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2D nanomaterials for various sustainable applications

Posted By Graphene Council, Monday, August 17, 2020

Dr Lakhveer Singh, Assistant Professor, Department of Environmental Science, SRM University-AP, Andhra Pradesh has edited a book on “Adapting 2D Nanomaterials for Advanced Applications” which is published in the globally renowned publishing house American Chemical Society. The book emphasizes on his collaborative work with Dr Durga Mahapatra, TERI Deakin Nanobiotechnology Center (TDNBC), TERI, India on 2D nanomaterials for various sustainable applications such as energy production and storage, biosensor, water treatment etc.

2D nanomaterials, or graphene equivalents, possess an exceptional array of characteristics due to their unique structure, configuration, and properties. Such materials have gained attention for countless applications due to their progression into wide varieties of crystallographic structures via abundant elemental compositions. These characteristics distinctively impart qualities to their unique chemical reaction capabilities and adjustable structural properties and therefore enable applications in energy transitions, storage, and conservation.

In his research, Dr Lakhveer has developed a variety of nanomaterials and catalysts having several applications. He mentions, “We have developed Mesoporous MnCo2O4 nanorods for electricity production, NiO, and CoO nanoparticles for biohydrogen production and Cu-ZnO nano heterojunction for degradation of chlorpyrifos pesticide.”

Recently, Dr Lakhveer has developed reduced graphene oxide and silver nanoparticles on a melamine sponge skeleton by a simple coating method in collaboration with Oregon State University, USA, and Xiamen University, China. The modified sponge retained the high porosity of the sponge substrate and exhibited photothermal properties. This material provides a new idea for the recovery of heavy crude oil and provides new applications for photothermal-conversion materials.

Dr Lakhveer is currently vested in developing efficient and economical nanocatalysts that possess commercial applications in the energy and water sectors. In the next few months, he will be publishing two more books in the American Chemical Society (ACS) and Elsevier. These books will focus on novel electrodes, nano catalytic materials, and subnanometric-scale catalysts having applicability at the Nanoscale.

Tags:  2D nanomaterials  Graphene  Lakhveer Singh  nanoparticles  SRM University 

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Engineers develop better graphene sieve that could advance clean water efforts

Posted By Graphene Council, Monday, August 17, 2020
Developing atomically thin graphene membranes used to separate salt from water is extraordinarily complex and the effort grows more crucial as population growth, industrialization and climate change strain freshwater resources.

Vanderbilt engineering researchers report a breakthrough in scalable fabrication of graphene membrane with a sealing technology that corrects variations in the pore size so they remain small enough to trap salt ions and small molecules but allow water to pass.

One of the most complex engineering challenges when making membranes so thin is to maintain integrity in the uniformity of the pores, which entails drilling atomically precise holes in a one-atom thick sheet of carbon atoms. “A single large hole can cause high leakage and compromise membrane performance,” said Piran Kidambi, assistant professor of chemical and biomolecular engineering.

“How do you poke trillions of holes between the size of 0.3 and 0.6 nanometers over a square centimeter of material that is just one-atom thick? That is 3 angstroms tolerance using processes that are scalable and roll-to-roll manufacturing compatible,” Kidambi said. An angstrom is one ten-billionth of a meter.

Kidambi and team members have designed a simple defect-sealing technique based on a gatekeeper analogy.  While most prior studies formed holes in graphene membranes as a final step, this team flipped the process on its head. They formed holes in the graphene first using a low-temperature chemical vapor deposition (CVD) process followed by ultra violet light in the presence of ozone gas and used the size of the holes as a gatekeeper.

A sealant molecule on one side has to pass through the gate to meet another molecule on the other side and form a seal. If the size of the molecule is smaller than the gate, it will pass through, meet the other molecule and seal the gate. If the size of the molecule is larger than the gate, it will not pass and the gate remains open.

