Tag Archives: Brown University

Bioceramic armour: tough and clear

This story about a mollusk and its armour eventually led me back to one of my favourite science writers, David L. Chandler at the Massachusetts Institute of Technology (MIT). First, here’s an excerpt from a March 30, 2014 news item on ScienceDaily,

The shells of a sea creature, the mollusk Placuna placenta, are not only exceptionally tough, but also clear enough to read through. Now, researchers at MIT have analyzed these shells to determine exactly why they are so resistant to penetration and damage — even though they are 99 percent calcite, a weak, brittle mineral.

The shells’ unique properties emerge from a specialized nanostructure that allows optical clarity, as well as efficient energy dissipation and the ability to localize deformation, the researchers found. The results are published this week in the journal Nature Materials, in a paper co-authored by MIT graduate student Ling Li and professor Christine Ortiz.

A March 30, 2014 MIT press release (I’m not positive Chandler wrote this but he is the press contact) describes both the engineered bioceramic armour and the mollusk’s naturally occurring armour,

Engineered ceramic-based armor, while designed to resist penetration, often lacks the ability to withstand multiple blows, due to large-scale deformation and fracture that can compromise its structural integrity, Ortiz says. In transparent armor systems, such deformation can also obscure visibility.

Creatures that have evolved natural exoskeletons — many of them ceramic-based — have developed ingenious designs that can withstand multiple penetrating attacks from predators. The shells of a few species, such as Placuna placenta, are also optically clear.

To test exactly how the shells — which combine calcite with about 1 percent organic material — respond to penetration, the researchers subjected samples to indentation tests, using a sharp diamond tip in an experimental setup that could measure loads precisely. They then used high-resolution analysis methods, such as electron microscopy and diffraction, to examine the resulting damage.

The material initially isolates damage through an atomic-level process called “twinning” within the individual ceramic building blocks: A crystal breaks up into a pair of mirror-image regions that share a common boundary, rather like a butterfly’s wings. This twinning process occurs all around the stressed region, helping to form a kind of boundary that keeps the damage from spreading outward.

The MIT researchers found that twinning then activates “a series of additional energy-dissipation mechanisms … which preserve the mechanical and optical integrity of the surrounding material,” Li says. This produces a material that is 10 times more efficient in dissipating energy than the pure mineral, Li adds.

The properties of this natural armor make it a promising template for the development of bio-inspired synthetic materials for both commercial and military applications — such as eye and face protection for soldiers, windows and windshields, and blast shields, Ortiz says.

Huajian Gao, a professor of engineering at Brown University who was not involved in this research, calls it “an excellent and elegant piece of work.” He says it “successfully demonstrates the effectiveness of nanoscale deformation twins in energy dissipation in bioceramics, and should be able to inspire and guide the development of manmade ceramic materials.” He adds, “As a first-of-its-kind [demonstration of] the effectiveness of deformation twins in natural materials, this work should have huge practical impact.”

The work was supported by the National Science Foundation; the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies; the National Security Science and Engineering Faculty Fellowships Program; and the Office of the Assistant Secretary of Defense for Research and Engineering.

The researchers have produced an image showing how the mollusk shell reacts to being damaged,

A Scanning Electron Microscope (SEM) image of the region surrounding an indentation the researchers made in a piece of shell from Placuna placenta. The image shows the localization of damage to the area immediately surrounding the stress. Image: Ling Li and James C. Weaver. Courtesy: MIT

A Scanning Electron Microscope (SEM) image of the region surrounding an indentation the researchers made in a piece of shell from Placuna placenta. The image shows the localization of damage to the area immediately surrounding the stress.
Image: Ling Li and James C. Weaver. Courtesy: MIT

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

Pervasive nanoscale deformation twinning as a catalyst for efficient energy dissipation in a bioceramic armour by Ling Li & Christine Ortiz. Nature Materials (2014) doi:10.1038/nmat3920 Published online 30 March 2014

This paper is behind a paywall.

Borophene at Brown University (US)

It’s still theory at this point but researchers at Brown University (Rhode Island, US) have produced experimental proof that a single layer of boron atoms in a lattice reminiscent of  but not identical to a graphene layer is possible. A Jan. 28, 2014 news item on Azonano describes the research,

Researchers from Brown University have shown experimentally that a boron-based competitor to graphene is a very real possibility.

Graphene has been heralded as a wonder material. Made of a single layer of carbon atoms in a honeycomb arrangement, graphene is stronger pound-for-pound than steel and conducts electricity better than copper. Since the discovery of graphene, scientists have wondered if boron, carbon’s neighbor on the periodic table, could also be arranged in single-atom sheets. Theoretical work suggested it was possible, but the atoms would need to be in a very particular arrangement.

Boron has one fewer electron than carbon and as a result can’t form the honeycomb lattice that makes up graphene. For boron to form a single-atom layer, theorists suggested that the atoms must be arranged in a triangular lattice with hexagonal vacancies — holes — in the lattice.

