Tag Archives: CNTs

Carbon nanotubes burst forth (in a phallic manner) from the flames

Is this or is this not a phallic image?

Caption: This is a carbon nanotube growth. Credit: ITbM, Nagoya University

Caption: This is a carbon nanotube growth.
Credit: ITbM, Nagoya University

I suppose you could also describe it as a finger. In any event, the research associated with this image concerns a newly observed similarity between carbon nanotube (CNT) growth and hydrocarbon combustion (fuel combustion), according to an April 1, 2014 news item on ScienceDaily,

Professor Stephan Irle of the Institute of Transformative Bio-Molecules (WPI-ITbM) at Nagoya University and co-workers at Kyoto University, Oak Ridge National Lab (ORNL), and Chinese research institutions have revealed through theoretical simulations that the molecular mechanism of carbon nanotube (CNT) growth and hydrocarbon combustion actually share many similarities. In studies using acetylene molecules (ethyne; C2H2, a molecule containing a triple bond between two carbon atoms) as feedstock, the ethynyl radical (C2H), a highly reactive molecular intermediate was found to play an important role in both processes forming CNTs and soot, which are two distinctively different structures. The study published online on January 24, 2014 in Carbon, is expected to lead to identification of new ways to control the growth of CNTs and to increase the understanding of fuel combustion processes.

A March 31, 2014 Institute of Transformative Bio-Molecules (ITbM), Nagoya University press release (also on EurekAlert but dated April 1, 2014), which originated the news item, provides some specifics about carbon nanotubes and about the research,

CNTs are molecules with a cylindrical nanostructure (nano = 10-9 m or 1 / 1,000,000,000 m [one billionth of a metre]). Arising from their unique physical and chemical properties, CNTs have found technological applications in the fields of electronics, optics and materials science. CNTs can be synthesized by a method called chemical vapor deposition, where hydrocarbon vapor molecules are deposited on transition metal catalysts under a flow of non-reactive gas at high temperatures. Current issues with this method are that the CNTs are usually produced as mixtures of nanotubes with various diameters and different sidewall structures. Theoretical simulations coordinated by Professor Irle have looked into the molecular mechanisms of CNT growth using acetylene molecules as feedstock (Figure 1). The outcome of their research provides insight into identifying new parameters that can be varied to improve the control over product distributions in the synthesis of CNTs.

High level theoretical calculations using quantum chemical molecular dynamics were performed to study the early stages of CNT growth from acetylene molecules on small iron (Fe38) clusters. Previous mechanistic studies have postulated complete breakdown of hydrocarbon source gases to atomic carbon before CNT growth. “Our simulations have shown that acetylene oligomerization and cross-linking reactions between hydrocarbon chains occur as major reaction pathways in CNT growth, along with decomposition to atomic carbon” says Professor Stephan Irle, who led the research, “this follows hydrogen-abstraction acetylene addition (HACA)-like mechanisms that are commonly observed in combustion processes” he continues.

Combustion processes are known to proceed by the hydrogen-abstraction acetylene addition (HACA)-like mechanism. Initiation of the mechanism begins with hydrogen atom abstraction from a precursor molecule followed by acetylene addition, and the repetitive cycle leads to formation of ring-structured polycylic aromatic carbons (PAHs). In this process, the highly reactive ethynyl radical (C2H) is continually being regenerated, extending the rings of PAHs and eventually forming soot. The same key reactive intermediate is observed in CNT growth and acts as an organocatalyst (a catalyst based on an organic molecule) facilitating hydrogen transfer reactions across growing hydrocarbon clusters. The simulations identify an intriguing bifurcation process by which hydrogen-rich hydrocarbon species enrich hydrogen content creating non-CNT byproducts, and hydrogen-deficient hydrocarbon species enrich carbon content leading to CNT growth … .

“We started this type of research from 2000, and long simulation time has been a great challenge to conduct full simulations across all participating molecules, due to the relatively high strength of the carbon-hydrogen bond. [emphasis mine] By establishing and using a fast method of calculation, we were able to successfully incorporate hydrogen in our calculations for the first time, which led to this new understanding revealing the similarity between CNT growth and hydrocarbon combustion processes. This finding is very intriguing in the sense that these processes were long considered to proceed by completely different mechanisms” elaborates Professor Irle.

