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Graphene providing a firm foundation for a more sustainable construction industry

Posted By Graphene Council, Wednesday, September 23, 2020

If we want to achieve a zero carbon world we literally need to build it in a different way. Here, James Baker, CEO of Graphene@Manchester talks about the need to support and accelerate graphene innovation to help make building materials much more sustainable in a bid to meet regional and national net zero targets.

• Greater Manchester (UK) aims to ensure all new buildings and infrastructure built in the city-region to be net zero by 2028

• Innovation in new materials and processes could help build a zero carbon world from the foundations up – but this pioneering work needs to be expedited through national investment to keep pace with policy ambitions

• A recent review has suggested the addition of just 0.03% graphene powder can increase the strength of concrete by a conservative average of 25%

• A UK advanced research catalyst modelled on the USA’s Advanced Research Projects Agency should adopt a ‘fail fast, learn fast’ series of projects to fast-track the testing of sustainable building materials

A headline aim of Greater Manchester’s ambitious policy blueprint for homes, jobs and the environment proposes all new buildings and infrastructure that are built in the city-region to be net zero for carbon emissions by 2028 – a move the local authority has said is key to achieving its overarching pledge to become a carbon-neutral region by 2038.

Under the new policy, buildings will be required to produce no operational carbon emissions. But another important consideration is to look at the opportunities to support carbon-neutral construction and encouraging ‘greener’ supply chains.

Innovation in new materials and processes will help planners to build a zero carbon world from the foundations up.

Graphene and 2D materials can help provide some of the technology breakthroughs needed for sustainable construction – and an obvious candidate is putting graphene in concrete. According to Chatham House, the international affairs institute, the global production of cement – the ‘glue’ that holds concrete together – accounts for a staggering 8% of the world’s CO2 production.

Interestingly, recent experiments with graphene enhanced concrete have been really promising. Adrian Nixon, editor of the Nixene Journal (an independent publication dedicated to graphene and 2D materials science news), has conducted a review of the various studies on adding tiny amounts of graphene and graphene oxide to concrete. Adrian said the addition of just 0.03% graphene powder increased the strength of concrete by a conservative average of 25%.

So, bearing in mind worldwide cement production equates to 8% of all global CO2 emissions, it could therefore be argued that by effectively reducing all concrete production by a quarter through the addition of graphene, we could in turn see this run through the supply chain and potentially deliver a 2% reduction in CO2 levels. That is an exciting proposition and one that could be debated at great length – but the essential point is this; adding a modest amount of graphene to a building material such as concrete could have a transformational impact on our environment.

And why not connect our sustainable cities of the future with a ‘graphene road’? Pioneering work with Highways England and the Graphene Engineering Innovation Centre is looking at developments to build more resilient road surfaces and motorway infrastructure that would support advances in both safety and performance. Hopefully, this will mean less potholes – but we could also feasibly have roads that one day feature embedded technologies that are more receptive to the next generation of electric cars and vehicles.

Another example of graphene-based sustainability is at the other end of the product lifecycle and how to better reclaim materials from redundant structures and unwanted fittings. My colleague Dr Vivek Koncherry from Graphene@Manchester has a proven method of adding tiny amounts of graphene to discarded tyres that once chopped up and reformed can produce a recycled product that has the performance that almost matches brand new rubber. What if we applied a similar method to re-purpose old building materials so we can build something brand new?

The disruptive role of graphene and 2D materials in sustainable construction is very exciting and works across the sector – but we need to rapidly accelerate the innovation if we are to realistically hit any of our targets. I would ask decision-makers act in number of ways:

UK National:

Grand challenge for building: I have previously welcomed UK government plans for an advanced research catalyst modelled on America’s Advanced Research Projects Agency (ARPA). I would recommend that a nationally-funded programme of ‘fail fast, learn fast’ development projects are commissioned and funded by this type of body to fast-track the testing of sustainable building materials. This work could be expedited by delegating across the UK with, for example, regional expertise at The University of Manchester leading on graphene enhanced products. This grand challenge approach is similar to the UK’s national Faraday battery challenge that is looking to transform energy storage technologies.