“That was the prediction,” said Lai-Sheng Wang, professor of chemistry at Brown, “but nobody had made anything to show that’s the case.”

Wang and his research group, which has studied boron chemistry for many years, have now produced the first experimental evidence that such a structure is possible. In a paper published on January 20 in Nature Communications, Wang and his team showed that a cluster made of 36 boron atoms (B36) forms a symmetrical, one-atom thick disc with a perfect hexagonal hole in the middle.

Here’s an image that illustrates ‘borophene’,

Caption: This shows a 36-atom cluster of boron, left, arranged as a flat disc with a hexagonal hole in the middle, fits the theoretical requirements for making a one-atom-thick boron sheet, right, a theoretical nanomaterial dubbed "borophene." Credit: Wang Lab / Brown University

Caption: This shows a 36-atom cluster of boron, left, arranged as a flat disc with a hexagonal hole in the middle, fits the theoretical requirements for making a one-atom-thick boron sheet, right, a theoretical nanomaterial dubbed “borophene.”
Credit: Wang Lab / Brown University

The Jan. 27, 2014 Brown University news release (also on EurekAlert), which originated the news item, provides details about how the research was conducted,

The work required a combination of laboratory experiments and computational modeling. In the lab, Wang and his student, Wei-Li Li, probe the properties of boron clusters using a technique called photoelectron spectroscopy. They start by zapping chunks of bulk boron with a laser to create vapor of boron atoms. A jet of helium then freezes the vapor into tiny clusters of atoms. Those clusters are then zapped with a second laser, which knocks an electron out of the cluster and sends it flying down a long tube that Wang calls his “electron racetrack.” The speed at which the electron flies down the racetrack is used to determine the cluster’s electron binding energy spectrum — a readout of how tightly the cluster holds its electrons. That spectrum serves as fingerprint of the cluster’s structure.

Wang’s experiments showed that the B36 cluster was something special. It had an extremely low electron binding energy compared to other boron clusters. The shape of the cluster’s binding spectrum also suggested that it was a symmetrical structure.

To find out exactly what that structure might look like, Wang turned to Zachary Piazza, one of his graduate students specializing in computational chemistry. Piazza began modeling potential structures for B36 on a supercomputer, investigating more than 3,000 possible arrangements of those 36 atoms. Among the arrangements that would be stable was the planar disc with the hexagonal hole.

“As soon as I saw that hexagonal hole,” Wang said, “I told Zach, ‘We have to investigate that.’”

To ensure that they have truly found the most stable arrangement of the 36 boron atoms, they enlisted the help of Jun Li, who is a professor of chemistry at Tsinghua University in Beijing and a former senior research scientist at Pacific Northwest National Laboratory (PNNL) in Richland, Wash. Li, a longtime collaborator of Wang’s, has developed a new method of finding stable structures of clusters, which would be suitable for the job at hand. Piazza spent the summer of 2013 at PNNL working with Li and his students on the B36 project. They used the supercomputer at PNNL to examine more possible arrangements of the 36 boron atoms and compute their electron binding spectra. They found that the planar disc with a hexagonal hole matched very closely with the spectrum measured in the lab experiments, indicating that the structure Piazza found initially on the computer was indeed the structure of B36.

That structure also fits the theoretical requirements for making borophene, which is an extremely interesting prospect, Wang said. The boron-boron bond is very strong, nearly as strong as the carbon-carbon bond. So borophene should be very strong. Its electrical properties may be even more interesting. Borophene is predicted to be fully metallic, whereas graphene is a semi-metal. That means borophene might end up being a better conductor than graphene.

“That is,” Wang cautions, “if anyone can make it.”

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

Planar hexagonal B36 as a potential basis for extended single-atom layer boron sheets by Zachary A. Piazza, Han-Shi Hu, Wei-Li Li, Ya-Fan Zhao, Jun Li, & Lai-Sheng Wang. Nature Communications 5, Article number: 3113 doi:10.1038/ncomms4113 Published 20 January 2014

This paper is behind a paywall.

Recycling carbon dioxide with gold nanoparticles

Researchers at Brown University (in Providence, Rhode Island) have developed a technique using gold nanoparticles to capture carbon dioxide and turn it into carbon monoxide (from the Oct. 24, 2013 Brown University news release [also on EurekAlert]),

It’s a 21st-century alchemist’s dream: turning Earth’s superabundance of carbon dioxide — a greenhouse gas — into fuel or useful industrial chemicals. Researchers from Brown have shown that finely tuned gold nanoparticles can do the job. The key is maximizing the particles’ long edges, which are the active sites for the reaction.[This paragraph is present only on the Brown website news release]

By tuning gold nanoparticles to just the right size, researchers from Brown University have developed a catalyst that selectively converts carbon dioxide (CO2) to carbon monoxide (CO), an active carbon molecule that can be used to make alternative fuels and commodity chemicals.

“Our study shows potential of carefully designed gold nanoparticles to recycle CO2 into useful forms of carbon,” said Shouheng Sun, professor of chemistry and one of the study’s senior authors. “The work we’ve done here is preliminary, but we think there’s great potential for this technology to be scaled up for commercial applications.”

