Tag Archives: iron oxide nanoparticle

Magnetic nanopowder for mobile 6G technology

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It seems a little early to be talking about 6G technology, given that in Canada 5G technology is not fully implemented (from a February 8, 2021 article [unchanged as November 18, 2021] by Stephen Clark for whistleout.ca), Note: A link has been removed,

Should I Buy a 5G Phone Now?

There is no rush to buy a 5G phone for most Canadians. Current 5G smartphones offer other premium features such as leading edge Qualcomm CPU performance, brilliant OLED screens and recording video at 8K resolution. These devices can also cost well over $1,000, so you don’t shop for a 5G phone if that’s the only premium feature you are looking for. We expect that Canadians won’t see coast-to-coast coverage by 5G cell towers until at least 2022 [emphasis mine]. Besides, Canada’s 4G LTE mobile performance is among the fastest in the world, serves 99% of Canadians and 4G smartphones will continue to be supported for many years.

A study released by OpenSignal found Canadian 5G networks among the top 5 best in the world for mobile gaming. …

It’s good not to get too focused on one’s naval as there are many other countries in the world and it’s likely at least some, if not most, are more advanced with their 5G technology deployment and are looking forward to 6G. (See this November 1, 2021 University of Tokyo news release “Japan and Finland collaborate to develop 6G” on EurekAlert.)

Now to 6G news, this June 28, 2021 news item on phys.org describes a new technique for producing the new materials necessary for a future 6G deployment,

Material scientists have developed a fast method for producing epsilon iron oxide and demonstrated its promise for next-generation communications devices. Its outstanding magnetic properties make it one of the most coveted materials, such as for the upcoming 6G generation of communication devices and for durable magnetic recording. The work was published in the Journal of Materials Chemistry C, a journal of the Royal Society of Chemistry.

A June 23, 2021 Moscow Institute of Physics and Technology (MIPT) press release, which originated the news item, describes the work in detail,

Iron oxide (III) is one of the most widespread oxides on Earth. It is mostly found as the mineral hematite (or alpha iron oxide, α-Fe2O3). Another stable and common modification is maghemite (or gamma modification, γ-Fe2O3). The former is widely used in industry as a red pigment, and the latter as a magnetic recording medium. The two modifications differ not only in crystalline structure ( alpha-iron oxide has hexagonal syngony and gamma-iron oxide has cubic syngony) but also in magnetic properties.

In addition to these forms of iron oxide (III), there are more exotic modifications such as epsilon-, beta-, zeta-, and even glassy. The most attractive  phase is epsilon iron oxide, ε-Fe2O3. This modification has an extremely high coercive force (the ability of the material to resist an external magnetic field). The strength reaches 20 kOe at room temperature, which is comparable to the parameters of magnets based on expensive rare-earth elements. Furthermore, the material absorbs electromagnetic radiation in the sub-terahertz frequency range (100-300 GHz) through the effect of natural ferromagnetic resonance.The frequency of such resonance is one of the criteria for the use of materials in wireless communications devices – the 4G standard uses megahertz and 5G uses tens of gigahertz. There are plans to use the sub-terahertz range as a working range in the sixth generation (6G) wireless technology, which is being prepared for active introduction in our lives from the early 2030s.

The resulting material is suitable for the production of converting units or absorber circuits at these frequencies. For example, by using composite ε-Fe2O3 nanopowders it will be possible to make paints that absorb electromagnetic waves and thus shield rooms from extraneous signals, and protect signals from interception from the outside. The ε-Fe2O3 itself can also be used in 6G reception devices.

Epsilon iron oxide is an extremely rare and difficult form of iron oxide to obtain. Today, it is produced in very small quantities, with the process itself taking up to a month. This, of course, rules out its widespread application. The authors of the study developed a method for accelerated synthesis of epsilon iron oxide capable of reducing the synthesis time to one day (that is, to carry out a full cycle of more than 30 times faster!) and increasing the quantity of the resulting product. The technique is simple to reproduce, cheap and can be easily implemented in industry, and the materials required for the synthesis – iron and silicon – are among the most abundant elements on Earth.