Regional:

• ‘Lighthouse’ projects: with innovation delegated to regional centres of excellence, it would be ideal if local authorities looked to support exemplar build projects that are made wholly or partly from sustainable materials. These would act as ‘lighthouse’ projects and provide a full-scale demonstrators on real world application of new building technology. For example, Greater Manchester could look to build a stretch of road featuring a graphene-enhanced surface or commission a public building or bridge that is made, or partly made, using graphene concrete for examle.

Green procurement: local authorities could consider introducing planning recommendations at the bidding/competition stage to proactively attract contractors who are willing to use new and sustainable building materials within their development projects.

Tags:  2D materials  Graphene  Graphene Engineering Innovation Centre  James Baker  Vivek Koncherry 

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A fresh sense of possibility

Posted By Graphene Council, Wednesday, September 23, 2020
Harsh environments that are inhospitable to existing technologies could now be monitored using sensors based on graphene. An intriguing form of carbon, graphene comprises layers of interconnected hexagonal rings of carbon atoms, a structure that yields unique electronic and physical properties with possibilities for many applications.

“Graphene has been projected as a miracle material for years now, but its application in harsh environmental conditions was unexplored,” says Sohail Shaikh, who has developed the new sensors, together with KAUST's Muhammad Hussain. 

“Existing sensor technologies operate in a very limited range of environmental conditions, failing or becoming unreliable if there is much deviation,” Shaikh adds.

The new robust sensor relies on changes in the electrical resistance of graphene in response to varying temperature, salinity and the acidity of a solution measured as pH. The system has potential to monitor additional variables, including pressure and water flow rates.

The researchers point out that sensing for multiple variables can be incorporated into a single device, greatly increasing its usefulness.

The graphene is transferred onto a flexible sheet of polyimide polymer, and it can be connected to appropriate electronic systems to collect and transmit the signals for whichever environmental variable is being monitored. The data could be transmitted wirelessly using standard Bluetooth technology. 

The greatest practical advance is in the resilience of the system that allows it to tolerate temperatures as high as 650 degrees Celsius, high salinity, varying pressure, intense radiation, reactive chemicals, high humidity or any combination of these conditions. The sensors can also offer advantages in sensitivity, for example, achieving a 260 percent sensitivity increase in temperature sensing relative to an existing alternative. 

As Hussain explains: "Our study is the first to show decisively the prospects of graphene as a sensing material for a variety of harsh environmental conditions." 

Likely real-world applications include monitoring conditions in ocean water, body fluids, the oil and gas industry, space exploration, and many situations involving exposure to chemicals that would damage existing sensors.  

The sensor’s thin structure and flexibility also makes it suitable for use in wearable technologies for divers and athletes, or in medical applications. 

The researchers believe that continual developments linking electronic devices with Internet of Things (IoT) and Internet of Everything (IoE) technologies will bring many needs and opportunities for their robust and flexible sensors. 

Tags:  Electronics  Graphene  KAUST  Muhammad Hussain  polymer  Sensors  Sohail Shaikh 

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Center for Nanoscale Science renewed at $18 million for six years

Posted By Graphene Council, Wednesday, September 23, 2020
The Center for Nanoscale Science, a National Science Foundation Materials Science and Engineering Center (MRSEC), has again successfully renewed its NSF support in the highly competitive MRSEC program. The new iteration of the center encompasses two of NSF's Big Ideas -- "Quantum Leap" and "Harnessing the Data Revolution."

More than 20 Penn State faculty are involved in the MRSEC's two new interdisciplinary research groups (IRGs). IRG1, 2D Polar Metals and Heterostructures, is led by Joshua Robinson, professor of materials science and engineering and Jun Zhu, professor of physics. It pioneers new methods of encasing two-dimensional metals in graphene to achieve exceptional optical properties and intriguing potential for quantum devices and biosensing. Before the IRG's pioneering work, only gold among metals was known to resist oxidation in the air. Penn State researchers are now extending that critical property across wide swathes of the periodic table.

