Category Archives: graphene

Artificial graphene with buckyballs

A July 21, 2022 news item on Nanowerk describes graphene in its ‘natural’ state and explains what ‘artificial’ graphene is although there is no mention of why variants are a hot topic,

Graphene consists of carbon atoms that crosslink in a plane to form a flat honeycomb structure. In addition to surprisingly high mechanical stability, the material has exciting electronic properties: The electrons behave like massless particles, which can be clearly demonstrated in spectrometric experiments.

Measurements reveal a linear dependence of energy on momentum, namely the so-called Dirac cones – two lines that cross without a band gap – i.e. an energy difference between electrons in the conduction band and those in the valence bands.

Variants in graphene architecture

Artificial variants of graphene architecture are a hot topic in materials research right now. Instead of carbon atoms, quantum dots of silicon have been placed, ultracold atoms have been trapped in the honeycomb lattice with strong laser fields, or carbon monoxide molecules have been pushed into place on a copper surface piece by piece with a scanning tunneling microscope, where they could impart the characteristic graphene properties to the electrons of the copper.

A July 21, 2022 Helmholtz-Zentrum Berlin (HZB) press release (also on EurekAlert), which originated the news item, describes research into whether or not layering buckyballs onto gold would result in artificial graphene,

Artificial graphene with buckyballs?

A recent study suggested that it is infinitely easier to make artificial graphene using C60 molecules called buckyballs [or buckminsterfullerenes or, more generically, fullerenes]. Only a uniform layer of these needs to be vapor-deposited onto gold for the gold electrons to take on the special graphene properties. Measurements of photoemission spectra appeared to show a kind of Dirac cone.

Analysis of band structures at BESSY II

“That would be really quite amazing,” says Dr. Andrei Varykhalov, of HZB, who heads a photoemission and scanning tunneling microscopy group. “Because the C60 molecule is absolutely nonpolar, it was hard for us to imagine how such molecules would exert a strong influence on the electrons in the gold.” So Varykhalov and his team launched a series of measurements to test this hypothesis.

In tricky and detailed analyses, the Berlin team was able to study C60 layers on gold over a much larger energy range and for different measurement parameters. They used angle-resolved ARPES spectroscopy at BESSY II [third-generation synchrotron radiation source], which enables particularly precise measurements, and also analysed electron spin for some measurements.

Normal behavior

“We see a parabolic relationship between momentum and energy in our measured data, so it’s a very normal behavior. These signals come from the electrons deep in the substrate (gold or copper) and not the layer, which could be affected by the buckyballs,” explains Dr. Maxim Krivenkov, lead author of the study. The team was also able to explain the linear measurement curves from the previous study. “These measurement curves merely mimic the Dirac cones; they are an artifact, so to speak, of a deflection of the photoelectrons as they leave the gold and pass through the C60 layer,” Varykhalov explains. Therefore, the buckyball layer on gold cannot be considered an artificial graphene.

Caption: Measurement data from BESSY II before and after deposition of C60 molecules demonstrate the replication of the band structure and the emergence of cone-like band crossings. A scanning electron microscopy of the buckyballs on gold is superimposed in the centre. Credit: HZB

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

On the problem of Dirac cones in fullerenes on gold by M. Krivenkov, D. Marchenko, M. Sajedi, A. Fedorov, O. J. Clark, J. Sánchez-Barriga, E. D. L. Rienks, O. Rader and A. Varykhalov. Nanoscale, 2022,14, 9124-9133 First published: 23 May 2022

This paper is open access.

Could buckyballs and carbon nanotubes come from the dust and gas of dying stars?

In this picture of the Spirograph Nebula, a dying star about 2,000 light-years from Earth, NASA’s Hubble Space Telescope revealed some remarkable textures weaving through the star’s envelope of dust and gas. UArizona researchers have now found evidence that complex carbon nanotubes could be forged in such environments.. Credit: NASA and The Hubble Heritage Team (STScI/AURA)

It’s always interesting to come across different news releases announcing the same research. In this case I have two news releases, one from the US National Science Foundation (NSF) and one from the University of Arizona. Let’s start with the July 19, 2022 news item on phys.org (originated by the US NSF),

Astronomers at the University of Arizona have developed a theory to explain the presence of the largest molecules known to exist in interstellar gas.

The team simulated the environment of dying stars and observed the formation of buckyballs (carbon atoms linked to three other carbon atoms by covalent bonds) and carbon nanotubes (rolled up sheets of single-layer carbon atoms). The findings indicate that buckyballs and carbon nanotubes can form when silicon carbide dust — known to be proximate to dying stars — releases carbon in reaction to intense heat, shockwaves and high energy particles.

Here’s the rest of the July 18, 2022 NSF news release, Note: A link has been removed,

“We know from infrared observations that buckyballs populate the interstellar medium,” said Jacob Bernal, who led the research. “The big problem has been explaining how these massive, complex carbon molecules could possibly form in an environment saturated with hydrogen, which is what you typically have around a dying star.”

Rearranging the structure of graphene (a sheet of single-layer carbon atoms) could create buckyballs and nanotubes. Building on that, the team heated silicon carbide samples to temperatures that would mimic the aura of a dying star and observed the formation of nanotubes.

“We were surprised we could make these extraordinary structures,” Bernal said. “Chemically, our nanotubes are very simple, but they are extremely beautiful.”

Buckyballs are the largest molecules currently known to occur in interstellar space. It is now known that buckyballs containing 60 to 70 carbon atoms are common.

“We know the raw material is there, and we know the conditions are very close to what you’d see near the envelope of a dying star,” study co-author Lucy Ziurys said. “Shock waves pass through the envelope, and the temperature and pressure conditions have been shown to exist in space. We also see buckyballs in planetary nebulae — in other words, we see the beginning and the end products you would expect in our experiments.”