I’m always impressed with the determination and persistence scientists demonstrate in their work and taking almost 14 years to study hydrocarbon combustion and carbon nanotube  growth in such detail is another among many, many such examples.

For the curious, here’s a link to and a citation for the paper,

Quantum chemical simulations reveal acetylene-based growth mechanisms in the chemical vapor deposition synthesis of carbon nanotubes by Ying Wang, Xingfa Gao, Hu-Jun Qian, Yasuhito Ohta, Xiaona Wu, Gyula Eres, Keiji Morokuma, and Stephan Irle, Carbon 72, 22-37 (2014). DOI:10.1016/j.carbon.2014.01.020

This paper is behind a paywall.

Bayer MaterialScience divests itself of carbon nanotube and graphene patents

Last year’s announcement from Bayer MaterialScience about withdrawing from the carbon nanotube market (featured in my May 9, 2013 posting) has now been followed with news of the company’s sale of its intellectual property (patents) associated with carbon nanotubes (CNTs) and graphene. From a March 31, 2014 news item on Nanowerk,

After concluding its research work on carbon nanotubes (CNT) and graphenes, Bayer MaterialScience is divesting itself of fundamental intellectual property in this field. The company FutureCarbon GmbH, based in Bayreuth, Germany, will acquire, as leading provider of carbon-based composites, the bulk of the corresponding patents from the past ten years. The two parties have now signed an agreement to this effect. The financial details of the transfer will not be disclosed.

The March 31, 2014 Bayer news release, which originated the news item, describes the winning bidder,

FutureCarbon GmbH is a leading innovator and provider of novel, carbon-based composites. As a specialist in the manufacture and in particular the refinement of various carbon materials, FutureCarbon enables a broad range of strategic industries, to easily utilize the extraordinary properties of carbon materials in their products.

“We enjoy a long-standing development partnership with Bayer. We are happy that we were able to acquire the Bayer patents for further market realization of the technology. They expand our applications base substantially and open up new possibilities and business segments for us,” said Dr. Walter Schütz, managing director of the Bayreuth company.

After Bayer MaterialScience announced the conclusion of its CNT projects in May 2013, various companies indicated their interest in making concrete use of intellectual property developed before the decision was made for FutureCarbon as ideal partner for taking over the accomplished knowledge.

About FutureCarbon GmbH
FutureCarbon specializes in the development and manufacture of carbon nanomaterials and their refinement to create what are called carbon supercomposites, primary products for further industrial processing. Carbon supercomposites are combinations of materials that unfold the special characteristics of carbon nano-materials in the macroscopic world of real applications. All of our materials are manufactured on an industrial scale.

You can find out more about FutureCarbon here.

Smart suits for US soldiers—an update of sorts from the Lawrence Livermore National Laboratory

The US military has funded a program named: ‘Dynamic Multifunctional Material for a Second Skin Program’ through its Defense Threat Reduction Agency’s (DTRA) Chemical and Biological Technologies Department and Sharon Gaudin’s Feb. 20,  2014 article for Computer World offers a bit of an update on this project,which was first reported in 2012,

A U.S. soldier is on patrol with his squad when he kneels to check something out, unknowingly putting his knee into a puddle of contaminants.

The soldier isn’t harmed, though, because he or she is wearing a smart suit that immediately senses the threat and transforms the material covering his knee into a protective state that repels the potential deadly bacteria.

Scientists at the Lawrence Livermore National Laboratory, a federal government research facility in Livermore, Calif., are using nanotechnology to create clothing designed to protect U.S. soldiers from chemical and biological attacks.

“The threat is nanoscale so we need to work in the nano realm, which helps to keep it light and breathable,” said Francesco Fornasiero, a staff scientist at the lab. “If you have a nano-size threat, you need a nano-sized defense.”

Fornasiero said the task is a difficult one, and the suits may not be ready for the field for another 10 to 20 years. [emphasis mine]

One option is to use carbon nanotubes in a layer of the suit’s fabric. Sweat and air would be able to easily move through the nanotubes. However, the diameter of the nanotubes is smaller than the diameter of bacteria and viruses. That means they would not be able to pass through the tubes and reach the person wearing the suit.