The scientists were trying to solve a major problem with recycling carbon dioxide when using gold (from the news release),

Converting CO2 to CO isn’t easy. Prior research has shown that catalysts made of gold foil are active for this conversion, but they don’t do the job efficiently. The gold tends to react both with the CO2 and with the water in which the CO2 is dissolved, creating hydrogen byproduct rather than the desired CO.

The Brown research team decided to try gold nanoparticles and had a surprising result (from the news release),

The Brown experimental group, led by Sun and Wenlei Zhu, a graduate student in Sun’s group, wanted to see if shrinking the gold down to nanoparticles might make it more selective for CO2. They found that the nanoparticles were indeed more selective, but that the exact size of those particles was important. Eight nanometer particles had the best selectivity, achieving a 90-percent rate of conversion from CO2 to CO. Other sizes the team tested — four, six, and 10 nanometers — didn’t perform nearly as well.

“At first, that result was confusing,” said Andrew Peterson, professor of engineering and also a senior author on the paper. “As we made the particles smaller we got more activity, but when we went smaller than eight nanometers, we got less activity.”

The researchers investigated further and found a relationship between size and shape which affects the gold nanoparticles’ performance (from the news release),

To understand what was happening, Peterson and postdoctoral researcher Ronald Michalsky used a modeling method called density functional theory. They were able to show that the shapes of the particles at different sizes influenced their catalytic properties.

“When you take a sphere and you reduce it to smaller and smaller sizes, you tend to get many more irregular features — flat surfaces, edges and corners,” Peterson said. “What we were able to figure out is that the most active sites for converting CO2 to CO are the edge sites, while the corner sites predominantly give the by-product, which is hydrogen. So as you shrink these particles down, you’ll hit a point where you start to optimize the activity because you have a high number of these edge sites but still a low number of these corner sites. But if you go too small, the edges start to shrink and you’re left with just corners.”

Now that they understand exactly what part of the catalyst is active, the researchers are working to further optimize the particles. “There’s still a lot of room for improvement,” Peterson said. “We’re working on new particles that maximize these active sites.”

The researchers believe these findings could be an important new avenue for recycling CO2 on a commercial scale.

“Because we’re using nanoparticles, we’re using a lot less gold than in a bulk metal catalyst,” Sun said. “That lowers the cost for making such a catalyst and gives the potential to scale up.”

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

Monodisperse Au Nanoparticles for Selective Electrocatalytic Reduction of CO2 to CO by Wenlei Zhu, Ronald Michalsky, Önder Metin, Haifeng Lv, Shaojun Guo, Christopher J. Wright, Xiaolian Sun, Andrew A. Peterson, and Shouheng Sun. J. Am. Chem. Soc., DOI: 10.1021/ja409445p Publication Date (Web): October 24, 2013
Copyright © 2013 American Chemical Society

This article is behind a paywall.

Should October 2013 be called ‘the month of graphene’?

Since the Oct. 10-11, 2013 Graphene Flagship (1B Euros investment) launch, mentioned in my preview Oct. 7, 2013 posting, there’ve been a flurry of graphene-themed news items both on this blog and elsewhere and I’ve decided to offer a brief roundup what I’ve found elsewhere.

Dexter Johnson offers a commentary in the pithily titled, Europe Invests €1 Billion to Become “Graphene Valley,” an Oct. 15, 2013 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) Note: Links have been removed,

The initiative has been dubbed “The Graphene Flagship,” and apparently it is the first in a number of €1 billion, 10-year plans the EC is planning to launch. The graphene version will bring together 76 academic institutions and industrial groups from 17 European countries, with an initial 30-month-budget of €54M ($73 million).

Graphene research is still struggling to find any kind of applications that will really take hold, and many don’t expect it will have a commercial impact until 2020. What’s more, manufacturing methods are still undeveloped. So it would appear that a 10-year plan is aimed at the academic institutions that form the backbone of this initiative rather than commercial enterprises.

Just from a political standpoint the choice of Chalmers University in Sweden as the base of operations for the Graphene Flagship is an intriguing choice. …

I have to agree with Dexter that choosing Chalmers University over the University of Manchester where graphene was first isolated is unexpected. As a companion piece to reading Dexter’s posting in its entirety and which features a video from the flagship launch, you might want to try this Oct. 15, 2013 article by Koen Mortelmans for Youris (h/t Oct. 15, 2013 news item on Nanowerk),

Andre Konstantin Geim is the only person who ever received both a Nobel and an Ig Nobel. He was born in 1958 in Russia, and is a Dutch-British physicist with German, Polish, Jewish and Ukrainian roots. “Having lived and worked in several European countries, I consider myself European. I don’t believe that any further taxonomy is necessary,” he says. He is now a physics professor at the University of Manchester. …

He shared the Noble [Nobel] Prize in 2010 with Konstantin Novoselov for their work on graphene. It was following on their isolation of microscope visible grapheme flakes that the worldwide research towards practical applications of graphene took off.  “We did not invent graphene,” Geim says, “we only saw what was laid up for five hundred year under our noses.”