A June 16, 2022 University of Arizona news release by Daniel Stolte (also on EurekAlert) takes a context-rich approach to writing up the proposed theory for how buckyballs and carbon nanotubes (CNTs) form (Note: Links have been removed),

In the mid-1980s, the discovery of complex carbon molecules drifting through the interstellar medium garnered significant attention, with possibly the most famous examples being Buckminsterfullerene, or “buckyballs” – spheres consisting of 60 or 70 carbon atoms. However, scientists have struggled to understand how these molecules can form in space.

In a paper accepted for publication in the Journal of Physical Chemistry A, researchers from the University of Arizona suggest a surprisingly simple explanation. After exposing silicon carbide – a common ingredient of dust grains in planetary nebulae – to conditions similar to those found around dying stars, the researchers observed the spontaneous formation of carbon nanotubes, which are highly structured rod-like molecules consisting of multiple layers of carbon sheets. The findings were presented on June 16 [2022] at the 240th Meeting of the American Astronomical Society in Pasadena, California.

Led by UArizona researcher Jacob Bernal, the work builds on research published in 2019, when the group showed that they could create buckyballs using the same experimental setup. The work suggests that buckyballs and carbon nanotubes could form when the silicon carbide dust made by dying stars is hit by high temperatures, shock waves and high-energy particles, leaching silicon from the surface and leaving carbon behind.

The findings support the idea that dying stars may seed the interstellar medium with nanotubes and possibly other complex carbon molecules. The results have implications for astrobiology, as they provide a mechanism for concentrating carbon that could then be transported to planetary systems.

“We know from infrared observations that buckyballs populate the interstellar medium,” said Bernal, a postdoctoral research associate in the UArizona Lunar and Planetary Laboratory. “The big problem has been explaining how these massive, complex carbon molecules could possibly form in an environment saturated with hydrogen, which is what you typically have around a dying star.”

The formation of carbon-rich molecules, let alone species containing purely carbon, in the presence of hydrogen is virtually impossible due to thermodynamic laws. The new study findings offer an alternative scenario: Instead of assembling individual carbon atoms, buckyballs and nanotubes could result from simply rearranging the structure of graphene – single-layered carbon sheets that are known to form on the surface of heated silicon carbide grains.

This is exactly what Bernal and his co-authors observed when they heated commercially available silicon carbide samples to temperatures occurring in dying or dead stars and imaged them. As the temperature approached 1,050 degreesCelsius, small hemispherical structures with the approximate size of about 1 nanometer were observed at the grain surface. Within minutes of continued heating, the spherical buds began to grow into rod-like structures, containing several graphene layers with curvature and dimensions indicating a tubular form. The resulting nanotubules ranged from about 3 to 4 nanometers in length and width, larger than buckyballs. The largest imaged specimens were comprised of more than four layers of graphitic carbon. During the heating experiment, the tubes were observed to wiggle before budding off the surface and getting sucked into the vacuum surrounding the sample.

“We were surprised we could make these extraordinary structures,” Bernal said. “Chemically, our nanotubes are very simple, but they are extremely beautiful.”

Named after their resemblance to architectural works by Richard Buckminster Fuller, fullerenes are the largest molecules currently known to occur in interstellar space, which for decades was believed to be devoid of any molecules containing more than a few atoms, 10 at most. It is now well established that the fullerenes C60 and C70, which contain 60 or 70 carbon atoms, respectively, are common ingredients of the interstellar medium.

One of the first of its kind in the world, the transmission electron microscope housed at the Kuiper Materials Imaging and Characterization Facility at UArizona is uniquely suited to simulate the planetary nebula environment. Its 200,000-volt electron beam can probe matter down to 78 picometers – the distance of two hydrogen atoms in a water molecule – making it possible to see individual atoms. The instrument operates in a vacuum closely resembling the pressure – or lack thereof – thought to exist in circumstellar environments.

While a spherical C60 molecule measures 0.7 nanometers in diameter, the nanotube structures formed in this experiment measured several times the size of C60, easily exceeding 1,000 carbon atoms. The study authors are confident their experiments accurately replicated the temperature and density conditions that would be expected in a planetary nebula, said co-author Lucy Ziurys, a UArizona Regents Professor of Astronomy, Chemistry and Biochemistry.

“We know the raw material is there, and we know the conditions are very close to what you’d see near the envelope of a dying star,” she said. “There are shock waves that pass through the envelope, so the temperature and pressure conditions have been shown to exist in space. We also see buckyballs in these planetary nebulae – in other words, we see the beginning and the end products you would expect in our experiments.”

These experimental simulations suggest that carbon nanotubes, along with the smaller fullerenes, are subsequently injected into the interstellar medium. Carbon nanotubes are known to have high stability against radiation, and fullerenes are able to survive for millions of years when adequately shielded from high-energy cosmic radiation. Carbon-rich meteorites, such as carbonaceous chondrites, could contain these structures as well, the researchers propose.

According to study co-author Tom Zega, a professor in the UArizona Lunar and Planetary Lab, the challenge is finding nanotubes in these meteorites, because of the very small grain sizes and because the meteorites are a complex mix of organic and inorganic materials, some with sizes similar to those of nanotubes.

“Nonetheless, our experiments suggest that such materials could have formed in interstellar space,” Zega said. “If they survived the journey to our local part of the galaxy where our solar system formed some 4.5 billion years ago, then they could be preserved inside of the material that was left over.”

Zega said a prime example of such leftover material is Bennu, a carbonaceous near-Earth asteroid from which NASA’s UArizona-led OSIRIS-REx mission scooped up a sample in October 2020. Scientists are eagerly awaiting the arrival of that sample, scheduled for 2023.  