IRG2, Crystalline Oxides with High Entropy, is led by Jon-Paul Maria, professor of materials science and engineering and Ismaila Dabo, associate professor of materials science and engineering. It seeks to write a new chapter in the crystal chemistry rulebook by creating materials that take advantage of the enormous number of ways that different kinds of atoms can be arranged onto a common crystal lattice. This innovative technique enables Penn State researchers to put atoms into environments that they normally do not assume, with potential applications across a wide domain, from new energy materials to new quantum devices, guided by a close interplay of theory, computation, data and experiment.

"These two intriguing research directions define new materials platforms- whole classes of new materials - that are being pioneered here at Penn State," says Vin Crespi, the director of the Center for Nanoscale Science.

The MRSEC also provides career development opportunities for dozens of graduate students with a focus during this renewal on sustainability in research practice and outcomes. A recently launched educational website, "Mission: Materials Science," will expand its content and reach out to youth audiences through a new partnership with the local Discovery Space museum. Outreach through participation in summer science camps, STEM programs for students who are blind or visually impaired, and partnerships with universities that serve underrepresented students will remain core to the Center's mission.

Program Director for Education and Outreach Kristin Dreyer said, "The best and most effective messengers for communicating important science concepts to youth and public audiences and inspiring the next generation of materials scientists are current researchers themselves. My colleague, Tiffany Mathews, and I get to help make those opportunities happen and provide the necessary support for our members to do it successfully."

The Center for Nanoscale Science is among eight MRSECs successfully renewing their funding along with three new centers, and has been funded continuously since 2000.

According to NSF, "The U.S. economy and its competitiveness depend on innovation, an essential part of which is fueled by technological breakthroughs in basic research. Our comfort, work, and well-being depend on the development of new materials for anything ranging from smart electronics to implantable medical devices."

Tags:  biosensor  Center for Nanoscale Science  Graphene  Jon-Paul Maria  Joshua Robinson  National Science Foundation  Penn State  quantum material 

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Successful Trial in FRP Structures Opens Up the Global Boatbuilding Market

Posted By Graphene Council, Wednesday, September 23, 2020
PureGRAPH® products successfully demonstrated in the boat building sector with test results proving a 59% increase in ultimate flexural stress compared to existing fibre reinforced polymer composite material.  PureGRAPH® additives used in combination with glass fibre materials and commercially available resins has led to significantly enhanced laminate boat structure materials and gives First Graphene the potential to unlock the global boat building market.

First Graphene Limited, is pleased to advise on a successful collaboration with Ascent Shipwrights working on the development of PureGRAPH® enhanced composite construction materials used in fiberglass boat building applications.

Composite boats are fabricated using a composite core material sandwiched between layers of fibre reinforced polymer (FRP) to create a strong and lightweight structure.

The incorporation of PureGRAPH® into the FRP laminate aimed to improve the mechanical properties of the overall composite system, whilst also providing an additional barrier to moisture intake and hydrolysis attack.

The Company reports that initial test work has been completed using a conventional high strength core material to evaluate the performance of increasing PureGRAPH® 20 concentrations compared to a control system being used at present. The composite materials were produced using existing production methods at Ascent Shipwrights to generate the results displayed in Figure 1.

Figure 1 details significant increase of 59.4% in ultimate flexural stress for a 1% addition rate of PureGRAPH® 20 within the FRP laminate. This result demonstrates the enormous potential for PureGRAPH® enhanced composite structures within the boat building industry and how the material can easily be incorporated within an existing production process.

Larger scale testing is being planned to look at a variety of core materials and PureGRAPH® enhanced FRP compositions. Further laminates have been produced for accelerated weathering testing, where improvements in hydrolysis resistance, water diffusion and UV resistance are anticipated.  FGR will provide updates to the market as test work progresses.