“Although the epsilon-iron oxide phase was obtained in pure form relatively long ago, in 2004, it still has not found industrial application due to the complexity of its synthesis, for example as a medium for magnetic – recording. We have managed to simplify the technology considerably,” says Evgeny Gorbachev, a PhD student in the Department of Materials Sciences at Moscow State University and the first author of the work.

The key to successful application of materials with record-breaking characteristics is research into their fundamental physical properties. Without in-depth study, the material may be undeservedly forgotten for many years, as has happened more than once in the history of science. It was the tandem of materials scientists at Moscow State University, who synthesised the compound, and physicists at MIPT, who studied it in detail, that made the development a success.

“Materials with such high ferromagnetic resonance frequencies have enormous potential for practical applications. Today, terahertz technology is booming: it is the Internet of Things, it is ultra-fast communications, it is more narrowly focused scientific devices, and it is next-generation medical technology. While the 5G standard, which was very popular last year, operates at frequencies in the tens of gigahertz, our materials are opening the door to significantly higher frequencies (hundreds of gigahertz), which means that we are already dealing with 6G standards and higher. Now it’s up to engineers, we are happy to share the information with them and look forward to being able to hold a 6G phone in our hands,” says Dr. Liudmila Alyabyeva, Ph.D., senior researcher at the MIPT Laboratory of Terahertz Spectroscopy , where the terahertz research was carried out.

Here’s a link to and a citation for the paper,

Tuning the particle size, natural ferromagnetic resonance frequency and magnetic properties of ε-Fe2O3 nanoparticles prepared by a rapid sol–gel method by Evgeny Gorbachev, Miroslav Soshnikov, Mingxi Wu, Liudmila Alyabyeva, Dmitrii Myakishev, Ekaterina Kozlyakova, Vasilii Lebedev, Evgeny Anokhin, Boris Gorshunov, Oleg Brylev, Pavel Kazin, Lev Truso. J. Mater. Chem. C, 2021,9, 6173-6179 DOI: https://doi.org/10.1039/D1TC01242H First published 26 Apr 2021

This paper is behind a paywall.

New iron oxide nanoparticle as an MRI (magnetic resonance imaging) contrast agent

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This high-resolution transmission electron micrograph of particles made by the research team shows the particles’ highly uniform size and shape. These are iron oxide particles just 3 nanometers across, coated with a zwitterion layer. Their small size means they can easily be cleared through the kidneys after injection. Courtesy of the researchers

A Feb. 14, 2017 news item on ScienceDaily announces a new MRI (magnetic resonance imaging) contrast agent,

A new, specially coated iron oxide nanoparticle developed by a team at MIT [Massachusetts Institute of Technology] and elsewhere could provide an alternative to conventional gadolinium-based contrast agents used for magnetic resonance imaging (MRI) procedures. In rare cases, the currently used gadolinium agents have been found to produce adverse effects in patients with impaired kidney function.

A Feb. 14, 2017 MIT news release (also on EurekAlert), which originated the news item, provides more technical detail,

 

The advent of MRI technology, which is used to observe details of specific organs or blood vessels, has been an enormous boon to medical diagnostics over the last few decades. About a third of the 60 million MRI procedures done annually worldwide use contrast-enhancing agents, mostly containing the element gadolinium. While these contrast agents have mostly proven safe over many years of use, some rare but significant side effects have shown up in a very small subset of patients. There may soon be a safer substitute thanks to this new research.

In place of gadolinium-based contrast agents, the researchers have found that they can produce similar MRI contrast with tiny nanoparticles of iron oxide that have been treated with a zwitterion coating. (Zwitterions are molecules that have areas of both positive and negative electrical charges, which cancel out to make them neutral overall.) The findings are being published this week in the Proceedings of the National Academy of Sciences, in a paper by Moungi Bawendi, the Lester Wolfe Professor of Chemistry at MIT; He Wei, an MIT postdoc; Oliver Bruns, an MIT research scientist; Michael Kaul at the University Medical Center Hamburg-Eppendorf in Germany; and 15 others.