“Asteroid Bennu could have preserved these materials, so it is possible we may find nanotubes in them,” Zega said.

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

Destructive Processing of Silicon Carbide Grains: Experimental Insights into the Formation of Interstellar Fullerenes and Carbon Nanotubes by Jacob J. Bernal, Thomas J. Zega, and Lucy M. Ziurys. J. Phys. Chem. A 2022, XXXX, XXX, XXX-XXX DOI: https://doi.org/10.1021/acs.jpca.2c01441 Publication Date:June 27, 2022 © 2022 American Chemical Society

This paper is behind a paywall.

Efficient hydrogen evolution reaction with graphene-based NiSe2 nanocrystalline array

Should this work make its way from the laboratory to the market it could prove helpful in the drive to move away from fossil fuels, from a July 15, 2022 news item on Nanowerk,

In the face of low electrolytic water splitting catalytic activity, the development of efficiency and stable electrolytic catalyst for hydrogen evolution reaction is critical necessary. Moreover, the rather high price with insufficient supply of noble mental namely platinum and palladium has become the obstacle of their large-scale applications.

A research group of Lixu Lei from Southeast University [China] and Fajun Li from Suzhou University just reported a novel graphene based NiSe2 [nickel diselenide] nanocrystalline array prepared through a two-step microwave and subsequent selenization treatment. They found their unique structural advantages —— the ultrafine uniform dispersion of NiSe2 nanocrystallines in the reduced graphite oxide as substrate has an additional synergistic effect on promoting the conductivity and stability.

A July 15, 2022 Higher Education Press news release on EurekAlert, which originated the news item, provides more detail about the work,

Nickel selenide electrocatalysts for hydrogen evolution reaction with high efficiency and low-cost, has favorable potential future application prospect. Nevertheless, the high overpotential and poor stability limited their practical applications. Carbon materials including graphene, carbon nanotubes etc. possess extraordinary thermal stability and electric conductivity, can be ideal protective skeleton structures of electrocatalysts. By combining the NiSe2 nanoparticles with graphene sheet in an in-situ growth manner assisted with microwave irradiation, the electrocatalytic performance of hydrogen evolution reaction was optimized remarkably in this work.

The electrocatalytic activity for hydrogen evolution reaction of the composite proven can reach up to 158 mV overpotential at 10 mA/cm2 and has an extremely stable performance in the 100 h H2 production test. These results provide a useful idea for the development of newly high efficiency electrocatalyst for hydrogen evolution reaction.

About Higher Education Press

Founded in May 1954, Higher Education Press Limited Company (HEP), affiliated with the Ministry of Education, is one of the earliest institutions committed to educational publishing after the establishment of P. R. China in 1949. After striving for six decades, HEP has developed into a major comprehensive publisher, with products in various forms and at different levels. Both for import and export, HEP has been striving to fill in the gap of domestic and foreign markets and meet the demand of global customers by collaborating with more than 200 partners throughout the world and selling products and services in 32 languages globally. Now, HEP ranks among China’s top publishers in terms of copyright export volume and the world’s top 50 largest publishing enterprises in terms of comprehensive strength.

The Frontiers Journals series published by HEP includes 28 English academic journals, covering the largest academic fields in China at present. Among the series, 13 have been indexed by SCI, 6 by EI, 2 by MEDLINE, 1 by A&HCI. HEP’s academic monographs have won about 300 different kinds of publishing funds and awards both at home and abroad.

About Frontiers in Energy

Frontiers in Energy, a peer-reviewed international journal launched in January 2007, presents a unique platform for reporting the most advanced research and strategic thinking on energy technology. The Journal publishes review and mini-review articles, original research articles, perspective, news & highlights, viewpoints, comments, etc. by individual researchers and research groups. The journal is strictly peer-reviewed and accepts only original submissions in English. The scope of the Journal covers (but not limited to): energy conversion and utilization; renewable energy; energy storage; hydrogen and fuel cells; carbon capture, utilization and storage; advanced nuclear technology; smart grids and microgrids; power and energy systems; power cells and electric vehicles; building energy conservation, energy and environment; energy economy and policy, etc. Interdisciplinary papers are encouraged.

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

In situ growth of NiSe2 nanocrystalline array on graphene for efficient hydrogen evolution reaction by Shuai Ji, Changgan Lai, Huan Zhou, Helin Wang, Ling Ma, Cong Wang, Keying Zhang, Fajun Li & Lixu Lei. Frontiers in Energy (2022) DOI: https://doi.org/10.1007/s11708-022-0827-7 Published 10 June 2022

This paper is behind a paywall.

Extending a wig’s life with a nanocomposite

A June 13, 2022 American Chemical Society (ACS) news release (also on EurekAlert) announces a nanocomposite that could make wigs last longer,

For some people, wigs are a fun and colorful fashion accessory, but for those with hair loss from alopecia or other conditions, they can provide a real sense of normalcy and boost self-confidence. Whether made from human or synthetic strands, however, most hairpieces lose their luster after being worn day after day. Now, researchers in ACS Applied Materials & Interfaces report a new way to make wigs more durable and long lasting.

Wigs come in all colors of the rainbow and in every style imaginable. Some cover the whole head, while others are “extensions,” sections of hair that clip onto existing locks to make them look fuller or longer. Hairpieces can be made of real human strands or synthetic materials, but either way, washing, UV exposure from the sun and repeated styling can cause these products to become dry and brittle. To extend the wearable life of wigs, some researchers have spray-coated a layer of graphene oxide on them, whereas other teams have immersed wig hairs in a keratin/halloysite nanocomposite. Because it’s difficult to cover an entire hairpiece with these methods, Guang Yang, Huali Nie and colleagues wanted to see if a nanocomposite applied with a tried-and-true approach for coating surfaces with ultrathin films — known as the Langmuir-Blodgett (LB) technique — could improve coverage and increase durability.