Geim and Novoselov are often thought to have succeeded in separating graphene from graphite by peeling it off with ordinary duct tape until there only remained a layer. Graphene could then be observed with a microscope, because of the partial transparency of the material. That is, after dissolving the duct tape material in acetone, of course. That is also the story Geim himself likes to tell.

However, he did not use – as the urban myth goes – graphite from a common pencil. Instead, he used a carbon sample of extreme purity, specially imported. He also used ultrasound techniques. But, probably the urban legend will survive, as did Archimedes’ bath and Newtons apple. “It is nice to keep some of the magic,” is the expression Geim often uses when he does not want a nice story to be drowned in hard facts or when he wants to remain discrete about still incomplete, but promising research results.

Mortelmans’ article fills in some gaps for those not familiar with the graphene ‘origins’ story while Tim Harper’s July 22, 2012 posting on Cientifica’s (an emerging technologies consultancy where Harper is the CEO and founder) TNT blog offers an insight into Geim’s perspective on the race to commercialize graphene with a paraphrased quote for the title of Harper’s posting, “It’s a bit silly for society to throw a little bit of money at (graphene) and expect it to change the world.” (Note: Within this context, mention is made of the company’s graphene opportunities report.)

With all this excitement about graphene (and carbon generally), the magazine titled Carbon has just published a suggested nomenclature for 2D carbon forms such as graphene, graphane, etc., according to an Oct. 16, 2013 news item on Nanowerk (Note: A link has been removed),

There has been an intense research interest in all two-dimensional (2D) forms of carbon since Geim and Novoselov’s discovery of graphene in 2004. But as the number of such publications rise, so does the level of inconsistency in naming the material of interest. The isolated, single-atom-thick sheet universally referred to as “graphene” may have a clear definition, but when referring to related 2D sheet-like or flake-like carbon forms, many authors have simply defined their own terms to describe their product.

This has led to confusion within the literature, where terms are multiply-defined, or incorrectly used. The Editorial Board of Carbon has therefore published the first recommended nomenclature for 2D carbon forms (“All in the graphene family – A recommended nomenclature for two-dimensional carbon materials”).

This proposed nomenclature comes in the form of an editorial, from Carbon (Volume 65, December 2013, Pages 1–6),

All in the graphene family – A recommended nomenclature for two-dimensional carbon materials

  • Alberto Bianco
    CNRS, Institut de Biologie Moléculaire et Cellulaire, Immunopathologie et Chimie Thérapeutique, Strasbourg, France
  • Hui-Ming Cheng
    Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China
  • Toshiaki Enoki
    Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan
  • Yury Gogotsi
    Materials Science and Engineering Department, A.J. Drexel Nanotechnology Institute, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
  • Robert H. Hurt
    Institute for Molecular and Nanoscale Innovation, School of Engineering, Brown University, Providence, RI 02912, USA
  • Nikhil Koratkar
    Department of Mechanical, Aerospace and Nuclear Engineering, The Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180, USA
  • Takashi Kyotani
    Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
  • Marc Monthioux
    Centre d’Elaboration des Matériaux et d’Etudes Structurales (CEMES), UPR-8011 CNRS, Université de Toulouse, 29 Rue Jeanne Marvig, F-31055 Toulouse, France
  • Chong Rae Park
    Carbon Nanomaterials Design Laboratory, Global Research Laboratory, Research Institute of Advanced Materials, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Republic of Korea
  • Juan M.D. Tascon
    Instituto Nacional del Carbón, INCAR-CSIC, Apartado 73, 33080 Oviedo, Spain
  • Jin Zhang
    Center for Nanochemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China

This editorial is behind a paywall.

Celebrate women in science on Oct. 15, 2013 and participate in a Wikipedia: Ada Lovelace Day 2013 edit-a-thon

Founded in 2009 by Suw Charman-Anderson, Ada Lovelace Day (Oct. 15) is on its way to realizing its goal of bringing more recognition to and celebrating women in science. From Charman-Anderson’s Oct. 15, 2013 posting for the Guardian Science blogs (Note: Links have been removed),

When I started the day five years ago, my goal was to collect these stories not only to inspire girls to study the STEM subjects, but also to provide support to women pursuing careers in these usually male-dominated fields.

Ada Lovelace is the ideal figurehead for this project: She was the world’s first computer programmer, and the first person to realise that a general purpose computing machine such as Charles Babbage’s Analytical Engine could do more than just calculate large tables of numbers. It could, she said, create music and art, given the right inputs. The Analytical Engine, she wrote, “weaves algebraic patterns just as the Jacquard loom weaves flowers and leaves”.

This daughter of “mad, bad and dangerous to know” Lord Byron achieved this distinction despite the fierce prejudices of the 19th Century. Her tutor Augustus De Morgan echoed the accepted view of the time when he said that maths problems presented “a very great tension of mind beyond the strength of a woman’s physical power”.

