Biocompatible energy storage device that runs on body fluids
Korean researchers have developed an implantable supercapacitor that could be used to power future medical devices
Implantable devices aren’t new – pacemakers, which use electrical impulses to regulate the beating of a heart – have improved the quality of life for millions of people since the 1960s. But they can be rejected by a patient’s immune system, and their battery needs to be replaced every 6-10 years. With people living longer than ever, there’s a growing need for reliable, low-cost implantable devices. In particular, the race is on to improve their biocompatibility and to find a way to power them. In both cases, a Korean-UK collaboration may already be a step ahead.
Writing in a recent issue of Nano Energy [DOI: 10.1016/j.nanoen.2017.02.018], they report on the development of a novel energy storage device that operates in-vivo, and makes use of the ions naturally present in the body. Rather than batteries or fuel cells, they looked at supercapacitors. But unlike the architecture used in a traditional capacitor, here the electrolyte is not packaged between the electrodes. Rather, body fluids that contain various ions – like Na+, K+, Ca2+, Cl-, and HCO3- – act as an aqueous electrolyte.
This choice could limit the operating voltage of the capacitor, so to improve the device’s energy density, the team tested different combinations of positive and negative electrode materials. The toxicity of MnO2 – a well-established anode material – was found to be too high for use in this implantable device. But when tested in vitro with two types of fibroblast-like cells, a composite of MnO2 nanoparticles, embedded in multi-walled carbon nanotubes (MWCNTs), had a much lower toxicity, and so was used to form the anode. For the cathode, they used phosphidated activated carbon (pAC), which displayed excellent cell viability in toxicity tests.
These active materials were deposited onto a flexible tantalum substrate, and surgically implanted into the hypodermis of a rodent. A small solar panel was used to supply energy to the implanted capacitor. The electrical characteristics of this MnO2-MWCNT/body fluid/ pAC capacitor were impressive too – after 1000 charge-discharge cycles, the device retained 99% of its initial capacitance, suggesting it could be suitable for long-term use.
The authors believe that this study “…is the first to describe an implanted electrode that delivers stored electricity to the interior of a mammal.” If so, it could be a step on the way to designing an energy storage system for use in implantable medical devices for humans.
J. S. Chae, N-S Heo, C. H. Kwak, W-S Cho, G. H. Seol, W-S Yoon, H-K Kim, D. J. Fray, A.T. Ezhil Vilian, Y-K Han, Y. S. Huh, K. C. Roh. “A biocompatible implant electrode capable of operating in body fluids for energy storage devices” Nano Energy 34 (2017) 86–92. DOI: 10.1016/j.nanoen.2017.02.018
Diamond Fiberglass acquires Fibrex Corp
Diamond Fiberglass, a US manufacturer of glass fiber reinforced plastic vessels, has closed its asset acquisition of Fibrex Corporation, a composite chemical pipe, header systems and duct manufacturer.
Fibrex will be integrated into Diamond Fiberglass. Fibrex will continue to fabricate from its current location in Burlington, WA with the same production management and staff. Corporate functions will be moved to Victoria, Texas, USA.
‘The addition of Fibrex to Diamond Fiberglass' portfolio of custom, engineer-to-order composite equipment represents another important strategic expansion for our company,’ said Don Porr, president of Diamond Fiberglass. ‘The addition of the Fibrex product line, including the IntegraLine and IntegraHeader products will supplement our growing need for FRP piping systems. These products will benefit our customers who seek a single source supply for the design, fabrication and field installation of FRP/GRP engineered pipe.’
This story uses material from Diamond Fiberglass, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Carbon fiber specialist named to standards board
Jim Wright, vice president of operations for US-based Proof Research, a company that designs and manufactures carbon fiber composite firearms for military and commercial applications, has been named to the National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board (NIST MEP).