The researchers first developed a keratin and graphene oxide nanocomposite as the coating material. To coat hairs with the LB method, they dipped a few human or synthetic hairs into water in a special apparatus with moveable side barriers. After the nanocomposite was spread on the water’s surface with an atomizer, the barriers were moved inward to compress the film— like the trash compactor that almost crushed the heroes in the movie Star Wars. After 30 minutes, the researchers lifted the hairs out of the water, and as they did so, the film coated the locks.

Compared to the immersion technique, the LB method provided more coverage. In addition, hairs treated with the LB approach sustained less UV damage, were less prone to breakage and could hold more moisture than those that were simply immersed in the nanocomposite. They also dissipated heat better and generated less static electricity when rubbed with a rubber sheet. The researchers say that the method can be scaled up for use by companies that manufacture wigs.

The authors acknowledge funding from the Fundamental Research Funds for the Central Universities, the Shanghai Natural Science Foundation, the Shanghai Pujiang Program, the Natural Science Foundation of Shandong Province, and the Shanghai International Cooperative Project of the Belt and Road.

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

High-Performance Wigs via the Langmuir–Blodgett Deposition of Keratin/Graphene Oxide Nanocomposite by Shan Du, Tiantian He, Huali Nie, and Guang Yang. ACS Appl. Mater. Interfaces 2022, 14, 23, 27233–27241 DOI: https://doi.org/10.1021/acsami.2c05965 Publication Date:June 3, 2022 Copyright © 2022 American Chemical Society

This paper is behind a paywall.

World’s smallest record features Christmas classic “Rockin’ Around the Christmas Tree”

Scientists like to have a little fun too as this December 23, 2022 news item on Nanowerk shows,

Measuring only 40 micrometres in diameter, researchers at DTU Physics have made the smallest record ever cut. Featuring the first 25 seconds of the Christmas classic “Rocking Around the Christmas Tree” [sic], the single is cut using a new nano-sculpting machine – the Nanofrazor – recently acquired from Heidelberg Instruments. The Nanofrazor can engrave 3D patterns into surfaces with nanoscale resolution, allowing the researchers to create new nanostructures that may pave the way for novel technologies in fields such as quantum devices, magnetic sensors and electron optics.

”I have done lithography for 30 years, and although we’ve had this machine for a while, it still feels like science fiction. We’ve done many experiments, like making a copy of the Mona Lisa in a 12 by 16-micrometre area with a pixel size of ten nanometers. We’ve also printed an image of DTU’s founder – Hans Christian Ørsted – in an 8 by 12-micrometre size with a pixel size of 2.540.000 DPI. To get an idea of the scale we are working at, we could write our signatures on a red blood cell with this thing,” says Professor Peter Bøggild from DTU Physics.

“The most radical thing is that we can create free-form 3D landscapes at that crazy resolution – this grey-scale nanolithography is a true game-changer for our research”.

The scientists show how they inscribed the song onto the world’s smallest record (Note 1: You will not hear the song. Note 2: i don’t know how many times I’ve seen news releases about audio files (a recorded song, fish singing, etc.) that are not included … sigh),

A December 22, 2022 Technical University of Denmark press release (also on EurekAlert), which originated the news item, provides detail about the work,

Nanoscale Christmas record – in stereo
The Nanofrazor is not like a printer adding material to a medium; instead, it works like a CNC (computer numerical controle) machine removing material at precise locations, leaving the desired shape behind. In the case of the miniature pictures of Mona Lisa and H.C. Ørsted, the final image is defined by the line-by-line removal of polymer until a perfect grey-scale image emerges. To Peter Bøggild, an amateur musician and vinyl record enthusiast, the idea of cutting a nanoscale record was obvious.

“We decided that we might as well try and print a record. We’ve taken a snippet of Rocking Around The Christmas Tree and have cut it just like you would cut a normal record—although, since we’re working on the nanoscale, this one isn’t playable on your average turntable. The Nanofrazor was put to work as a record-cutting lathe – converting an audio signal into a spiralled groove on the surface of the medium. In this case, the medium is a different polymer than vinyl. We even encoded the music in stereo – the lateral wriggles is the left channel, whereas the depth modulation contains the right channel. It may be too impractical and expensive to become a hit record. To read the groove, you need a rather costly atomic force microscope or the Nanofrazor, but it is definitely doable.”

High-speed, low-cost nanostructures

The NOVO Foundation grant BIOMAG, which made the Nanofrazor dream possible, is not about cutting Christmas records or printing images of famous people. Peter Bøggild and his colleagues, Tim Booth and Nolan Lassaline, have other plans. They expect that the Nanofrazor will allow them to sculpt 3D nanostructures in extremely precise detail and do so at high speed and low cost – something that is impossible with existing tools.

“We work with 2D materials, and when these ultrathin materials are carefully laid down on the 3D landscapes, they follow the contours of the surface. In short, they curve, and that is a powerful and entirely new way of “programming” materials to do things that no one would believe were possible just fifteen years ago. For instance, when curved in just the right way, graphene behaves as if there is a giant magnetic field when there is, in fact, none. And we can curve it just the right way with the Nanofrazor,” says Peter Bøggild.

Associate professor Tim Booth adds:

“The fact that we can now accurately shape the surfaces with nanoscale precision at pretty much the speed of imagination is a game changer for us. We have many ideas for what to do next and believe that this machine will significantly speed up the prototyping of new structures. Our main goal is to develop novel magnetic sensors for detecting currents in the living brain within the BIOMAG project. Still, we also look forward to creating precisely sculpted potential landscapes with which we can better control electron waves. There is much work to do.”

