Category Archives: graphene

Graphene in art preservation and restoration

A July 5, 2021 news item on phys.org announces a new technology for preserving and restoring your paintings,

The exposure of colors used in artworks to ultraviolet (UV) and visible light in the presence of oxidizing agents triggers color degradation, fading and yellowing. These degradation mechanisms can lead to irreversible alteration of artworks. Protective varnishes and coatings currently used to protect art paintings are not acceptable solutions, since their removal requires the use of solvents, which can affect adversely the underlying work surface.

A team of researchers from the Institute of Chemical Engineering Sciences of Foundation for Research and Technology-Hellas (FORTH/ ICE-HT), the Department of Chemical Engineering of the University of Patras, and the Center for Colloid and Surface Science (CSGI) of the University of Florence, led by Professor Costas Galiotis, had the innovative ideato use graphene veils for the protection of paintings against environmental degradation.

A July 2, 2021 Foundation for Research and Technology – Hellas (FORTH) press release, which originated the news item, provides more details,

Since its isolation in 2004 by Geim [Andre Geim] and Novoselov [Konstantin Novoselov] from the University of Manchester (Nobel Prize in Physics in 2010), graphene has been termed as a ‘wonder material’ due to its exceptional properties that have already been used in many applications and products. The graphene veil used in this work is a flexible, transparent film, produced by the technique of chemical vapor deposition. It has a monoatomic thickness and, since there are no size limitations in the other dimensions (length and width), it can cover any required large surface areas.

The results from measurements performed in the above mentioned laboratories, showed that this membrane is impermeable to moisture, the oxidizing agents and other harmful pollutants and also can absorb a large amount of harmful ultraviolet radiation. Finally, in contrast to other protective means, it is demonstrated that these graphene coatings are relatively easy to remove without damaging the surface of the artworks.

[downloaded from https://phys.org/news/2021-07-graphene-paving-methods-art.html]

Before getting to the link and citation for the paper, here’s the abstract, which helps fill n a few more details,

Modern and contemporary art materials are generally prone to irreversible colour changes upon exposure to light and oxidizing agents. Graphene can be produced in thin large sheets, blocks ultraviolet light, and is impermeable to oxygen, moisture and corrosive agents; therefore, it has the potential to be used as a transparent layer for the protection of art objects in museums, during storage and transportation. Here we show that a single-layer or multilayer graphene veil, produced by chemical vapour deposition, can be deposited over artworks to protect them efficiently against colour fading, with a protection factor of up to 70%. We also show that this process is reversible since the graphene protective layer can be removed using a soft rubber eraser without causing any damage to the artwork. We have also explored a complementary contactless graphene-based route for colour protection that is based on the deposition of graphene on picture framing glass for use when the directapplication of graphene is not feasible due to surface roughness or artwork fragility. Overall, the present results are a proof of concept of the potential use of graphene as an effective and removable protective advanced material to prevent colour fading in artworks.

And now, a link to and a citation for the paper,

Preventing colour fading in artworks with graphene veils by M. Kotsidi, G. Gorgolis, M. G. Pastore Carbone, G. Anagnostopoulos, G. Paterakis, G. Poggi, A. Manikas, G. Trakakis, P. Baglioni & C. Galiotis. Nature Nanotechnology (2021) DOI: https://doi.org/10.1038/s41565-021-00934-z Published 01 July 2021

This paper is behind a paywall.

A graphene ‘camera’ and your beating heart: say cheese

Comparing it to a ‘camera’, even with the quotes, is a bit of a stretch for my taste but I can’t come up with a better comparison. Here’s a video so you can judge for yourself,

Caption: This video repeats three times the graphene camera images of a single beat of an embryonic chicken heart. The images, separated by 5 milliseconds, were measured by a laser bouncing off a graphene sheet lying beneath the heart. The images are about 2 millimeters on a side. Credit: UC Berkeley images by Halleh Balch, Alister McGuire and Jason Horng

A June 16, 2021 news item on ScienceDaily announces the research,

Bay Area [San Francisco, California] scientists have captured the real-time electrical activity of a beating heart, using a sheet of graphene to record an optical image — almost like a video camera — of the faint electric fields generated by the rhythmic firing of the heart’s muscle cells.

A University of California at Berkeley (UC Berkeley) June 16, 2021 news release (also on EurekAlert) by Robert Sanders, which originated the news item, provides more detail,

The graphene camera represents a new type of sensor useful for studying cells and tissues that generate electrical voltages, including groups of neurons or cardiac muscle cells. To date, electrodes or chemical dyes have been used to measure electrical firing in these cells. But electrodes and dyes measure the voltage at one point only; a graphene sheet measures the voltage continuously over all the tissue it touches.

The development, published online last week in the journal Nano Letters, comes from a collaboration between two teams of quantum physicists at the University of California, Berkeley, and physical chemists at Stanford University.

“Because we are imaging all cells simultaneously onto a camera, we don’t have to scan, and we don’t have just a point measurement. We can image the entire network of cells at the same time,” said Halleh Balch, one of three first authors of the paper and a recent Ph.D. recipient in UC Berkeley’s Department of Physics.

While the graphene sensor works without having to label cells with dyes or tracers, it can easily be combined with standard microscopy to image fluorescently labeled nerve or muscle tissue while simultaneously recording the electrical signals the cells use to communicate.

