TL;DR
- Metasurfaces are nanoscale structures that interact with light. Today, most metasurfaces use monolith-like nanopillars to focus, shape and control light. The taller the nanopillar, the more time it takes for light to pass through the nanostructure, giving the metasurface more versatile control of each color of light. But very tall pillars tend to fall or cling together. What if, instead of building tall structures, you went the other way? In a recent paper, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) developed a metasurface that uses very deep, very narrow holes, rather than very tall pillars, to focus light to a single spot.
- A group of researchers led by scientists from the RIKEN Center for Emergent Matter Science and the University of Tokyo have created an unusual material — a soft crystal made of molecules known as a catenanes — that behaves in a novel way that could be used in applications such as films that capture carbon dioxide molecules. The research was published in Nature.
- Scientists hope that tiny sacs of material excreted by cells — so-called extracellular vesicles — can be used to deliver drugs inside the body. Researchers now show that these nano-bubbles can transport protein drugs that reduce inflammation caused by different diseases. The technique shows promising results in animal models.
- A team of scientists has discovered a new physical phenomenon: complex braided structures made of tiny magnetic vortices known as skyrmions. Skyrmions were first detected experimentally a little over a decade ago and have since been the subject of numerous studies, as well as providing a possible basis for innovative concepts in information processing that offer better performance and lower energy consumption. Furthermore, skyrmions influence the magnetoresistive and thermodynamic properties of a material. The discovery, therefore, has relevance for both applied and basic research.
- New research has found that pathogens that form biofilms can evolve to survive nanosilver treatment. The study is the first to demonstrate that long-term nanosilver treatment can increase the risk of recurrent infections.
- Electrical engineers have discovered that changing the physical shape of a class of materials commonly used in electronics can extend their use into the visible and ultraviolet parts of the electromagnetic spectrum. Already commercially used in detectors, lenses and optical fibers, chalcogenide glasses may now find a home in applications such as underwater communications, environmental monitoring, and biological imaging.
- A research team has been using high-intensity X-rays to observe a single catalyst nanoparticle at work. The experiment has revealed for the first time how the chemical composition of the surface of individual nanoparticles changes under reaction conditions, making it more active. This study marks an important step towards a better understanding of real, industrial catalytic materials.
- Researchers describe a highly accurate way to assemble multiple micron-scale optical devices extremely close together on a single chip. The approach could allow high-volume manufacturing of chip-based optical systems that would enable more compact optical communications devices and advanced imagers.
- Researchers led by Edwin Fohtung, an associate professor of materials science and engineering at Rensselaer Polytechnic Institute, have developed a new technique for revealing defects in nanostructured vanadium oxide, a widely used transition metal with many potential applications including electrochemical anodes, optical applications, and supercapacitors. In the research — which was published in an article in the Royal Chemical Society journal CrystEngComm, and also featured on the cover of the edition — the team detailed a lensless microscopy technique to capture individual defects embedded in vanadium oxide nanoflakes.
- A UCLA-led team of engineers and chemists has taken a major step forward in the development of microbial fuel cells — a technology that utilizes natural bacteria to extract electrons from organic matter in wastewater to generate electrical currents. A study detailing the breakthrough was recently published in Science.
- And more!
Nanotech Market
Nanotechnology deals with the ability to see, understand, measure, predict, produce or control matter at 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 potential to design risk-free and effective immunization strategies. In the post COVID-19 period, 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.
Latest News & Researches
A High Aspect Ratio Inverse-Designed Holey Metalens
by Soon Wei Daniel Lim, Maryna L. Meretska, Federico Capasso in Nano Letters
Metasurfaces are nanoscale structures that interact with light. Today, most metasurfaces use monolith-like nanopillars to focus, shape and control light. The taller the nanopillar, the more time it takes for light to pass through the nanostructure, giving the metasurface more versatile control of each color of light. But very tall pillars tend to fall or cling together. What if, instead of building tall structures, you went the other way?
In a recent paper, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) developed a metasurface that uses very deep, very narrow holes, rather than very tall pillars, to focus light to a single spot.
The new metasurface uses more than 12 million needle-like holes drilled into a 5-micrometer silicon membrane, about 1/20 the thickness of hair. The diameter of these long, thin holes is only a few hundred nanometers, making the aspect ratio — the ratio of the height to width — nearly 30:1.
