graphene Flagship  National Physical Laboratory  Olga Kazakova  pollution  Sensors 

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Sustainable material for carbon dioxide capture

Posted By Graphene Council, Monday, December 9, 2019
In a joint research study from Sweden, scientists from Chalmers University of Technology and Stockholm University have developed a new material for capturing carbon dioxide. The new material offers many benefits – it is sustainable, has a high capture rate, and has low operating costs. The research has been published in the journal ACS Applied Materials & Interfaces.

Carbon Capture and Storage (CCS) is a technology that attracts a lot of attention and debate. Large investments and initiatives are underway from politicians and industry alike, to capture carbon dioxide emissions and tackle climate change. So far, the materials and processes involved have been associated with significant negative side effects and high costs. But now, new research from Chalmers University of Technology and Stockholm University in Sweden has demonstrated the possibility of a sustainable, low-cost alternative with excellent, selective carbon dioxide-capturing properties.

The new material is a bio-based hybrid foam, infused with a high amount of CO2-adsorbing ‘zeolites’ – microporous aluminosilicates. This material has been shown to have very promising properties. The porous, open structure of the material gives it a great ability to adsorb the carbon dioxide.

“In the new material, we took zeolites, which have excellent capabilities for capturing carbon dioxide, and combined them with gelatine and cellulose, which has strong mechanical properties. Together, this makes a durable, lightweight, stable material with a high reusability. Our research has shown that the cellulose does not interfere with the zeolites’ ability to adsorb carbon dioxide. The cellulose and zeolites together therefore create an environmentally friendly, affordable material,” says Walter Rosas Arbelaez, PhD student at Chalmers' Department of Chemistry and Chemical Engineering and one of the researchers behind the study.

Fits well with the ongoing developments within CCS and CCU

The researchers’ work has yielded important knowledge and points the way for further development of sustainable carbon capture technology. Currently, the leading CCS technology uses ‘amines’, suspended in a solution. This method has several problems – amines are inherently environmentally unfriendly, larger and heavier volumes are required, and the solution causes corrosion in pipes and tanks. Additionally, a lot of energy is required to separate the captured carbon dioxide from the amine solution for reuse. The material now presented avoids all of these problems. In future applications, filters of various kinds could be easily manufactured.

“This research fits well with the ongoing developments within CCS and CCU (Carbon Capture and Utilisation) technology, as a sustainable alternative with great potential. In addition to bio-based materials being more environmentally friendly, the material is a solid – once the carbon dioxide has been captured, it is therefore easier and more efficient to separate it than from the liquid amine solutions,” says Professor Anders Palmqvist, research leader for the study at Chalmers.

Overcoming a difficult obstacle – vital breakthrough

Zeolites have been proposed for carbon capture for a long time, but so far, the obstacle has been that ordinary, larger zeolite particles are difficult to work with when they are processed and implemented in different applications. This has prevented them from being optimally used. But the way the zeolite particles have been prepared this time – as smaller particles in a suspension – means they can be readily incorporated in and supported by the highly porous cellulose foam. Overcoming this obstacle has been a vital breakthrough of the current study.

“What surprised us most was that it was possible to fill the foam with such a high proportion of zeolites. When we reached 90% by weight, we realized that we had achieved something exceptional. We see our results as a very interesting piece of the puzzle in the search for a solution to the complex challenge of being able to reduce the amount of carbon dioxide in the Earth's atmosphere quickly enough to meet climate goals,” says Walter Rosas Arbelaez.

Tags:  ACS Applied Materials & Interfaces  Anders Palmqvist  Carbon Dioxide  Chalmers University of Technology  Graphene  Stockholm University  Walter Rosas Arbelaez 

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Graphene sponge helps lithium sulphur batteries reach new potential

Posted By Graphene Council, Friday, May 3, 2019
Updated: Wednesday, May 1, 2019
To meet the demands of an electric future, new battery technologies will be essential. One option is lithium sulphur batteries, which offer a theoretical energy density more than five times that of lithium ion batteries. Researchers at Chalmers University of Technology, Sweden, recently unveiled a promising breakthrough for this type of battery, using a catholyte with the help of a graphene sponge.

The researchers' novel idea is a porous, sponge-like aerogel, made of reduced graphene oxide, that acts as a free-standing electrode in the battery cell and allows for better and higher utilisation of sulphur.

A traditional battery consists of four parts. First, there are two supporting electrodes coated with an active substance, which are known as an anode and a cathode. In between them is an electrolyte, generally a liquid, allowing ions to be transferred back and forth. The fourth component is a separator, which acts as a physical barrier, preventing contact between the two electrodes whilst still allowing the transfer of ions.

The researchers previously experimented with combining the cathode and electrolyte into one liquid, a so-called 'catholyte'. The concept can help save weight in the battery, as well as offer faster charging and better power capabilities. Now, with the development of the graphene aerogel, the concept has proved viable, offering some very promising results.

Taking a standard coin cell battery case, the researchers first insert a thin layer of the porous graphene aerogel.

"You take the aerogel, which is a long thin cylinder, and then you slice it - almost like a salami. You take that slice, and compress it, to fit into the battery," says Carmen Cavallo of the Department of Physics at Chalmers, and lead researcher on the study. Then, a sulphur-rich solution - the catholyte - is added to the battery. The highly porous aerogel acts as the support, soaking up the solution like a sponge.

"The porous structure of the graphene aerogel is key. It soaks up a high amount of the catholyte, giving you high enough sulphur loading to make the catholyte concept worthwhile. This kind of semi-liquid catholyte is really essential here. It allows the sulphur to cycle back and forth without any losses. It is not lost through dissolution - because it is already dissolved into the catholyte solution," says Carmen Cavallo.