Postdoc Nolan Lassaline (who cut the Christmas record), was recently awarded a DKK 2 Mio. VILLUM EXPERIMENT grant to create “quantum soap bubbles” in graphene. He will use the grant – and the Nanofrazor – to explore new ways of structuring nanomaterials and develop novel ways of manipulating electrons in atomically thin materials.

“Quantum soap bubbles are smooth electronic potentials where we add artificially tailored disorders. By doing so, we can manipulate how electrons flow in graphene. We hope to understand how electrons move in engineered disordered potentials and explore if this could become a new platform for advanced neural networks and quantum information processing.”

The Nanofrazor system is now part of the DTU Physics NANOMADE’s unique fabrication facility for air-sensitive 2D materials and devices and part of E-MAT, a greater ecosystem for air-sensitive nanomaterials processing and fabrication led by Prof. Nini Pryds, DTU Energy.

While it’s not an audio file from the smallest record, this features Brenda Lee (who first recorded the song in 1958) in a ‘singalong’ version of “Rockin’ Around the Christmas Tree,”

Bøggild was last featured here in a December 24, 2021 posting “Season’s Greetings with the world’s thinnest Christmas tree.”

Have a lovely Christmas/Winter Solstice/Kwanzaa/Hannukah/Saturnalia/??? celebration!

Fast hydrogen separation with graphene-wrapped zeolite membranes for clean energy

A May 18, 2022 news item on phys.org highlights the problem with using hydrogen as an energy source,

The effects of global warming are becoming more serious, and there is a strong demand for technological advances to reduce carbon dioxide emissions. Hydrogen is an ideal clean energy which produces water when burned. To promote the use of hydrogen energy, it is essential to develop safe, energy-saving technologies for hydrogen production and storage. Currently, hydrogen is made from natural gas, so it is not appropriate for decarbonization. Using a lot of energy to separate hydrogen would not make it qualify as clean energy.

Polymer separation membranes have the great advantage of enlarging the separation membrane and increasing the separation coefficient. However, the speed of permeation through the membrane is extremely low, and high pressure must be applied to increase the permeation speed. Therefore, a large amount of energy is required for separation using a polymer separation membrane. The goal is to create a new kind of separation membrane technology that can achieve separation speeds that are 50 times faster than that of conventional separation membranes.

A May 18, 2022 Shinshu University (Japan) press release on EurekAlert, which originated the news item, describes a proposed solution to the hydrogen problem,

The graphene-wrapped molecular-sieving membrane prepared in this study has a separation factor of 245 and a permeation coefficient of 5.8 x 106 barrers, which is more than 100 times better than that of conventional polymer separation membranes. If the size of the separation membrane is increased in the future, it is very probable that an energy-saving separation process will be established for the separation of important gases such as carbon dioxide and oxygen as well as hydrogen.

As seen in the transmission electron microscope image in Figure 1 [not shown], graphene is wrapped around the MFI-type zeolite crystal, being hydrophobic. The wrapping uses the principles of colloidal science to keep graphene and zeolite crystal planes close to each other due to reduction of the repulsive interaction. About 5 layers of graphene enclose zeolite crystals in this figure. Around the red arrow, there is a narrow interface space where only hydrogen can permeate. Graphene is also present on hydrophobic zeolite, so the structure of the zeolite crystal cannot be seen with this. Since a strong attractive force acts between graphene, the zeolite crystals wrapped with graphene are in close contact with each other by a simple compression treatment and does not let any gas through.

Figure 2 [not shown] shows a model in which zeolite crystals wrapped with graphene are in contact with each other. The surface of the zeolite crystal has grooves derived from the structure, and there is an interfacial channel between zeolite and graphene through which hydrogen molecules can selectively permeate. The model in which the black circles are connected is graphene, and there are nano-windows represented by blanks in some places. Any gas can freely permeate the nanowindows, but the very narrow channels between graphene and zeolite crystal faces allow hydrogen to permeate preferentially. This structure allows efficient separation of hydrogen and methane. On the other hand, the movement of hydrogen is rapid because there are many voids between the graphene-wrapped zeolite particles. For this reason, ultra-high-speed permeation is possible while maintaining the high separation factor of 200 or more.

Figure 3 [not shown] compares the hydrogen separation factor and gas permeation coefficient for methane with the previously reported separation membranes, which is called Robeson plot. Therefore, this separation membrane separates hydrogen at a speed of about 100 times while maintaining a higher separation coefficient than conventional separation membranes. The farther in the direction of the arrow, the better the performance. This newly developed separation membrane has paved the way for energy-saving separation technologies for the first time.

In addition, this separation principle is different from the conventional dissolution mechanism with polymers and the separation mechanism with pore size in zeolite separation membranes, and it depends on the separation target by selecting the surface structure of zeolite or another crystal. High-speed separation for any target gas is possible in principle. For this reason, if the industrial manufacturing method of this separation membrane and the separation membrane becomes scalable, the chemical industry, combustion industry, and other industries can be significantly improved energy consumption, leading to a significant reduction in carbon dioxide emissions. Currently, the group is conducting research toward the establishment of basic technology for rapidly producing a large amount of enriched oxygen from air. The development of enriched oxygen manufacturing technologies will revolutionize the steel and chemical industry and even medicine.

The figures referenced in the press release are best seen in the context of the paper. I can show you part of Figure 1,

Caption: The black circle connection is a one-layer graphene model, and the nano window is shown as blank. Red hydrogen permeates the gap between graphene and the surface of the zeolite crystal. On the other hand, large CH4 molecules are difficult to permeate. Credit: Copyright©2022 The Authors, License 4.0 (CC BY-NC)

For the rest of Figure 1 and more figures, here’s a link to and a citation for the paper,

Ultrapermeable 2D-channeled graphene-wrapped zeolite molecular sieving membranes for hydrogen separation by Radovan Kukobat, Motomu Sakai, Hideki Tanaka, Hayato Otsuka, Fernando Vallejos-Burgos, Christian Lastoskie, Masahiko Matsukata, Yukichi Sasaki, Kaname Yoshida, Takuya Hayashi and Katsumi Kaneko. Science Advances 18 May 2022 Vol 8, Issue 20 DOI: 10.1126/sciadv.abl3521

This paper is open access.