It is the first time that holes with such a high aspect ratio have been used in meta-optics.
“This approach may be used to create large achromatic metalenses that focus various colors of light to the same focal spot, paving the way for a generation of high-aspect ratio flat optics, including large-area broadband achromatic metalenses,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper.
“If you tried to make pillars with this aspect ratio, they would fall over,” said Daniel Lim, a graduate student at SEAS and co-first author of the paper. “The holey platform increases the accessible aspect ratio of optical nanostructures without sacrificing mechanical robustness.”
Just like with nanopillars, which vary in size to focus light, the holey metalens has holes of varying size precisely positioned over the 2 mm lens diameter. The hole size variation bends the light towards the lens focus.
“Holey metasurfaces add a new dimension to lens design by controlling the confinement and propagation of light over a wide parameter space and make new functionalities possible,” said Maryna Meretska, a postdoctoral fellow at SEAS and co-first author of the paper. “Holes can be filled in with nonlinear optical materials, which will lead to multi-wavelength generation and manipulation of light, or with liquid crystals to actively modulate the properties of light.”
The metalenses were fabricated using conventional semiconductor industry processes and standard materials, allowing it to be manufactured at scale in the future.
An elastic metal–organic crystal with a densely catenated backbone
by Wenjing Meng, Shun Kondo, Takuji Ito, Kazuki Komatsu, Jenny Pirillo, Yuh Hijikata, Yuichi Ikuhara, Takuzo Aida & Hiroshi Sato in Nature
A group of researchers led by scientists from the RIKEN Center for Emergent Matter Science and the University of Tokyo have created an unusual material — a soft crystal made of molecules known as a catenanes — that behaves in a novel way that could be used in applications such as films that capture carbon dioxide molecules. The research was published in Nature.
A catenane is a type of molecule in which two or more rings interlock, like the rings that magicians use in their tricks, and can slide along each other, creating conformational changes that can give materials interesting properties. These types of molecules are found in nature, where they often act as molecular machines. Up until now, chains of catenanes — known as polycatenanes — have been created, but scientists have never explored three-dimensional crystals made up of these molecules.
The group set to explore this, and created a new material by growing crystals of catenanes and cobalt ions in a solvent. By carefully controlling the arrangements of catenane molecules through the formation of coordination bonds with the cobalt ions, they thought they might be able to create a three-dimensional network consisting almost solely of the catenanes, which work together to create novel functions.
The researchers then used single-crystal X-ray diffraction to examine the structure of the soft crystal.
While the researchers were essentially exploring what types of properties such materials might have, they were surprised by the results of the analysis. First, in agreement with their expectations, they found that by weight, catenanes made up more than 90 percent of the crystal. Interestingly, they found that it was porous, with holes that could adsorb solvent, or gaseous molecules, and that the pore shape changed as the guest molecules entered or exited the structure.
In addition, using a technique of nano-indentation to study the mechanical properties, they found that the material deformed easily when pressed mechanically — and that its Young’s modulus, an index of the ease with which it deforms, is comparable to that of polypropylene, a plastic used in packaging materials and other uses — and that, surprisingly, it returned to its original shape, without damage, upon removal of the force. Furthermore, when they tried to compress it, they found that it compressed most in a specific direction, and they were able to explain its deformable nature by showing that actually, the rings of the catenane molecules were slipping, allowing the material to compress.
According to Hiroshi Sato, who led the research, “We believe these results could lead to the creation of innovative porous materials that can adsorb and desorb gas molecules such as carbon dioxide simply by pinching and releasing them with our fingers.”
Amelioration of systemic inflammation via the display of two different decoy protein receptors on extracellular vesicles
by Dhanu Gupta, Oscar P.B Wiklander, André Görgens, Mariana Conceição, Giulia Corso, Xiuming Liang, YiqiSeow, SriramBalusu, Ulrika Feldin, BeklemBostancioglu, Rim Jawad, Doste R Mamand, Yi Xin Fiona Lee, et al. in Nature Biomedical Engineering
Scientists hope that tiny sacs of material excreted by cells — so-called extracellular vesicles — can be used to deliver drugs inside the body. Researchers at Karolinska Institutet now show that these nano-bubbles can transport protein drugs that reduce inflammation caused by different diseases. The technique, which is presented in Nature Biomedical Engineering, shows promising results in animal models.
