NT/ Nanoscale material offers a new way to control fire
Nanotechnology & nanomaterials biweekly vol.39, 15th August — 29th August
TL;DR
- High-temperature flames are used to create a wide variety of materials — but once you start a fire, it can be difficult to control how the flame interacts with the material you are trying to process. Researchers have now developed a technique that utilizes a molecule-thin protective layer to control how the flame’s heat interacts with the material — taming the fire and allowing users to finely tune the characteristics of the processed material.
- Graphene nanoribbons have outstanding properties that can be precisely controlled. Researchers have succeeded in attaching electrodes to individual atomically precise nanoribbons, paving the way for precise characterization of the fascinating ribbons and their possible use in quantum technology.
- Chemists have discovered that tiny gold ‘seed’ particles, a key ingredient in one of the most common nanoparticle recipes, are one and the same as gold buckyballs, 32-atom spheres that are cousins of the Nobel Prize-winning carbon buckyballs discovered in 1985.
- For now, cyborgs exist only in fiction, but the concept is becoming more plausible as science progresses. And now, researchers are reporting that they have developed a proof-of-concept technique to ‘tattoo’ living cells and tissues with flexible arrays of gold nanodots and nanowires. With further refinement, this method could eventually be used to integrate smart devices with living tissue for biomedical applications, such as bionics and biosensing.
- The study reveals an important discovery in the realm of nanomachines within living systems. Prof. Sason Shaik from the Hebrew University of Jerusalem and Dr. Kshatresh Dutta Dubey from Shiv Nadar University, conducted molecular-dynamics simulations of Cytochromes P450 (CYP450s) enzymes, revealing that these enzymes exhibit unique soft-robotic properties.
- Engineers have developed a breakthrough technique to make the processing of nanosensors cheaper, greener, and more effective by using a single drop of ethanol to replace heat processing of nanoparticle networks, allowing a wider range of materials to be used to make these sensors.
- New research has achieved a significant breakthrough in color switching for nanocrystals, unlocking exciting possibilities for a simple, energy-efficient display design and for tunable light sources needed in numerous technologies. The discovery also has potential applications in sensitive sensors for various substances, including biological and neuroscience uses, as well as advancements in quantum communication technologies. This nanomaterial breakthrough holds the promise of inspiring exciting innovations in the future.
- Sandwich compounds are special chemical compounds used as basic building blocks in organometallic chemistry. So far, their structure has always been linear. Recently, researchers made stacked sandwich complexes form a nano-sized ring. The physical and other properties of these cyclocene structures will now be further investigated.
- Two molecular languages at the origin of life have been successfully recreated and mathematically validated, thanks to pioneering work by Canadian scientists at Université de Montréal.
Nanotech Market
Nanotechnology deals with the ability to see, understand, measure, predict, produce or control matter at the nanoscale (below 100 nanometers). The realm of nanotechnology lies between 0.1 and 100 nanometers, wherein a nanometer is defined as one-thousandth of a micron. As a versatile technology with widespread applications in a wide range of end-use sectors, nanotechnology is currently facing a mixed bag of challenges and opportunities as the COVID-19 pandemic continues to spread across the globe. With the world fighting its biggest public health crisis in history, nanotechnology healthcare applications are storming into the spotlight led by the focus on nano intervention in terms of designing effective ways to identify, diagnose, treat and eliminate the spread of COVID-19 infections. Their role as nanocarriers has the potential to design risk-free and effective immunization strategies. In the post-COVID-19 period, the use of nanotechnology solutions in the production of a multitude of devices & products will continue to grow.
Amid the COVID-19 crisis, the global market for Nanotechnology estimated at US$42.2 Billion in the year 2020, is projected to reach a revised size of US$70.7 Billion by 2026, growing at a CAGR of 9.2% over the analysis period. Nanocomposites, one of the segments analyzed in the report, is projected to record a 8.7% CAGR and reach US$35.4 Billion by the end of the analysis period. After a thorough analysis of the business implications of the pandemic and its induced economic crisis, growth in the Nanomaterials segment is readjusted to a revised 10.1% CAGR for the next 7-year period.
Global nanotechnology market to reach US $126.8 billion by the year 2027. Amid the COVID-19 crisis, the global market for Nanotechnology is estimated at US $54.2 billion in the year 2020, and is projected to reach a revised size of US $126 billion.