But Ada persevered in her studies, and De Morgan recognised her brilliance when he said that had she been a man, she would have had the potential to become “an original mathematical investigator, perhaps of first-rate eminence”.

Sydney Brownstone has written an Oct. 15, 2013 article about an Ada Lovelace Day Wikipedia event (on the Fast Company website; Note: Links have been removed),

Take Wikipedia, for example. Despite the fact that our communal encyclopedia provides a wealth of accessible information, women make up fewer than 15% of the project’s editors. (For further information, see the Wikipedia article “Wikipedia: Systemic bias.”) Oftentimes, the lack of gender parity results in a dearth of articles about, or including, important female figures in society. That’s what science journalist and BrainPOP news director Maia Weinstock found when she started editing Wikipedia articles back in 2007: Women who should be included in the STEM (science, technology, engineering, and math) achievement canon were simply missing from the archives. Or, when they were included, their stories were often stubs that left out the magnitude of their contributions.

In attempt to rectify some of these wrongs, Weinstock organized a Wikipedia Edit-a-thon held on last year’s Ada Lovelace day, a holiday dedicated to celebrating achievements of women in STEM fields, named for the pioneering 19th-century scientist (who, thankfully, has an extensive Wikipedia entry). Today [Oct. 15, 2013], Weinstock is organizing another round of editing at Brown University, in which some 40 contributors will help write articles from scratch or expand stubs on women pioneers. [emphasis mine]

In addition to the meetup at Brown University (Rhode Island, US), remote participation is also being encouraged in the Edit-a-thon from 3 pm to 8:30 pm EDT today (Oct. 15, 2013). You can find out more about the event (in person or remote) on this page: Wikipedia:Meetup/Ada Lovelace Edit-a-thon 2013 – Brown.

Brava to all women involved in STEM (science, technology, engineering, and mathematics) everywhere!

Looking blue? Maybe it’s silver nanoparticles

Looking blue can mean feeling sad or it can indicate that you have argyria, a condition caused by ingesting too much silver. An Oct. 29, 2012 news item on Nanowerk about research on argyria taking place at Brown University reveals the latest insight on the cause for this condition,

Researchers from Brown University have shown for the first time how ingesting too much silver can cause argyria, a rare condition in which patients’ skin turns a striking shade of grayish blue.

“It’s the first conceptual model giving the whole picture of how one develops this condition,” said Robert Hurt, professor of engineering at Brown and part of the research team. “What’s interesting here is that the particles someone ingests aren’t the particles that ultimately cause the disorder.”

Scientists have known for years argyria had something to do with silver. The condition has been documented in people who (ill advisedly) drink antimicrobial health tonics containing silver nanoparticles and in people who have had extensive medical treatments involving silver. Tissue samples from patients showed silver particles actually lodged deep in the skin, but it wasn’t clear how they got there.

As it turns out, argyria is caused by a complex series of chemical reactions, Hurt said. His paper on the subject, authored with Brown colleagues Jingyu Liu, Zhongying Wang, Frances Liu, and Agnes Kane, is published in the journal ACS Nano (“Chemical Transformations of Nanosilver in Biological Environments” [behind a paywall]).

The Oct. 25, 2012 Brown University news release (which originated the news item) provides more detail,

Hurt and his team have been studying the environmental impact of silver, specifically silver nanoparticles, for years. They’ve found that nanosilver tends to corrode in acidic environments, giving off charged ions — silver salts — that can be toxic in large amounts. Hurt’s graduate student, Jingyu Liu (now a postdoctoral fellow at the National Institute of Standards and Technology), thought those same toxic ions might also be produced when silver enters the body, and could play a role in argyria.

To find out, the researchers mixed a series chemical treatments that could simulate what might happen to silver inside the body. One treatment simulated the acidic environment in the gastrointestinal tract; one mimicked the protein content of the bloodstream; and a collagen gel replicated the base membranes of the skin.

They found that nanosilver corrodes in stomach acid in much the same way it does in other acidic environments. Corrosion strips silver atoms of electrons, forming positively charged silver salt ions. Those ions can easily be taken into the bloodstream through channels that absorb other types of salt. That’s a crucial step, Hurt said. Silver metal particles themselves aren’t terribly likely to make it from the GI tract to the blood, but when they’re transformed into a salt, they’re ushered right through.

From there, Hurt and his team showed that silver ions bind easily with sulfur present in blood proteins, which would give them a free ride through the bloodstream. Some of those ions would eventually end up in the skin, where they’d be exposed to light.

To re-create this end stage, the researchers shined ultraviolet light on collagen gel containing silver ions. The light caused electrons from the surrounding materials to jump onto the unstable ions, returning them to their original state — elemental silver. This final reaction is ultimately what turns patients’ skin blue. The photoreaction is similar to the way silver is used in black and white photography [emphasis mine]. When exposed to light, silver salts on a photographic film reduce to elemental silver and darken, creating an image.

