NT/ Solving mysteries of metallic glass at the nanoscale
Nanotechnology & nanomaterials biweekly vol.48, 22nd January — 5th February
TL;DR
- The matter of how metals deform or respond to external stresses has been extensively studied among metallurgists for centuries. When it comes to conventional metals — the crystalline kind with atoms that line up in neat patterns — the process is fairly well understood. But for the deformation of metallic glasses and other amorphous metals, easy answers have been elusive, particularly when it comes to how things work at the nanoscale. In a new study, researchers look at the physical quirks of how these metals behave at very small sizes — insights that could lead to new ways of creating metallic glasses.
- Oxidation can degrade the properties and functionality of metals. However, a research team recently found that severely oxidized metallic glass nanotubes can attain an ultrahigh recoverable elastic strain, outperforming most conventional super-elastic metals. They also discovered the physical mechanisms underpinning this super-elasticity. Their discovery implies that oxidation in low-dimension metallic glass can result in unique properties for applications in sensors, medical devices and other nanodevices.
- Carbon nanostructures could become easier to design and synthesize thanks to a machine-learning method that predicts how they grow on metal surfaces. The new approach will make it easier to exploit the unique chemical versatility of carbon nanotechnology.
- Nanoclusters (NCs) of transition metals like cobalt or nickel have widespread applications in drug delivery and water purification, with smaller NCs exhibiting improved functionalities. Downsizing NCs is, however, usually challenging. Now, scientists have demonstrated functional NC formation with atomic-scale precision. They successfully grew cobalt NCs on flat copper surfaces using molecular arrays as traps. This breakthrough paves the way for advancements like single-atom catalysis and spintronics miniaturization.
- Scientists have harnessed the power of specially made nanostructures to enhance the neural response in a locust’s brain to specific odors and to improve their identification of those odors.
- MXene nanoparticle scaffolds have been shown to stimulate muscle growth, making them a promising option to treat muscle loss and damage. Now, researchers explain the molecular mechanisms behind their positive influence on muscle regeneration. This discovery can advance MXene scaffolds, potentially improving muscle reconstruction surgeries and establishing them as a standard medical practice for muscle recovery.
- Scientists have developed a universal method for producing a wide variety of designed metallic and semiconductor 3D nanostructures — the potential base materials for next-generation semiconductor devices, neuromorphic computing, and advanced energy applications. The new method, which uses a ‘hacked’ form of DNA that instructs molecules to organize themselves into targeted 3D patterns, is the first of its kind to produce robust nanostructures from multiple material classes.
- A collaborative research team has fabricated a soccer ball-shaped construction using edge-to-edge assembly of 2D semiconductor materials. The research has been featured on the cover of the online edition of the Angewandte Chemie International Edition journal.
- A team of Rice University researchers mapped out how flecks of 2D materials move in liquid ⎯ knowledge that could help scientists assemble macroscopic-scale materials with the same useful properties as their 2D counterparts.
- Quantum dots are a kind of artificial atom: just a few nanometers in size and made of semiconductor materials, they can emit light of a specific color or even single photons, which is important for quantum technologies. These quantum dots made of perovskite nanocrystals can be mixed with liquids to form a dispersion, which makes them easy to process further. Moreover, their special optical properties make them shine more brightly than many other quantum dots. They can also be produced more cheaply, which makes them interesting for applications in displays, for instance. A team of researchers at ETH Zurich and Empa, have now demonstrated how these promising properties of perovskite quantum dots can be improved further. They used chemical methods for surface treatment and quantum mechanical effects that had never before been observed in perovskite quantum dots.
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 an 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
Size-dependent deformation behavior in nanosized amorphous metals suggesting transition from collective to individual atomic transport
by Naijia Liu et al in Nature Communications
The matter of how metals deform or respond to external stresses has been extensively studied among metallurgists for centuries. When it comes to conventional metals — the crystalline kind with atoms that line up in neat patterns — the process is fairly well understood. But for the deformation of metallic glasses and other amorphous metals, easy answers have been elusive, particularly when it comes to how things work at the nanoscale. In a new study, Prof. Jan Schroers looks at the physical quirks of how these metals behave at very small sizes — insights that could lead to new ways of creating metallic glasses.
Materials with the strength of metal but with the pliability of plastic, metallic glasses are being developed for a broad range of applications: aerospace, space, robotics, consumer electronics, sporting goods, and biomedical uses.
These materials owe their properties to their unique atomic structures: when metallic glasses cool from a liquid to a solid, their atoms settle into a random arrangement and do not crystallize the way traditional metals do. However preventing atoms from crystallizing is tricky, and any insights into their workings could go a long way toward more efficient production of metallic glass.
“To advance fabrication and use of amorphous metals, a fundamental and complete understanding of their size- and temperature-dependent deformation is required,” the study’s authors write.
In the last few decades, it’s been well-established that at the macroscopic scale, atoms move en masse when deforming at temperatures that allow flow.
“They deform in a collective way, almost like honey,” said Schroers, the Robert Higgin Professor of Mechanical Engineering and Materials Science. “You see all of these atoms kind of moving collectively together.”
But what happens when nanoscale-size samples deform? Using zirconium copper and other metallic glass samples in a soft state, the Schroers lab decided to find out.
“Naijia Liu, the grad student in my lab, created smaller and smaller samples, and at some point he could show that they don’t deform that way anymore,” Schroers said. At sample sizes of 100 nanometers or smaller, things began to veer from the standard rules.