“The ease with which you can image an entire region of a sample could be especially useful in the study of neural networks that have all sorts of cell types involved,” said another first author of the study, Allister McGuire, who recently received a Ph.D. from Stanford and. “If you have a fluorescently labeled cell system, you might only be targeting a certain type of neuron. Our system would allow you to capture electrical activity in all neurons and their support cells with very high integrity, which could really impact the way that people do these network level studies.”

Graphene is a one-atom thick sheet of carbon atoms arranged in a two-dimensional hexagonal pattern reminiscent of honeycomb. The 2D structure has captured the interest of physicists for several decades because of its unique electrical properties and robustness and its interesting optical and optoelectronic properties.

“This is maybe the first example where you can use an optical readout of 2D materials to measure biological electrical fields,” said senior author Feng Wang, UC Berkeley professor of physics. “People have used 2D materials to do some sensing with pure electrical readout before, but this is unique in that it works with microscopy so that you can do parallel detection.”

The team calls the tool a critically coupled waveguide-amplified graphene electric field sensor, or CAGE sensor.

“This study is just a preliminary one; we want to showcase to biologists that there is such a tool you can use, and you can do great imaging. It has fast time resolution and great electric field sensitivity,” said the third first author, Jason Horng, a UC Berkeley Ph.D. recipient who is now a postdoctoral fellow at the National Institute of Standards and Technology. “Right now, it is just a prototype, but in the future, I think we can improve the device.”

Graphene is sensitive to electric fields

Ten years ago, Wang discovered that an electric field affects how graphene reflects or absorbs light. Balch and Horng exploited this discovery in designing the graphene camera. They obtained a sheet of graphene about 1 centimeter on a side produced by chemical vapor deposition in the lab of UC Berkeley physics professor Michael Crommie and placed on it a live heart from a chicken embryo, freshly extracted from a fertilized egg. These experiments were performed in the Stanford lab of Bianxiao Cui, who develops nanoscale tools to study electrical signaling in neurons and cardiac cells.

The team showed that when the graphene was tuned properly, the electrical signals that flowed along the surface of the heart during a beat were sufficient to change the reflectance of the graphene sheet.

“When cells contract, they fire action potentials that generate a small electric field outside of the cell,” Balch said. “The absorption of graphene right under that cell is modified, so we will see a change in the amount of light that comes back from that position on the large area of graphene.”

In initial studies, however, Horng found that the change in reflectance was too small to detect easily. An electric field reduces the reflectance of graphene by at most 2%; the effect was much less from changes in the electric field when the heart muscle cells fired an action potential.

Together, Balch, Horng and Wang found a way to amplify this signal by adding a thin waveguide below graphene, forcing the reflected laser light to bounce internally about 100 times before escaping. This made the change in reflectance detectable by a normal optical video camera.

“One way of thinking about it is that the more times that light bounces off of graphene as it propagates through this little cavity, the more effects that light feels from graphene’s response, and that allows us to obtain very, very high sensitivity to electric fields and voltages down to microvolts,” Balch said.

The increased amplification necessarily lowers the resolution of the image, but at 10 microns, it is more than enough to study cardiac cells that are several tens of microns across, she said.

Another application, McGuire said, is to test the effect of drug candidates on heart muscle before these drugs go into clinical trials to see whether, for example, they induce an unwanted arrhythmia. To demonstrate this, he and his colleagues observed the beating chicken heart with CAGE and an optical microscope while infusing it with a drug, blebbistatin, that inhibits the muscle protein myosin. They observed the heart stop beating, but CAGE showed that the electrical signals were unaffected.

Because graphene sheets are mechanically tough, they could also be placed directly on the surface of the brain to get a continuous measure of electrical activity — for example, to monitor neuron firing in the brains of those with epilepsy or to study fundamental brain activity. Today’s electrode arrays measure activity at a few hundred points, not continuously over the brain surface.

“One of the things that is amazing to me about this project is that electric fields mediate chemical interactions, mediate biophysical interactions — they mediate all sorts of processes in the natural world — but we never measure them. We measure current, and we measure voltage,” Balch said. “The ability to actually image electric fields gives you a look at a modality that you previously had little insight into.”

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

Graphene Electric Field Sensor Enables Single Shot Label-Free Imaging of Bioelectric Potentials by Halleh B. Balch, Allister F. McGuire, Jason Horng, Hsin-Zon Tsai, Kevin K. Qi, Yi-Shiou Duh, Patrick R. Forrester, Michael F. Crommie, Bianxiao Cui, and Feng Wang. Nano Lett. 2021, XXXX, XXX, XXX-XXX OI: https://doi.org/10.1021/acs.nanolett.1c00543 Publication Date: June 8, 2021 © 2021 American Chemical Society

This paper is behind a paywall.

New water treatment with 3D-printed graphene aerogels

Caption: Graphene aerogel on a single tissue. Credit: University at Buffalo

That image of the graphene aerogel on a tissue shows off its weightlessness very well.

Here’s more about the graphene aerogel water treatment from an April 14, 2021 news item on Nanowerk,

Graphene excels at removing contaminants from water, but it’s not yet a commercially viable use of the wonder material.

That could be changing.

In a recent study, University at Buffalo [UB] engineers report a new process of 3D printing graphene aerogels that they say overcomes two key hurdles — scalability and creating a version of the material that’s stable enough for repeated use — for water treatment.