“Think of it like a fishing net that catches only large fish,” said Peifu Cheng, postdoctoral scholar in chemical and biomolecular engineering and a member of Kidambi’s lab. Their paper— Facile Size-Selective Defect Sealing in Large-Area Atomically Thin Graphene Membranes for Sub-Nanometer Scale Separations—is published in the American Chemical Society’s journal Nano Letters. Authors include Vanderbilt graduate student Nicole Moehring and undergraduate Mattigan Kelly; Wonhee Ko, An-Ping Li and Juan Carlos Idrobo, Center for Nanophase Materials Science at Oak Ridge National Laboratory; and Michael Boutilier, Western University (Canada) chemical and biochemical engineering professor.

“We show that a polymerization technique after nanopore formation in graphene not only seals larger defects (>0.5 nanometer) and macroscopic tears, but also successfully preserves the smaller sub-nanometer pores,” Kidambi said.

The graphene membrane can separate 0.28 nanometer (water) from 0.66 nanometer (hydrated salt ions) via a simple size-selective defect sealing technique. For comparison, one inch is equal to 25,400,000 nanometers. The researchers used table salt (NaCl) and potassium chloride (KCl), a salt that occurs naturally seawater or underground brackish water, as well as the amino acid L-tryptophan and the water-soluble vitamin B-12 in their experiments.

“To the best of our knowledge, this is the first demonstration of size-selective defect sealing for nanoporous atomically thin membranes,” Kidambi said. “In addition, we obtained water permeance 23 times higher than commercially available water treatment/desalination membranes, along with salt rejection greater than 97% and small molecule rejection of about 100%.”

In terms of membrane upgrades and alleviating barriers to commercialization, the team’s graphene treatment is a novel advance. “Flipping pore creation and creating a size-selective sealing technique is a significant contribution to membrane advancements,” Kidambi said.

Their work has the potential for transformative advances in high-quality commercial graphene membranes that filter a variety of microscopic ions and molecules, including salts, proteins or nanoparticles, and relevant to industrial applications beyond water desalination, such as gas separations. Such membranes also should be useful for chemical, biological and medical research and the purification of substances used in pharmaceuticals.

Tags:  chemical vapor deposition  Graphene  Mattigan Kelly  nanoparticles  Nicole Moehring  Peifu Cheng  Piran Kidambi  Vanderbilt University 

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Coffee stains inspire optimal printing technique for electronics

Posted By Graphene Council, Monday, August 17, 2020
Have you ever spilled your coffee on your desk? You may then have observed one of the most puzzling phenomena of fluid mechanics – the coffee ring effect. This effect has hindered the industrial deployment of functional inks with graphene, 2D materials, and nanoparticles because it makes printed electronic devices behave irregularly.

Now, after studying this process for years, a team of researchers have created a new family of inks that overcomes this problem, enabling the fabrication of new electronics such as sensors, light detectors, batteries and solar cells.

Coffee rings form because the liquid evaporates quicker at the edges, causing an accumulation of solid particles that results in the characteristic dark ring. Inks behave like coffee – particles in the ink accumulate around the edges creating irregular shapes and uneven surfaces, especially when printing on hard surfaces like silicon wafers or plastics.

Researchers, led by Tawfique Hasan from the Cambridge Graphene Centre of the University of Cambridge, with Colin Bain from the Department of Chemistry of Durham University, and Meng Zhang from School of Electronic and Information Engineering of Beihang University, studied the physics of ink droplets combining particle tracking in high-speed micro-photography, fluid mechanics, and different combinations of solvents.

Their solution: alcohol, specifically a mixture of isopropyl alcohol and 2-butanol. Using these, ink particles tend to distribute evenly across the droplet, generating shapes with uniform thickness and properties. Their results are reported in the journal Science Advances.

“The natural form of ink droplets is spherical – however, because of their composition, our ink droplets adopt pancake shapes,” said Hasan.