Craig McGuckin, Managing Director for First Graphene Ltd., said: “Following on from the significant improvements achieved with the introduction of PureGRAPH® into fiberglass pools this is our first extension into the boat building market.  FGR identified Ascent Shipwrights as an ideal collaborator and moved quickly to evaluate graphene technology.”

Ascent Shipwrights have been impressed with the ease of introducing PureGRAPH® into their operations and have indicated their intention to move towards the use of PureGRAPH® in future operations.

The significant improvements achieve in flexural strength opens up the opportunity to provide significant improvements to ocean going fiberglass boats while having the capacity to reduce the weight of recreational power and sail craft.

Daniel Roberts, Managing Director for Ascent Shipwrights., said “Working with FGR we have achieved a quick turnaround on the incorporation of their PureGRAPH® powder into our resin process.  The light weighting and strength improvements offer excellent opportunities for our business.”

Tags:  Ascent Shipwrights  composite  Craig McGuckin  Daniel Roberts  First Graphene  Graphene  Neil Armstrong  polymer 

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Investigating high temperature superconductors

Posted By Graphene Council, Wednesday, September 23, 2020
Researchers from the ARC Centre of Excellence in Future Low Energy Electronic Technologies (FLEET) used the Soft X-ray Spectroscopy beamline at the Australian Synchrotron to investigate the structure of a promising high-temperature superconductor, a calcium-doped graphene material.

The FLEET Centre has provided a detailed description of the research, published in The Chemistry of Materials, on their website.

In characterising the material, the investigators wanted to clarify where the calcium went after it was added to a sample consisting of a single layer of graphene on a silicon carbide substrate.

Measurements at the Australian Synchrotron were able to pinpoint that the calcium atoms were located, unexpectedly, near the silicon carbide surface.

Dr Anton Tadich, an instrument scientist on the SXR beamline, member of FLEET and co-author, explained why the Synchrotron was useful in the investigation.

“In order to confirm if a new graphene monolayer formed on the surface, as well as understanding how injected calcium atoms positioned themselves around that newly formed layer, in a process known as intercalation, the research team required an extremely surface-sensitive chemical fingerprinting technique,” said Tadich.

The technique that could provide the information was high resolution x-ray photoelectron spectroscopy (XPS) on the soft X-ray spectroscopy beamline.

Synchrotron-based XPS is a highly surface-sensitive chemical probe, which offers key advantages over its laboratory-based counterpart.

“The ability to 'tune' the x-ray energy for a given element is quite powerful; not only does it maximise the signal from a desired element, at the same time it is possible to enhance the signal from the topmost atomic layers of the sample relative to the bulk; disentangling contributions to the spectrum from different depths.”

The FLEET investigators led by PhD student Jimmy Kotsakidis in the group of Prof Michael Fuhrer and Tadich prepared the intercalated samples in-situ, which were then transferred under vacuum to the XPS chamber.

“The focus quickly turned to the carbon and silicon signal from the top few atomic layers, where all the chemistry was happening,” said Tadich.

“From the carbon signal, we saw a clear signature of the formation of an additional graphene layer.“

Importantly, the silicon spectra revealed that the calcium intercalated underneath the buffer layer, which is a partially-bonded carbon layer on the surface of the silicon carbide. 

“The combined results showed that the intercalation caused the buffer layer to ‘unstitch’ itself from the silicon carbide, lifting it off to form a new layer of graphene!” explained Tadich.

Their finding was contrary to previous studies, which had assumed that the intercalant atoms simply slid in between the original graphene layer and the surface.

The FLEET researchers concluded that the resultant 'bi-layer' graphene, when combined with the presence of the intercalant below it, could result in a form of superconducting graphene with a high transition temperature.

Tags:  Anton Tadich  ARC Centre of Excellence  Australian Synchrotron  Energy  Graphene  Jimmy Kotsakidis  superconductor 

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Developing roof coatings technology for the twenty-first century

Posted By Graphene Council, Tuesday, September 22, 2020
Roofing Today spoke to Blocksil Coatings about applying graphene to their corrosion resistant coating. 