“The goal is to safely remove contaminants from water without releasing any problematic chemical residue,” says study co-author Nirupam Aich, PhD, assistant professor of environmental engineering at the UB School of Engineering and Applied Sciences. “The aerogels we’ve created hold their structure when put in water treatment systems, and they can be applied in diverse water treatment applications.”

An April 14, 2021 UB news release (also on EurekAlert) by Melvin Bankhead III, which originated the news item, explains the breakthrough in more detail,

An aerogel is a light, highly porous solid formed by replacement of liquid in a gel with a gas so that the resulting solid is the same size as the original. They are similar in structural configuration to Styrofoam: very porous and lightweight, yet strong and resilient.

Graphene is a nanomaterial formed by elemental carbon and is composed of a single flat sheet of carbon atoms arranged in a repeating hexagonal lattice.

To create the right consistency of the graphene-based ink, the researchers looked to nature. They added to it two bio-inspired polymers — polydopamine (a synthetic material, often referred to as PDA, that is similar to the adhesive secretions of mussels), and bovine serum albumin (a protein derived from cows).

In tests, the reconfigured aerogel removed certain heavy metals, such as lead and chromium, that plague drinking water systems nationwide. It also removed organic dyes, such as cationic methylene blue and anionic Evans blue, as well as organic solvents like hexane, heptane and toluene.

To demonstrate the aerogel’s reuse potential, the researchers ran organic solvents through it 10 times. Each time, it removed 100% of the solvents. The researchers also reported the aerogel’s ability to capture methylene blue decreased by 2-20% after the third cycle.

The aerogels can also be scaled up in size, Aich says, because unlike nanosheets, aerogels can be printed in larger sizes. This eliminates a previous problem inherent in large-scale production, and makes the process available for use in large facilities, such as in wastewater treatment plants, he says. He adds the aerogels can be removed from water and reused in other locations, and that they don’t leave any kind of residue in the water.

Aich is part of a collaboration between UB and the University of Pittsburgh, led by UB chemistry professor Diana Aga, PhD, to find methods and tools to degrade per- and polyfluoroalkyl substances (PFAS), toxic materials so difficult to break down that they are known as “forever chemicals.” Aich notes the similarities to his work with 3D aerogels, and he hopes results from the two projects can be brought together to create more effective methods of removing waterborne contaminants.

“We can use these aerogels not only to contain graphene particles but also nanometal particles which can act as catalysts,” Aich says. “The future goal is to have nanometal particles embedded in the walls and the surface of these aerogels and they would be able to degrade or destroy not only biological contaminants, but also chemical contaminants.”

Aich, Chi, and Masud [Arvid Masud, PhD] hold a pending patent for the graphene aerogel described in the study, and they are looking for industrial partners to commercialize this process.

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

Emerging investigator series: 3D printed graphene-biopolymer aerogels for water contaminant removal: a proof of concept by Arvid Masud, Chi Zhoub and Nirupam Aich. Environ. Sci.: Nano, 2021,8, 399-414 DOI: https://doi.org/10.1039/D0EN00953A First published online: 09 Dec 2020

This paper is behind a paywall.

Concrete collapse and research into durability

I have two items about concrete buildings, one concerns the June 24, 2021 collapse of a 12-storey condominium building in Surfside, close to Miami Beach in Florida. There are at least 20 people dead and, I believe, over 120 are still unaccounted for (July 2, 2021 Associated Press news item on Canadian Broadcasting Corporation news online website).

Miami collapse

Nate Berg’s June 25, 2021 article for Fast Company provides an instructive overview of the building collapse (Note: A link has been removed),

Why the building collapsed is not yet known [emphasis mine]. David Darwin is a professor of civil engineering at the University of Kansas and an expert in reinforced concrete structures, and he says the eventual investigation of the Surfside collapse will explore all the potential causes, ranging from movement in the foundation before the collapse, corrosion in the debris, and excessive cracking in the part of the building that remains standing. “There are all sorts of potential causes of failure,” Darwin says. “At this point, speculation is not helpful for anybody.”

Sometimes I can access the entire article, and at other times, only a few paragraphs; I hope you get access to all of it as it provides a lot of information.

The Surfside news puts this research from Northwestern University (Chicago, Illinois) into much sharper relief than might otherwise be the case. (Further on I have some information about the difference between cement and concrete and how cement leads to concrete.)

Smart cement for more durable roads and cities

Coincidentally, just days before the Miami Beach building collapse, a June 21, 2021 Northwestern University news release (also on EurekAlert), announced research into improving water and fracture resistance in cement,

Forces of nature have been outsmarting the materials we use to build our infrastructure since we started producing them. Ice and snow turn major roads into rubble every year; foundations of houses crack and crumble, in spite of sturdy construction. In addition to the tons of waste produced by broken bits of concrete, each lane-mile of road costs the U.S. approximately $24,000 per year to keep it in good repair.

Engineers tackling this issue with smart materials typically enhance the function of materials by increasing the amount of carbon, but doing so makes materials lose some mechanical performance. By introducing nanoparticles into ordinary cement, Northwestern University researchers have formed a smarter, more durable and highly functional cement.

The research was published today (June 21 [2021]) in the journal Philosophical Transactions of the Royal Society A.

With cement being the most widely consumed material globally and the cement industry accounting for 8% of human-caused greenhouse gas emissions, civil and environmental engineering professor Ange-Therese Akono turned to nanoreinforced cement to look for a solution. Akono, the lead author on the study and an assistant professor in the McCormick School of Engineering, said nanomaterials reduce the carbon footprint of cement composites, but until now, little was known about its impact on fracture behavior.