Extracellular vesicles (EVs) are important in inter-cellular communication as carriers of biological signals. They are nanometre-sized membrane-coated packages excreted by cells that can deliver fatty acids, proteins and genetic material to different tissues.
The tiny bubbles are found naturally in bodily fluids, are able to pass through biological barriers, like the blood-brain barrier, and can be used as natural carriers of therapeutic substances. Consequently, EVs have garnered growing interest as potential drugs.
Using biomolecular techniques, researchers at Karolinska Institutet have coated the outer EV membrane with therapeutic proteins, more precisely receptors that bind to the inflammatory substances TNF-α and interleukin 6 (IL 6).
TNF-α and IL 6 form in the body under inflammatory conditions such as multiple sclerosis (MS) and inflammatory bowel disease (IBD), and play a key part in inflammation and subsequent tissue damage. This knowledge has resulted in the development of biological drugs that dampen the inflammatory response by inhibiting TNF-α and IL 6.
In the present study, the researchers tried to inhibit the inflammatory substances using therapeutic EVs that express on their membranes the receptors that bind to IL 6 and TNF-α.
“We used different methods to optimise the expression of receptors and tested the different variants of EVs in inflammatory cell models to identify which strategy gave the greatest anti-inflammatory effect,” says Dhanu Gupta, doctoral student at the Department of Laboratory Medicine, Karolinska Institutet, joint first author of the study with departmental colleague Oscar Wiklander.
The researchers then examined the effects of therapeutic EVs in three relevant inflammatory animal models for sepsis (blood poisoning), MS and IBD.
In the animal model for sepsis, treatment significantly improved survival, suggesting a successful dampening of the inflammatory response.
In the MS model, the researchers also found a significant reduction in the neurological symptoms seen in MS flare-ups. Treatment with EVs expressing both receptors also showed a significant increase in survival in mouse models for IBD.
“Our findings are an important step in the right direction and demonstrate that EVs can be a promising treatment for inflammation, but the technique also has great potential for many other diseases,” says Samir EL Andaloussi, principal investigator at the Department of Laboratory Medicine, Karolinska Institutet and joint last author of the study with Joel Nordin from the same department.
Magnetic skyrmion braids
by Fengshan Zheng, Filipp N. Rybakov, Nikolai S. Kiselev, Dongsheng Song, András Kovács, Haifeng Du, Stefan Blügel & Rafal E. Dunin-Borkowski in Nature Communications
A team of scientists from Germany, Sweden and China has discovered a new physical phenomenon: complex braided structures made of tiny magnetic vortices known as skyrmions. Skyrmions were first detected experimentally a little over a decade ago and have since been the subject of numerous studies, as well as providing a possible basis for innovative concepts in information processing that offer better performance and lower energy consumption. Furthermore, skyrmions influence the magnetoresistive and thermodynamic properties of a material. The discovery therefore has relevance for both applied and basic research.
Strings, threads and braided structures can be seen everywhere in daily life, from shoelaces to woolen pullovers, from plaits in a child’s hair to the braided steel cables that are used to support countless bridges. These structures are also commonly seen in nature and can, for example, give plant fibers tensile or flexural strength. Physicists at Forschungszentrum Jülich, together with colleagues from Stockholm and Hefei, have discovered that such structures exist on the nanoscale in alloys of iron and the metalloid germanium.
These nanostrings are each made up of several skyrmions that are twisted together to a greater or lesser extent, rather like the strands of a rope. Each skyrmion itself consists of magnetic moments that point in different directions and together take the form of an elongated tiny vortex. An individual skyrmion strand has a diameter of less than one micrometer. The length of the magnetic structures is limited only by the thickness of the sample; they extend from one surface of the sample to the opposite surface.
Earlier studies by other scientists had shown that such filaments are largely linear and almost rod-shaped. However, ultra-high-resolution microscopy investigations undertaken at the Ernst Ruska-Centre in Jülich the theoretical studies at Jülich’s Peter Grünberg Institute have revealed a more varied picture: the threads can in fact twist together to varying degrees. According to the researchers, these complex shapes stabilise the magnetic structures, making them particularly interesting for use in a range of applications.