Why can’t they produce graphene at usable (industrial) scales?

Kevin Wyss, PhD chemistry student at Rice University, has written an explanation of why graphene is not produced in quantities that make it usable in industry in his November 29, 2022 essay for The Conversation (h/t Nov. 29, 2022 phys.org news item), Note: Links have been removed from the following,

“Future chips may be 10 times faster, all thanks to graphene”; “Graphene may be used in COVID-19 detection”; and “Graphene allows batteries to charge 5x faster” – those are just a handful of recent dramatic headlines lauding the possibilities of graphene. Graphene is an incredibly light, strong and durable material made of a single layer of carbon atoms. With these properties, it is no wonder researchers have been studying ways that graphene could advance material science and technology for decades.

Graphene is a fascinating material, just as the sensational headlines suggest, but it is only just starting be used in real-world applications. The problem lies not in graphene’s properties, but in the fact that it is still incredibly difficult and expensive to manufacture at commercial scales.

Wyss highlights the properties that make graphene so attractive, from the November 29, 2022 essay (Note: Links have been removed from the following),

… The material can be used to create flexible electronics and to purify or desalinate water. And adding just 0.03 ounces (1 gram) of graphene to 11.5 pounds (5 kilograms) of cement increases the strength of the cement by 35%.

As of late 2022, Ford Motor Co., with which I worked as part of my doctoral research, is one of the the only companies to use graphene at industrial scales. Starting in 2018, Ford began making plastic for its vehicles that was 0.5% graphene – increasing the plastic’s strength by 20%.

There are two ways of producing graphene as Wyss notes in his November 29, 2022 essay (Note: Links have been removed from the following),

Top-down synthesis [emphasis mine], also known as graphene exfoliation, works by peeling off the thinnest possible layers of carbon from graphite. Some of the earliest graphene sheets were made by using cellophane tape to peel off layers of carbon from a larger piece of graphite.

The problem is that the molecular forces holding graphene sheets together in graphite are very strong, and it’s hard to pull sheets apart. Because of this, graphene produced using top-down methods is often many layers thick, has holes or deformations, and can contain impurities. Factories can produce a few tons of mechanically or chemically exfoliated graphene per year, and for many applications – like mixing it into plastic – the lower-quality graphene works well.

Bottom-up synthesis [emphasis mine] builds the carbon sheets one atom at a time over a few hours. This process – called vapor deposition – allows researchers to produce high-quality graphene that is one atom thick and up to 30 inches across. This yields graphene with the best possible mechanical and electrical properties. The problem is that with a bottom-up synthesis, it can take hours to make even 0.00001 gram – not nearly fast enough for any large scale uses like in flexible touch-screen electronics or solar panels, for example.

Current production methods of graphene, both top-down and bottom-up, are expensive as well as energy and resource intensive, and simply produce too little product, too slowly.

Wyss has written an informative essay and, for those who need it, he has included an explanation of the substance known as graphene.

Study rare physics with electrically tunable graphene devices

An April 7, 2022 news item on Nanowerk announces graphene research that could lead to advances in optoelectronics (Note: Links have been removed),

An international team, co-led by researchers at The University of Manchester’s National Graphene Institute (NGI) in the UK and the Penn State [Pennsylvania State University] College of Engineering in the US, has developed a tunable graphene-based platform that allows for fine control over the interaction between light and matter in the terahertz (THz) spectrum to reveal rare phenomena known as exceptional points.

The team published their results in Science (“Topological engineering of terahertz light using electrically tuneable exceptional point singularities”).

The work could advance optoelectronic technologies to better generate, control and sense light and potentially communications, according to the researchers. They demonstrated a way to control THz waves, which exist at frequencies between those of microwaves and infrared waves. The feat could contribute to the development of ‘beyond-5G’ wireless technology for high-speed communication networks.

An April 8, 2022 University of Manchester press release (also on EurekAlert but published on April 7, 2022) delves further into the research,

Weak and strong interactions

Light and matter can couple, interacting at different levels: weakly, where they might be correlated but do not change each other’s constituents; or strongly, where their interactions can fundamentally change the system. The ability to control how the coupling shifts from weak to strong and back again has been a major challenge to advancing optoelectronic devices — a challenge researchers have now solved.

“We have demonstrated a new class of optoelectronic devices using concepts of topology — a branch of mathematics studying properties of geometric objects,” said co-corresponding author Coskun Kocabas, professor of 2D device materials at The University of Manchester. “Using exceptional point singularities, we show that topological concepts can be used to engineer optoelectronic devices that enable new ways to manipulate terahertz light.”

Kocabas is also affiliated with the Henry Royce Institute for Advanced Materials, headquartered in Manchester.

Exceptional points are spectral singularities — points at which any two spectral values in an open system coalesce. They are, unsurprisingly, exceptionally sensitive and respond to even the smallest changes to the system, revealing curious yet desirable characteristics, according to co-corresponding author Şahin K. Özdemir, associate professor of engineering science and mechanics at Penn State.

“At an exceptional point, the energy landscape of the system is considerably modified, resulting in reduced dimensionality and skewed topology,” said Özdemir, who is also affiliated with the Materials Research Institute, Penn State. “This, in turn, enhances the system’s response to perturbations, modifies the local density of states leading to the enhancement of spontaneous emission rates and leads to a plethora of phenomena. Control of exceptional points, and the physical processes that occur at them, could lead to applications for better sensors, imaging, lasers and much more.”