While drying, the new ink droplets deform smoothly across the surface, spreading particles consistently. Using this universal formulation, manufacturers could adopt inkjet printing as a cheap, easy-to-access strategy for the fabrication of electronic devices and sensors. The new inks also avoid the use of polymers or surfactants – commercial additives used to tackle the coffee ring effect, but at the same time thwart the electronic properties of graphene and other 2D materials.

Most importantly, the new methodology enables reproducibility and scalability – researchers managed to print 4500 nearly identical devices on a silicon wafer and plastic substrate. In particular, they printed gas sensors and photodetectors, both displaying very little variations in performance. Previously, printing a few hundred such devices was considered a success, even if they showed uneven behaviour.

“Understanding this fundamental behaviour of ink droplets has allowed us to find this ideal solution for inkjet printing all kinds of two-dimensional crystals,” said first author Guohua Hu. “Our formulation can be easily scaled up to print new electronic devices on silicon wafers, or plastics, and even in spray painting and wearables, already matching or exceeding the manufacturability requirements for printed devices.”

Beyond graphene, the team has optimised over a dozen ink formulations containing different materials. Some of them are graphene two-dimensional ‘cousins’ such as black phosphorus and boron nitride, others are more complex structures like heterostructures – ‘sandwiches’ of different 2D materials – and nanostructured materials. Researchers say their ink formulations can also print pure nanoparticles and organic molecules.This variety of materials could boost the manufacturing of electronic and photonic devices, as well as more efficient catalysts, solar cells, batteries and functional coatings.

The team expects to see industrial applications of this technology very soon. Their first proofs of concept – printed sensors and photodetectors – have shown promising results in terms of sensitivity and consistency, exceeding the usual industry requirements. This should attract investors interested in printed and flexible electronics.

“Our technology could speed up the adoption of inexpensive, low-power, ultra-connected sensors for the internet of things,” said Hasan. “The dream of smart cities will come true.”

Tags:  2D materials  Graphene  nanoparticles  Tawfique Hasan  University of Cambridge 

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Scientists develop new material for longer-lasting fuel cells

Posted By Graphene Council, Thursday, July 23, 2020
In the study, published today in the journal Nanoscale, researchers produced graphene via a special, scalable technique and used it to develop hydrogen fuel cell catalysts. They showed that this new type of graphene-based catalyst was more durable than commercially available catalysts and matched their performance. 

Hydrogen fuel cells convert chemical energy into electrical power by combining hydrogen and oxygen with the aid of catalysts. As the only by-product of the reaction is water, they provide an efficient and environmentally friendly power source.

Platinum is the most widely used catalyst for these fuel cells, but its high cost is a big problem for the commercialisation of hydrogen fuel cells. To address this issue, commercial catalysts are typically made by decorating tiny nanoparticles of platinum onto a cheaper carbon support, however the poor durability of the material greatly reduces the lifetime of current fuel cells.

Previous research has suggested graphene could be an ideal support material for fuel cells due to its corrosion resistance, high surface area and high conductivity. However, the graphene used in the majority of experiments to-date contains many defects, meaning that the predicted improved resistance has not yet been achieved.

The technique described in the study produces high-quality graphene decorated with platinum nanoparticles in a one-pot synthesis. This process could be scaled up for mass production, opening up the use of graphene-based catalysts for widespread energy applications.

Improved durability
The researchers confirmed the durability of the graphene-based catalyst using a type of test based on those recommended by the US Department of Energy (DoE), known as accelerated stress tests. Using these tests, the scientists showed that loss in activity over the same testing period was around 30 per cent lower in the newly developed graphene-based catalyst, compared with commercial catalysts.

Gyen Ming Angel, PhD student and first author of the study, from University College London (UCL), said: “The DoE sets tests and targets for fuel cell durability, with one accelerated stress test to simulate normal operating conditions and one to simulate the high voltages experienced when starting up and shutting down the fuel cell.