Latest News & Research
Spatially Directed Pyrolysis via Thermally Morphing Surface Adducts
by Chuanshen Du, Paul Gregory, Dhanush U. Jamadgni, Alana M. Pauls, Julia J. Chang, Rick W. Dorn, Andrew Martin, E. Johan Foster, Aaron J. Rossini, Martin Thuo in Angewandte Chemie International Edition
High-temperature flames are used to create a wide variety of materials — but once you start a fire, it can be difficult to control how the flame interacts with the material you are trying to process. Researchers have now developed a technique that utilizes a molecule-thin protective layer to control how the flame’s heat interacts with the material — taming the fire and allowing users to finely tune the characteristics of the processed material.
“Fire is a valuable engineering tool — after all, a blast furnace is only an intense fire,” says Martin Thuo, corresponding author of a paper on the work and a professor of materials science and engineering at North Carolina State University. “However, once you start a fire, you often have little control over how it behaves.
“Our technique, which we call inverse thermal degradation (ITD), employs a nanoscale thin film over a targeted material. The thin film changes in response to the heat of the fire, and regulates the amount of oxygen that can access the material. That means we can control the rate at which the material heats up — which, in turn, influences the chemical reactions taking place within the material. Basically, we can fine-tune how and where the fire changes the material.”
Here’s how ITD works. You start out with your target material, such as a cellulose fiber. That fiber is then coated with a nanometer thick layer of molecules. The coated fibers are then exposed to an intense flame. The outer surface of the molecules combusts easily, raising the temperature in the immediate vicinity. But the inner surface of the molecular coating chemically changes, creating an even thinner layer of glass around the cellulose fibers. This glass limits the amount of oxygen that can access the fibers, preventing the cellulose from bursting into flames. Instead, the fibers smolder — burning slowly, from the inside out.
“Without the ITD’s protective layer, applying flame to cellulose fibers would just result in ash,” Thuo says. “With the ITD’s protective layer, you end up with carbon tubes. “We can engineer the protective layer in order to tune the amount of oxygen that reaches the target material. And we can engineer the target material in order to produce desirable characteristics.”
The researchers conducted proof-of-concept demonstrations with cellulose fibers to produce microscale carbon tubes.
The researchers could control the thickness of the carbon tube walls by controlling the size of the cellulose fibers they started with; by introducing various salts to the fibers (which further controls the rate of burning); and by varying the amount of oxygen that passes through the protective layer.
“We have several applications in mind already, which we will be addressing in future studies,” Thuo says. “We’re also open to working with the private sector to explore various practical uses, such as developing engineered carbon tubes for oil-water separation — which would be useful for both industrial applications and environmental remediation.”
Contacting individual graphene nanoribbons using carbon nanotube electrodes
by Jian Zhang, Liu Qian, Gabriela Borin Barin, Abdalghani H. S. Daaoub, Peipei Chen, Klaus Müllen, Sara Sangtarash, Pascal Ruffieux, Roman Fasel, Hatef Sadeghi, Jin Zhang, Michel Calame, Mickael L. Perrin in Nature Electronics
Quantum technology is promising, but also perplexing. In the coming decades, it is expected to provide us with various technological breakthroughs: smaller and more precise sensors, highly secure communication networks, and powerful computers that can help develop new drugs and materials, control financial markets, and predict the weather much faster than current computing technology ever could.
To achieve this, we need so-called quantum materials: substances that exhibit pronounced quantum physical effects. One such material is graphene. This two-dimensional structural form of carbon has unusual physical properties, such as extraordinarily high tensile strength, thermal and electrical conductivity — as well as certain quantum effects. Restricting the already two-dimensional material even further, for instance, by giving it a ribbon-like shape, gives rise to a range of controllable quantum effects.
This is precisely what Mickael Perrin’s team leverage in their work: For several years now, scientists in Empa’s Transport at Nanoscale Interfaces laboratory, headed by Michel Calame, have been conducting research on graphene nanoribbons under Perrin’s leadership.
“Graphene nanoribbons are even more fascinating than graphene itself,” explains Perrin. “By varying their length and width, as well as the shape of their edges, and by adding other atoms to them, you can give them all kinds of electrical, magnetic, and optical properties.”
Research on promising ribbons isn’t easy. The narrower the ribbon, the more pronounced its quantum properties are — but it also becomes more difficult to access a single ribbon at a time. This is precisely what must be done in order to understand the unique characteristics and possible applications of this quantum material and distinguish them from collective effects.