What they found was that at this size, the samples’ chemical composition would never change if the atoms continued to move collectively. What happened instead was that the atoms moved individually, and at a certain point, the metal began deforming rapidly.
“So if you go smaller and smaller, then the atoms, they don’t flow anymore. What they do instead is travel individually over the surface.”
That’s significant because atoms are known to move faster on the surface of crystalline materials. So, the smaller the sample, the greater proportion of the material is on, or close to a surface. In order to deform, atoms take an extra distance by using such a fast surface path as it allows general faster deformation. It’s an insight into an area of physics that still has many unanswered questions.
“We know essentially everything about crystals, and we know essentially everything about gases,” Schroers said. “But in the scientific community, we do not know the liquid state well. Things move around too quickly, so observation methods are challenged and as the order in a liquid is non-periodic, we can’t reduce the problem to a smaller unit.”
Schroers’ lab currently focuses on which alloys are most promising for creating metallic glasses through this method. “
The alloy should comprise similar elements, but not too similar, as otherwise the template on which they are growing cannot be formed into a glass,” Schroers said.
Besides the scientific impact of their new findings, Schroers said, the study has significance on a technological level. Instead of the current technique of avoiding crystallization through very fast cooling, these findings provide researchers with a novel method to slowly grow metastable materials. These materials include metallic glasses and even others that previously weren’t possible to make with other techniques.
Oxidation-induced superelasticity in metallic glass nanotubes
by Fucheng Li, Zhibo Zhang, Huanrong Liu, Wenqing Zhu, Tianyu Wang, Minhyuk Park, Jingyang Zhang, Niklas Bönninghoff, Xiaobin Feng, Hongti Zhang, Junhua Luan, Jianguo Wang, Xiaodi Liu, Tinghao Chang, Jinn P. Chu, Yang Lu, Yanhui Liu, Pengfei Guan, Yong Yang in Nature Materials
Oxidation can degrade the properties and functionality of metals. However, a research team co-led by scientists from City University of Hong Kong (CityU) recently found that severely oxidized metallic glass nanotubes can attain an ultrahigh recoverable elastic strain, outperforming most conventional super-elastic metals. They also discovered the physical mechanisms underpinning this super-elasticity. Their discovery implies that oxidation in low-dimension metallic glass can result in unique properties for applications in sensors, medical devices and other nanodevices.
In recent years, the functional and mechanical properties of low-dimensional metals, including nanoparticles, nanotubes and nanosheets, have garnered attention for their potential applications in small-scale devices, such as sensors, nano-robots and metamaterials.
However, most metals are electrochemically active and susceptible to oxidation in ambient environments, which often degrades their properties and functionalities.
“Metallic nanomaterials have a high surface-to-volume ratio, which can be up to 108m-1. So in principle, they are expected to be particularly prone to oxidation,” said Professor Yang Yong, in the Department of Mechanical Engineering at CityU, who led the research team together with his collaborators.
“To use low-dimensional metals to develop next-generation devices and metamaterial, we must thoroughly understand the adverse effects of oxidation on the properties of these nanometals and then find a way to overcome them.”
Therefore, Professor Yang and his team investigated oxidation in nanometals, and in sharp contrast to their expectation, they found that severely oxidized metallic glass nanotubes and nanosheets can attain an ultrahigh recoverable elastic strain of up to about 14% at room temperature, which outperforms bulk metallic glasses, metallic glass nanowires, and many other super-elastic metals.
They made metallic glass nanotubes with an average wall thickness of just 20nm, and fabricated nanosheets from different substrates, such as sodium chloride, polyvinyl alcohol and conventional photoresist substrates, with different levels of oxygen concentration.
They then conducted 3D atom probe tomography (APT) and electron energy loss spectroscopy measurements.
In both results, oxides were dispersed within the metallic glass nanotubes and nanosheets, unlike conventional bulk metals, in which a solid oxide layer forms on the surface.
As the oxygen concentration in the samples increased owing to metal-substrate reactions, connected and percolating oxide networks were formed inside the nanotubes and nanosheets.
In-situ microcompression measurements also revealed that the severely oxidized metallic glass nanotubes and nanosheets exhibited a recoverable strain of 10–20%, which was several times more than that of most conventional superelastic metals, such as shape memory alloys and gum metals.
The nanotubes also had an ultra-low elastic modulus of about 20–30 GPa.
To understand the mechanism behind this, the team conducted atomistic simulations, which indicated that the superelasticity originates from severe oxidation in the nanotubes and can be attributed to the formation of a damage-tolerant percolation network of nano-oxides in the amorphous structure.
These oxide networks not only restrict atomic-scale plastic events during loading, but also lead to the recovery of elastic rigidity on unloading in metallic glass nanotubes.
“Our research introduces a nano-oxide engineering approach for low-dimensional metallic glasses. The morphology of nano-oxides within metallic-glass nanotubes and nanosheets can be manipulated by adjusting the oxide concentration, ranging from isolated dispersions to a connected network,” said Professor Yang.
“With this approach, we can develop a class of heterogeneous nanostructured ceramic-metal composites by blending metals with oxides at the nanoscale. Such composites have great potential for various future commercial applications and nanodevices working in harsh environments, such as sensors, medical devices, micro- and nano-robots, springs and actuators,” he added.
Active machine learning model for the dynamic simulation and growth mechanisms of carbon on metal surface
by Di Zhang, Peiyun Yi, Xinmin Lai, Linfa Peng, Hao Li in Nature Communications
Carbon nanostructures could become easier to design and synthesize thanks to a machine learning method that predicts how they grow on metal surfaces. The new approach, developed by researchers at Japan’s Tohoku University and China’s Shanghai Jiao Tong University, will make it easier to exploit the unique chemical versatility of carbon nanotechnology.