"Most research studies in the graphene space only evaluate using one of the recommended tests. However, since we have high-quality graphene in our material, we have managed to achieve high durability in both tests and under long testing periods, which is important for the future commercialisation of these materials. We look forward to incorporating our new catalyst into commercial technology and realising the advantages of longer-life fuel cells.”

Professor Dan Brett, Professor of Electrochemical Engineering at UCL, said: “Satisfying global energy demands without damaging the environment is one of the great modern challenges. Hydrogen fuel cells can provide cleaner energy and are already used in some cars as an alternative to petrol or diesel. However, a big barrier to their widespread commercialisation is the ability for catalysts to withstand extensive cycling required for their use in energy applications. We’ve shown that by using graphene instead of the typical amorphous carbon as a support material we can create ultra-durable catalysts.”

Unlocking graphene's potential
Graphene is made from a single layer of carbon atoms arranged in a hexagonal lattice. Despite its relatively simple structure, graphene is thought to have remarkable properties including high electrical conductivity, high transparency and high flexibility.

Dr. Patrick Cullen, Lecturer in Renewable Energy from Queen Mary University of London, said: “Over the years, there’s been a lot of hype around graphene and the vast number of promising applications for this material. However, the research community is still waiting for its full potential to be realised, and this has led to some negativity around this proposed ‘wonder material’. This view isn’t helped by the fact that many research studies on graphene use defective versions of graphene. We hope that this paper can restore faith in graphene and show that this material holds great potential for improving technology, like fuel cells, now and in the future.”

Tags:  Dan Brett  Fuel Cells  Graphene  Gyen Ming Angel  nanoparticles  Patrick Cullen  University College London 

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Graphene smart textiles developed for heat adaptive clothing

Posted By Graphene Council, Thursday, June 18, 2020
New research on the two-dimensional (2D) material graphene has allowed researchers to create smart adaptive clothing which can lower the body temperature of the wearer in hot climates.

A team of scientists from The University of Manchester’s National Graphene Institute have created a prototype garment to demonstrate dynamic thermal radiation control within a piece of clothing by utilising the remarkable thermal properties and flexibility of graphene. The development also opens the door to new applications such as, interactive infrared displays and covert infrared communication on textiles.

The human body radiates energy in the form of electromagnetic waves in the infrared spectrum (known as blackbody radiation). In a hot climate it is desirable to make use the full extent of the infrared radiation to lower the body temperature which can be achieved by using infrared-transparent textiles. As for the opposite case, infrared-blocking covers are ideal to minimise the energy loss from the body. Emergency blankets are a common example used to deal with treating extreme cases of body temperature fluctuation.

The collaborative team of scientists demonstrated the dynamic transition between two opposite states by electrically tuning the infrared emissivity (the ability to radiate energy) of graphene layers integrated onto textiles.

One-atom thick graphene was first isolated and explored in 2004 at The University of Manchester. Its potential uses are vast and research has already led to leaps forward in commercial products including; batteries, mobile phones, sporting goods and automotive.

The new research published today in journal Nano Letters, demonstrates that the smart optical textile technology can change its thermal visibility. The technology uses graphene layers to control of thermal radiation from textile surfaces.

The successful demonstration of the modulation of optical properties on different forms of textile can leverage the ubiquitous use of fibrous architectures and enable new technologies operating in the infrared and other regions of the electromagnetic spectrum for applications including textile displays, communication, adaptive space suits, and fashion. Professor Coskun Kocabas

Professor Coskun Kocabas, who led the research, said: “Ability to control the thermal radiation is a key necessity for several critical applications such as temperature management of the body in excessive temperature climates. Thermal blankets are a common example used for this purpose. However, maintaining these functionalities as the surroundings heats up or cools down has been an outstanding challenge.”

Prof Kocabas added: “The successful demonstration of the modulation of optical properties on different forms of textile can leverage the ubiquitous use of fibrous architectures and enable new technologies operating in the infrared and other regions of the electromagnetic spectrum for applications including textile displays, communication, adaptive space suits, and fashion.”