In a new study published recently in the journal Nature Electronics, Perrin and Empa researcher Jian Zhang, together with an international team, have succeeded for the first time in contacting individual long and atomically precise graphene nanoribbons.
Not a trivial task: “A graphene nanoribbon that is just nine carbon atoms wide measures as little as 1 nanometer in width,” Zhang says.
To ensure that only a single nanoribbon is contacted, the researchers employed electrodes of a similar size: They used carbon nanotubes that were also only 1 nanometer in diameter.
Precision is key for such a delicate experiment. It begins with the source materials. The researchers obtained the graphene nanoribbons via a strong and long-standing collaboration with Empa’s nanotech surfaces laboratory, headed by Roman Fasel.
“Roman Fasel and his team have been working on graphene nanoribbons for a long time and can synthesize many different types with atomic precision from individual precursor molecules,” Perrin explains. The precursor molecules came from the Max Planck Institute for Polymer Research in Mainz.
As is often required for advancing the state of the art, interdisciplinarity is key, and different international research groups were involved, each bringing their own specialty to the table: The carbon nanotubes were grown by a research group at Peking University, and to interpret the results of the study, the Empa researchers collaborated with computational scientists at the University of Warwick. “A project like this would not be possible without collaboration,” Zhang emphasizes.
Contacting individual ribbons by nanotubes posed a considerable challenge for the researchers.
“The carbon nanotubes and the graphene nanoribbons are grown on separate substrates,” Zhang explains. “First, the nanotubes need to be transferred to the device substrate and contacted by metal electrodes. Then we cut them with high-resolution electron-beam lithography to separate them into two electrodes.”
Finally, the ribbons are transferred onto the same substrate. Precision is key: Even the slightest rotation of the substrates can significantly reduce the probability of successful contact.
“Having access to high-quality infrastructure at the Binnig and Roher Nanotechnology Center at IBM Research in Rüschlikon was essential to test and implement this technology,” Perrin says.
The scientists confirmed the success of their experiment through charge transport measurements.
“Because quantum effects are usually more pronounced at low temperature, we performed the measurements at temperatures close to absolute zero in a high vacuum,” Perrin explains. But he is quick to add yet another particularly promising quality of graphene nanoribbons: “Due to the extremely small size of these nanoribbons, we expect their quantum effects to be so robust that they are observable even at room temperature.”
This, the researcher says, could allow us to design and operate chips that actively harness quantum effects without the need for elaborate cooling infrastructure.
“This project enables the realization of single nanoribbon devices, not only to study fundamental quantum effects such as how electrons and phonons behave at the nanoscale, but also to exploit such effects for applications in quantum switching, quantum sensing, and quantum energy conversion,” adds Hatef Sadeghi, a professor at the Univeristy of Warwick who collaborated on the project.
Graphene nanoribbons are not ready for commercial applications just yet, and there is still a lot of research to be done. In a follow-up study, Zhang and Perrin aim to manipulate different quantum states on a single nanoribbon. In addition, they plan on creating devices based on two ribbons connected in series, forming a so-called double quantum dot. Such a circuit could serve as a qubit — the smallest unit of information in a quantum computer. Moreover, Perrin, in the context of his recently obtained ERC Starting Grant and an SNSF Eccellenza Professorial Fellowship, plans to explore the use of nanoribbons as highly-efficient energy converters. In his inaugural lecture at ETH Zurich, he paints a picture of a world, in which we can harness electricity from temperature difference, while hardly losing any energy as heat — this would indeed be a real quantum leap.
Atomically precise nanoclusters predominantly seed gold nanoparticle syntheses
by Liang Qiao, Nia Pollard, Ravithree D. Senanayake, Zhi Yang, Minjung Kim, Arzeena S. Ali, Minh Tam Hoang, Nan Yao, Yimo Han, Rigoberto Hernandez, Andre Z. Clayborne, Matthew R. Jones in Nature Communications
Rice University chemists have discovered that tiny gold “seed” particles, a key ingredient in one of the most common nanoparticle recipes, are one and the same as gold buckyballs, 32-atom spherical molecules that are cousins of the carbon buckyballs discovered at Rice in 1985.