The growth of carbon nanostructures on a variety of surfaces, including as atomically thin films, has been widely studied, but little is known about the dynamics and atomic-level factors governing the quality of the resulting materials.
“Our work addresses a crucial challenge for realizing the potential of carbon nanostructures in electronics or energy processing devices,” says Hao Li of the Tohoku University team.
The wide range of possible surfaces and the sensitivity of the process to several variables make direct experimental investigation challenging.
The researchers therefore turned to machine learning simulations as a more effective way to explore these systems. With machine learning, various theoretical models can be combined with data from chemistry experiments to predict the dynamics of carbon crystalline growth and determine how it can be controlled to achieve specific results.
The simulation program explores strategies and identifies which ones work and which don’t, without the need for humans to guide every step of the process. The researchers tested this approach by investigating simulations of the growth of graphene, a form of carbon, on a copper surface.
After establishing the basic framework, they showed how their approach could also be applied to other metallic surfaces, such as titanium, chromium and copper contaminated with oxygen.
The distribution of electrons around the nuclei of atoms in different forms of graphene crystals can vary. These subtle differences in atomic structure and electron arrangement affect the overall chemical and electrochemical properties of the material.
The machine learning approach can test how these differences affect the diffusion of individual atoms and bonded atoms and the formation of carbon chains, arches and ring structures. The team validated the results of the simulations through experiments and found that they closely matched.
“Overall, our work provides a practical and efficient method for designing metallic or alloy substrates to achieve desired carbon nanostructures and explore further opportunities,” Li says.
He adds that future work will build on this to investigate topics such as the interfaces between solids and liquids in advanced catalysts and the chemical properties of materials used for processing and storing energy.
On-surface growth of transition-metal cobalt nanoclusters using a 2D crown-ether array
by Toyo Kazu Yamada, Ryohei Nemoto, Fumi Nishino, Takuya Hosokai, Chi-Hsien Wang, Masaki Horie, Yuri Hasegawa, Satoshi Kera, Peter Krüger in Journal of Materials Chemistry C
Nanoclusters (NCs) are crystalline materials that typically exist on the nanometer (10–9 m) scale. They are composed of atoms or molecules in combination with metals like cobalt, nickel, iron, and platinum, and have found several interesting applications across diverse fields, including drug delivery, catalysis, and water purification. A reduction in the size of NCs can unlock additional potential, allowing for processes such as single-atom catalysis. In this context, the coordination of organic molecules with individual transition-metal atoms shows promise for further advancement in this field.
An innovative approach to further reduce the size of NCs involves introducing metal atoms into self-assembled monolayer films on flat surfaces. However, it is crucial to exercise caution in ensuring that the arrangement of metal atoms on these surfaces does not disrupt the ordered nature of these monolayer films.
Now, in a recent study featured in the Journal of Materials Chemistry C, Dr. Toyo Kazu Yamada from the Graduate School of Engineering at Chiba University, along with Masaki Horie from the Department of Chemical Engineering at National Tsing Hua University, Satoshi Kera from the Institute for Molecular Science, and Peter Krüger also from the Graduate School of Engineering at Chiba University, have showcased the surface growth of cobalt atoms on molecular ring arrays at room temperature.
Talking to us about this advancement. Dr. Yamada says, “This advanced method of functional nanocluster formation with atomic-scale precision can be utilized in the development of highly efficient catalysts or in quantum computing.”
In the study, the team used ring-shaped molecular structures called “crown ethers,” which contain benzene and bromine rings.
These structures were used to trap and grow cobalt NCs on flat copper surfaces.
The resulting cobalt NCs were of two sizes, 1.5 nm and 3.6 nm. To understand their properties and structure further, various techniques were employed, including low-temperature scanning tunneling microscopy and spectroscopy (STM and STS), angle-resolved photoelectron spectroscopy (ARPES) with low energy electron diffraction (LEED), and density functional theory (DFT) calculations.
The analysis revealed the formation of stable surface sites to which the cobalt atoms could attach.
In addition, the formation of these stable surface sites was found to be influenced by the electronic hybridization (mixing) between the crown ethers and cobalt.
Once the cobalt atom was trapped, it acted like a nucleation center, attracting other cobalt atoms to form an NC. Additionally, unlike the usual behavior of crown ether molecules in solution, these molecules did not trap the metal atom at the center of the crown ring.
Instead, the metal atom was at the edge, because of the presence of bromine atoms at that location.
Discussing the long-term potential of these findings, Dr. Yamada says, “The use of this approach in applications such as single-atom catalysis, miniaturization of spintronics media, and quantum computing will contribute to the development of an information-based society in a way that reduces carbon dioxide (CO2) production.”
In summary, the team successfully demonstrated the growth of cobalt NCs by exploiting the trapping potential of two-dimensional crown ether molecules on a copper surface. The chemical behavior of the crown ether molecules deviated from typical interactions observed in solution, by trapping cobalt atoms at the edge, and not the center. Importantly, the method demonstrated effective and large-scale production of NCs with well-defined size and morphology at room temperature.