NIST MEP is a public-private partnership with centers in all 50 states and Puerto Rico dedicated to serving small and medium-sized manufacturers. Last year, MEP centers interacted with 25,445 manufacturers, leading to US$9.3 billion in new and retained sales, US$1.4 billion in cost savings, US$3.5 billion in new client investments, and the creation and retention of more than 86,602 jobs.
‘NIST’s Manufacturing Extension Partnership helps lead and define the United States as a world leader in manufacturing,’ Wright said. ‘I am truly humbled by the diversity and experience of the existing board members and am very excited about the opportunity to work within this team to advance manufacturing in the United States.’
This story uses material from NIST MEP, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Renishaw installs AM system at aerospace center
Renishaw’s RenAM 500M system has been installed at the Centre for Advanced Aerospace Technologies (CATEC) in Seville, Spain. It is the first installation of this new machine in the Iberian Peninsula.
CATEC is a technology center that develops R&D activities within the aerospace sector in Andalusia.
The RenAM 500M is a laser powder bed fusion additive manufacturing (AM) system designed specifically for the production of metal components on the factory floor. It features automated powder and waste handling systems.
‘CATEC is actively working on the development of aerospace applications with additive manufacturing technology, covering all the stages of the production cycle to support companies in the implementation of this technology,’ said Fernando Lasagni, head of materials and processes development at CATEC. ‘This involves parameterizing various aeronautical alloys so that they can be manufactured to the highest quality standards. Due to the industrial strength of the RenAM 500M system, its increased manufacturing capacity (in volume) and the high power of the laser (500W), the short-term objective will be to achieve manufacturing parameters that ensure the aeronautical quality of the materials.’
Renishaw has installed its latest RenAM 500M additive manufacturing system at CATEC.
This story uses material from Renishaw, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Specially selected papers from Applied Materials Today
To celebrate the latest CiteScoreTracker value of 5.57 for Applied Materials Today, the Editor-in-Chief Dr Martin Pumera has specially selected three articles to highlight. These articles are now free to access for the next six months.
- Two dimensional and layered transition metal oxides, Kourosh Kalantar-zadeh, Jian Zhen Ou, Torben Daeneke, Arnan Mitchell, Takayoshi Sasaki, Michael S. Fuhrer
- Assessing extraterrestrial regolith material simulants for in-situ resource utilisation based 3D printing, Athanasios Goulas, Jon G.P. Binner, Russell A. Harris, Ross J. Friel
- Nitrogen-doped mesoporous carbon thin film for binder-free supercapacitor, Pan Hu, Donghui Meng, Guohua Ren, Rongxin Yan, Xinsheng Peng
CiteScore is a new standard that gives a comprehensive, transparent and current view of a journal’s impact. CiteScore metrics calculate the citations from all documents in year one to all documents published in the prior three years for a title. The next annual CiteScore calculation is scheduled for Spring 2017.
Applied Materials Today is a multi-disciplinary, rapid-publication journal focused on cutting edge applications of novel materials. The latest CiteScoreTracker value demonstrates the high quality of the original research articles and reviews published in the journal.
More information on CiteScore metrics can be found here.
To submit to Applied Materials Today, visit the journal homepage.
CF compound used for Prius door frame
Mitsubishi Rayon’s carbon fiber sheet molding compound (SMC) has been adopted for the rear door frame of the new Prius PHV, launched by Toyota Motor Corporation.
In line with the tightening of fuel efficiency regulations and carbon dioxide emission controls, interest in vehicle weight reduction has been growing in the automotive market, the company says. However, the scope of application of carbon fiber reinforced plastics (CFRP) has been limited to models such as luxury cars.
Mitsubishi says that its SMC can be processed into components in a short period of time, i.e. roughly 2 to 5 minutes, by press molding. When compared to prepreg intermediate materials (uncut carbon fiber fabric impregnated with resin), this SMC features high formability for molding complicated shaped parts. It also exhibits close-to-uniform mechanical properties. This allows engineers to readily use the carbon fiber material and achieve lighter components with higher strength, according to the company.