While I find the notion that the body’s reaction to silver is similar to the processing of silver in black and white photography, it’s the discussion about toxicity that most interests me. The scientists at Brown are suggesting that   standard ‘ingestable’ silver could be more dangerous than silver nanoparticles when they are consumed in the body,

This research, however, “would be one piece of evidence that you could treat nanoparticles in the same way as other forms of silver,” Hurt says.

That’s because the bioavailable form of silver — the form that is absorbed into the bloodstream — is the silver salt that’s made in the stomach. Any elemental silver that’s ingested is just the raw material to make that bioavailable salt. So ingesting silver in any form, be it nano or not, would have basically the same effect, Hurt said.

“The concern in this case is the total dose of silver, not what form it’s in,” Hurt said. “This study implies that silver nanoparticles will be less toxic than an equivalent amount of silver salt, at least in this exposure scenario [emphasis mine].”

This research provides more evidence supporting Dr. Andrew Maynard’s contention that creating definitions and regulations for nanomaterials based on size may not be the best approach. Here’s his response to my question (in an Oct. 24, 2011 posting) about the then newly adopted Health Canada definition (which includes size) for nanomaterials,

The problem is that, while the Health Canada is a valiant attempt to craft a definition based on the current state of science, it is still based on a premise – that size within a well defined range is a robust indicator of novel risk – that is questionable [emphasis mine].  Granted, they try to compensate for the limitations of this premise, but the result still smacks of trying to shoehorn the science into an assumption of what is important.

One can only wait as the evidence continues to mount on one side or the other. In the meantime, I don’t one can ever go wrong with BB King, one of the great blues guitar players (Blues Boys Tune),

It’s the length, not the size that matters with nanofibres such as carbon nanotubes

The Aug. 22, 2012 news item on Nanowerk by way of Feedzilla features some research at the University of Edinburgh which determined that short nanofibres do not have the same effect on lung cells as longer fibres do. From the news item, here’s a description of why this research was undertaken

Nanofibres, which can be made from a range of materials including carbon, are about 1,000 times smaller than the width of a human hair and can reach the lung cavity when inhaled.

This may lead to a cancer known as mesothelioma, which is known to be caused by breathing in asbestos fibres, which are similar to nanofibres.

I wrote about research at Brown University which explained why some fibres get stuck in lung cells in a Sept. 22, 2011 posting titled, Why asbestos and carbon nanotubes are so dangerous to cells. The short answer is: if the tip is rounded, the cell mistakes the fibre for a sphere and, in error, it attempts to absorb it. Here’s some speculation on my part about what the results might mean (from my Sept. 22, 2011 posting),

The whole thing has me wondering about long vs. short carbon nanotubes. Does this mean that short carbon nanotubes can be ingested successfully? If so, at what point does short become too long to ingest?

The University of Edinburgh Aug. 22, 2012 news release provides answer to last year’s  speculation about length,

The University study found that lung cells were not affected by short fibres that were less than five-thousandths of a millimetre long.

However, longer fibres can reach the lung cavity, where they become stuck and cause disease.

We knew that long fibres, compared with shorter fibres, could cause tumours but until now we did not know the cut-off length at which this happened. Knowing the length beyond which the tiny fibres can cause disease is important in ensuring that safe fibres are made in the future as well as helping to understand the current risk from asbestos and other fibres, [said] Ken Donaldson, Professor of Respiratory Toxicology.

Sometimes, I surprise myself. I think I’ll take a moment to bask. … Done now!

Here’s my final thought, while this research suggests short length nanofibres won’t cause mesothelioma, this doesn’t rule out  other potential problems. So, let’s celebrate this new finding and then get back to investigating nanofibres and their impact on health.

Get the platinum out

They’ve been using platinum catalysts, in fuel cells and metal-air batteries, which over the last five years has ranged in cost from just under $800/oz to over $2200/oz. My March 13, 2012 posting about fuel cells noted that the use of expensive metals that are not very efficient catalysts was holding back their development and entry into the marketplace,

Advances in fuel-cell technology have been stymied by the inadequacy of metals studied as catalysts. The drawback to platinum, other than cost, is that it absorbs carbon monoxide in reactions involving fuel cells powered by organic materials like formic acid. A more recently tested metal, palladium, breaks down over time.

Now chemists at Brown University have created a triple-headed metallic nanoparticle that they say outperforms and outlasts all others at the anode end in formic-acid fuel-cell reactions.

Another group of researchers at Stanford University and other institutions is suggesting an alternative to a platinum catalyst, a multi-walled carbon nanotube. From the May 27, 2012 news release written by Mark Shwartz on EurekAlert,

Multi-walled carbon nanotubes riddled with defects and impurities on the outside could replace some of the expensive platinum catalysts used in fuel cells and metal-air batteries, according to scientists at Stanford University. Their findings are published in the May 27 online edition of the journal Nature Nanotechnology.

“Platinum is very expensive and thus impractical for large-scale commercialization,” said Hongjie Dai, a professor of chemistry at Stanford and co-author of the study. “Developing a low-cost alternative has been a major research goal for several decades.”