Carbon buckyballs are hollow 60-atom molecules that were co-discovered and named by the late Rice chemist Richard Smalley. He dubbed them “buckminsterfullerenes” because their atomic structure reminded him of architect Buckminster Fuller’s geodesic domes, and the “fullerene” family has grown to include dozens of hollow molecules.
In 2019, Rice chemists Matthew Jones and Liang Qiao discovered that golden fullerenes are the gold “seed” particles chemists have long used to make gold nanoparticles. The find came just a few months after the first reported synthesis of gold buckyballs, and it revealed chemists had unknowingly been using the golden molecules for decades.
“What we’re talking about is, arguably, the most ubiquitous method for generating any nanomaterial,” Jones said. “And the reason is that it’s just so incredibly simple. You don’t need specialized equipment for this. High school students can do it.”
Jones, Qiao and co-authors from Rice, Johns Hopkins University, George Mason University and Princeton University spent years compiling evidence to verify the discovery and recently published their results in Nature Communications.
Jones, an assistant professor in chemistry and materials science and nanoengineering at Rice, said the knowledge that gold nanoparticles are synthesized from molecules could help chemists uncover the mechanisms of those syntheses.
“That’s the big picture for why this work is important,” he said.
Jones said researchers discovered in the early 2000s how to use gold seed particles in chemical syntheses that produced many shapes of gold nanoparticles, including rods, cubes and pyramids.
“It’s really appealing to be able to control particle shape, because that changes many of the properties,” Jones said. “This is the synthesis that almost everyone uses. It’s been used for 20 years, and for that whole period of time, these seeds were simply described as ‘particles.’”
Jones and Qiao, a former postdoctoral researcher in Jones’ lab, weren’t looking for gold-32 in 2019, but they noticed it in mass spectrometry readings. The discovery of carbon-60 buckyballs happened in a similar way. And the coincidences don’t stop there. Jones is the Norman and Gene Hackerman Assistant Professor in Chemistry at Rice. Smalley, who shared the 1996 Nobel Prize in Chemistry with Rice’s Robert Curl and the United Kingdom’s Harold Kroto, was a Hackerman chair in chemistry at Rice for many years prior to his death in 2005.
Confirming that the widely used seeds were gold-32 molecules rather than nanoparticles took years of effort, including state-of-the-art imaging by Yimo Han’s research group at Rice and detailed theoretical analyses by the groups of both Rigoberto Hernandez at Johns Hopkins and Andre Clayborne at George Mason.
Jones said the distinction between nanoparticle and molecule is important and a key to understanding the study’s potential impact.
“Nanoparticles are typically similar in size and shape, but they are not identical,” Jones said. “If I make a batch of 7-nanometer spherical gold nanoparticles, some of them will have exactly 10,000 atoms, but others might have 10,023 or 9,092.
“Molecules, on the other hand, are perfect,” he said. “I can write out a formula for a molecule. I can draw a molecule. And if I make a solution of molecules, they are all exactly the same in the number, type and connectivity of their atoms.”
Jones said nanoscientists have learned how to synthesize many useful nanoparticles, but progress has often come via trial and error because “there is virtually no mechanistic understanding” of their synthesis.
“The problem here is pretty straightforward,” he said. “It’s like saying, ‘I want you to bake me a cake, and I’m gonna give you a bunch of white powders, but I’m not going to tell you what they are.’ Even if you have a recipe, if you don’t know what the starting materials are, it’s a nightmare to figure out what ingredients are doing what. I want nanoscience to be like organic chemistry, where you can make essentially whatever you want, with whatever properties you want,” Jones said.
He said organic chemists have exquisite control over matter “because chemists before them did incredibly detailed mechanistic work to understand all of the precise ways in which those reactions operate. We are very, very far from that in nanoscience, but the only way we’ll ever get there is by doing work like this and understanding, mechanistically, what we’re starting with and how things form. That’s the ultimate goal.”
Toward Single Cell Tattoos: Biotransfer Printing of Lithographic Gold Nanopatterns on Live Cells
by Kam Sang Kwok, Yi Zuo, Soo Jin Choi, Gayatri J. Pahapale, Luo Gu, David H. Gracias in Nano Letters
For now, cyborgs exist only in fiction, but the concept is becoming more plausible as science progresses. And now, researchers are reporting in ACS’ Nano Letters that they have developed a proof-of-concept technique to “tattoo” living cells and tissues with flexible arrays of gold nanodots and nanowires. With further refinement, this method could eventually be used to integrate smart devices with living tissue for biomedical applications, such as bionics and biosensing.