However, chemicals that might be used in a chemical attack are small enough to fit through the nanotubes. To block them, researchers are adding a layer of polymer threads that extend up from the top of the nanotubes, like stalks of grass coming up from the ground.

The threads are designed to recognize the presence of chemical agents. When that happens, they swell and collapse on top of the nanotubes, blocking anything from entering them.

A second option that the Lawrence Livermore scientists are working on involves similar carbon nanotubes but with catalytic components in a polymer mesh that sits on top of the nanotubes. The components would destroy any chemical agents they come in contact with. After the chemicals are destroyed, they are shed off, enabling the suit to handle multiple attacks.

An October 6, 2012 (NR-12-10-06) Lawrence Livermore National Laboratory (LLNL) news release details the -project and the proponents,

Lawrence Livermore National Laboratory scientists and collaborators are developing a new military uniform material that repels chemical and biological agents using a novel carbon nanotube fabric.

The material will be designed to undergo a rapid transition from a breathable state to a protective state. The highly breathable membranes would have pores made of a few-nanometer-wide vertically aligned carbon nanotubes that are surface modified with a chemical warfare agent-responsive functional layer. Response to the threat would be triggered by direct chemical warfare agent attack to the membrane surface, at which time the fabric would switch to a protective state by closing the CNT pore entrance or by shedding the contaminated surface layer.

High breathability is a critical requirement for protective clothing to prevent heat-stress and exhaustion when military personnel are engaged in missions in contaminated environments. Current protective military uniforms are based on heavyweight full-barrier protection or permeable adsorptive protective overgarments that cannot meet the critical demand of simultaneous high comfort and protection, and provide a passive rather than active response to an environmental threat.

To provide high breathability, the new composite material will take advantage of the unique transport properties of carbon nanotube pores, which have two orders of magnitude faster gas transport rates when compared with any other pore of similar size.

“We have demonstrated that our small-size prototype carbon nanotube membranes can provide outstanding breathability in spite of the very small pore sizes and porosity,” said Sangil Kim, another LLNL scientist in the Biosciences and Biotechnology Division. “With our collaborators, we will develop large area functionalized CNT membranes.”

Biological agents, such as bacteria or viruses, are close to 10 nanometers in size. Because the membrane pores on the uniform are only a few nanometers wide, these membranes will easily block biological agents.

However, chemical agents are much smaller in size and require the membrane pores to be able to react to block the threat. To create a multifunctional membrane, the team will surface modify the original prototype carbon nanotube membranes with chemical threat responsive functional groups. The functional groups on the membrane will sense and block the threat like gatekeepers on entrance. A second response scheme also will be developed: Similar to how a living skin peels off when challenged with dangerous external factors, the fabric will exfoliate upon reaction with the chemical agent. In this way, the fabric will be able to block chemical agents such as sulfur mustard (blister agent), GD and VX nerve agents, toxins such as staphylococcal enterotoxin and biological spores such as anthrax.

The project is funded for $13 million over five years with LLNL as the lead institution. The Livermore team is made up of Fornasiero [Francesco Fornasiero], Kim and Kuang Jen Wu. Other collaborators and institutions involved in the project include Timothy Swager at Massachusetts Institute of Technology, Jerry Shan at Rutgers University, Ken Carter, James Watkins, and Jeffrey Morse at the University of Massachusetts-Amherst, Heidi Schreuder-Gibson at Natick Soldier Research Development and Engineering Center, and Robert Praino at Chasm Technologies Inc.

“Development of chemical threat responsive carbon nanotube membranes is a great example of novel material’s potential to provide innovative solutions for the Department of Defense CB needs,” said Tracee Harris, the DTRA science and technology manager for the Dynamic Multifunctional Material for a Second Skin Program. “This futuristic uniform would allow our military forces to operate safely for extended time periods and successfully complete their missions in environments contaminated with chemical and biological warfare agents.”

The Laboratory has a history in developing carbon nanotubes for a wide range of applications including desalination. “We have an advanced carbon nanotube platform to build and expand to make advancements in the protective fabric material for this new project,” Wu said.