For the study, the Stanford team used multi-walled carbon nanotubes consisting of two or three concentric tubes nested together. The scientists showed that shredding the outer wall, while leaving the inner walls intact, enhances catalytic activity in nanotubes, yet does not interfere with their ability to conduct electricity.

“A typical carbon nanotube has few defects,” said Yanguang Li, a postdoctoral fellow at Stanford and lead author of the study. “But defects are actually important to promote the formation of catalytic sites and to render the nanotube very active for catalytic reactions.”

Here’s how it works, from the May 27, 2012 news release on EurekAlert,

For the study, Li and his co-workers treated multi-walled nanotubes in a chemical solution. Microscopic analysis revealed that the treatment caused the outer nanotube to partially unzip and form nanosized graphene pieces that clung to the inner nanotube, which remained mostly intact.

“We found that adding a few iron and nitrogen impurities made the outer wall very active for catalytic reactions,” Dai said. “But the inside maintained its integrity, providing a path for electrons to move around. You want the outside to be very active, but you still want to have good electrical conductivity. If you used a single-wall carbon nanotube you wouldn’t have this advantage, because the damage on the wall would degrade the electrical property.”

These are two different perspectives on the reason for why fuel cells and other batteries have not had the expected impact on the marketplace. The team at Brown University states the problem as an issue with the effectiveness of the metal catalysts where the Stanford-led team states the problem as being the cost of the metal used. Dexter Johnson in a March 9, 2012 posting on the Nanoclast blog on the IEEE (Institute of Electrical and Electronics Engineers) website suggested a third issue,

One of the fundamental problems with fuel cells has been the cost of producing hydrogen. While hydrogen is, of course, the most abundant element, it attaches itself to other elements like nitrogen or fluorine, and perhaps most ubiquitously to oxygen to create the water molecule. The process used to separate hydrogen out into hydrogen gas for powering fuel cells now relies on electricity produced from fossil fuels, negating some of the potential environmental benefits.

In his May 30, 2012 posting about this new work from Stanford, Dexter notes yet another issue impeding widespread commercialization,

… but the two main issues that have prevented fuel cells from gaining wider adoption—at least in the area of powering automobiles—are the costs of isolating hydrogen and building an infrastructure that would deliver that hydrogen to the automobiles.

Dexter mentions another application (metal-air batteries) that may benefit more from this latest work (from Dexter’s May 30, 2012 posting),

I think it’s all together possible that researchers at IBM and the US national labs who have been working on metal-air batteries for years now might be somewhat more interested in this line of research than fuel-cell manufacturers.

As one of the researchers notes (from the May 27, 2012 news release on EurekAlert),

“Lithium-air batteries are exciting because of their ultra-high theoretical energy density, which is more than 10 times higher than today’s best lithium ion technology,” Dai said. “But one of the stumbling blocks to development has been the lack of a high-performance, low-cost catalyst. Carbon nanotubes could be an excellent alternative to the platinum, palladium and other precious-metal catalysts now in use.”

The Stanford team made one other discovery as they were testing the carbon nanotubes,

The Stanford study might also have resolved a long-standing scientific controversy about the chemical structure of catalytic active sites where oxygen reactions occur. “One group of scientists believes that iron impurities are bonded to nitrogen at the active site,” Li said. “Another group believes that iron contributes virtually nothing, except to promote active sites made entirely of nitrogen.”

To address the controversy, the Stanford team enlisted scientists at Oak Ridge National Laboratory to conduct atomic-scale imaging and spectroscopy analysis of the nanotubes. The results showed clear, visual evidence of iron and nitrogen atoms in close proximity.

“For the first time, we were able to image individual atoms on this kind of catalyst,” Dai said. “All of the images showed iron and nitrogen close together, suggesting that the two elements are bonded. This kind of imaging is possible, because the graphene pieces are just one-atom thick.”

Dai noted that the iron impurities, which enhanced catalytic activity, actually came from metal seeds that were used to make the nanotubes and were not intentionally added by the scientists. The discovery of these accidental yet invaluable bits of iron offered the researchers an important lesson. “We learned that metal impurities in nanotubes must not be ignored,” Dai said.

Brain-controlled robotic arm means drinking coffee by yourself for the first time in 15 years

The video shows a woman getting herself a cup of coffee for the first time in 15 years. She’s tetraplegic (aka quadraplegic) and is participating in a research project funded by DARPA (US Defense Advanced Research Projects Agency) for developing neuroprostheses.

Kudos to the researchers and to the woman for her courage and persistence. The May 17, 2012 news item on Nanowerk provides some background,

DARPA launched the Revolutionizing Prosthetics program in 2006 to advance the state of upper-limb prosthetic technology with the goals of improving quality of life for service-disabled veterans and ultimately giving them the option of returning to duty. [emphasis mine] Since then, Revolutionizing Prosthetics teams have developed two anthropomorphic advanced modular prototype prosthetic arm systems, including sockets, which offer increased range of motion, dexterity and control options. Through DARPA-funded work and partnerships with external researchers, the arm systems and supporting technology continue to advance.