“Mathematics contains a great variety of these structures. Now we know that this theoretical knowledge can be translated into real physical phenomena,” Jülich physicist Dr. Nikolai Kiselev is pleased to report. “These types of structures inside magnetic solids suggest unique electrical and magnetic properties. However, further research is needed to verify this.”
To explain the discrepancy between these studies and previous ones, the researcher points out that analyses using an ultra-high-resolution electron microscope do not simply provide an image of the sample, as in the case of, for example, an optical microscope. This is because quantum mechanical phenomena come into play when the high energy electrons interact with those in the sample.
“It is quite feasible that other researchers have also seen these structures under the microscope, but have been unable to interpret them. This is because it is not possible to directly determine the distribution of magnetization directions in the sample from the data obtained. Instead, it is necessary to create a theoretical model of the sample and to generate a kind of electron microscope image from it,” explains Kiselev. “If the theoretical and experimental images match, one can conclude that the model is able to represent reality.” In ultra-high-resolution analyses of this kind, Forschungszentrum Jülich with its Ernst Ruska-Centre counts as one of the leading institutions worldwide.
Evolution of biofilm-forming pathogenic bacteria in the presence of nanoparticles and antibiotic: adaptation phenomena and cross-resistance
by Riti Mann, Amy Holmes, Oliver McNeilly, Rosalia Cavaliere, Georgios A. Sotiriou, Scott A. Rice, Cindy Gunawan in Journal of Nanobiotechnology
New research from the University of Technology Sydney (UTS) has found that pathogens that form biofilms can evolve to survive nanosilver treatment. The study is the first to demonstrate that long-term nanosilver treatment can increase the risk of recurrent infections.
Nanosilver is a potent antimicrobial that is currently used in medical devices such as internal catheters, as well as wound dressings, in particular for burn wounds, to fight or prevent infections. It is also one of the most commercialised antimicrobial nanoparticles, and has been incorporated into consumer products from personal care products, such as soaps and toothpaste, to washing machines and fridges, even children’s products, such as in kids socks to prevent odour.
Researchers at UTS’s iThree Institute studied nanosilver adaptation phenomena in the bacterium Pseudomonas aeruginosa, in its biofilm form of growth, and observed a novel adaptation mechanism not seen in previous planktonic growth studies. Following prolonged treatment, nanosilver killed 99.99% of the bacterial population with only 0.01% cells surviving for longer. This minute fraction of ‘persisters’ resumed normal growth upon discontinuation of the nanoparticle treatment.
“Understanding how pathogens develop adaptation mechanisms to nanoparticles is key in our effort to overcome the phenomena, including in biofilms as the major form of growth of pathogenic bacteria. This is to protect the efficacy of important alternative antimicrobials, like nanosilver, in this era of increasing antibiotic resistance,” said lead author Dr Cindy Gunawan.
The study first author, Dr Riti Mann, said the research findings will also help develop strategies on the better management of nanoparticle use as antimicrobials, in particular those that involving long-term exposures.
“Based on this study, we recommend monitoring patients not only during, but also after prolonged use of nanoparticle treatment for safeguarding against recurrent infections.
“The scientific evidence that bacteria can adapt to nanoparticles means we need effective regulation of the use of nanoparticles, with clear risks versus benefits assessment and clear antimicrobial targets. With limited development of new effective antibiotics over the past decades, we need to preserve the efficacy of the alternative antimicrobials to fight untreatable infections, saving lives and billions of dollars in healthcare,” said Dr Gunawan.
The bacterium used in the study, Pseudomonas aeruginosa, often attach themselves on catheter surfaces, as well as to wounds and lung linings, growing biofilms, which can be difficult to control.
Near-infrared to ultra-violet frequency conversion in chalcogenide metasurfaces
by Jiannan Gao, Maria Antonietta Vincenti, Jesse Frantz, Anthony Clabeau, Xingdu Qiao, Liang Feng, Michael Scalora, Natalia M. Litchinitser in Nature Communications
Electrical engineers at Duke University have discovered that changing the physical shape of a class of materials commonly used in electronics and near- and mid-infrared photonics — chalcogenide glasses — can extend their use into the visible and ultraviolet parts of electromagnetic spectrum. Already commercially used in detectors, lenses and optical fibers, chalcogenide glasses may now find a home in applications such as underwater communications, environmental monitoring and biological imaging.