I took a snippet from their article (dated September 2020). See the full article at Roofing Todays website on page 11

Andy Gent, Commercial Director at AGM, has worked with Blocksil from the beginning of the project and said:

Blocksil's idea to use our graphene within their corrosion resistant roof coating has taken everyone forward in terms of coating technology.

Chris Knowles, Chief Technical Officer at Blocksil commented:

We believe it is time the industry moved into the 21st Century and away from older, less efficient coatings and we're determined to help that happen.

Tags:  Andy Gent  Applied Graphene Materials  Blocksil Coatings  Chris Knowles  coatings  corrosion  Graphene 

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Paragraf and NPL Demonstrate that Paragraf’s Graphene Hall Effect Sensors are ready for High-radiation Applications in Space and Beyond

Posted By Graphene Council, Monday, September 21, 2020
Paragraf, the leader in graphene-based transformative electronic sensors and devices, has demonstrated the ability of its graphene Hall Effect sensors to withstand high levels of radiation. The discovery, based on testing from the National Physical Laboratory (NPL), proves that ‘unpackaged’ Hall Effect sensors can be used in high-radiation environments such as space. The project was funded by Innovate UK, the UK’s innovation agency.

Used to measure the magnitude of magnetic fields, Hall Effect sensors are a critical electronic component in a variety of applications, from proximity sensing and speed detection through to current sensing. However, historically, their deployment in high-radiation environments such as satellites and nuclear power plants has faced significant challenges. This is because conventional sensors made from silicon and other semiconductor materials react adversely to neutron radiation, unless they are encapsulated in radiation-hardened packaging. This entails a more complex, lengthy, and costly manufacturing process and may require the sensor to be replaced over time if, for example, the packaging is damaged.

By contrast, tests conducted by NPL have shown that following exposure to a neutron dose of 241 mSv/hour – which is about 30,000 times the expected typical neutron dose rate in the International Space Station – Paragraf graphene Hall Effect sensors are not affected by this level of radiation. This is the first time that a commercially available, graphene-based electronic device has proved impervious to neutron irradiation.

In situations where power and weight savings are as critical as radiation tolerance, for example on satellites and other space vehicles, Paragraf Hall Effect sensors really come into their own – requiring only pW’s of power and weighing only fractions of a gram.

Ivor Guiney, co-founder of Paragraf, commented: “NPL’s findings have the potential to be a game changer when it comes to high-performance satellites and other critical high-radiation applications such as nuclear decommissioning. Owing to the exceptional mechanical strength and high transparency of graphene, our Hall Effect sensor can be used reliably in high-radiation applications without requiring packaging. This is key to improving reliability and durability while reducing manufacturing costs and time to market.”

The ability of graphene Hall Effect sensors to perform under high-radiation conditions will pave the way for the deployment of a broader range of electronics in harsh environments. Thanks to Paragraf’s scalable manufacturing process for large-area graphene deposition, it may soon be possible to produce other radiation-resistant graphene-based electronic devices. This will help ensure that all critical electronics, beyond sensors, are reliable and durable even in harsh environments.

Héctor Corte-Leon at NPL added: “Our first set of findings is very promising, and we are now expecting more positive outcomes over the next few months. Testing graphene-based electronics is key to demonstrating whether they can be used in harsh environments where, traditionally, their deployment has been limited.”

Graphene Hall Effect sensors from Paragraf are now set to undergo further radiation testing (alpha, beta and gamma radiation) as well as high-frequency testing. This is expected to open-up new opportunities across critical applications such as current sensing. The project, funded by Innovate UK, the UK’s innovation agency, started in October 2019, and is due to run until the end of 2020.

Tags:  Electronics  Graphene  Héctor Corte-Leon  Innovate UK  Ivor Guiney  National Physical Laboratory  Paragraf  Sensors 

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Laser used to transfer graphene for tech applications

Posted By Graphene Council, Monday, September 21, 2020
Laser has been used to cut to shape and deposit graphene on a target substrate in a single step process, potentially lowering device fabrication time and cost. Graphene patches with diameters as small as 30 micrometers were transferred onto technologically relevant substrates.