This story uses material from Mitsubishi, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Huntsman reveals future of composites in automotive
Huntsman Advanced Materials has conducted a survey covering the use of composites in the automotive industry.
The survey involved conducting in-depth interviews across the world with more than 160 respondents, including automotive suppliers, original equipment manufacturers (OEMs) and engineers, the company said.
The results reportedly show that CO2 emissions and fuel efficiency regulations are key drivers for the use of lighter weight materials, but affordability and the long-term availability of carbon fiber are preventing more manufacturers from using composites in mass production. According to respondents, fiber-reinforced composites will become more widely adopted by the premium and sports automotive sector over the next ten years and will likely reach mainstream car segments in the longer term. The development of electronic cars will also influence the use of composites, as manufacturers look to develop lightweight and more energy-efficient models.
‘Carrying out this survey was a key investment into understanding the dynamics of the automotive industry, and allowed us to gain valuable insights that can channel our innovation funnel towards technical solutions needed by the industry,’ said Nastassja Kelley, marketing director EMEAI, at Huntsman Advanced Materials. ‘Thanks to the detailed responses of our customers, we can better understand the drivers and challenges that they face in using composites. For example, according to the results, a lack of understanding around how best to design with composites is an important factor in fiber-reinforced plastic composites not reaching mass production scale.’
This story uses material from Huntsman, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Caterpillar continues move into 3D printing
Additive manufacturing (AM) specialist FIT AG and Caterpillar Inc, the global construction equipment company, have entered into a strategic alliance agreement. FIT AG and Caterpillar plan to focus on design and printing of aluminum and titanium parts in the heavy equipment manufacturing arena.
According to Caterpillar, the relationship will complement its ongoing work in the company’s additive manufacturing factory.
‘Not only will Caterpillar now have access to FIT AG’s cutting-edge technologies in additive manufacturing but this alliance will also help accelerate our adoption of 3D printing,’ said Stacey DelVecchio, Caterpillar Additive Manufacturing project manager.
The strategic alliance between FIT AG and Caterpillar will have an initial three-year term and will evolve to the next step based on the success of the alliance.
This story uses material from Caterpillar, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Divergent and SLM join forces for automotive AM
Divergent 3D, which makes 3D printing software, has entered into a strategic development partnership with SLM Solutions Group, a manufacturer of 3D metal printing equipment. The companies plan to develop specific hardware and software for high-volume production of vehicles incorporating additive manufacturing (AM).
Divergent 3D’s software-hardware platform enabled by 3D metal printing is designed to improve th economics and environmental impact of designing and manufacturing complex structures such as cars.
Additive manufacturing has long been used throughout the auto industry for small-scale pilot programs focused on developing individual 3D-printed components for production. Divergent 3D and SLM Solutions’ objective is to build lighter, structurally safe, more cost-efficient and environmentally responsible automobiles.
‘By working together with Divergent, we can help to provide manufacturers with the tools to build more profitable, innovative and environmentally sustainable vehicles while dramatically reducing manufacturing capital cost and providing almost unlimited design flexibility,’ said Hans-Joachim Ihde, chairman of the supervisory board and founder of SLM Solutions.
This story uses material from SLM, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Now the plastic twain shall meet
There is currently no efficient technology that can repurpose a plastics waste stream containing polyethylene (PE) and polypropylene (PP), these two polymers, which account for two-thirds of the world's plastics, are too different. Now, Geoffrey Coates and his colleagues at Cornell University, Ithaca, New York, have collaborated with the Bates group from the University of Minnesota, Minneapolis, USA, to develop a multiblock polymer additive to remedy this situation. A small amount of their additive used in a novel process can bring PE and PP together at last to create a mechanically tough recycled polymer and avoid the need for a costly separation to recycle the two separately. [G Coates et al., Science (2017); DOI: 10.1126/science.aah5744]
Fundamentally, despite being hydrocarbons PE and PP are immiscible. The common grades of PE and isotactic PP in packaging and countless other products do not adhere or blend and so represented an intractable recycling problem. Coates and postdoctoral researcher James Eagan working with Anne LaPointe and former Cornell visiting scientist Rocco DiGirolamo think they may have unraveled an answer ending years of efforts on the part of polymer scientists around the globe. Just a dash of their tetrablock polymer, which contains alternating PE and PP segments, is sufficient to allow the materials to blend.