As the name implies, chalcogenide glasses contain one or more chalcogens — chemical elements such as sulfur, selenium and tellurium. But there’s one member of the family they leave out: oxygen. Their material properties make them a strong choice for advanced electronic applications such as optical switching, ultra-small direct laser writing (think tiny rewritable CDs) and molecular fingerprinting. But because they strongly absorb wavelengths of light in the visible and ultraviolet parts of electromagnetic spectrum, chalcogenide glasses have long been constrained to the near- and mid-infrared with respect to their applications in photonics.
“Chalcogenides have been used in the near- and mid-IR for a long time, but they’ve always had this fundamental limitation of being lossy at visible and UV wavelengths,” said Natalia Litchinitser, professor of electrical and computer engineering at Duke. “But recent research into how nanostructures affect the way these materials respond to light indicated that there might be a way around these limitations.”
In recent theoretical research into the properties of gallium arsenide (GaAs), a semiconductor commonly used in electronics, Litchinitser’ s collaborators, Michael Scalora of the US Army CCDC Aviation and Missile Center and Maria Vincenti of the University of Brescia predicted that nanostructured GaAs might respond to light differently than its bulk or even thin film counterparts. Because of the way that high intensity optical pulses interact with the nanostructured material, very thin wires of the material lined up next to one another might create higher-order harmonic frequencies (shorter wavelengths) that could travel through them.
Imagine a guitar string that is tuned to resonate at 256 Hertz — otherwise known as middle C. The researchers were proposing that if fabricated just right, this string when plucked might also vibrate at frequencies one or two octaves higher in small amounts.
Litchinitser and her PhD student Jiannan Gao decided to see if the same might be true for chalcogenide glasses. To test the theory, colleagues at the Naval Research Laboratory deposited a 300-nanometer-thin film of arsenic trisulfide onto a glass substrate that was next nanostructured using electron beam lithography and reactive ion etching to produce arsenic trisulfide nanowires of 430 nanometers wide and 625 nanometers apart.
Even though arsenic trisulfide completely absorbs light above 600 THz — roughly the color of cyan — the researchers discovered their nanowires were transmitting tiny signals at 846 THz, which is squarely in the ultraviolet spectrum.
“We found that illuminating a metasurface made of judiciously designed nanowires with near-infrared light resulted in generation and transmission of both the original frequency and its third harmonic, which was very unexpected because the third harmonic falls into the range where the material should be absorbing it,” Litchinitser said.
This counterintuitive result is due to the effect of nonlinear third harmonic generation and its “phase locking” with the original frequency. “The initial pulse traps the third harmonic and sort of tricks the material into letting them both pass through without any absorption,” Litchinitser said.
Moving forward, Litchinitser and her colleagues are working to see if they can engineer different shapes of chalcogenides that can carry these harmonic signals even better than the initial nanostrips. For example, they believe that pairs of long, thin, Lego-like blocks spaced certain distances apart might create a stronger signal at both third and second harmonic frequencies. They also predict that stacking multiple layers of these metasurfaces on top of one another might enhance the effect.
If successful, the approach could unlock a wide range of visible and ultraviolet applications for popular electronic material and mid-infrared photonic materials that have long been shut out of these higher frequencies.
Single alloy nanoparticle x-ray imaging during a catalytic reaction
by Young Yong Kim, Thomas F. Keller, Tiago J. Goncalves, Manuel Abuin, Henning Runge, Luca Gelisio, Jerome Carnis, Vedran Vonk, Philipp N. Plessow, Ivan A. Vartaniants, Andreas Stierle in Science Advances
A DESY-led research team has been using high-intensity X-rays to observe a single catalyst nanoparticle at work. The experiment has revealed for the first time how the chemical composition of the surface of an individual nanoparticle changes under reaction conditions, making it more active. The team led by DESY’s Andreas Stierle is presenting its findings in the journal Science Advances. This study marks an important step towards a better understanding of real, industrial catalytic materials.