Augmenting insect olfaction performance through nano-neuromodulation
by Prashant Gupta, Rishabh Chandak, Avishek Debnath, Michael Traner, Brendan M. Watson, Hengbo Huang, Hamed Gholami Derami, Harsh Baldi, Shantanu Chakrabartty, Baranidharan Raman, Srikanth Singamaneni in Nature Nanotechnology
Our sensory systems are highly adaptable. A person who cannot see after turning off a light in the night slowly achieves superior power to see even small objects. Women often attain a heightened sense of smell during pregnancy. How can the same sensory system that was underperforming can also exceed the expectation based on its prior performance?
Since nature has perfected its sensory systems over evolutionary time scales, an interdisciplinary team of researchers in the McKelvey School of Engineering at Washington University in St. Louis tapped into these capabilities to adapt the system on demand to perform at its peak performance.
Their tools to achieve this goal: locusts and nanomaterials too small to see.
Srikanth Singamaneni and Barani Raman, both professors in the McKelvey School of Engineering, led a team that harnessed the power of specially made nanostructures that can absorb light and create heat, known as the photothermal effect, and act as containers to store and release chemicals on demand.
They used these nanostructured materials to boost neural response in the locust’s brain to specific odors and to improve their identification.
Singamaneni, the Lilyan & E. Lisle Hughes Professor in the Department of Mechanical Engineering & Materials Science, and Raman, professor of biomedical engineering, have collaborated for years with Shantanu Chakrabartty, the Clifford W. Murphy Professor in the Preston M. Green Department of Electrical & Systems Engineering, to harness the superior sensing capabilities of the locust olfactory system.
Recently they demonstrated the feasibility of using a bio-hybrid electronic nose for sensing explosive vapors.
“We let the biology do the harder job of converting information about vaporous chemicals into an electrical neural signal,” Raman said. “These signals are detected in the insect antennae and are transmitted to the brain. We can place electrodes in the brain, measure the locusts’ neural response to odors, and use them as fingerprints to distinguish between chemicals.”
The idea, though sound, has a potential roadblock.
“We are limited by the number of electrodes and where we can place them,” Singamaneni said. “Since we will get only a partial signal, we want to amplify this signal. This is where we turned to heat and neuromodulation to enhance the signal we get.”
In the new research, the team used two strategies to boost the locusts’ ability to detect odors.
First, the team created a biocompatible and biodegradable polydopamine nanoparticle that converts light to heat through a process called photothermal effect.
“Heat affects diffusion,” Raman said. “Imagine adding cold milk to hot coffee. The idea is to use the heat generated by nanostructures to locally heat, for example, a nanoheater, and enhance the neural activity.”
Second, these nanostructured materials can be made to load chemicals for storage.
However, they need to be encapsulated by a covering material. The team used a phase-change material called tetradecanol which is solid at room temperature and transitions to liquid upon heating. When heated, the same nanoheaters will ooze the chemicals stored within them in addition to generating heat. Singamaneni and the team stored octopamine, a neuromodulator involved in various functions, and released it on demand. Usually, these neuromodulators are released based on the needs of the organism. However, using the nanostructured heaters, they were released on demand to enhance the neural signals.
“Our study presents a generic strategy to reversibly enhance neural signals at the brain site where we place the electrodes,” Raman said. “The nano-enabled neuromodulation strategy we developed opens new opportunities to realize tailored cyborg chemical sensing approaches,” said Prashant Gupta, a graduate student in Singamaneni’s lab and first author of the paper. “This approach would change an existing passive approach where information is simply read into an active one where the capabilities of the neural circuits as a basis for information processing are fully used.”
Highly Aligned Ternary Nanofiber Matrices Loaded with MXene Expedite Regeneration of Volumetric Muscle Loss
by Moon Sung Kang, Yeuni Yu, Rowoon Park, Hye Jin Heo, Seok Hyun Lee, Suck Won Hong, Yun Hak Kim, Dong-Wook Han in Nano-Micro Letters
Tissue engineering, which involves the use of grafts or scaffolds to aid cell regeneration, is emerging as a key medical practice for treating volumetric muscle loss (VML), a condition where a significant amount of muscle tissue is lost beyond the body’s natural regenerative capacity. To improve surgical outcomes, traditional muscle grafts are giving way to artificial scaffold materials, with MXene nanoparticles (NPs) standing out as a promising option.
MXene NPs are 2D materials primarily composed of transition-metal carbides and nitride. They are highly electrically conductive, can accommodate a wide range of functional groups, and have stacked structures that promote cell interactions and muscle growth. While there have been practical demonstrations in the laboratory showcasing their ability to promote the reconstruction of skeletal muscles, the specific mechanism by which they do so remains unclear.
To address this gap, Associate Professor Yun Hak Kim from the Department of Anatomy and Department of Biomedical Informatics alongside Professors Suck Won Hong, and Dong-Wook Han from the Department of Cogno-Mechatronics Engineering at Pusan National University, developed nanofibrous matrices containing MXene NPs as scaffolds.
They used DNA sequencing to reveal the genes and biological pathways activated by MXene NPs to aid in muscle regeneration.
These findings mark a significantly advancement in the use of MXene scaffolds for treating muscle damage.
“This discovery posits a prospective avenue for the utilization of these materials to augment the efficacy of muscle tissue regeneration post-injury or damage,” explains Professor Kim.
In the initial phase, the team created a nanofibrous PCM matrix containing poly(lactide-co-ε-caprolactone) (P), reinforced with collagen ©, and Ti3C2Tx MXene nanoparticles (M). To determine the specific effect of MXene NPs on muscle growth, they prepared three controls: pristine PLCL (P), PLCL with Collagen (PC), and PLCL with MXene (PM). On testing all the scaffolds on mouse models with induced volumetric muscle loss, the researchers observed a significant increase in the overall number of muscle cells in PCM-treated mice compared to the other groups.