Platform composition

The platform the researchers developed consists of a graphene-based tunable THz resonator, with a gold-foil gate electrode forming a bottom reflective mirror. Above it, a graphene layer is book-ended with electrodes, forming a tunable top mirror. A non-volatile ionic liquid electrolyte layer sits between the mirrors, enabling control of the top mirror’s reflectivity by changing the applied voltage. In the middle of the device, between the mirrors, are molecules of alpha lactose, a sugar commonly found in milk.  

The system is controlled by two adjusters. One raises the lower mirror to change the length of the cavity — tuning the frequency of resonation to couple the light with the collective vibrational modes of the organic sugar molecules, which serve as a fixed number of oscillators for the system. The other adjuster changes the voltage applied to the top graphene mirror — altering the graphene’s reflective properties to transition the energy loss imbalances to adjust coupling strength. The delicate, fine tuning shifts weakly coupled terahertz light and organic molecules to become strongly coupled and vice versa.

“Exceptional points coincide with the crossover point between the weak and strong coupling regimes of terahertz light with collective molecular vibrations,” Özdemir said.

He noted that these singularity points are typically studied and observed in the coupling of analogous modes or systems, such as two optical modes, electronic modes or acoustic modes.

“This work is one of rare cases where exceptional points are demonstrated to emerge in the coupling of two modes with different physical origins,” Kocabas said. “Due to the topology of the exceptional points, we observed a significant modulation in the magnitude and phase of the terahertz light, which could find applications in next-generation THz communications.”

Unprecedented phase modulation in the THz spectrum

As the researchers apply voltage and adjust the resonance, they drive the system to an exceptional point and beyond. Before, at and beyond the exceptional point, the geometric properties — the topology — of the system change.

One such change is the phase modulation, which describes how a wave changes as it propagates and interacts in the THz field. Controlling the phase and amplitude of THz waves is a technological challenge, the researchers said, but their platform demonstrates unprecedented levels of phase modulation. The researchers moved the system through exceptional points, as well as along loops around exceptional points in different directions, and measured how it responded through the changes. Depending on the system’s topology at the point of measurement, phase modulation could range from zero to four magnitudes larger.

“We can electrically steer the device through an exceptional point, which enables electrical control on reflection topology,” said first author M. Said Ergoktas. “Only by controlling the topology of the system electronically could we achieve these huge modulations.” 

According to the researchers, the topological control of light-matter interactions around an exceptional point enabled by the graphene-based platform has potential applications ranging from topological optoelectronic and quantum devices to topological control of physical and chemical processes.

Contributors include Kaiyuan Wang, Gokhan Bakan, Thomas B. Smith, Alessandro Principi and Kostya S. Novoselov, University of Manchester; Sina Soleymani, graduate student in the Penn State Department of Engineering Science and Mechanics; Sinan Balci, Izmir Institute of Technology, Turkey; Nurbek Kakenov, who conducted work for this paper while at Bilkent University, Turkey.

I love the language in this press release, especially, ‘spectral singularities’. The explanations are more appreciated and help to make this image more than a pretty picture,

Caption: An international team, co-led by researchers at The University of Manchester’s National Graphene Institute (NGI) in the UK and the Penn State College of Engineering in the US, has developed a tunable graphene-based platform that allows for fine control over the interaction between light and matter in the terahertz (THz) spectrum to reveal rare phenomena known as exceptional points. The feat could contribute to the development of beyond-5G wireless technology for high-speed communication networks. Credit: Image Design, Pietro Steiner, The University of Manchester

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

Topological engineering of terahertz light using electrically tunable exceptional point singularities by M. Said Ergoktas, Sina Soleymani, Nurbek Kakenov, Kaiyuan Wang, Thomas B. Smith, Gokhan Bakan, Sinan Balci, Alessandro Principi, Kostya S. Novoselov, Sahin K. Ozdemir, and Coskun Kocabas. Science • 7 Apr 2022 • Vol 376, Issue 6589 • pp. 184-188 • DOI: 10.1126/science.abn6528

This paper is behind a paywall.

Oddly, there is an identical press release dated April 8, 2022 on the Pennsylvania State University website with a byline for By Ashley J. WennersHerron and Alan Beck. Interestingly the first author is from Penn State and the second author is from the University of Manchester.

Graphene Week (September 5 – 9, 2022) is a celebration of 10 years of the Graphene Flagship

Back in 2013 the European Union announced two huge targeted research investments €1B each for the Graphene Flagship and the Human Brain Project to be distributed over 10 years. (I have an overview of the Graphene Flagship’s high points from 2013-15 in my April 22, 2016 posting.)

Now at the ten year mark and its final days, the Graphene Flagship is celebrating 10 years with a Graphene Week (from an August 30, 2022 Graphene Flagship press release on EurekAlert),

Graphene Week is a celebration of 10 years of the Graphene Flagship, a European Commission funded research project worth over €1 billion in funding. Held at BMW Welt — the exhibition space of one of the Graphene Flagship’s industrial partners based in Germany — the conference includes a comprehensive program of speakers, exhibitions, posters and a free pavilion.

The program includes a session on the European Chip Act, a notable point of debate for the continent. The act promises to mobilise more than €43 billion of both public and private investments to alleviate the global chip shortage. Graphene Week will demonstrate the potential of graphene-enabled alternatives to traditional semiconductors with the findings of the 2D-Experimental Pilot Line (2D-EPL).

The 2D-EPL is a €20 million project to integrate 2D materials into silicon wafers. The project has recently completed its first multi-project wafer (MPW) run, producing graphene integrated silicon wafers to academic and industrial customers.