This study built on the same group’s previous research using graphene to create thermal camouflage which was able to fool infrared cameras. The new research can also be integrated into existing mass-manufacture textile materials such as cotton. To demonstrate, the team developed a prototype product within a t-shirt allowing the wearer to project coded messages invisible to the naked eye but readable by infrared cameras.

“We believe that our results are timely showing the possibility of turning the exceptional optical properties of graphene into novel enabling technologies. The demonstrated capabilities cannot be achieved with conventional materials.

“The next step for this area of research is to address the need for dynamic thermal management of earth-orbiting satellites. Satellites in orbit experience excesses of temperature, when they face the sun and they freeze in the earth’s shadow. Our technology could enable dynamic thermal management of satellites by controlling the thermal radiation and regulate the satellite temperature on demand.” said Kocabas.

Professor Sir Kostya Novoselov was also involved in the research: “This is a beautiful effect, intrinsically routed in the unique band structure of graphene. It is really exciting to see that such effects give rise to these high-tech applications.” he said.

Tags:  2D material  Coskun Kocabas  Graphene  nanoparticles  textile  University of Manchester 

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Risk analyses for nanoparticles Nanosafety research without animal experiments

Posted By Graphene Council, Thursday, June 18, 2020
They are already in use in, say, cosmetics and the textile industry: Nanoparticles in sun blockers protect us from sunburn, and clothing with silver nanoparticles slows down bacterial growth. But the use of these tiny ingredients is also linked to the responsibility of being able to exclude negative effects for health and the environment. Nanoparticles belong to the still poorly characterized class of nanomaterials, which are between one and 100 nanometers in size and have a wide range of applications, for example in exhaust gas catalytic converters, wall paints, plastics and in nanomedicine. As new and unusual as nanomaterials are, it is still not clear whether or not they pose any risks to humans or the environment.

This is where risk analyses and life cycle assessments (LCA) come into play, which used to rely strongly on animal experiments when it came to determining the harmful effects of a new substance, including toxicity. Today, research is required to reduce and replace animal experiments wherever possible. Over the past 30 years, this approach has led to a substantial drop in animal testing, particularly in toxicological tests. The experience gained with conventional chemicals cannot simply be transferred to novel substances such as nanoparticles, however. Empa scientists are now developing new approaches, which should allow another substantial reduction in animal testing while at the same time enabling the safe use of nanomaterials.

"We are currently developing a new, integrative approach to analyze the risks of nanoparticles and to perform life cycle assessments," says Beatrice Salieri from Empa's Technology and Society lab in St. Gallen. One new feature, and one which differs from conventional analyses, is that, in addition to the mode of action of the substance under investigation, further data is included, such as the exposure and fate of a particle in the human body, so that a more holistic view is incorporated into the risk assessment.

These risk analyses are based on the nanoparticles' biochemical properties in order to develop suitable laboratory experiments, for example with cell cultures. To make sure the results from the test tube ("in vitro") also apply to the conditions in the human body ("in vivo"), the researchers use mathematical models ("in silico"), which, for instance, rely on the harmfulness of a reference substance. "If two substances, such as silver nanoparticles and silver ions, act in the very same way, the potential hazard of the nanoparticles can be calculated from that," says Salieri. 

But for laboratory studies on nanoparticles to be conclusive, a suitable model system must first be developed for each type of nanoparticle. "Substances that are inhaled are examined in experiments with human lung cells," explains Empa researcher Peter Wick who is heading the "Particles-Biology Interactions" lab in St. Gallen. On the other hand, intestinal or liver cells are used to simulate digestion in the body.

This not only determines the damaging dose of a nanoparticle in cell culture experiments, but also includes all biochemical properties in the risk analysis, such as shape, size, transport patterns and the binding – if any – to other molecules. For example, free silver nanoparticles in a cell culture medium are about 100 times more toxic than silver nanoparticles bound to proteins. Such comprehensive laboratory analyses are incorporated into so-called kinetic models, which, instead of a snapshot of a situation in the test tube, can depict the complete process of particle action.