To understand how MXene nanoparticles (NPs) impact muscle regeneration and growth at the molecular level, the researchers introduced C2C12 myoblasts, which are precursors of muscle cells, onto PC and PCM matrices.
The objective was to analyze the differences in gene expression levels between the two matrices.
Within the PCM matrix, a heightened production of inducible nitric oxide synthase (iNOS) and serum/glucocorticoid-regulated kinase 1 (SGK1) was identified-two proteins closely associated with calcium signaling and muscle regeneration.
These results suggest that MXenes promote calcium ion (Ca2+) deposition around cells. This heightened levels of intracellular Ca2+ triggers the activation of genes that produce iNOS and SGK1 proteins. SGK1 influences the mTOR-AKT pathway, promoting cell proliferation, survival, and myogenesis-the conversion of myoblasts to muscle fibers.
Simultaneously, iNOS increases the production of nitric oxide (NO), contributing to myoblast proliferation and muscle fiber fusion. The combined effects lead to the development of mature muscle tissue. The aligned PCM nanofibrous matrices offer biophysical cues for intracellular biochemical signaling, guiding myogenic behaviors.
This discovery contributes to our understanding of MXene’s potential to regrow muscle and holds promise for refining scaffold designs to enhance this process further.
“Within 5 to 10 years, this research may yield groundbreaking treatments for muscle injuries. MXene NP-infused matrices could become a routine in medical practice for athletes, people with muscle-related ailments, and those recuperating from muscle-related traumas or surgeries,” Prof.
Kim optimistically states. ‘These NPs might enhance muscle regeneration methods, offering improved outcomes for reconstructive surgeries and conditions like muscular dystrophy, where muscle function is compromised,’ he further adds.
The MXene NP-infused matrices hold potential for customization to meet diverse needs in treating muscle loss injuries.
This customization may involve adjusting composition, structure, or properties to match specific patient requirements, like size, shape, or bioactivity enhancement. Tailoring these materials could offer personalized solutions for various muscle loss severities.
Additionally, the observed enhanced muscle regeneration could aid in a more efficient recovery, potentially reducing post-treatment rehabilitation needs.
These matrices, with controllable mechanical properties, hold promise for enhancing in vivo muscle regeneration. Further research into MXene promises expanded clinical applications, potentially benefiting human well-being.
Three-dimensional nanoscale metal, metal oxide, and semiconductor frameworks through DNA-programmable assembly and templating
by Aaron Michelson, Ashwanth Subramanian, Kim Kisslinger, Nikhil Tiwale, Shuting Xiang, Eric Shen, Jason S. Kahn, Dmytro Nykypanchuk, Hanfei Yan, Chang-Yong Nam, Oleg Gang in Science Advances
Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, Columbia University, and Stony Brook University have developed a universal method for producing a wide variety of designed metallic and semiconductor 3D nanostructures — the potential base materials for next-generation semiconductor devices, neuromorphic computing, and advanced energy applications. The new method, which uses a “hacked” form of DNA that instructs molecules to organize themselves into targeted 3D patterns, is the first of its kind to produce robust nanostructures from multiple material classes.
“We have been using DNA to program nanoscale materials for more than a decade,” said corresponding author Oleg Gang, a professor of chemical engineering and of applied physics and materials science at Columbia Engineering and leader of the Soft and Bio Nanomaterials Group at the Center for Functional Nanomaterials (CFN). CFN is a DOE Office of Science user facility at Brookhaven Lab. “Now, by building on previous achievements, we have developed a method for converting these DNA-based structures into many types of functional inorganic 3D nano-architectures, and this opens tremendous opportunities for 3D nanoscale manufacturing.”
CFN is a leader in researching self-assembly, the process by which molecules spontaneously organize themselves. In particular, scientists at CFN are experts at DNA-directed assembly. Researchers program strands of DNA to “direct” the self-assembly process towards molecular arrangements that give rise to beneficial properties, such as electrical conductivity, photosensitivity, and magnetism. Then, those structures can be scaled up to functional materials. To date, CFN has used DNA-directed assembly to produce switchable thin films, 3D nanosuperconductors, and more.
“We have demonstrated various types of structures we can organize using DNA-directed assembly. But, to take this research to the next level, we can’t only rely on DNA,” Gang said. “We needed to expand upon our method to make more robust structures with more specific functionality for advanced technologies like microelectronics and semiconductor devices.”
Recently, Gang and colleagues, including several students, were able to grow silica, an oxidized form of silicon, onto a DNA lattice. The addition of silica created a much more robust structure, but the procedure was not widely applicable to different materials. The team still needed further research to develop a method that could produce metallic and semiconductor materials in an efficient way.
To build out a more universal method for producing 3D nanostructures, researchers in CFN’s Soft and Bio Nanomaterials Group collaborated with the Center’s Electronic Nanomaterials Group.
“The relationship between different research groups at CFN is very fruitful for everyone,” said lead author Aaron Michelson, a postdoctoral researcher at CFN who began this research as a Columbia graduate student. “Our bio and soft matter labs are next door to material synthesis labs, which are next door to electron microscopy labs, so it’s a very synergistic relationship. The culture of CFN makes it easier to iterate on research, and on top of that we are surrounded by all the leading equipment we need.”