During the conference Max Lemme of AMO GmbH in Germany and Sanna Arpiainen, of VTT Finland will discuss this subject along with the European Commission’s Thomas Skordas, Deputy Director General of DG CNECT and Bert De Colvenaer, Executive Director, KDT Joint Undertaking. Attendees can find the full program here.

The conference covers a large range of topics: from composites and medicine, to electronics and sensors. Beyond fundamental research, the talks by industry experts and European scientists will explore how graphene and related materials are disrupting critical European industries.

Graphene Week is co-chaired by Georg Duesberg from Bundeswehr University Munich and Elmar Bonaccurso, from Airbus Germany. In addition to Airbus, representatives from Lufthansa and other partners from the AEROGrAFT project will be in attendance, showcasing their graphene air filtration application for aircraft.   aircraft. 

Graphene Week will also host its Graphene Innovation Forum, a dedicated space for scientists to meet those in industry. Interactive panel discussions with industrial representatives will dive into future trends of graphene applications. The Innovation forum will feature speakers from both the Graphene Flagship’s large industrial partners including Medica, Lufthansa, Nokia and Airbus and smaller companies including Graphene Flagship spin-offs Emberion, BeDimensional and Qurv.

The Open Forum will collate some of the leading experts of the Graphene Flagship for a panel discussion on the success of graphene research and innovation where the audience is encouraged to ask questions. And the Diversity in Graphene initiative will offer a panel discussion focused on career development and professional use of social media.

The Graphene Flagship welcomes the public to explore the Graphene Pavilion in BMW Welt. The exhibition will showcase applications for graphene for cars, planes, phones and cities, together with product demos and videos. This pavilion will be free and open to the public from 9am on Friday 9 September to 6pm on Sunday 11 September.

“The Graphene Flagship is one of the largest ever EU projects, forming a network of 171 academic and industrial partners from 22 countries,” explained Jari Kinaret, Director of the Graphene Flagship. “In the 17th  edition, Graphene Week provides an opportunity to demonstrate the successes of the project and the ongoing legacy it will have on Europe’s industry. We look forward to welcoming our academic and industrial partners to join us in Munich for this celebration.”

More information on Graphene Week, access to the speaker line up and full scientific program can be found on the Graphene Flagship website. Registration provides access to all scientific sessions, sponsored sessions, access to the exhibition, conference material and more. To register click here.

This is the BMW Welt,

Looks like something out of a science fiction movie, eh?

You can find (Graphene Flagship spinoff companies), Emberion website here, BeDimensional website here, and Qurv Technologies website here.

A graphene-inorganic-hybrid micro-supercapacitor made of fallen leaves

I wonder if this means the end to leaf blowers. That is almost certainly wishful thinking as the researchers don’t seem to be concerned with how the leaves are gathered.

The schematic illustration of the production of femtosecond laser-induced graphene. Courtesy of KAIST

A January 27, 2022 news item on Nanowerk announces the work (Note: A link has been removed),

A KAIST [Korea Advanced Institute of Science and Technology] research team has developed graphene-inorganic-hybrid micro-supercapacitors made of fallen leaves using femtosecond laser direct laser writing (Advanced Functional Materials, “Green Flexible Graphene-Inorganic-Hybrid Micro-Supercapacitors Made of Fallen Leaves Enabled by Ultrafast Laser Pulses”).

A January 27, 2022 KAIST press release (also on EurekAlert but published January 26, 2022), which originated the news item, delves further into the research,

The rapid development of wearable electronics requires breakthrough innovations in flexible energy storage devices in which micro-supercapacitors have drawn a great deal of interest due to their high power density, long lifetimes, and short charging times. Recently, there has been an enormous increase in waste batteries owing to the growing demand and the shortened replacement cycle in consumer electronics. The safety and environmental issues involved in the collection, recycling, and processing of such waste batteries are creating a number of challenges.

Forests cover about 30 percent of the Earth’s surface and produce a huge amount of fallen leaves. This naturally occurring biomass comes in large quantities and is completely biodegradable, which makes it an attractive sustainable resource. Nevertheless, if the fallen leaves are left neglected instead of being used efficiently, they can contribute to fire hazards, air pollution, and global warming.

To solve both problems at once, a research team led by Professor Young-Jin Kim from the Department of Mechanical Engineering and Dr. Hana Yoon from the Korea Institute of Energy Research developed a novel technology that can create 3D porous graphene microelectrodes with high electrical conductivity by irradiating femtosecond laser pulses on the leaves in ambient air. This one-step fabrication does not require any additional materials or pre-treatment. 

They showed that this technique could quickly and easily produce porous graphene electrodes at a low price, and demonstrated potential applications by fabricating graphene micro-supercapacitors to power an LED and an electronic watch. These results open up a new possibility for the mass production of flexible and green graphene-based electronic devices.

Professor Young-Jin Kim said, “Leaves create forest biomass that comes in unmanageable quantities, so using them for next-generation energy storage devices makes it possible for us to reuse waste resources, thereby establishing a virtuous cycle.” 

This research was published in Advanced Functional Materials last month and was sponsored by the Ministry of Agriculture Food and Rural Affairs, the Korea Forest Service, and the Korea Institute of Energy Research.

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

Green Flexible Graphene–Inorganic-Hybrid Micro-Supercapacitors Made of Fallen Leaves Enabled by Ultrafast Laser Pulses by Truong-Son Dinh Le, Yeong A. Lee, Han Ku Nam, Kyu Yeon Jang, Dongwook Yang, Byunggi Kim, Kanghoon Yim, Seung-Woo Kim, Hana Yoon, Young-Jin Kim. Advanced Functional Materials DOI: https://doi.org/10.1002/adfm.202107768 First published: 05 December 2021

This paper is behind a paywall.