“The role of nanoparticles in this application has not been understood before now, so this is a major breakthrough,” Akono said. “As a fracture mechanics expert by training, I wanted to understand how to change cement production to enhance the fracture response.”

Traditional fracture testing, in which a series of light beams is cast onto a large block of material, involves lots of time and materials and seldom leads to the discovery of new materials.

By using an innovative method called scratch testing, Akono’s lab efficiently formed predictions on the material’s properties in a fraction of the time. The method tests fracture response by applying a conical probe with increasing vertical force against the surface of microscopic bits of cement. Akono, who developed the novel method during her Ph.D. work, said it requires less material and accelerates the discovery of new ones.

“I was able to look at many different materials at the same time,” Akono said. “My method is applied directly at the micrometer and nanometer scales, which saves a considerable amount of time. And then based on this, we can understand how materials behave, how they crack and ultimately predict their resistance to fracture.”

Predictions formed through scratch tests also allow engineers to make changes to materials that enhance their performance at the larger scale. In the paper, graphene nanoplatelets, a material rapidly gaining popularity in forming smart materials, were used to improve the resistance to fracture of ordinary cement. Incorporating a small amount of the nanomaterial also was shown to improve water transport properties including pore structure and water penetration resistance, with reported relative decreases of 76% and 78%, respectively.

Implications of the study span many fields, including building construction, road maintenance, sensor and generator optimization and structural health monitoring.

By 2050, the United Nations predicts two-thirds of the world population will be concentrated in cities. Given the trend toward urbanization, cement production is expected to skyrocket.

Introducing green concrete that employs lighter, higher-performing cement will reduce its overall carbon footprint by extending maintenance schedules and reducing waste.

Alternately, smart materials allow cities to meet the needs of growing populations in terms of connectivity, energy and multifunctionality. Carbon-based nanomaterials including graphene nanoplatelets are already being considered in the design of smart cement-based sensors for structural health monitoring.

Akono said she’s excited for both follow-ups to the paper in her own lab and the ways her research will influence others. She’s already working on proposals that look into using construction waste to form new concrete and is considering “taking the paper further” by increasing the fraction of nanomaterial that cement contains.

“I want to look at other properties like understanding the long-term performance,” Akono said. “For instance, if you have a building made of carbon-based nanomaterials, how can you predict the resistance in 10, 20 even 40 years?”

The study, “Fracture toughness of one- and two-dimensional nanoreinforced cement via scratch testing,” was supported by the National Science Foundation Division of Civil, Mechanical and Manufacturing Innovation (award number 18929101).

Akono will give a talk on the paper at The Royal Society’s October [2021] meeting, “A Cracking Approach to Inventing Tough New Materials: Fracture Stranger Than Friction,” which will highlight major advances in fracture mechanics from the past century.

I don’t often include these kinds of photos (one or more of the researchers posing (sometimes holding something) for the camera but I love the professor’s first name, Ange-Therese (which means angel in French, I don’t know if she ever uses the French spelling for Thérèse),

Caption: Professor Ange-Therese Akono holds a sample of her smart cement. Credit: Northwestern University

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

Fracture toughness of one- and two-dimensional nanoreinforced cement via scratch testing by Ange-Therese Akono. Philosophical Transactions of the Royal Society A: Mathematical, Physical & Engineering Sciences 2021 379 (2203): 20200288 DOI: 10.1098/rsta.2020.0288 Published June 21, 2021

This paper appears to be open access.

Cement vs. concrete

Andrew Logan’s April 3, 2020 article for MIT (Massachusetts Institute of Technology) News is a very readable explanation of how cement and concrete differ and how they are related,

There’s a lot the average person doesn’t know about concrete. For example, it’s porous; it’s the world’s most-used material after water; and, perhaps most fundamentally, it’s not cement.

Though many use “cement” and “concrete” interchangeably, they actually refer to two different — but related — materials: Concrete is a composite made from several materials, one of which is cement. [emphasis mine]

Cement production begins with limestone, a sedimentary rock. Once quarried, it is mixed with a silica source, such as industrial byproducts slag or fly ash, and gets fired in a kiln at 2,700 degrees Fahrenheit. What comes out of the kiln is called clinker. Cement plants grind clinker down to an extremely fine powder and mix in a few additives. The final result is cement.

“Cement is then brought to sites where it is mixed with water, where it becomes cement paste,” explains Professor Franz-Josef Ulm, faculty director of the MIT Concrete Sustainability Hub (CSHub). “If you add sand to that paste it becomes mortar. And if you add to the mortar large aggregates — stones of a diameter of up to an inch — it becomes concrete.”

Final thoughts

I offer my sympathies to the folks affected by the building collapse and my hopes that research will lead the way to more durable cement and, ultimately, concrete buildings.

2021 version of graphene-enhanced sports shoes/sneakers/running shoes/runners/trainers

My June 21, 2018 posting was the last time these graphene-enhanced sports shoes/sneakers/running shoes/runners/trainers were mentioned here (it was also the first time). The latest version features newly graphene-enhanced shoe soles that last twice as long as the industry standard according to a March 30, 2021 article by Robert Lea for Azonano (Note: A link has been removed),

Thanks to researchers at the University of Manchester and UK-based sportswear manufacturer Inov-8, graphene can now be found at the tips of your toes as well as your fingers.