Scientists in the Electronic Nanomaterials Group pioneered a novel material synthesis technique called vapor-phase infiltration. This technique bonds a precursor chemical, in vapor form, to a nanoscale lattice, penetrating beyond the surface and deep into the material’s structure. Conducting this technique on the silica structures Gang’s team had previously built, using precursors with metallic elements, enabled the researchers to produce 3D metallic structures.
“We were already using this technique for other applications, like improving microelectronics materials or gas separation membranes for hydrogen, when we realized it could be applied to DNA-directed assembly,” said co-corresponding author Chang-Yong Nam, a scientist in the Electronic Nanomaterials Group at CFN. Nam leads the research program on developing vapor-phase infiltration synthesis methods for microelectronics and energy technology applications. “That was very exciting.”
The team also experimented with liquid-phase infiltration, another technique that forms chemical bonds on a material’s surface, except with a liquid precursor. In this case, the team bonded different metal salts to silica, forming a variety of metallic structures.
“By incorporating single-element and multi-element coatings through liquid- and vapor-phase infiltration techniques, we preserved the underlying DNA lattice while enabling the production of 3D inorganic nanostructures,” Gang said.
Michelson added, “Another way to think about how we’ve built these structures is to compare it to building a house. First, you construct the bones — the lumber in the house or the silica in these materials. Then, you start adding on functional components, like insulation or metallic elements.”
The variety of functional components available, for both houses and nanomaterials, is vast. For example, to protect homes against storms, some houses need hurricane-resistant windows, and some houses need a raised foundation. Other houses need a combination of unique, functional components like these — and the same is true for nanomaterials. So, to enable the production of the widest variety of functional nanostructures through a single method, the team decided to stack both infiltration techniques.
“Stacking these techniques showed much more depth of control than has ever been accomplished before,” Michelson said. “Whatever vapors are available as precursors for vapor-phase infiltration can be coupled with various metal salts compatible with liquid-phase infiltration to create more complex structures. For example, we were able to combine platinum, aluminum, and zinc on top of one nanostructure.”
This universal method was extremely effective for producing 3D nanostructures of a wide variety of material compositions — to such an extent that it surprised the researchers. The team was able to produce 3D nanostructures containing different combinations of zinc, aluminum, copper, molybdenum, tungsten, indium, tin, and platinum. This is the first demonstration of its kind for creating highly structured 3D nanomaterials.
“One of the most surprising things about this experiment is that we were able to successfully produce so many different material compositions of nanostructures using an identical process protocol in a manner that is straightforward, repeatable, and robust,” Michelson said. “Typically for research like this, you need to spend a considerable amount of time with just one class of materials trying to get it to work, day in and day out. Whereas here, nearly everything we tried worked quickly, and at some point, we just had to stop producing structures because we wanted to write about it.”
To prove the success of this method for each nanostructure they developed, down to the finest level of detail, the researchers leveraged expertise and world-class imaging facilities at CFN and the National Synchrotron Light Source II (NSLS-II). NSLS-II is a DOE Office of Science user facility at Brookhaven Lab that produces ultrabright x-rays to illuminate the physical, chemical, and electronic makeup of samples at the atomic scale.
“Not only did we create all of these nanostructures, but we fully characterized each of them to try to understand and process them further,” Michelson said. “Initially, these materials might exist in some intermediate state, which we could further process to a final, more functional and useful state.”
There are several properties needed to make useful materials for technologies like semiconductor devices. For this study, the researchers imparted electrical conductivity and photoactivity on the 3D nanostructures. For example, they started with an insulating material and then, through their new DNA-directed assembly method that incorporates two infiltration techniques, they added on semiconducting metal oxides, such as zinc oxide, so the nanostructure could inherit its electrical conductivity and photoluminescence. Finally, for all their end products, they brought the samples to imaging facilities across Brookhaven Lab to see their volumetric makeup.
At CFN, the team used the electron microscopy facility to produce high resolution views of their structures after vapor-phase infiltration, liquid-phase infiltration, and stacking both techniques — for every precursor used. They leveraged a combination of transmission electron microscopes and scanning electron microscopes, which generate pictures with nanoscale resolution by analyzing how electrons bounce off or pass through the samples, respectively. These techniques enabled the researchers to produce picturesque views of their nanostructures and map their chemical arrangements with high precision and in small areas of their samples.
To gain 3D views of this information across larger areas, the team used the Complex Materials Scattering (CMS) beamline and the Hard X-ray Nanoprobe (HXN) beamline at NSLS-II. CMS is a partner beamline that is jointly operated by NSLS-II and CFN. There, the researchers directed NSLS-II’s ultrabright x-rays at their samples, observing how the x-rays scattered to infer the nanostructures’ 3D atomic arrangements. Meanwhile, HXN provided direct 3D imaging of both the structures and their chemical “maps.”
The researchers used HXN’s premier technique, x-ray nanotomography, which functions similarly to a medical CT scan. The beamline captures 180 2D projections of the sample, rotating it one degree at a time. Then, computers construct a 3D image from the series of projections. But unlike CT scans, HXN incorporates a nanoprobe to capture the projections with nanometer resolution.
“This type of chemical detail cannot be captured by other techniques or any other facility,” said co-author Hanfei Yan, lead beamline scientist at HXN. “And this information was very important for this study because of the nanostructures’ complexity. Uncovering the elemental distribution helped us determine whether the new method was effective and if the coatings fully penetrated the lattice.”