Finally, with the aid of complex algorithms, the expected biological phenomena can be calculated from these data. "Instead of 'mixing in' an animal experiment every now and then, we can determine the potential risks of nanoparticles on the basis of parallelisms with well-known substances, new data from lab analyses and mathematical models," says Empa researcher Mathias Rösslein. In future, this might also enable us to realistically represent the interactions between different nanoparticles in the human body as well as the characteristics of certain patient groups, such as elderly people or patients with several diseases, the scientist adds.

As a result of these novel risk analyses for nanoparticles, the researchers also hope to accelerate the development and market approval of new nanomaterials. They are already being applied in the "Safegraph" project, one of the projects in the EU's "Graphene Flagship" initiative, in which Empa is involved as a partner. Risk analyses and LCA for the new "wonder material" graphene are still scarce. Empa researchers have recently been able to demonstrate initial safety analyses of graphene and graphene related materials in fundamental in vitro studies. In this way, projects such as Safegraph can now better identify potential health risks and environmental consequences of graphene, while at the same time reducing the number of animal experiments.

Tags:  Beatrice Salieri  Empa  Graphene  Medicine  nanomaterials  nanoparticles 

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Eavesdropping on single molecules with light by replaying the chatter

Posted By Graphene Council, Wednesday, May 6, 2020
The structure of individual molecules and their properties, such as chirality, are difficult to monitor in real time. It turns out that by temporarily bridging molecules together we can provide a lens into their dynamics.

A study led by Prof. Frank Vollmer at the University of Exeter’s Living Systems Institute has exposed new pathways for investigating biochemical reactions at the nanoscale. Thiol/disulfide exchange at equilibrium has not yet been fully scrutinised at the single-molecule level, in part because this cannot be optically resolved in bulk samples.

Light can, however, circulate around micron-sized glass spheres to form resonances. The trapped light can then repeatedly interact with its surrounding environment. By attaching gold nanoparticles to the sphere, light is enhanced and spatially confined down to the size of viruses and amino acids.

The resulting optoplasmonic coupling allows for the detection of biomolecules that approach the nanoparticles while they attach to the gold, detach, and interact in a variety of ways.

Despite the sensitivity of this technique, there is lacking specificity. Molecules as simple as atomic ions can be detected and certain dynamics can be discerned, yet we cannot necessarily discriminate them.

The breakthroughs reported in Nature Communications ("Optoplasmonic characterisation of reversible disulfide interactions at single thiol sites in the attomolar regime") have proceeded to amend this.

Reaction pathways regulated by disulfide bonds can constrain interactions to single thiol sensing sites on the nanoparticles. The high fidelity of this approach establishes precise probing of the characteristics of molecules undergoing the reaction.

By placing linkers on the gold surface, interactions with thiolated species are isolated for based on their charge and the cycling itself.

Sensor signals have clear patterns related to whether reducing agent is present. If it is, the signal oscillates in a controlled way, while if it is not, the oscillations become stochastic. For each reaction the monomer or dimer state of the leaving group can be resolved.

Surprisingly, the optoplasmonic resonance shifts in frequency and/or changes in linewidth when single molecules interact with it. In many cases this result suggests a plasmon-vibrational coupling that could help identify individual molecules, finally achieving characterisation.

"This excellent work by my PhD student, Serge Vincent, paves the way for many future single-molecule analysis techniques that we have only been dreaming about," Professor Frank Vollmer adds. "It is a crucial step for our project ULTRACHIRAL. ULTRACHIRAL seeks to develop breakthroughs in how we use light to analyse chiral molecules."