Catalysts are materials that promote chemical reactions without being consumed themselves. Today, catalysts are used in numerous industrial processes, from fertiliser production to manufacturing plastics. Because of this, catalysts are of huge economic importance. A very well-known example is the catalytic converter installed in the exhaust systems of cars. These contain precious metals such as platinum, rhodium and palladium, which allow highly toxic carbon monoxide (CO) to be converted into carbon dioxide (CO2) and reduce the amount of harmful nitrogen oxides (NOx).
“In spite of their widespread use and great importance, we are still ignorant of many important details of just how the various catalysts work,” explains Stierle, head of the DESY NanoLab. “That’s why we have long wanted to study real catalysts while in operation.” This is not easy, because in order to make the active surface as large as possible, catalysts are typically used in the form of tiny nanoparticles, and the changes that affect their activity occur on their surface.
In the framework of the EU project Nanoscience Foundries and Fine Analysis (NFFA), the team from DESY NanoLab has developed a technique for labelling individual nanoparticles and thereby identifying them in a sample.
“For the study, we grew nanoparticles of a platinum-rhodium alloy on a substrate in the lab and labelled one specific particle,” says co-author Thomas Keller from DESY NanoLab and in charge of the project at DESY. “The diameter of the labelled particle is around 100 nanometres, and it is similar to the particles used in a car’s catalytic converter.” A nanometre is a millionth of a millimetre.
Using X-rays from the European Synchrotron Radiation Facility ESRF in Grenoble, France, the team was not only able to create a detailed image of the nanoparticle; it also measured the mechanical strain within its surface.
“The surface strain is related to the surface composition, in particular the ratio of platinum to rhodium atoms,” explains co-author Philipp Pleßow from the Karlsruhe Institute of Technology (KIT), whose group computed strain as a function of surface composition. By comparing the observed and computed facet-dependent strain, conclusions can be drawn concerning the chemical composition at the particle surface. The different surfaces of a nanoparticle are called facets, just like the facets of a cut gemstone.
When the nanoparticle is grown, its surface consists mainly of platinum atoms, as this configuration is energetically favoured. However, the scientists studied the shape of the particle and its surface strain under different conditions, including the operating conditions of an automotive catalytic converter. To do this, they heated the particle to around 430 degrees Celsius and allowed carbon monoxide and oxygen molecules to pass over it.
“Under these reaction conditions, the rhodium inside the particle becomes mobile and migrates to the surface because it interacts more strongly with oxygen than the platinum,” explains Pleßow. This is also predicted by theory.
“As a result, the surface strain and the shape of the particle change,” reports co-author Ivan Vartaniants, from DESY, whose team converted the X-ray diffraction data into three-dimensional spatial images. “A facet-dependent rhodium enrichment takes place, whereby additional corners and edges are formed.”
The chemical composition of the surface, and the shape and size of the particles have a significant effect on their function and efficiency. However, scientists are only just beginning to understand exactly how these are connected and how to control the structure and composition of the nanoparticles. The X-rays allow researchers to detect changes of as little as 0.1 in a thousand in the strain, which in this experiment corresponds to a precision of about 0.0003 nanometres (0.3 picometres).
“We can now, for the first time, observe the details of the structural changes in such catalyst nanoparticles while in operation,” says Stierle, Lead Scientist at DESY and professor for nanoscience at the University of Hamburg. “This is a major step forward and is helping us to understand an entire class of reactions that make use of alloy nanoparticles.” Scientists at KIT and DESY now want to explore this systematically at the new Collaborative Research Centre 1441, funded by the German Research Foundation (DFG) and entitled “Tracking the Active Sites in Heterogeneous Catalysis for Emission Control (TrackAct).”
“Our investigation is an important step towards analysing industrial catalytic materials,” Stierle points out. Until now, scientists have had to grow model systems in the laboratory in order to conduct such investigations. “In this study, we have gone to the limit of what can be done. With DESY’s planned X-ray microscope PETRA IV, we will be able to look at ten times smaller individual particles in real catalysts, and under reaction conditions.”