Advances in electronics have enabled manufacturers to make integrated circuits and sensors with nanoscale resolution. More recently, laser printing and other techniques have made it possible to assemble flexible devices that can mold to curved surfaces. But these processes often use harsh chemicals, high temperatures or pressure extremes that are incompatible with living cells. Other methods are too slow or have poor spatial resolution. To avoid these drawbacks, David Gracias, Luo Gu and colleagues wanted to develop a nontoxic, high-resolution, lithographic method to attach nanomaterials to living tissue and cells.
The team used nanoimprint lithography to print a pattern of nanoscale gold lines or dots on a polymer-coated silicon wafer. The polymer was then dissolved to free the gold nanoarray so it could be transferred to a thin piece of glass. Next, the gold was functionalized with cysteamine and covered with a hydrogel layer, which, when peeled away, removed the array from the glass. The patterned side of this flexible array/hydrogel layer was coated with gelatin and attached to individual live fibroblast cells. In the final step, the hydrogel was degraded to expose the gold pattern on the surface of the cells. The researchers used similar techniques to apply gold nanoarrays to sheets of fibroblasts or to rat brains. Experiments showed that the arrays were biocompatible and could guide cell orientation and migration.
The researchers say their cost-effective approach could be used to attach other nanoscale components, such as electrodes, antennas and circuits, to hydrogels or living organisms, thereby opening up opportunities for the development of biohybrid materials, bionic devices and biosensors.
Nanomachines in living matters: the soft-robot cytochrome P450
by Sason Shaik, Kshatresh Dutta Dubey in Trends in Chemistry
Study reveals an important discovery in the realm of nanomachines within living systems. Prof. Sason Shaik from the Hebrew University of Jerusalem and Dr. Kshatresh Dutta Dubey from Shiv Nadar University, conducted molecular-dynamics simulations of Cytochromes P450 (CYP450s) enzymes, revealing that these enzymes exhibit unique soft-robotic properties.
Cytochromes P450 (CYP450s) are enzymes found in living organisms and play a crucial role in various biological processes, particularly in the metabolism of drugs and xenobiotics. The researchers’ simulations demonstrated that CYP450s possess a fourth dimension — the ability to sense and respond to stimuli, making them soft-robot nanomachines in “living matters.”
In the catalytic cycle of these enzymes, a molecule called a substrate binds to the enzyme. This leads to a process called oxidation. The enzyme’s structure has a confined space that allows it to act like a sensor and a soft robot. It interacts with the substrate using weak interactions, like soft impacts. These interactions transfer energy, causing parts of the enzyme and the molecules inside it to move. This movement generates ultimately a special substance called oxoiron species, which serves the enzyme to oxidize a variety of different substances.
The key takeaway from these molecular-dynamics simulations is that the catalytic cycle of CYP450s is complex but follows a logical sequence. The enzyme’s restricted space, strategic residue placements, and channels allow it to be a sensitive sensor of the substrate, its own heme changes, and conformational shifts in the active site. This sensing-response capability creates a soft-robot with a fourth dimension of sensing, something previously unseen in regular 3D matter.
“We have discovered that CYP450s act as soft-robot machines in ‘living matters,’ displaying a remarkable sensing and response-action capability. This is an exciting revelation, and we believe that similar mechano-transduction mechanisms of soft-impact cues might be at work in other soft-robot machines in nature,” stated Prof. Sason Shaik, one of the lead researchers.
The findings open up new avenues in soft-robotics research, as 4D materials are gaining significance, driven by external triggers. These materials, such as hydrogels produced through 3D printing, resemble enzymes in their ability to sense and induce changes. The implications of this discovery extend beyond the realm of biology and chemistry, potentially revolutionizing fields like artificial intelligence design and self-evolving polymers/gels synthesis.
Dr. Kshatresh Dutta Dubey, co-researcher of the study, added, “We are entering an exciting era for chemistry, where soft-robotics and intelligent design of nanomachines can lead to unprecedented advancements. The future may witness the creation of self-evolving polymers and perpetual nanomachines capable of synthesizing new molecules at will.”
The scientists believe that the integration of the soft-robotic language and machine programming could accelerate progress in the development of 4D materials and unlock the full potential of soft-robotics.