Tags:  Frank Vollmer  Graphene  nanoparticles  Sensors  University of Exeter 

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IIT Guwahati research team develops hierarchically structured graphene oxide nanosheets that can selectively separate oily or aqueous contaminates from respective emulsions

Posted By Graphene Council, Thursday, April 23, 2020
Researchers of Indian Institute of Technology Guwahati have developed a graphene-based superhydrophobic materials that can separate oil and water from both oil-in-water and water-in-oil emulsions, respectively.

Their work has recently been published in the Royal Society’s journal, Chemical Science. The research paper has been authored by Dr. Uttam Manna, Associate Professor, Department of Chemistry, IIT Guwahati, along with his research scholars Mr. Avijit Das, Mr. Kousik Maji, and Mr. Sarajit Naska.

Oil–water separation techniques have a number of industrial and environmental applications. Various porous and bulk substrates such as sponge that are made superhydrophobic, have been used to absorb oil from oil-water emulsions. The IIT Guwahati team has shown the efficacy of hierarchically structured graphene oxide nanosheets in removing oil or aqueous contaminates from respective emulsions, thereby effecting separation of oil and water.
Superhydrophobic materials – materials with extreme water repellence – are considered the best materials for removing oil from water, and they are being extensively studied for applications such as water purification and self-cleaning surfaces. The problem with superhydrophobic materials is that they are generally not scalable, or use environmentally toxic products such as fluorinated polymers/small molecules, or have poor mechanical and chemical stability. Moreover, the conventional spongy superhydrophobic materials are inherently less appropriate for separating oil-in-water emulsion due to poor accessibility of the dispersed oil droplets to the oil absorbing superhydrophobic interface.

“The hydrophobicity of materials is largely governed by the physical architecture and the chemical composition, and so such materials can be rationally created by combining low-surface-energy materials with hierarchical roughness”, explains Dr. Manna. This is exactly what the group has done in its quest for oil-water separating materials. They have manipulated graphene, a form of carbon, to have superhydrophobic properties suitable for separation of oil from water in emulsions.

The study of graphene for such applications is not unprecedented. Since the award of the Nobel prize to its creators in 2010, graphene – two dimensional structures of carbon – has been extensively studied for a variety of applications. Composed of pure carbon, graphene is similar to graphite but with characteristics that make it extraordinarily light and strong, giving it a moniker of “wonder material” in present day materials science research. Research all over the world have attempted to engineer the structure and composition of graphene to get surface roughness and low surface energy, suitable for use in applications that require superhydrophobicity. Such engineering is challenging and complicated.

The IIT Guwahati team has developed a facile method to produce graphene oxide-polymer composite with hierarchical topography and low surface energy chemistry in the confined space. Such graphene oxide species showed ‘confined-super- water-repellence’. They further deposited iron oxide nanoparticles on the two dimensional nanosheets, which made the entire material magnetically active.

“Our graphene oxide composites were able to separate oil from water in emulsions with high efficiency” says Dr. Manna. The uniqueness was that the separation could be brought about even under extremes of pH, salinity, surfactant contaminations etc., as is seen in real life scenarios. The IIT Guwahati’s graphene oxide species was capable of selectively soaking up tiny crude-oil droplets in oil-to-water emulsions with high absorption capacity (above 1000 wt%), as well as coalescing larger oil droplets of emulsions from water-in-oil emulsions.

“Further functionalization of this chemically/magnetically active 2D-nano-interface could help in the development of functional interfaces for various applications related to energy, catalysis and healthcare”, says Dr. Manna.

Tags:  2D materials  Graphene  graphene oxide nanosheets  Indian Institute of Technology Guwahati  nanoparticles  Uttam Manna  water purification 

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Pushing the Limits of 2D Supramolecules

Posted By Graphene Council, Saturday, April 18, 2020
Scientists at the University of South Florida have reached a new milestone in the development of two-dimensional supramolecules – the building blocks that make areas of nanotechnology and nanomaterial advancement possible.