Spatially dense integration of micron-scale devices from multiple materials on a single chip via transfer-printing
by Dimitars Jevtics, Jack A. Smith, John McPhillimy, Benoit Guilhabert, Paul Hill, Charalambos Klitis, Antonio Hurtado, Marc Sorel, Hark Hoe Tan, Chennupati Jagadish, Martin D. Dawson, Michael J. Strain in Optical Materials Express
Researchers have developed a highly accurate way to assemble multiple micron-scale optical devices extremely close together on a single chip. The new approach could one day allow high-volume manufacturing of chip-based optical systems that would enable more compact optical communications devices and advanced imagers.
“The development of electronics that are based on silicon transistors has enabled increasingly more powerful and flexible systems on a chip,” Dimitars Jevtics from the University of Strathclyde in the UK. “Optical systems on a chip, however, require integration of different materials on a single chip and, therefore, have not seen the same development in scale as silicon electronics.”
Jevtics and colleagues describe their new transfer printing process and demonstrate its ability to place devices made of multiple materials on a single chip, all integrated within a footprint similar in size to the devices themselves. While other methods are typically limited to a single material, this new approach provides a toolbox of materials from which future systems designers can draw.
“On-chip optical communications, for example, will require the assembly of optical sources, channels and detectors onto sub-assemblies that can be integrated with silicon chips,” said Jevtics. “Our transfer printing process could be scaled up to integrate thousands of devices made from different materials onto a single wafer. This would enable micron-scale optical devices to be incorporated into future computer chips for high-density communications or into lab-on-a-chip bio-sensing platforms.”
One of the biggest challenges for assembling multiple devices on a chip is trying to place them very close together without disturbing devices that are already on the chip. To accomplish this, the researchers developed a method based on reversible adhesion in which a device is picked up and released from its growth substrate and placed onto a new surface.
The new method uses a soft polymer stamp mounted on a robotic motion control stage to pick up an optical device from the substrate on which it was made. The substrate onto which it will be placed is then positioned under the suspended device and accurately aligned using a microscope. Once aligned properly, the two surfaces are brought into contact, which releases the device from the polymer stamp and deposits it onto the target surface. Advances in accurate micro-assembly robotics, nanofabrication techniques and microscopy image processing helped make this approach possible.
“By carefully designing the geometry of the stamp to match the device and controlling the stickiness of the polymer material, we can engineer whether a device will be picked up or released,” said Jevtics. “When optimized, this process does not induce any damage and can be scaled up using automation to be compatible with wafer-scale manufacturing.”
To demonstrate the new technique, the researchers integrated aluminum gallium arsenide, diamond and gallium nitride optical resonators onto a single chip. These optical resonators exhibited good optical transmission, demonstrating that the integration worked well.
They also used the printing approach to create semiconductor nanowire lasers by placing nanowires onto host surfaces in spatially dense arrangements. Scanning electronic microscopy measurements of the separation between the nanowires demonstrated a spatial accuracy in the 100-nanometer range. By placing semiconductor nanowires on silicon dioxide, they were able to create a multi-wavelength nanolaser system.
“As a manufacturing technique, this printing approach is not limited to optical devices,” said Jevtics. “We hope that electronics specialists will also see possibilities for how it could be applied in future systems.”
As a next step, the researchers are working to replicate these results with larger numbers of devices to show that it works at larger scales. They also want to combine their transfer printing approach with an automated alignment technique they developed previously to enable rapid measurement, selection and transfer of hundreds of isolated devices for applications in imaging and hybrid optical circuits.
Silver nanoparticles boost charge-extraction efficiency in Shewanella microbial fuel cells
by Bocheng Cao, Zipeng Zhao, Lele Peng, Hui-Ying Shiu, Mengning Ding, Frank Song, Xun Guan, Calvin K. Lee, Jin Huang, Dan Zhu, Xiaoyang Fu, Gerard C. L. Wong, Chong Liu, Kenneth Nealson, Paul S. Weiss, Xiangfeng Duan and Yu Huang in Science
A UCLA-led team of engineers and chemists has taken a major step forward in the development of microbial fuel cells — a technology that utilizes natural bacteria to extract electrons from organic matter in wastewater to generate electrical currents.