Michelson said, “HXN provided us with spatial and elemental resolution that we couldn’t achieve anywhere else. HXN helped us confirm that not only were these coatings present on the material surfaces, but they actually were volumetric to the sample.” The group previously used this technique to reveal the 3D structure of DNA lattices with single particle resolution. Now, this technique enabled them to reveal the arrangements of metallic and semiconductor nanofeatures deep within the sample, which was important for verifying the fidelity and power of their fabrication method.
Having confirmed the success of their new method, CFN will now work to apply the method to more complex research and offer it to visiting scientists. As a user facility, CFN makes its capabilities and expertise available to “users” across the country and the world. Assisting user experiments not only provides outside researchers with tools they would not normally have access to, but it opens the door to new collaborations and scientific ideation that otherwise would never be realized.
“We develop these materials and methods, and that is interesting for our own programs at CFN, but we would also like to see users utilizing these methods for their own research,” Gang said. “We are always aiming to scale up our methods and connect new researchers to our developments. We want our work to benefit the wider scientific community, not just Brookhaven Lab.”
The ecosystem of CFN’s expertise and facilities that benefited this research is also a benefit to users, and CFN is constantly expanding its offerings and making them more accessible. For example, scientists are looking to implement the new research method into one of the Center’s newest tools, a liquid-handling robot.
Soccer Ball‐like Assembly of Edge‐to‐edge Oriented 2D‐silica Nanosheets: A Promising Catalyst Support for High‐Temperature Reforming
by Sun Woo Jang et al in Angewandte Chemie International Edition
A collaborative research team has fabricated a soccer ball-shaped construction using edge-to-edge assembly of 2D semiconductor materials. The research has been featured on the cover of the online edition of the Angewandte Chemie International Edition journal.
The research team, led by Professor In Su Lee and Ph.D. candidate Sun Woo Jang from the Department of Chemistry at Pohang University of Science and Technology (POSTECH), along with Professor Kwangjin An from the Department of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology (UNIST), successfully controlled the interaction between the edges of 2D-silica nanosheets (2D-SiNS) to create a soccer ball-like structure.
The planar structure of 2D nanosheets exhibit unique mechanical and optical properties, making them versatile in semiconductor devices, catalysts, sensors, and many other sectors. The strong attraction of intermolecular forces (van der Waals) between sheets typically results in a structure where faces are in direct contact, compromising mechanical stability for catalytic functionality.
In the study, the research team developed an edge-to-edge assembly technique for 2D-SiNS. In the case of 2D-SiNS, charge distribution varies based on surface curvature or structural characteristics, and typically, the edge region is sensitive to differences in charge distribution.
The research team leveraged this property to induce interactions between the edges of 2D-SiNS. Unlike traditional face-to-face assembly, this technique focuses on the assembly of edges.
This breakthrough allowed the researchers to assemble 2D-SiNS into hollow soccer ball-shaped structures, demonstrating exceptional mechanical stability and durability even under challenging conditions, including high temperatures and various solvents. Moreover, this structure prevented unintentional aggregation of nanostructures and inhibited the formation of coke, which impedes catalytic activity.
Such structural characteristics significantly increased the assembled 2D-SiNS surface area, improving the efficiency of catalytic reactions and facilitating the smooth movement of reactants. Importantly, when subjected to continuous reactions at high temperatures, it demonstrated outstanding catalytic activity and durability in producing hydrogen and carbon monoxide from methane and carbon dioxide.
The lead researcher of the study, Professor In Su Lee, said, “I am delighted not only about the enhanced understanding of nano-scale material assembly but also about our paving the way for the development of stable and functional 2D nanomaterials.”
Brownian Diffusion of Hexagonal Boron Nitride Nanosheets and Graphene in Two Dimensions
by Utana Umezaki et al in ACS Nano
A team of Rice University researchers mapped out how flecks of 2D materials move in liquid ⎯ knowledge that could help scientists assemble macroscopic-scale materials with the same useful properties as their 2D counterparts.
“Two-dimensional nanomaterials are extremely thin — only several atoms thick — sheet-shaped materials,” said Utana Umezaki, a Rice graduate student who is a lead author on a study published in ACS Nano. “They behave very differently from materials we’re used to in daily life and can have really useful properties: They can withstand a lot of force, resist high temperatures and so on. To take advantage of these unique properties, we have to find ways to turn them into larger-scale materials like films and fibers.”
In order to maintain their special properties in bulk form, sheets of 2D materials have to be properly aligned ⎯ a process that often occurs in solution phase. Rice researchers focused on graphene, which is made up of carbon atoms, and hexagonal boron nitride, a material with a similar structure to graphene but composed of boron and nitrogen atoms.
“We were particularly interested in hexagonal boron nitride, which is sometimes called ‘white graphene’ and which, unlike graphene, doesn’t conduct electricity but has high tensile strength and is chemically resistant,” said Angel Martí, a professor of chemistry, bioengineering, materials science and nanoengineering and chair of Rice’s chemistry department. “One of the things that we realized is that the diffusion of hexagonal boron nitride in solution was not very well understood.
“In fact, when we consulted the literature, we found that the same was true for graphene. We couldn’t find an account of diffusion dynamics at the single molecule level for these materials, which is what motivated us to tackle this problem.”
The researchers used a fluorescent surfactant, i.e. glowing soap, to tag the nanomaterial samples and render their motion visible. Videos of this motion allowed researchers to map out the trajectories of the samples and determine the relationship between their size and how they move.
“From our observation, we found an interesting trend between the speed of their movement and their size,” Umezaki said. “We could express the trend with a relatively simple equation, which means we can predict the movement mathematically.”