The team chemically welded together two strips of plastic using different multi-block polymers as adhesives. Mechanical stress tests failed with low molecular weight diblock polymer welds relatively quickly but the group's tetrablock additive made a composite stronger than the individual plastic strips, which themselves broke under stress.
"People have done things like this before," Coates concedes, "but they'll typically use 10 percent of a soft material, so you don't get the nice plastic properties, you get something that's not quite as good as the original material," he explains. "What's exciting about this," he adds, "is that we can go to as low as 1 percent of our additive, and you get a plastic alloy that really has super-great properties." Not only does this tetrablock polymer show promise for improving recycling, Eagan adds, it could spawn a whole new class of mechanically tough polymer blends. "If you could make a milk jug with 30 percent less material because it's mechanically better, think of the sustainability of that," Eagan enthuses. "You're using less plastic, less oil, you have less stuff to recycle, you have a lighter product that uses less fossil fuel to move it."
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".
Perovskite nanofiber could help store renewable energy
One of the keys to building electric cars that can travel longer distances and to powering more homes with renewable energy is developing efficient and highly capable energy storage systems. Materials researchers at Georgia Institute of Technology have now created a nanofiber that could help produce the next generation of rechargeable batteries and increase the efficiency of hydrogen production from water electrolysis.
In a paper published in Nature Communications, the researchers describe their development of a double perovskite nanofiber that can be used as a highly efficient catalyst for ultrafast oxygen evolution reactions (OER). This is one of the central electrochemical processes in hydrogen-based energy and the newer metal-air batteries.
"Metal-air batteries, such as those that could power electric vehicles in the future, are able to store a lot of energy in a much smaller space than current batteries," explained Meilin Liu, a professor in the Georgia Tech School of Materials Science and Engineering. "The problem is that the batteries lack a cost-efficient catalyst to improve their efficiency. This new catalyst will improve that process."
The new catalytic nanofiber possesses a perovskite crystal structure. "This unique crystal structure and the composition are vital to enabling better activity and durability for the application," Liu said.
The perovskite oxide fiber is fabricated via an electrospinning process, during which the researchers used a technique called composition tuning – or ‘co-doping’ – to improve the intrinsic activity of the catalyst by approximately 4.7 times. The fiber is just 20nm in diameter, which is the thinnest diameter yet reported for electrospun perovskite oxide nanofibers.
The researchers found that the new nanofiber showed markedly enhanced OER capability when compared with existing catalysts. The new nanofiber's mass-normalized catalytic activity was about 72 times greater than the initial powder catalyst, and 2.5 times greater than iridium oxide, which is considered a state of the art catalyst by current standards.
That increase in catalytic activity comes in part from the larger surface area achieved with nanofibers, the researchers said. Synthesizing the perovskite structure into a nanofiber also boosted its intrinsic activity, which improved how efficiently it worked as a catalyst for OER.
"This work not only represents an advancement in the development of highly efficient and durable electrocatalysts for OER but may also provide insight into the effect of nanostructures on the intrinsic OER activity," the researchers wrote.
Beyond its use in the development of rechargeable metal-air batteries, the new catalyst could also lead to more efficient fuel cell technologies that could aid in the creation of renewable energy systems.