The preferred method for production of large-area graphene is chemical vapour deposition (CVD), which allows roll-to-roll scalable production of good quality material. CVD is widely used to create graphene films and devices for industrial and research applications. The CVD process is most commonly restricted to growth on catalytic substrates, such as thin copper films.

In order to produce finished devices, such as field effect transistors, graphene needs to be transferred onto a technologically usable substrate, most commonly a silicon or silica wafer. The common methods of transferring graphene involve polymer intermediary overlayers, application of lithographic masking layers and chemical etching, steps that increase process complexity and reduce the quality of the pristine graphene. Laser-induced localized transfer bypasses all these steps, simplifying device fabrication.

Laser-induced transfer utilizes high power femtosecond laser pulses to “peel” graphene off a substrate. A possible explanation for the underlying physical mechanism is thermal expansion of the substrate, in this case nickel metal, which leads to a rupture of the graphene sheet at the edges of the laser-illuminated area. The research team, joining forces from the UK, Greece, Spain and Israel, having published their results in the journal Applied Surface Science, believes that laser transfer has the potential to eliminate many time-consuming lithographic processing steps, allowing precise, direct application of 2D materials with complex shapes to specific locations on a device, although they acknowledge that the process should be further refined to improve on the quality of the transferred material.

Tags:  2D materials  chemical vapour deposition  CVD  Graphene  Graphenea 

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Soil check: How much water does your soil contain?

Posted By Graphene Council, Monday, September 21, 2020
Researchers use ultra-small graphene particles to develop a new soil moisture sensor. Anyone who has tried their hand at growing plants, be it an amateur gardener or a seasoned farmer, would be familiar with the perils of under- or over-watering a sapling. Plants require the right amount of water for their healthy growth, and to figure out when and how much to water one has to know the existing moisture levels in the soil. When it comes to keeping track of the watering schedule for a large number of plants, such as for a field of crops, there is a need for an affordable, easy-to-use soil moisture sensor that can accurately measure the water content in the soil. 

A recent study, published in the journal Carbon, demonstrates the workings of a soil moisture sensor made from graphene quantum dots, which are nanometer-sized fragments of graphene. The study was conducted by a team of researchers from the Indian Institute of Technology, Bombay (IIT Bombay), Gauhati University, and Dhirubhai Ambani Institute of Information and Communication Technology, Gandhinagar. It was funded by the Department of Science and Technology, the University Grants Commission and the Assam Science Technology and Environmental Council.

Graphene is made up of a sheet of carbon atoms arranged in a honeycomb-like pattern. Over the years, studies have explored the use of graphene quantum dots — disc-shaped materials made of a few layers of graphene, measuring mere nanometers — for a variety of sensing applications. While extensive research is being carried out on the synthesis of graphene quantum dots, the challenge remains in designing a method that results in a good yield of uniformly-sized particles. Additionally, the process must be scalable and easily adaptable for its  commercialisation.

“Our motivations behind this study was to devise a simple, inexpensive and scalable approach for synthesising graphene quantum dots, and to develop an affordable soil moisture sensor that is suitable for large scale use,” says Prof Hemen Kalita, who is the lead author of this study. He is an Assistant Professor at the Gauhati University and previously was a doctoral student with Prof M Aslam at IIT Bombay. 

The researchers have proposed a method to produce graphene quantum dots as small as 3–5 nanometre from easily available and low-cost graphene oxide. They coated a thin film of graphene oxide onto a carbon electrode and placed it inside an electrolyte solution. When an electric current is applied to the setup, the carbon bonds in the graphene oxide get cleaved, and molecules of the electrolyte occupy those gaps in the graphene oxide layer. Eventually, they form quantum dots of graphene having oxygen-containing chemical groups. 

“At a laboratory scale, we were successful in synthesising graphene quantum dots through our novel approach, and we have filed a patent for the synthesis method,” says Prof Kalita. 