Capillary‐Driven Self‐Assembled Microclusters for Highly Performing UV Photodetectors
by Xiaohu Chen, Darren Bagnall, Noushin Nasiri in Advanced Functional Materials
Macquarie University engineers have developed a new technique to make the manufacture of nanosensors far less carbon-intensive, much cheaper, more efficient, and more versatile, substantially improving a key process in this trillion-dollar global industry.
The team has found a way to treat each sensor using a single drop of ethanol instead of the conventional process that involves heating materials to high temperatures.
Their research, published in the Journal of Advanced Functional Materials, is titled, ‘Capillary-driven self-assembled microclusters for highly performing UV detectors’.
“Nanosensors are usually made up of billions of nanoparticles deposited onto a small sensor surface — but most of these sensors don’t work when first fabricated,” says corresponding author Associate Professor Noushin Nasiri, head of the Nanotech Laboratory at Macquarie University’s School of Engineering.
The nanoparticles assemble themselves into a network held together by weak natural bonds which can leave so many gaps between nanoparticles that they fail to transmit electrical signals, so the sensor won’t function.
Associate Professor Nasiri’s team uncovered the finding while working to improve ultraviolet light sensors, the key technology behind Sunwatch, which saw Nasiri become a 2023 Eureka Prize finalist.
Nanosensors have huge surface-to-volume ratio made up of layers of nanoparticles, making them highly sensitive to the substance they are designed to detect. But most nanosensors don’t work effectively until heated in a time-consuming and energy-intensive 12-hour process using high temperatures to fuse layers of nanoparticles, creating channels that allow electrons to pass through layers so the sensor will function.
“The furnace destroys most polymer-based sensors, and nanosensors containing tiny electrodes, like those in a nanoelectronic device, can melt. Many materials can’t currently be used to make sensors because they can’t withstand heat,” Associate Professor Nasiri says.
However, the new technique discovered by the Macquarie team bypasses this heat-intensive process, allowing nanosensors to be made from a much broader range of materials.
“Adding one droplet of ethanol onto the sensing layer, without putting it into the oven, will help the atoms on the surface of the nanoparticles move around, and the gaps between nanoparticles disappear as the particles to join to each other,” Associate Professor Nasiri says.
“We showed that ethanol greatly improved the efficiency and responsiveness of our sensors, beyond what you would get after heating them for 12 hours.”
The new method was discovered after the study’s lead author, postgraduate student Jayden (Xiaohu) Chen, accidentally splashed some ethanol onto a sensor while washing a crucible, in an incident that would usually destroy these sensitive devices.
“I thought the sensor was destroyed, but later realised that the sample was outperforming every other sample we’ve ever made,” Chen says.
Associate Professor Nasiri says that the accident might have given them the idea, but the method’s effectiveness depended on painstaking work to identify the exact volume of ethanol used.
“When Jayden found this result, we went back very carefully trying different quantities of ethanol. He was testing over and over again to find what worked,” she says. “It was like Goldilocks — three microlitres was too little and did nothing effective, 10 microlitres was too much and wiped the sensing layer out, five microlitres was just right!”
The team has patents pending for the discovery, which has the potential to make a very big splash in the nanosensor world.
“We have developed a recipe for making nanosensors work and we have tested it with UV light sensors, and also with nanosensors that detect carbon dioxide, methane, hydrogen and more — the effect is the same,” says Associate Professor Nasiri. “After one correctly measured droplet of ethanol, the sensor is activated in around a minute. This turns a slow, highly energy-intensive process into something far more efficient.”
Electric-field-induced colour switching in colloidal quantum dot molecules at room temperature
by Yonatan Ossia, Adar Levi, Yossef E. Panfil, Somnath Koley, Einav Scharf, Nadav Chefetz, Sergei Remennik, Atzmon Vakahi, Uri Banin in Nature Materials
While nanocrystals offer color tunability and are used in various technologies, achieving different colors requires using different nanocrystals for each color, and dynamic switching between colors has not been possible. A team of Researchers at the Institute of Chemistry and The Center for Nanoscience and Nanotechnology at The Hebrew University of Jerusalem, including graduate student Yonatan Ossia with seven other members, and led by Prof. Uri Banin, have now come up with an innovative solution to this problem. By developing a system of an “artificial molecule” made of two coupled semiconductor nanocrystals which emit light in two different colors, fast and instantaneous color switching was demonstrated.