Some of the catholyte solution is applied to the separator as well, in order for it to fulfil its electrolyte role. This also maximises the sulphur content of the battery.

Most batteries currently in use, in everything from mobile phones to electric cars, are lithium-ion batteries. But this type of battery is nearing its limits, so new chemistries are becoming essential for applications with higher power requirements. Lithium sulphur batteries offer several advantages, including much higher energy density. The best lithium ion batteries currently on the market operate at about 300 watt-hours per kg, with a theoretical maximum of around 350. Lithium sulphur batteries meanwhile, have a theoretical energy density of around 1000-1500 watt-hours per kg.

"Furthermore, sulphur is cheap, highly abundant, and much more environmentally friendly. Lithium sulphur batteries also have the advantage of not needing to contain any environmentally harmful fluorine, as is commonly found in lithium ion batteries," says Aleksandar Matic, Professor at Chalmers Department of Physics, who leads the research group behind the paper.

The problem with lithium sulphur batteries so far has been their instability, and consequent low cycle life. Current versions degenerate fast and have a limited life span with an impractically low number of cycles. But in testing of their new prototype, the Chalmers researchers demonstrated an 85% capacity retention after 350 cycles.

The new design avoids the two main problems with degradation of lithium sulphur batteries - one, that the sulphur dissolves into the electrolyte and is lost, and two, a 'shuttling effect', whereby sulphur molecules migrate from the cathode to the anode. In this design, these undesirable issues can be drastically reduced.

Tags:  Aleksandar Matic  Battery  Carmen Cavallo  Chalmers University of Technology  Graphene  Li-ion Batteries  Lithium 

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New research uses graphene sensors to detect ultralow concentrations of NO2

Posted By Graphene Council, Wednesday, April 10, 2019
Updated: Wednesday, April 10, 2019
The research, as published in ACS Sensors, was led by an international collaboration of scientists from Linköping University, Chalmers University of Technology, Royal Holloway, University of London and the University of Surrey.

The findings demonstrate why single-layer graphene should be used in sensing applications and opens doors to new technology for use in environmental pollution monitoring, new portable monitors and automotive and mobile sensors for a global real-time monitoring network.

As part of the research, graphene-based sensors were tested in conditions resembling the real environment we live in and monitored for their performance. The measurements included, combining NO2, synthetic air, water vapor and traces of other contaminants, all in variable temperatures, to fully replicate the environmental conditions of a working sensor.

Key findings from the research showed that, although the graphene-based sensors can be affected by co-adsorption of NO2 and water on the surface, at about room temperature, their sensitivity to NO2 increased significantly when operated at elevated temperatures, 150 °C. This shows graphene sensitivity to different gases can be tuned by performing measurements at different temperatures.

Testing also revealed a single-layer graphene exhibits two times higher carrier concentration response upon exposure to NO2 than bilayer graphene — demonstrating single-layer graphene as a desirable material for sensing applications.

Christos Melios, a lead scientist on the project from NPL, said: “Evaluating the sensor performance in conditions resembling the real environment is an essential step in the industrialisation process for this technology.

“We need to be able to clarify everything from cross-sensitivity, drift in analysis conditions and recovery times, to potential limitations and energy consumption, if we are to provide confidence and consider usability in industry.”

By developing these very small sensors and placing them in key pollution hotspots, there is a potential to create a next-generation pollution map – which will be able to pinpoint the source of pollution earlier, in unprecedented detail, outlining the chemical breakdown of data in high resolution in a wide variety of climates.

Christos continued: “The use of graphene into these types of gas sensors, when compared to the standard sensors used for air emissions monitoring, allows us to perform measurements of ultra-low sensitivity while employing low cost and low energy consumption sensors. This will be desirable for future technologies to be directly integrated into the Internet of Things.”

NO2 typically enters the environment through the burning of fuel, vehicle emissions, power plants, and off-road equipment. Extreme exposure to NO2 can increase the chances of respiratory infections and asthma. Long-term exposure can cause chronic lung disease and is linked to pollution related death across the world.  

Figures from the European Environment Agency also links NO2 pollution to premature deaths in the UK, with the UK being ranked as having the second highest number of annual deaths in Europe. In 2014, 14,050 deaths in the UK were recorded as being NO2 pollution related, 5,900 of which were recorded in London alone1.

When interacted with water and other chemicals, NO2 can also form into acid rain, which severely damages sensitive ecosystems, such as lakes and forests.

Existing legislation from the European Commission suggests hourly exposure to NO2 concentration should not be exceeded by more than 200 micrograms per cubic metre (µg/m3) or ~106 parts per billion (ppb), and no more than 18 times annually. This translates to an annual mean of 40 mg m3 (~21 ppb) NO2 concentration2

In central London, for example, the average NO2 concentration for 2017 showed concentration levels of NO2 ranged from 34.2 to 44.1 ppb per month, a huge leap from the yearly average.

These figures show there is an urgent need for a low-cost solution to mitigate the impact of NO2 in the air around us. This work could provide the answer to early detection and prevention of these types of pollutants, in line with the government’s Clean Air Strategy.

Further experimentation in this area could see the graphene-based sensors introduced into industry within the next 2–5 years, providing an unprecedented level of understanding of the presence of NO2 in our air.

Tags:  Chalmers University of Technology  Christos Melios  Graphene  Linköping University  National Physical Laboratory  Royal Holloway  Sensors  University of London  University of Surrey 

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