“Living energy-recovery systems utilizing bacteria found in wastewater offer a one-two punch for environmental sustainability efforts,” said co-corresponding author Yu Huang, a professor and chair of the Materials Science and Engineering Department at the UCLA Samueli School of Engineering. “The natural populations of bacteria can help decontaminate groundwater by breaking down harmful chemical compounds. Now, our research also shows a practical way to harness renewable energy from this process.”
The team focused on the bacteria genus Shewanella, which have been widely studied for their energy-generation capabilities. They can grow and thrive in all types of environments — including soil, wastewater and seawater — regardless of oxygen levels.
“Living energy-recovery systems utilizing bacteria found in wastewater offer a one-two punch for environmental sustainability efforts.” — Yu Huang
Shewanella species naturally break down organic waste matter into smaller molecules, with electrons being a byproduct of the metabolic process. When the bacteria grow as films on electrodes, some of the electrons can be captured, forming a microbial fuel cell that produces electricity.
However, microbial fuel cells powered by Shewanella oneidensis have previously not captured enough currents from the bacteria to make the technology practical for industrial use. Few electrons could move quickly enough to escape the bacteria’s membranes and enter the electrodes to provide sufficient electrical currents and power.
To address this issue, the researchers added nanoparticles of silver to electrodes that are composed of a type of graphene oxide. The nanoparticles release silver ions, which bacteria reduce to silver nanoparticles using electrons generated from their metabolic process and then incorporate into their cells. Once inside the bacteria, the silver particles act as microscopic transmission wires, capturing more electrons produced by the bacteria.
“Adding the silver nanoparticles into the bacteria is like creating a dedicated express lane for electrons, which enabled us to extract more electrons and at faster speeds,” said Xiangfeng Duan, the study’s other corresponding author and a professor of chemistry and biochemistry at UCLA.
With greatly improved electron transport efficiency, the resulting silver-infused Shewanella film outputs more than 80% of the metabolic electrons to an external circuit, generating power of 0.66 milliwatts per square centimeter — more than double the previous best for microbial-based fuel cells.
With the increased current and improved efficiencies, the study, which was supported by the Office of Naval Research, showed that fuel cells powered by silver-Shewanella hybrid bacteria may pave the way for sufficient power output in practical settings.
Imaging defects in vanadium(iii) oxide nanocrystals using Bragg coherent diffractive imaging
by Zachary Barringer et al. in CrystEngComm
Researchers led by Edwin Fohtung, an associate professor of materials science and engineering at Rensselaer Polytechnic Institute, have developed a new technique for revealing defects in nanostructured vanadium oxide, a widely used transition metal with many potential applications including electrochemical anodes, optical applications, and supercapacitors. In the research — which was published in an article in the Royal Chemical Society journal CrystEngComm, and also featured on the cover of the edition — the team detailed a lensless microscopy technique to capture individual defects embedded in vanadium oxide nanoflakes.
“These observations could help explain the origin of defects in structure, crystallinity, or composition gradients observed near grain boundaries in other thin-film or flake technologies,” said Fohtung, an expert in novel synchrotron scattering and imaging techniques. “We believe that our work has the potential to change how we view the growth and non-destructive three-dimensional imaging of nanomaterials.”
Vanadium oxide is currently used in many technological fields such as energy storage, and can also be used in constructing field-effect transistors owing to metal insulating transition behavior that can be adjusted with an electric field. However, strain and defects in the material can alter its functionality, creating the need for non-destructive techniques to detect those potential flaws.
The team developed a technique based on coherent X-ray diffraction imaging. This technique relies on a type of circular particle accelerator known as a synchrotron. Synchrotrons work by accelerating electrons through sequences of magnets until they reach almost the speed of light. These fast-moving electrons produce very bright intense light, predominantly in the X-ray region. This synchrotron light, as it is named, is millions of times brighter than light produced from conventional sources and 10 billion times brighter than the sun. Fohtung and his students have successfully used this light to develop techniques and capture minute matter such as atoms and molecules and now defects. When used to probe crystalline materials, this technique is known as Bragg coherent diffraction imaging (BCDI). In their research, the team used a BCDI approach to reveal nanoscale properties of electron densities in crystals, including strain and lattice defects.
MISC
Subscribe to Paradigm!
Medium. Twitter. Telegram. Telegram Chat. Reddit. LinkedIn.
Main sources
Research articles