Colored light and its tunability, are the basis to many essential modern day technologies: from lighting, displays, fast optical fiber-communication networks, and more. Upon taking color emitting semiconductors to the nanoscale (nano- one billionth of a meter, one hundred thousand times smaller than a human hair), an effect called quantum confinement comes into play: changing the size of the nanocrystal modifies the color of the emitted light. Thus, bright light sources can be obtained covering the entire visible spectrum. Due to the unique color tunability of such nanocrystals, and their facile fabrication and manipulation using wet-chemistry, they are already widely used in high-quality commercial displays, giving them excellent color quality along with significant energy saving characteristics. However, to this day, achieving different colors (such as needed for the different RGB pixels) required the use of different nanocrystals for each specific color, and dynamical switching between the different colors was not possible.
Although color tuning of single colloidal nanocrystals which behave as “Artificial atoms” has been previously investigated and implemented in prototype optoelectronic devices, changing colors actively has been challenging due to the diminished brightness inherently accompanying the effect, which only yielded a slight shift of the color. The research team overcame this limitation, by creating a novel molecule with two emission centers, where an electric field can tune the relative emission from each center, changing the color, yet, without losing brightness. The artificial molecule can be made such that one of its constituent nanocrystals is tuned to emit “green” light, while the other “red” light. The emission of this new dual color emitting artificial molecule is sensitive to external voltage inducing an electric field: one polarity of the field induces emission of light from the “red” center, and switching the field to the other polarity, the color emission is switched instantaneously to “green,” and vice versa. This color switching phenomena is reversible and immediate, as it does not include any structural motion of the molecule. This allows to obtain each of the two colors, or any combination of them, simply by applying the appropriate voltage on the device. This ability to precisely control color tuning in optoelectronic devices while preserving intensity, unlocks new possibilities in various fields including in displays, lighting, and nanoscale optoelectronic devices with adjustable colors, and also as a tool for sensitive field sensing for biological applications and neuroscience to follow the brain activity. Moreover, it allows to actively tune emission colors in single photon sources which are important for future quantum communication technologies.
Prof. Uri Banin from the Hebrew University of Jerusalem explained, “Our research is a big leap forward in nanomaterials for optoelectronics. This is an important step in our exposition of the idea of “nanocrystal chemistry” launched just a few years ago in our research group, where the nanocrystals are building blocks of artificial molecules with exciting new functionalities. Being able to switch colors so quickly and efficiently on the nanoscale as we have achieved has enormous possibilities. It could revolutionize advanced displays and create color-switchable single photon sources.”
By utilizing such quantum dot molecules with two emission centers, several specific colors of light using the same nanostructure can be generated. This breakthrough opens doors to developing sensitive technologies for detecting and measuring electric fields. It also enables new display designs where each pixel can be individually controlled to produce different colors, simplifying the standard RGB display design to a smaller basis of pixels, which has the potential to increase the resolution and energy savings of future commercial displays. This advancement in electric field induced color switching has immense potential for transforming device customization and field sensing, paving the way for exciting future innovations.
Synthesis and properties of cyclic sandwich compounds
by Luca Münzfeld, Sebastian Gillhuber, Adrian Hauser, Sergei Lebedkin, Pauline Hädinger, Nicolai D. Knöfel, Christina Zovko, Michael T. Gamer, Florian Weigend, Manfred M. Kappes, Peter W. Roesky in Nature
Sandwich complexes were developed about 70 years ago and have a sandwich-like structure. Two flat aromatic organic rings (the “slices of bread”) are filled with a single, central metal atom in between. Like the slices of bread, both rings are arranged in parallel. Adding further layers of ‘bread’ and ‘filling’ produces triple or multiple sandwiches. “These compounds are among the most important complexes used in modern organometallic chemistry,” says Professor Peter Roesky from KIT’s Institute for Inorganic Chemistry. One of them is the highly stable ferrocene, for which its “fathers” Ernst Otto Fischer and Geoffrey Wilkinson were awarded the Nobel Prize in Chemistry in 1973. Ferrocene consists of an iron ion and two five-membered aromatic organic rings. It is used in synthesis, catalysis, electrochemistry, and polymer chemistry.
For some time now, researchers at KIT and the University of Marburg have tried to arrange sandwich complexes in a ring.