Contrast agents, injected into the patient during an MRI procedure and designed to be quickly cleared from the body by the kidneys afterwards, are needed to make fine details of organ structures, blood vessels, and other specific tissues clearly visible in the images. Some agents produce dark areas in the resulting image, while others produce light areas. The primary agents for producing light areas contain gadolinium.

Iron oxide particles have been largely used as negative (dark) contrast agents, but radiologists vastly prefer positive (light) contrast agents such as gadolinium-based agents, as negative contrast can sometimes be difficult to distinguish from certain imaging artifacts and internal bleeding. But while the gadolinium-based agents have become the standard, evidence shows that in some very rare cases they can lead to an untreatable condition called nephrogenic systemic fibrosis, which can be fatal. In addition, evidence now shows that the gadolinium can build up in the brain, and although no effects of this buildup have yet been demonstrated, the FDA is investigating it for potential harm.

“Over the last decade, more and more side effects have come to light” from the gadolinium agents, Bruns says, so that led the research team to search for alternatives. “None of these issues exist for iron oxide,” at least none that have yet been detected, he says.

The key new finding by this team was to combine two existing techniques: making very tiny particles of iron oxide, and attaching certain molecules (called surface ligands) to the outsides of these particles to optimize their characteristics. The iron oxide inorganic core is small enough to produce a pronounced positive contrast in MRI, and the zwitterionic surface ligand, which was recently developed by Wei and coworkers in the Bawendi research group, makes the iron oxide particles water-soluble, compact, and biocompatible.

The combination of a very tiny iron oxide core and an ultrathin ligand shell leads to a total hydrodynamic diameter of 4.7 nanometers, below the 5.5-nanometer renal clearance threshold. This means that the coated iron oxide should quickly clear through the kidneys and not accumulate. This renal clearance property is an important feature where the particles perform comparably to gadolinium-based contrast agents.

Now that initial tests have demonstrated the particles’ effectiveness as contrast agents, Wei and Bruns say the next step will be to do further toxicology testing to show the particles’ safety, and to continue to improve the characteristics of the material. “It’s not perfect. We have more work to do,” Bruns says. But because iron oxide has been used for so long and in so many ways, even as an iron supplement, any negative effects could likely be treated by well-established protocols, the researchers say. If all goes well, the team is considering setting up a startup company to bring the material to production.

For some patients who are currently excluded from getting MRIs because of potential side effects of gadolinium, the new agents “could allow those patients to be eligible again” for the procedure, Bruns says. And, if it does turn out that the accumulation of gadolinium in the brain has negative effects, an overall phase-out of gadolinium for such uses could be needed. “If that turned out to be the case, this could potentially be a complete replacement,” he says.

Ralph Weissleder, a physician at Massachusetts General Hospital who was not involved in this work, says, “The work is of high interest, given the limitations of gadolinium-based contrast agents, which typically have short vascular half-lives and may be contraindicated in renally compromised patients.”

The research team included researchers in MIT’s chemistry, biological engineering, nuclear science and engineering, brain and cognitive sciences, and materials science and engineering departments and its program in Health Sciences and Technology; and at the University Medical Center Hamburg-Eppendorf; Brown University; and the Massachusetts General Hospital. It was supported by the MIT-Harvard NIH Center for Cancer Nanotechnology, the Army Research Office through MIT’s Institute for Soldier Nanotechnologies, the NIH-funded Laser Biomedical Research Center, the MIT Deshpande Center, and the European Union Seventh Framework Program.

Here’s a link to and a citation for the paper,

Exceedingly small iron oxide nanoparticles as positive MRI contrast agents by He Wei, Oliver T. Bruns, Michael G. Kaul, Eric C. Hansen, Mariya Barch, Agata Wiśniowsk, Ou Chen, Yue Chen, Nan Li, Satoshi Okada, Jose M. Cordero, Markus Heine, Christian T. Farrar, Daniel M. Montana, Gerhard Adam, Harald Ittrich, Alan Jasanoff, Peter Nielsen, and Moungi G. Bawendi. PNAS February 13, 2017 doi: 10.1073/pnas.1620145114 Published online before print February 13, 2017

This paper is behind a paywall.