The newest development on this project (Revolutionizing Prosthetics) comes from the BrainGate team (mentioned in my April 19, 2012 posting [scroll down about 1/5th of the way) many of whom are affiliated with Brown University.  Alison Abbott’s May 16, 2012 Nature article provides some insight into the latest research,

The study participants — known as Cathy and Bob — had had strokes that damaged their brain stems and left them with tetraplegia and unable to speak. Neurosurgeons implanted tiny recording devices containing almost 100 hair-thin electrodes in the motor cortex of their brains, to record the neuronal signals associated with intention to move.

The work is part of the BrainGate2 clinical trial, led by John Donoghue, director of the Brown Institute for Brain Science in Providence. His team has previously reported a trial in which two participants were able to move a cursor on a computer screen with their thoughts.

The neuroscientists are working closely with computer scientists and robotics experts. The BrainGate2 trial uses two types of robotic arm: the DEKA Arm System, which is being developed for prosthetic limbs in collaboration with US military, and a heavier robot arm being developed by the German Aerospace Centre (DLR) as an external assistive device.

In the latest study, the two participants were given 30 seconds to reach and grasp foam balls. Using the DEKA arm, Bob — who had his stroke in 2006 and was given the neural implant five months before the study —- was able to grasp the targets 62% of the time. Cathy had a 46% success rate with the DEKA arm and a 21% success rate with the DLR arm. She successfully raised the bottled coffee to her lips in four out of six trials.

Nature has published the research paper (citation):

Reach and grasp by people with tetraplegia using a neurally controlled robotic arm

Authors: Leigh R. Hochberg, Daniel Bacher, Beata Jarosiewicz, Nicolas Y. Masse, John D. Simeral, Joern Vogel, Sami Haddadin, Jie Liu, Sydney S. Cash, Patrick van der Smagt and John P. Donoghue

Nature, 485, 372–375 (17 May 2012) doi:10.1038/nature11076

The paper is behind a paywall but if you have access, it’s here.

In the excess emotion after watching that video, I forgot for a moment that the ultimate is to repair soldiers and hopefully get them back into the field.

US soldiers get batteries woven into their clothes

Last time I wrote about soldiers, equipment, and energy-efficiency (April 5, 2012 posting) the soldiers in question were British. Today’s posting focuses on US soldiers. From the May 7, 2012 news item on Nanowerk,

U.S. soldiers are increasingly weighed down by batteries to power weapons, detection devices and communications equipment. So the Army Research Laboratory has awarded a University of Utah-led consortium almost $15 million to use computer simulations to help design materials for lighter-weight, energy efficient devices and batteries.

“We want to help the Army make advances in fundamental research that will lead to better materials to help our soldiers in the field,” says computing Professor Martin Berzins, principal investigator among five University of Utah faculty members who will work on the project. “One of Utah’s main contributions will be the batteries.”

Of the five-year Army grant of $14,898,000, the University of Utah will retain $4.2 million for research plus additional administrative costs. The remainder will go to members of the consortium led by the University of Utah, including Boston University, Rensselaer Polytechnic Institute, Pennsylvania State University, Harvard University, Brown University, the University of California, Davis, and the Polytechnic University of Turin, Italy.

The new research effort is based on the idea that by using powerful computers to simulate the behavior of materials on multiple scales – from the atomic and molecular nanoscale to the large or “bulk” scale – new, lighter, more energy efficient power supplies and materials can be designed and developed. Improving existing materials also is a goal.

“We want to model everything from the nanoscale to the soldier scale,” Berzins says. “It’s virtual design, in some sense.”

“Today’s soldier enters the battle space with an amazing array of advanced electronic materials devices and systems,” the University of Utah said in its grant proposal. “The soldier of the future will rely even more heavily on electronic weaponry, detection devices, advanced communications systems and protection systems. Currently, a typical infantry soldier might carry up to 35 pounds of batteries in order to power these systems, and it is clear that the energy and power requirements for future soldiers will be much greater.” [emphasis mine]

“These requirements have a dramatic adverse effect on the survivability and lethality of the soldier by reducing mobility as well as the amount of weaponry, sensors, communication equipment and armor that the soldier can carry. Hence, the Army’s desire for greater lethality and survivability of its men and women in the field is fundamentally tied to the development of devices and systems with increased energy efficiency as well as dramatic improvement in the energy and power density of [battery] storage and delivery systems.”

Up to 35 lbs. of batteries? I’m trying to imagine what the rest of the equipment would weigh. In any event, they seem to be more interested in adding to the weaponry than reducing weight. At least, that’s how I understand “greater *lethality.” Nice of them to mention greater survivability too.

The British project is more modest, they are weaving e-textiles that harvest energy allowing British soldiers to carry fewer batteries. I believe field trials were scheduled for May 2012.

* Correction: leathility changed to lethality on July 31, 2013.