Using the graphene quantum dots, the researchers fabricated a soil moisture sensor which is smaller in size than a lentil seed. The moisture content value displayed by the sensor depends on the resistance measured across it, and with an increasing percentage of water content, there is a fall in resistance. When the sensor is inserted into moist soil, the oxygen atoms present in the graphene quantum dots interact with the hydrogen atoms of the water and form a layer of water molecules on the surface of the sensor. When an external voltage is applied to the sensor via a source meter, the loosely held water molecules in the upper layers get ionised and conduct electrical charge. This leads to a decrease in resistance of the sensor.  

The researchers tested the soil moisture sensors on samples of black and red soil. They found that the moisture content measured by the sensor closely matched the known water content of the soil samples. The sensor gives the final reading within 3 minutes and can be used again after 20 seconds.  

Further, the researchers tested the stability of the sensor by continuously using it over five months to measure the water content in soil samples. They found that the sensor gives a consistent reading throughout this time and works well for a range of soil water levels.  

“With extensive field testing and improved packaging, our sensors will be suitable for commercialisation. A few companies have approached us and initiated discussions with our team to take this project to the industry front,” says Prof Kalita. “We are aiming to develop stable and affordable sensors for the middle-class farmer community,” he signs off. 

Tags:  Gauhati University  Graphene  graphene oxide  Hemen Kalita  Sensors 

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Going with the flow for water purification

Posted By Graphene Council, Monday, September 21, 2020
Membrane separations have become critical to human existence, with no better example than water purification. As water scarcity becomes more common and communities start running out of cheap available water, they need to supplement their supplies with desalinated water from seawater and brackish water sources.

Lawrence Livermore National Laboratory (LLNL) researchers have created carbon nanotube (CNT) pores that are so efficient at removing salt from water that they are comparable to commercial desalination membranes. These tiny pores are just 0.8 nanometers (nm) in diameter. In comparison, a human hair is 60,000 nm across. The research appears on the cover of the Sept. 18 issue of the journal Science Advances.

The dominant technology for removing salt from water, reverse osmosis, uses thin-film composite (TFC) membranes to separate water from the ions present in saline feed streams. However, some fundamental performance issues remain. For example, TFC membranes are constrained by the permeability-selectivity trade-offs and often have insufficient rejection of some ions and trace micropollutants, requiring additional purification stages that increase the energy and cost.

Biological water channels, also known as aquaporins, provide a blueprint for the structures that could offer increased performance. They have an extremely narrow inner pore that squeezes water down to a single-file configuration that enables extremely high water permeability, with transport rates exceeding 1 billion water molecules per second through each pore.

“Carbon nanotubes represent some of the most promising scaffold structures for artificial water channels because of the low friction of water on their smooth inner surfaces, which mimic the biological water channels,” said Alex Noy, LLNL chemist and a lead co-author of the report.

The team developed CNT porins (CNTPs) — short segments of CNTs that self-insert into biomimetic membranes – which form artificial water channels that mimic aquaporin channel functionality and intrachannel single-file water arrangement. Researchers then measured water and chloride ion transport through 0.8-nm-diameter CNTPs using fluorescence-based assays. Computer simulations and experiments using CNT pores in lipid membranes demonstrated the mechanism for enhanced flow and strong ion rejection through inner channels of carbon nanotubes.

“This process allowed us to determine the accurate value of water-salt permselectivity in narrow CNT pores,” said LLNL materials scientist and lead co-author Tuan Anh Pham, who led the simulation efforts of the study. “Atomistic simulations provide a detailed molecular-scale view of water entering the CNTP channels and support the activation energy values.”

Other key contributors to the project included LLNL chemists Yuhao Li, Zhongwu Li and Fikret Aydin. Researchers from Southeast University in China and UC Merced also contributed.

The work was funded by the Department of Energy’s Office of Science and parts of it were performed as a part of the Center for Enhanced Nanofluidic Transport Energy Frontier Research Center.

Tags:  Alex Noy  carbon nanotube  Graphene  Lawrence Livermore National Laboratory  Tuan Anh Pham  water purification 

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