"Solar, wind, geothermal – those are becoming very inexpensive today. But the trouble is those renewable energies are intermittent in nature," Liu said. "When there is no wind, you have no power. But what if we could store the energy from the sun or the wind when there's an excess supply. We can use that extra electricity to produce hydrogen and store that energy for use when we need it."
According to Liu, that's where the new nanofiber catalysts could make a difference. "To store that energy, batteries are still very expensive," he said. "We need a good catalyst in order for the water electrolysis to be efficient. This catalyst can speed up electrochemical reactions in water splitting or metal air batteries."
This story is adapted from material from Georgia Institute of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.
Diab signs long-term contract with cabin interiors specialist
Diehl Aircabin, a producer of cabin interiors, for commercial aviation has signed a long-term agreement with Diab for the supply of Divinycell F and other structural foam core materials for cabin interior applications.
‘It has been a pleasure to work with Diehl, and we are very proud of being a supplier and partner with Diehl Aircabin,’ said Lennart Thalin, Diab executive group vice president, sales and segments.
This story uses material from DIAB, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Sinterite installs process development furnace at research center
Sinterite, a Gasbarre Furnace company, has installed a continuous belt furnace at the Air Liquide Shanghai Research & Technology Center in China. Air Liquide has recently constructed a 12,000 m² advanced technology center in Shanghai, China. The technology center houses offices, showroom, laboratories and a pilot demonstration department. The Sinterite Furnace will be used for development of the client’s sintering, brazing, annealing and heat treatment applications.
The Sinterite Furnace is a nine-zone 305 mm wide continuous belt atmosphere furnace design with a range of processing capabilities. The electrically-heated furnace is capable to 1150°C (2100°F) and rapid cooling with the Sinterite HyperCooler. Multiple configurations of atmosphere gas setups are possible (H2, N2, NH3, O2, CO2). The furnace, being primarily designed for the powder metallurgy sintering process, has dedicated delubrication, sintering and cooling sections. There are numerous possibilities available for delubrication, sintering and cooling process setups. The Sinterite HyperCooler inline rapid cooling system provides for the ability to employ traditional protected atmosphere cooling and sinter-hardening of compacted powder metal components.
This story uses material from Sinterite, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Developing amorphous metals for AM
Investor AM Ventures (AMV) and Exmet AB, which works with amorphous metal alloys, have entered into an investment agreement to develop Exmet's technology for the additive manufacturing (AM) of amorphous metals. The agreement also aims to shorten the time to market for new functional products. Exmet has set up manufacturing facilities with an EOS M 290 3D printing system and opened new offices in Stockholm.
Amorphous metal alloys, also known as bulk metallic glasses (BMG) and glassy alloys, lack the crystalline microstructure found in ordinary alloys, such as steels. According to Exmet, their development been hampered since the 1960s since no suitable and general manufacturing method has been available. Using Exmet AB's AM based technology the excellent properties of these glassy alloys can be better exploited as it removes the limits set by casting, melt spinning and thermoplastic forming in manufacturing of amorphous metals. The result is products of almost any alloy, such as iron, titanium, aluminum, magnesium or cobalt based, and shape, virtually unaffected by corrosion, with low magnetization loss. Exmet says that the extreme strength of the materials allows for greater weight reductions.
‘We are looking forward to support Exmet on their way to amorphous metal parts with completely new and unique properties,’ said Johann Oberhofer, executive vice president technology, AMV. ‘AMV also will assist Exmet and their customers when it comes to ramping up specific successful amorphous metal components to economic serial production to fully exploit the superior mechanical and magnetic properties of these components.’
This story uses material from Exmet, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Sigmatex announces Embraer supplier agreement
Carbon fiber textile supplier Sigmatex has announced a new supplier agreement with Embraer, reportedly one of the largest aerospace companies in the world.
Under the terms of the agreement Sigmatex will supply its multiaxial (NCF) carbon textile, sold under the sigmaMX range. The non-crimp textile is designed predominantly for aerospace and the multiaxial textiles can be manufactured with up to nine layers with varying angles and widths.