“We succeeded in producing chains, but no rings,” Roesky says, who coordinated the work of three teams at the two universities. “Thanks to the choice of the right ‘slice of bread’ or organic intermediate deck, we have now succeeded in forming nano-sized rings for the first time,” say Professor Manfred Kappes, who heads the Division of Physical Chemistry of Microscopic Systems at KIT, and Professor Florian Weigend, Head of the Applied Quantum Chemistry Unit of the University of Marburg.
The new nanoring consists of 18 building blocks and has an outer diameter of 3.8 nanometers. Depending on the metal used as the ‘filling’ of the sandwich, an orange-colored photoluminescence results. The new chemical compound was called ‘cyclocene’ by the researchers.
The three working groups carried out elaborate quantum chemical calculations to find out why the molecules could be arranged in a ring and no longer formed a chain of sandwich complexes. These calculations revealed that the driving force for the ring formation is the energy gained by the ring closure.
“Our challenge initially was to form a ring. Can other ring sizes be produced? Does this nanostructure possess unusual physical properties? This will be subject of further research. But it is clear now that we have added a new building block to our toolbox of organometallic chemistry. And this is great,” Roesky says.
Programming chemical communication: allostery vs multivalent mechanism
by Dominic Lauzon et al in Journal of the American Chemical Society
Two molecular languages at the origin of life have been successfully recreated and mathematically validated, thanks to pioneering work by Canadian scientists at Université de Montréal. The study opens new doors for the development of nanotechnologies with applications ranging from biosensing, drug delivery and molecular imaging.
Living organisms are made up of billions of nanomachines and nanostructures that communicate to create higher-order entities able to do many essential things, such as moving, thinking, surviving and reproducing.
“The key to life’s emergence relies on the development of molecular languages — also called signaling mechanisms — which ensure that all molecules in living organisms are working together to achieve specific tasks,” said the study’s principal investigator, UdeM bioengineering professor Alexis Vallée-Bélisle.
In yeasts, for example, upon detecting and binding a mating pheromone, billions of molecules will communicate and coordinate their activities to initiate union, said Vallée-Bélisle, holder of a Canada Research Chair in Bioengineering and Bionanotechnology.
“As we enter the era of nanotechnology, many scientists believe that the key to designing and programming more complex and useful artificial nanosystems relies on our ability to understand and better employ molecular languages developed by living organisms,” he said.
One well-known molecular language is allostery. The mechanism of this language is “lock-and-key”: a molecule binds and modifies the structure of another molecule, directing it to trigger or inhibit activity.
Another, lesser-known molecular language is multivalency, also known as the chelate effect. It works like a puzzle: as one molecule binds to another, it facilitates (or not) the binding of a third molecule by simply increasing its binding interface.
Although these two languages are observed in all molecular systems of all living organisms, it is only recently that scientists have started to understand their rules and principles — and so use these languages to design and program novel artificial nanotechnologies.
Researchers Alexis Vallée-Bélisle (left) and Dominic Lauzon (right) in the process of designing chemical languages using a DNA synthesizer. Credit: AméLie Philibert | Université de MontréAl
“Given the complexity of natural nanosystems, before now nobody was able to compare the basic rules, advantage or limitations of these two languages on the same system,” said Vallée-Bélisle.
To do so, his doctoral student Dominic Lauzon, first author of the study, had the idea of creating a DNA-based molecular system that could function using both languages.
“DNA is like Lego bricks for nanoengineers,” said Lauzon. “It’s a remarkable molecule that offers simple, programmable and easy-to-use chemistry.”
The researchers found that simple mathematical equations could well describe both languages, which unraveled the parameters and design rules to program the communication between molecules within a nanosystem.
For example, while the multivalent language enabled control of both the sensitivity and cooperativity of the activation or deactivation of the molecules, the corresponding allosteric translation only enabled control of the sensitivity of the response.
With this new understanding at hand, the researchers used the language of multivalency to design and engineer a programmable antibody sensor that allows the detection of antibodies over different ranges of concentration.
“As shown with the recent pandemic, our ability to precisely monitor the concentration of antibodies in the general population is a powerful tool to determine the people’s individual and collective immunity,” said Vallée-Bélisle.
In addition to expanding the synthetic toolbox to create the next generation of nanotechnology, the scientist’s discovery also shines a light on why some natural nanosystems may have selected one language over another to communicate chemical information.
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