In 2017 Inov-8 brought to the market the first running shoe that utilizes graphene in its grips, and 4 years later the manufacturer is still innovating, offering a wide range of products that rely on the wonder material. 

Now, as well as finding its way into the grips of the company’s running shoes, graphene is also found in the soles of the company’s latest long-distance running shoe too¹. 

Using graphene as part of the cushioning insole in trail running shoes has led to a shoe that lasts twice as long as leading competitors’ footwear, the company says.

When Inov-8 began their quest to use graphene to improve running shoes, the initial goal was to employ the material to create improved rubber grips that would not wear down as quickly as other running shoes and retain grip for longer during this slower wearing process.

The company teamed with the University of Manchester to make this goal a reality, …

The graphene-enhanced grip proved such a hit with consumers that in the four years since its induction, shoes featuring the outer-sole now account for 50% of overall sales.

Building upon the success of Inov-8’s graphene gripped running shoe, the company has expanded its use of the material to a midsole foam. The graphene replaces EVA foam plates of carbon which are traditionally used in this form of long-distance running shoe.

A March 24, 2021 University of Manchester press release describes the latest use of graphene in Inov-8’s shoes,

Sports footwear firm inov-8 has unveiled the world’s first running shoe to use a graphene-enhanced foam in the sole, bucking the widespread trend for carbon-plate technology and doubling the industry standard for longevity.

Developed in collaboration with graphene experts at The University of Manchester, the cushioned foam, called G-FLY™, features as part of inov-8’s new trail shoe, the TRAILFLY ULTRA G 300 MAX™, designed for ultramarathon and long-distance runners.

Tests have shown the foam delivers 25% greater energy return than standard EVA foams and is far more resistant to compressive wear. It therefore maintains optimum levels of underfoot bounce and comfort for much longer.

This helps runners maintain a faster speed over greater distances, aid their feet in feeling fresher for longer, and prolong the life of their footwear.

Michael Price, COO of Lake District-based inov-8, said: …

“We’ve worked incredibly hard for the past two years with the university and leading footwear industry veteran Doug Sheridan in developing this innovation. A team of 40 athletes from across the world tested prototype shoes and more than 50 mixes of graphene-enhanced foam. Trail test reports show G-FLY foam still performing well after 1,200km – double the industry standard.”

Dr Aravind Vijayaraghavan, Reader in Nanomaterials at the University, home to both the National Graphene Institute and Graphene Engineering Innovation Centre, said: “As well as on the trail, we also tested extensively in the laboratory, including subjecting the foam to aggressive ageing tests that mimic extensive use. Despite being significantly aged, the G-FLY foam still delivered more energy return than some unaged foams.

The company inov-8 can be found here.

Mechano-photonic artificial synapse is bio-inspired

The word ‘memristor’ usually pops up when there’s research into artificial synapses but not in this new piece of research. I didn’t see any mention of the memristor in the paper’s references either but I did find James Gimzewski from the University of California at Los Angeles (UCLA) whose research into brainlike computing (neuromorphic computing) is running parallel but separately to the memristor research.

Dr. Thamarasee Jeewandara has written a March 25, 2021 article for phys.org about the latest neuromorphic computing research (Note: Links have been removed)

Multifunctional and diverse artificial neural systems can incorporate multimodal plasticity, memory and supervised learning functions to assist neuromorphic computation. In a new report, Jinran Yu and a research team in nanoenergy, nanoscience and materials science in China and the US., presented a bioinspired mechano-photonic artificial synapse with synergistic mechanical and optical plasticity. The team used an optoelectronic transistor made of graphene/molybdenum disulphide (MoS2) heterostructure and an integrated triboelectric nanogenerator to compose the artificial synapse. They controlled the charge transfer/exchange in the heterostructure with triboelectric potential and modulated the optoelectronic synapse behaviors readily, including postsynaptic photocurrents, photosensitivity and photoconductivity. The mechano-photonic artificial synapse is a promising implementation to mimic the complex biological nervous system and promote the development of interactive artificial intelligence. The work is now published on Science Advances.

The human brain can integrate cognition, learning and memory tasks via auditory, visual, olfactory and somatosensory interactions. This process is difficult to be mimicked using conventional von Neumann architectures that require additional sophisticated functions. Brain-inspired neural networks are made of various synaptic devices to transmit information and process using the synaptic weight. Emerging photonic synapse combine the optical and electric neuromorphic modulation and computation to offer a favorable option with high bandwidth, fast speed and low cross-talk to significantly reduce power consumption. Biomechanical motions including touch, eye blinking and arm waving are other ubiquitous triggers or interactive signals to operate electronics during artificial synapse plasticization. In this work, Yu et al. presented a mechano-photonic artificial synapse with synergistic mechanical and optical plasticity. The device contained an optoelectronic transistor and an integrated triboelectric nanogenerator (TENG) in contact-separation mode. The mechano-optical artificial synapses have huge functional potential as interactive optoelectronic interfaces, synthetic retinas and intelligent robots. [emphasis mine]

As you can see Jeewandara has written quite a technical summary of the work. Here’s an image from the Science Advances paper,

Fig. 1 Biological tactile/visual neurons and mechano-photonic artificial synapse. (A) Schematic illustrations of biological tactile/visual sensory system. (B) Schematic diagram of the mechano-photonic artificial synapse based on graphene/MoS2 (Gr/MoS2) heterostructure. (i) Top-view scanning electron microscope (SEM) image of the optoelectronic transistor; scale bar, 5 μm. The cyan area indicates the MoS2 flake, while the white strip is graphene. (ii) Illustration of charge transfer/exchange for Gr/MoS2 heterostructure. (iii) Output mechano-photonic signals from the artificial synapse for image recognition.