“’We’re honoured to announce this agreement with Embraer, confirming our strong relationship,’ Paul McMullan, global commercial manager at Sigmatex said.
This story uses material from Sigmatex, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Kennametal one of the world's most ethical companies
Kennametal has been recognized as one of 2017’s World's Most Ethical Companies by the Ethisphere Institute, an organization which defines the standards of ethical business practices.
This marks the sixth consecutive year that Kennametal has received the distinction, which reportedly honors companies that consider the impact of their actions on their employees, investors, customers and other key stakeholders and use their values and culture to underpin their decisions.
‘We are proud to be regarded among the world's most ethical companies for six consecutive years, and will continue to work diligently to conduct business with the utmost integrity,’ said said president and CEO Ron De Feo.
Kennametal's executive team led by De Feo hosts Business Practice Summits in the Americas, EMEA and Asia Pacific regions to reinforce business standards and expectations across the organization and at all levels.
‘Over the last eleven years we have seen the shift in societal expectations, constant redefinition of laws and regulations and the geo-political climate,’ said Ethisphere's CEO, Timothy Erblich. ‘We have also seen how companies honored as the World's Most Ethical respond to these challenges. They invest in their local communities around the world, embrace strategies of diversity and inclusion, and focus on long term-ism as a sustainable business advantage.’
This story uses material from Kennametal, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Linde’s 2016: ‘high level’
Linde reports group revenue of €16.948 billion, up 0.2% after adjusting for exchange rate effects. Group operating profit was €4.098 billion, an increase of 2.7%.
‘Despite the low price of oil and the economic headwind, we were able to meet expectations and achieve increases in revenue and earnings after adjusting for exchange rate effects, especially in a strong fourth quarter,’ said Professor Dr Aldo Belloni, CEO. ‘We have increased our group margin and our operating cash flow has remained at a high level, so we have been able to maintain our dividend distribution which is geared towards continuity.’
In the Gases Division, revenue fell in the 2016 financial year by 1.8% to €14.892 billion (2015: €15.168 billion). After adjusting for exchange rate effects and changes in the price of natural gas, revenue increased by 1.4%. Operating profit in the Gases Division rose by 1.4% to €4.210 billion (2015: €4.151 bilion), giving an operating margin of 28.3%.
Linde reports that recent economic forecasts indicate that the global gases market will grow at a similar rate in 2017 to that seen in 2016. In contrast, the market environment in the international plant construction business could see a slight improvement, although it might continue to be beset by uncertainty. For the group as a whole, Linde is seeking to achieve an increase in revenue of 3% after adjusting for exchange rate effects.
This story uses material from Linde, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
MOU focuses on carbon fiber recycling
The Composite Recycling Technology Center (CRTC) based in Washington State, USA, and ELG Carbon Fiber Ltd (ELG) based in Coseley, UK, have signed a s (MOU) to collaborate on carbon fiber recycling.
Under the terms of the agreement, the CRTC and ELG will develop ways to use the carbon fiber that gets reclaimed through ELG’s pyrolysis process, and turn it into products that could positively impact people’s lives and our environment.
‘We are very excited about the opportunity to work closely with the CRTC and are already discussing some major projects that will kick-start the recycled carbon fiber industry on an international level,’ said Frazer Barnes, MD of ELG.
‘Today’s announcement represents a major milestone for the CRTC,’ said Robert Larsen, CEO of the CRTC. ‘Working closely with ELG means that we can provide a one-stop carbon fiber recycling team that addresses the needs of large-scale generators of carbon fiber scrap. It also provides the CRTC with a consistent supply of low-cost recycled carbon fiber and thermoplastics. When combined with our recycled carbon fiber pre-preg, it will create dozens of beneficial uses for this previously landfilled material.’