Graphene was found to move slower in the liquid solution, possibly due to the fact that its layers are thinner and more flexible than hexagonal boron nitride, giving rise to more friction. Researchers believe that the formula derived from the experiment could be used to describe how other 2D materials move in similar contexts.
“Understanding how diffusion in a confined environment works for these materials is important because ⎯ if we want to make fibers, for example ⎯ we extrude these materials through very thin injectors or spinnerets,” Martí said. “So this is the first step toward understanding how these materials start to assemble and behave when they are in this confined environment.”
As one of the first studies to investigate the hydrodynamics of 2D nanosheet materials, the research helps fill a gap in the field and could be instrumental to overcoming 2D material fabrication challenges.
“Our final objective with studying these building blocks is to be able to generate macroscopic materials,” Martí said.
Single-photon superradiance in individual caesium lead halide quantum dots
by Chenglian Zhu et al in Nature (2024)
&
Designer Phospholipid Capping Ligands for Soft Metal Halide Nanocrystals
Viktoriia Morad et al in Nature (2023)
Quantum dots are a kind of artificial atom: just a few nanometers in size and made of semiconductor materials, they can emit light of a specific color or even single photons, which is important for quantum technologies. The discoverers and pioneers of the commercial production of quantum dots were awarded the Nobel Prize in Chemistry in 2023. In recent years, quantum dots made of perovskites have attracted particular attention. Perovskites belong to a class of materials that have a similar structure to the mineral perovskite (calcium titanate). Quantum dots made of such materials were produced for the first time by ETH Zurich in 2015.
These quantum dots made of perovskite nanocrystals can be mixed with liquids to form a dispersion, which makes them easy to process further. Moreover, their special optical properties make them shine more brightly than many other quantum dots. They can also be produced more cheaply, which makes them interesting for applications in displays, for instance.
A team of researchers led by Maksym Kovalenko at ETH Zurich and Empa, working in collaboration with counterparts in Ukraine and the U.S., have now demonstrated how these promising properties of perovskite quantum dots can be improved further. They used chemical methods for surface treatment and quantum mechanical effects that had never before been observed in perovskite quantum dots. The researchers recently published their results in two papers in Nature.
Brightness is an important measure for quantum dots and is related to the number of photons the quantum dot emits per second. Quantum dots radiate photons of a specific color (and hence frequency) after being excited, for example, by ultraviolet light of a higher frequency.
This leads to the formation of an exciton consisting of an electron, which can now move more freely, and a hole — in other words, a missing electron — in the energetic band structure of the material. The excited electron can fall back to a lower energy state and thus recombine with the hole. If the energy released during this process is converted into a photon, the quantum dot emits light.
This doesn’t always work, however. “At the surface of the perovskite nanocrystals are ‘unhappy’ atoms that are missing a neighbor in the crystal lattice,” senior researcher Gabriele Raino explains. These edge atoms disturb the balance between positive and negative charge carriers inside the nanocrystal and can cause the energy released during a recombination to be converted into lattice vibrations instead of being emitted as light. As a result, the quantum dot “blinks,” meaning that it doesn’t shine continuously.
To prevent this from happening, Kovalenko and his team have developed tailor-made molecules known as phospholipids. “These phospholipids are very similar to the liposomes in which, for instance, the mRNA vaccine against the coronavirus is embedded in such a way as to make it stable in the bloodstream until it reaches the cells,” Kovalenko explains.
An important difference: the researchers optimized their molecules so that the polar (electrically sensitive) part of the molecule latches onto the surface of the perovskite quantum dots and makes sure that the “unhappy” atoms are provided with a charge partner.
The nonpolar part of the phospholipid that protrudes on the outside also makes it possible to turn quantum dots into a dispersion inside non-aqueous solutions such as organic solvents. The lipid coating on the surface of the perovskite nanocrystals is also important for their structural stability, as Kovalenko emphasizes:
“This surface treatment is absolutely essentially for anything we might want to do with the quantum dots.”
So far, Kovalenko and his team have demonstrated the treatment for quantum dots made of lead halide perovskites, but it can also be easily adapted to other metal halide quantum dots.
With the lipid surface it was possible to reduce the blinking of the quantum dots to such an extent to emit a photon in 95% of electron-hole recombination events. To make the quantum dot even brighter, however, the researchers had to increase the speed of the recombination itself — and that requires quantum mechanics.
An excited state, such as an exciton, decays when a dipole — positive and negative charges displace with respect to each other — interacts with the electromagnetic field of the vacuum. The larger the dipole, the faster the decay. One possibility of creating a larger dipole involves coherently coupling several smaller dipoles to each other. This can be compared to pendulum clocks that are mechanically connected and tick in step with each other after a certain length of time.
The researchers were able to show experimentally that the coherent coupling also works in perovskite quantum dots — with only a single exciton dipole that — through quantum mechanical effects — spreads out all over the volume of the quantum dot, thereby creating several copies of itself, as it were. The larger the quantum dot, the more copies can be created. These copies can bring about an effect known as superradiance, by which the exciton recombines much faster.
The quantum dot is consequently also ready more quickly to take up a new exciton and can thus emit more photons per second, making it even brighter. An important detail to note is that the faster quantum dot continues to emit single photons (not several photons at once), which makes it suitable for quantum technologies.
The improved perovskite quantum dots are not only of interest for light production and displays, says Kovalenko, but also in other less obvious fields. For instance, they could be used as light-activated catalysts in organic chemistry. Kovalenko is conducting research into such applications and several others, including within the framework of NCCR Catalysis.
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