You can find the paper here,

Bioinspired mechano-photonic artificial synapse based on graphene/MoS2 heterostructure by Jinran Yu, Xixi Yang, Guoyun Gao, Yao Xiong, Yifei Wang, Jing Han, Youhui Chen, Huai Zhang, Qijun Sun and Zhong Lin Wang. Science Advances 17 Mar 2021: Vol. 7, no. 12, eabd9117 DOI: 10.1126/sciadv.abd9117

This appears to be open access.

Stronger concrete with graphene derived from tires

I’ve become strangely fascinated with concrete these last few months. Possibly, this is a consequence of a lot more ‘concrete’ research being published. Here’s a March 29, 2021 news item on phys.org featuring work from Rice University (Texas, US),

This could be where the rubber truly hits the road.

Rice University scientists have optimized a process to convert waste from rubber tires into graphene that can, in turn, be used to strengthen concrete.

The environmental benefits of adding graphene to concrete are clear, chemist James Tour said.

“Concrete is the most-produced material in the world, and simply making it produces as much as 9% of the world’s carbon dioxide emissions,” Tour said. “If we can use less concrete in our roads, buildings and bridges, we can eliminate some of the emissions at the very start.”

A March 29, 2021 Rice University news release (also on EurekAlert), which originated the news item, provides context for the work and more technical details,

Recycled tire waste is already used as a component of Portland cement, but graphene has been proven to strengthen cementitious materials, concrete among them, at the molecular level.

While the majority of the 800 million tires discarded annually are burned for fuel or ground up for other applications, 16% of them wind up in landfills.

“Reclaiming even a fraction of those as graphene will keep millions of tires from reaching landfills,” Tour said.

The “flash” process introduced by Tour and his colleagues in 2020 has been used to convert food waste, plastic and other carbon sources by exposing them to a jolt of electricity that removes everything but carbon atoms from the sample.

Those atoms reassemble into valuable turbostratic graphene, which has misaligned layers that are more soluble than graphene produced via exfoliation from graphite. That makes it easier to use in composite materials.

Rubber proved more challenging than food or plastic to turn into graphene, but the lab optimized the process by using commercial pyrolyzed waste rubber from tires. After useful oils are extracted from waste tires, this carbon residue has until now had near-zero value, Tour said.

Tire-derived carbon black or a blend of shredded rubber tires and commercial carbon black can be flashed into graphene. Because turbostratic graphene is soluble, it can easily be added to cement to make more environmentally friendly concrete.

The research led by Tour and Rouzbeh Shahsavari of C-Crete Technologies is detailed in the journal Carbon.

The Rice lab flashed tire-derived carbon black and found about 70% of the material converted to graphene. When flashing shredded rubber tires mixed with plain carbon black to add conductivity, about 47% converted to graphene. Elements besides carbon were vented out for other uses.

The electrical pulses lasted between 300 milliseconds and 1 second. The lab calculated electricity used in the conversion process would cost about $100 per ton of starting carbon.

The researchers blended minute amounts of tire-derived graphene — 0.1 weight/percent (wt%) for tire carbon black and 0.05 wt% for carbon black and shredded tires — with Portland cement and used it to produce concrete cylinders. Tested after curing for seven days, the cylinders showed gains of 30% or more in compressive strength. After 28 days, 0.1 wt% of graphene sufficed to give both products a strength gain of at least 30%.

“This increase in strength is in part due to a seeding effect of 2D graphene for better growth of cement hydrate products, and in part due to a reinforcing effect at later stages,” Shahsavari said.

Set of tires on a sky background

I’m not sure where I got this stock shot but it is pretty (if tires can ever be described that way).

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

Flash Graphene from Rubber Waste by Paul A. Advincula, Duy Xuan Luong, Weiyin Chen, Shivaranjan Raghuraman, Rouzbeh Shahsavari, James M.Tour. Carbon Available online 28 March 2021 In Press, Journal Pre-proof DOI: https://doi.org/10.1016/j.carbon.2021.03.020

This paper is behind a paywall.

Impact of graphene flakes (nanoparticles) on neurons

This research suggests that graphene flakes might have an impact on anxiety-related behaviour. If I read the work correctly, the graphene flakes don’t exacerbate anxiety but, instead, may provide relief.

A March 10, 2021 news item on phys.org announces the research into graphene flakes and neurons (rat), Note: Links have been removed,

Effective, specific, with a reversible and non-harmful action: the identikit of the perfect biomaterial seems to correspond to graphene flakes, the subject of a new study carried out by SISSA—International School for Advanced Studies of Trieste, Catalan Institute of Nanoscience and Nanotechnology (ICN2) of Barcelona, and the National Graphene Institute of the University of Manchester, as part of the European Graphene Flagship project. This nanomaterial has demonstrated the ability to interact with the functions of the nervous system in vertebrates in a very specific manner, interrupting the building up of a pathological process that leads to anxiety-related behavior.