This story uses material from the CRTC, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
Magnet-controlled plasma bombardment produces uniform nanocubes
While nanoparticles sound like a recent discovery, these tiny structures have been used for centuries. The famous Lycurgus cup, made by 4th century Roman artisans, features dichroic glass with gold and silver nanoparticles sprinkled throughout. These nanoparticles give the cup a green appearance when illuminated from the front and a red appearance when illuminated from behind.
In the centuries since the time of the ancient artisans, researchers have come a long way in understanding nanoparticles, with nanocubes proving of particular interest due to their potential applications as biosensors and gas sensors. Nanocubes and other nanoparticles can be produced using either physical or chemical methods, but physical methods tend to be preferable because they are less likely to generate organic contaminants than chemical methods. Unfortunately, uniformly-sized nanocubes are difficult to produce in sufficient quantities by physical methods.
Now, researchers from the Nanoparticles by Design Unit at the Okinawa Institute of Science and Technology (OIST) Graduate University in Japan, together with colleagues in Finland and France, have discovered a new approach to overcoming this problem. The researchers describe this approach in a paper in Advanced Functional Materials.
“The cube shape is not the lowest energy structure for iron nanoparticles,” explains Jerome Vernieres from OIST, first author of the paper, “thus, we couldn’t rely on equilibrium thermodynamics considerations to self-assemble these nanocubes”. Instead, the OIST scientists, under the guidance of Mukhles Sowwan, exploited the possibilities offered by a technique called magnetron-sputtering inert-gas condensation to create their iron nanocubes.
In this method, argon gas is first heated to convert it into an ionized plasma. The researchers then use a magnet located behind a target made of the material that will form the basis for the nanoparticles – in this case, iron – to control the shape of the plasma and direct the argon ions towards the target, hence the name ‘magnetron’. This bombardment causes iron atoms to be sputtered away from the target and collide with argon atoms and each other to form nanocubes. The challenge, however, is to make these nanocubes as uniform as possible.
“Uniformity is key in sensing applications,” says Stephan Steinhauer, also from OIST “We needed a way to control the size, shape and number of the nanocubes during their production.”
To control the size and shape of these cubes, the researchers made a simple but significant observation: iron is magnetic in its own right! In other words, the researchers discovered they could exploit the intrinsic magnetism of the target itself as an innovative way to modify the magnetic field of the magnetron. In this way, they were able to manipulate the plasma where the particles are grown, and thus control the nanocube sizes during formation.
“This is the first time uniform iron nanocubes have been made using a physical method that can be scaled for mass production,” claims Vernieres. To better understand the mechanics of this process, the OIST team collaborated with researchers from the University of Helsinki in Finland to make theoretical calculations. “The work relied heavily on both experimental methods and theoretical calculations. The simulations were important for us to explain the phenomena we were observing,” says Panagiotis Grammatikopoulos from OIST.
Once the researchers had come up with a way to produce these uniform iron cubes, the next step was to build an electronic device that could utilize the nanocubes for sensing applications. “We noticed that these cubes were extremely sensitive to the levels of gaseous nitrogen dioxide (NO2),” says Steinhauer. “NO2 sensing is used for a variety of different purposes, from diagnosis of asthma patients to detecting environmental pollution, so we immediately saw an application for our work.”
In collaboration with researchers from the University of Toulouse in France, the researchers from the Nanoparticles by Design Unit built a prototype NO2 sensor that measured the change in electrical resistance of the iron nanocubes on exposure to NO2 gas. Because even a very tiny amount of NO2 can produce a measurable change in electrical resistance that is considerably larger than produced by other atmospheric pollutants, the iron nanocube-based sensor is both extremely sensitive and specific. “These nanocubes have many potential uses. The fact that we can produce a relatively large quantity of uniform nanocubes using an increasingly common synthesis method makes this research highly promising for industrial applications,” says Vernieres.
This story is adapted from material from the Okinawa Institute of Science and Technology Graduate University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.