Since the 2004 discovery of graphene, the world’s thinnest (one atom thick) and strongest (200 times stronger than steel) material, researchers have been working to further develop similar nanomaterials for industrial, pharmaceutical and other commercial uses. Thanks to its conductive properties and strength, graphene can be used in microelectronics to fortify mechanical materials and has recently enabled precise 3D imaging of nanoparticles.

 While work to develop new supramolecules capable of further applications has seen some success, those molecular formations are either small – less than 10 nanometers in size – or arbitrarily assemble, limiting their potential use. But now, new research published in "Nature Chemistry," outlines a profound leap forward in supramolecular progress.

“Our research team has been able to overcome one of the major supramolecular obstacles, developing a well-defined supramolecular structure that pushes the 20-nanometer scale,” said Xiaopeng Li, an associate professor in the USF Department of Chemistry and the study’s lead researcher. “It’s essentially a world record for this area of chemistry.”

Li, along with his USF research team, collaborated with Saw Wai Hia’s team at the Argonne National Laboratory and Ohio University, as well as several other U.S. and international research institutes on this effort.

Supramolecules are large molecular structures made up of individual molecules. Unlike traditional chemistry, which focuses on covalent bonds between atoms, supramolecular chemistry studies the noncovalent interactions between molecules themselves. Many times, these interactions lead to molecular self-assembly, naturally forming complex structures capable of performing a variety of functions.

In this latest study, the team was able to build a 20-nm-wide metallo-supramolecular hexagonal grid by combining intra- and intermolecular self-assembly processes. Li says the success of this work will advance further understanding of the design principles governing these molecular formations and could one day lead to the development of new materials with yet-to-be-discovered functions and properties.

Tags:  Argonne National Laboratory  Graphene  nanomaterial  nanoparticles  Ohio University  University of South Florida  Xiaopeng Li 

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Scientists Capture 3D Images of Nanoparticles, Atom by Atom, With Unprecedented Precision

Posted By Graphene Council, Saturday, April 11, 2020
Since their invention in the 1930s, electron microscopes have helped scientists peer into the atomic structure of ordinary materials like steel, and even exotic graphene. But despite these advances, such imaging techniques cannot precisely map out the 3D atomic structure of materials in a liquid solution, such as a catalyst in a hydrogen fuel cell, or the electrolytes in your car’s battery.

Now, researchers at Berkeley Lab, in collaboration with the Institute for Basic Science (IBS) in South Korea, Monash University in Australia, and UC Berkeley, have developed a technique that produces atomic-scale 3D images of nanoparticles tumbling in liquid between sheets of graphene, the thinnest material possible. Their findings were reported April 3 in the journal Science.

“This is an exciting result. We can now measure atomic positions in three dimensions down to a precision six times smaller than hydrogen, the smallest atom,” said study co-author Peter Ercius, a staff scientist at Berkeley Lab’s Molecular Foundry.

The technique, called 3D SINGLE (Structure Identification of Nanoparticles by Graphene Liquid cell Electron microscopy), employs one of the world’s most powerful microscopes at Berkeley Lab’s Molecular Foundry. The researchers captured thousands of images of eight platinum nanoparticles “trapped” in liquid between two graphene sheets – called a “graphene window.”

These graphene sheets – each one just an atom thick – are “strong enough to contain tiny pockets of liquid necessary to acquire high-quality images of the nanoparticles’ atomic arrangement,” Ercius explained.

The researchers then adapted computer algorithms originally designed for biological studies to combine many 2D images into atomic-resolution 3D images.

The achievement, which improves upon a technique first reported in 2015, marks a significant milestone for the researchers. “With 3D SINGLE, we can determine why such small nanoparticles are more efficient catalysts than larger ones in fuel cells and hydrogen vehicles,” Ercius said.

Tags:  Berkeley Lab  Graphene  Institute for Basic Science (IBS)  Monash University  Nanoparticles  Peter Ercius  University of California Berkeley 

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