“We previously showed that when graphene flakes are delivered to neurons they interfere spontaneously with excitatory synapses by transiently preventing glutamate release from presynaptic terminals,” says Laura Ballerini of SISSA, the leader of the team that carried out the research study “Graphene oxide prevents lateral amygdala dysfunctional synaptic plasticity and reverts long lasting anxiety behavior in rats,” recently published in Biomaterials.

A March 10, 2021 Scuola Internazionale Superiore di Studi Avanzati (SISSA) press release (also on EurekAlert), which originated the news item, provides more detail,

“We investigated whether such a reduction in synaptic activity was sufficient to modify related behaviours, in particular the pathological ones that develop due to a transient and localised hyper-function of excitatory synapses”. This approach would fortify the strategy of selective and transient targeting of synapses to prevent the development of brain pathologies by using the so-called precise medicine treatments.

To test this hypothesis, the team focused on post-traumatic stress disorder (PTSD) and carried out the experiments in two phases, in vivo and in vitro.

“We analysed defensive behaviours caused in rats [emphasis mine] by the presence of a predator, using the exposure to cat odour, to induce an aversive memory” explains Audrey Franceschi Biagioni of SISSA, the first author of the study. “If exposed to the predator odour, the rat has a defensive response, holing up, and this experience is so well-imprinted in the memory, that when the animal is placed in the same context even six days later, the animal remembers the odour of the predator and acts the same protective behaviour. This is a well-known and consolidated model, that we used to reproduce a stress behaviour. Exposure to the predator can modify neuronal connections – a phenomenon that is technically known as plasticity – and increases synaptic activity in a specific area of the amygdala that therefore represented the target of our study to test the effects of the nanomaterial”.

Laura Ballerini adds: “We hypothesised that graphene flakes that we showed to temporarily inhibit excitatory synapses (without causing inflammation, damage to neurons or other side effects) could be injected in the lateral amygdala when the plasticity associated with memory was consolidated. If the nanomaterial was efficient in blocking excitatory synapses, it should inhibit plasticity and decrease the anxiety related response. And this is what happened: the animals that were administered with graphene flakes, after six days, “forgot” the anxiety related responses, rescuing their behaviour”.

The second part of the research was performed in vitro. “In vivo we could observe only behavioural changes and could not evaluate the impact of the graphene flakes on synapses,” explains Giada Cellot, researcher at SISSA and first author of the study together with Audrey Franceschi Biagioni. “In vitro experiments allowed to work on a simplified model, to get insight about the mechanisms through which the graphene flakes can interact with neurons. We used neuronal cultures obtained from the amygdala, the region of the brain where the stress response occurs, and we observed that the effects of nanomaterials were specific for the excitatory synapses and a short exposure to graphene flakes could prevent the pathological plasticity of the synapses”.

Thanks to these findings, graphene flakes have shown their potential as nanotools (biomedical tools composed of nanomaterials) that could act in a specific and reversible way on synaptic activity to interrupt a pathological process and therefore they might be used also to transport drugs or for other applications in the field of precision medicine.

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

Graphene oxide prevents lateral amygdala dysfunctional synaptic plasticity and reverts long lasting anxiety behavior in rats by Audrey Franceschi Biagionia1, Giada Cellot, Elisa Pati, Neus Lozano, Belén Ballesteros, Raffaele Casani, Norberto Cysne Coimbra, Kostas Kostarelos, Laura Ballerini. Biomaterials Volume 271, April 2021, 120749 DOI: https://doi.org/10.1016/j.biomaterials.2021.120749

This paper is open access.

A standard for determining what it means to be graphene

How do you know if your ‘graphene’ light bulb has any graphene in it? How do you know if your orange juice is 100% orange juice? The answer to those questions is that you don’t. So, you must hope there are standards and regulations governing the answers. You must also hope that there are incentives (fines and/or jail time) for obeying those regulations.

In a March 15, 2021 news item on Nanowerk, you’ll find an announcement from the UK’s National Physical Laboratory about an international standard for graphene (Note: A link has been removed),

The National Physical Laboratory (NPL) in the UK in collaboration with international partners, have developed an ISO/IEC [International Standards Organization/International Electrotechnical Commission] standard, ISO/TS 21356-1:2021, for measuring the structural properties of graphene, typically sold as powders or in a liquid dispersion. The ISO/IEC standard allows the supply chain to answer the question ‘what is my material?’ and is based on methods developed with The University of Manchester in the NPL Good Practice Guide 145.

A March ??, 2021 NPL press release, which originated the news item, provides more details,

Over the last few years, graphene, a 2D material with many exciting properties and just one atom thick, has moved from the laboratory into real-world products such as cars and smartphones. However, there is still a barrier affecting the rate of its commercialisation, namely, understanding the true properties of the material. There is not just one type of material, but many, each with different properties that need matching to the many different applications where graphene can provide an improvement.

With hundreds of companies across the globe selling different materials labelled as ‘graphene’, and manufacturing it in different ways, end users who want to improve their products by incorporating few-layer graphene flakes are unable to compare and subsequently select the right material for their product.

Through standardised methods to enable the reliable and repeatable measurement of properties, such as the lateral flake size, flake thickness, level of disorder and specific surface area, industry will be able to compare the many materials available and instil trust in the supply chain.  In conjunction with the international ISO/IEC terminology standard led by NPL, ISO/TS 80004-13:2017, it will be possible for commercially available material to be correctly measured and labelled as graphene, few-layer graphene or graphite.

As the UK’s National Metrology Institute, NPL has been developing and standardising the required metrologically-robust methods for the measurement of graphene and related 2D materials to enable industry to use these materials and realise novel and improved products across many application areas.

The continuation of the NPL-led standardisation work within ISO TC229 (nanotechnologies) will allow the chemical properties of graphene related 2D materials to be determined, as well as the structural properties for different forms of graphene material, such as CVD-grown graphene. This truly international effort to standardise the framework of measurements for graphene is described in more detail in Nature Reviews Physics, including further technical discussion on the new ISO graphene measurement standard.

Dr Andrew J Pollard, Science Area Leader at NPL said: “It is exciting to see this new measurement standard now available for the growing graphene industry worldwide. Based on rigorous metrological research, this standard will allow companies to confidently compare technical datasheets for the first time and is the first step towards verified quality control methods.”

Dr Charles Clifford, Senior Research Scientist at NPL said: “It is fantastic to see this international standard published after several years of development.  To reach international consensus especially across the 37 member countries of ISO TC229 (nanotechnologies) is a testament both to the global interest in graphene and the importance of international cooperation.”

James Baker, CEO of Graphene@Manchester said: “Standardisation is crucial for the commercialisation of graphene in many different applications such as construction, water filtration, energy storage and aerospace. Through this international measurement standard, companies in the UK and beyond will be able to accelerate the uptake of this 21st Century material, now entering many significant markets.”

Here are links to the new standard ISO/TS 21356-1:2021 (Nanotechnologies — Structural characterization of graphene — Part 1: Graphene from powders and dispersions} and the NPL/University of Manchester’s 2017 edition of the Good Practice Guide.

Here’s a second link to the article along with a citation,

The importance of international standards for the graphene community by Charles A. Clifford, Erlon H. Martins Ferreira, Toshiyuki Fujimoto, Jan Herrmann, Angela R. Hight Walker, Denis Koltsov, Christian Punckt, Lingling Ren, Gregory J. Smallwood & Andrew J. Pollard. Nature Reviews Physics (2021) DOI: https://doi.org/10.1038/s42254-021-00278-6 Published 15 March 2021

This paper is behind a paywall.

Making carbon capture more efficient and cheaper with graphene filters

Years ago someone asked me if there was any nanotechnology research into carbon capture. I couldn’t answer the question at the time but since then I’ve been on the lookout for more on the topic. So, I’m happy to add this February 25, 2021 news item on Nanowerk to my growing number of carbon capture posts (Note: A link has been removed),

One of the main culprits of global warming is the vast amount of carbon dioxide pumped out into the atmosphere mostly from burning fossil fuels and the production of steel and cement. In response, scientists have been trying out a process that can sequester waste carbon dioxide, transporting it into a storage site, and then depositing it at a place where it cannot enter the atmosphere.

The problem is that capturing carbon from power plants and industrial emissions isn’t very cost-effective. The main reason is that waste carbon dioxide isn’t emitted pure, but is mixed with nitrogen and other gases, and extracting it from industrial emissions requires extra energy consumption – meaning a pricier bill.

Scientists have been trying to develop an energy-efficient carbon dioxide-filter. Referred to as a “membrane”, this technology can extract carbon dioxide out of the gas mix, which can then be either stored or converted into useful chemicals. “However, the performance of current carbon dioxide filters has been limited by the fundamental properties of currently available materials,” explains Professor Kumar Varoon Agrawal at EPFL’s School of Basic Sciences (EPFL Valais Wallis).

Now, Agrawal has led a team of chemical engineers to develop the world’s thinnest filter from graphene, the world-famous “wonder material” that won the Physics Nobel in 2010. But the graphene filter isn’t just the thinnest in the world, it can also separate carbon dioxide from a mix of gases such as those coming out of industrial emissions and do so with an efficiency and speed that surpasses most current filters.

A March 3, 2021 Ecole Polytechnique Fédérale de Lausanne (EPFL) press release (also on EurekAlert but published February 25, 2021), which originated the news item, delves further into the topic,

“Our approach was simple,” says Agrawal. “We made carbon dioxide-sized holes in graphene, which allowed carbon dioxide to flow through while blocking other gases such as nitrogen, which are larger than carbon dioxide.” The result is a record-high carbon dioxide-capture performance.

For comparison, current filters are required to exceed 1000 gas permeation units (GPUs), while their carbon-capturing specificity, referred to as their “carbon dioxide/nitrogen separation factor” must be above 20. The membranes that the EPFL scientists developed show more than ten-fold higher carbon dioxide permeance at 11,800 GPUs, while their separation factor stands at 22.5.

“We estimate that this technology will drop the cost of carbon capture close to $30 per ton of carbon dioxide, in contrast to commercial processes where the cost is two-to-four time higher,” says Agrawal. His team is now working on scaling up the process by developing a pilot plant demonstrator to capture 10 kg carbon dioxide per day, in a project funded by the Swiss government and Swiss industry.

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

Millisecond lattice gasification for high-density CO2– and O2-sieving nanopores in single-layer graphene by Shiqi Huang, Shaoxian Li, Luis Francisco Villalobos, Mostapha Dakhchoune, Marina Micari, Deepu J. Babu, Mohammad Tohidi Vahdat, Mounir Mensi, Emad Oveisi and Kumar Varoon Agrawal. Science Advances 24 Feb 2021: Vol. 7, no. 9, eabf0116 DOI: 10.1126/sciadv.abf0116

This paper appears to be open access.