The new uniforms could be deployed in the field in less than 10 years. [emphasis mine]

Since Gaudin’s 2014 article quotes one of the LLNL’s scientists, Francesco Fornasiero, with an estimate for the suit’s deployment into the field as 10 – 20 years as opposed to the “less than 10 years” estimated in the news release, I’m guessing the problem has proved more complex than was first anticipated.

For anyone who’s interested in more details about  US soldiers and nanotechnology,

  • May 1, 2013 article by Max Cacas for Signal Online provides more details about the overall Smart Skin programme and its goals.
  • Nov. 15, 2013 article by Kris Walker for Azonano.com describes the Smart Skin project along with others including the intriguingly titled: ‘Warrior Web’.
  • website for MIT’s (Massachusetts Institute of Technology) Institute for Soldier Nanotechnologies Note: The MIT researcher mentioned in the LLNL news release is a faculty member of the Institute for Soldier Nanotechnologies.
  • website for the Defense Threat Reduction Agency

Control the chirality, control your carbon nanotube

A Feb. 18, 2014 news item on ScienceDaily features a story not about a breakthrough but about a discovery that* could lead to one,

A single-walled carbon nanotube grows from the round cap down, so it’s logical to think the cap’s formation determines what follows. But according to researchers at Rice University, that’s not entirely so.

Theoretical physicist Boris Yakobson and his Rice colleagues found through exhaustive analysis that those who wish to control the chirality of nanotubes — the characteristic that determines their electrical properties — would be wise to look at other aspects of their growth.

The scientists have provided this image to illustrate chirality (‘twisting’) in carbon nanotubes,

Carbon nanotube caps are forced into shape by six pentagons among the array of hexagons in the single-atom-thick tube. Rice University researchers took a census of thousands of possible caps and found the energies dedicated to their formation have no bearing on the tube's ultimate chirality. Credit: Evgeni Penev/Rice University

Carbon nanotube caps are forced into shape by six pentagons among the array of hexagons in the single-atom-thick tube. Rice University researchers took a census of thousands of possible caps and found the energies dedicated to their formation have no bearing on the tube’s ultimate chirality.
Credit: Evgeni Penev/Rice University

The Feb. 17, 2014 Rice University news release (also on EurekAlert), which originated the news item, describe the process the scientists used to research chirality in carbon nanotubes,

To get a clear picture of how caps are related to nanotube chirality, the Rice group embarked upon a detailed, two-year census of the 4,500 possible cap formations for nanotubes of just two diameters, 0.8 and 1 nanometer, across 21 chiralities.

The cap of every nanotube has six pentagons – none of which may touch each other — among an array of hexagons, Penev said. They pull the cap and force it to curve, but their positions are not always the same from cap to cap.

But because a given chirality can have hundreds of possible caps, the determining factor for chirality must lie elsewhere, the researchers found. “The contribution of the cap is the elastic curvature energy, and then you just forget it,” Penev said.

“There are different factors that may be in play,” Yakobson said. “One is the energy portion dictated by the catalyst; another one may be the energy of the caps per se. So to get the big picture, we address the energy of the caps and basically rule it out as a factor in determining chirality.”

A nanotube is an atom-thick sheet of carbon atoms arranged in hexagons and rolled into a tube. Chirality refers to the hexagons’ orientation, and that angle controls how well the nanotube will conduct electricity.

A perfect conducting metallic nanotube would have the atoms arranged in “armchairs,” so-called because cutting the nanotube in half would make the top look like a series of wells with atoms for armrests. Turn the hexagons 30 degrees, though, will make a semiconducting “zigzag” nanotube.  Nanotubes can be one or the other, or the chiral angle can be anything in between, with a shifting range of electrical properties.

Getting control of these properties has been a struggle. Ideally, scientists could grow the specific kinds of nanotubes they need for an application, but in reality, they grow as a random assortment that must then be separated with a centrifuge or by other means.

Yakobson suspects the answer lies in tuning the interaction between the catalyst and the nanotube edge. “This study showed the energy involved in configuring the cap is reasonably flat,” he said. “That’s important to know because it allows us to continue to work on other factors.

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

Extensive Energy Landscape Sampling of Nanotube End-Caps Reveals No Chiral-Angle Bias for Their Nucleation by Evgeni S. Penev, Vasilii I. Artyukhov, and Boris I. Yakobson. ACS Nano, Article ASAP DOI: 10.1021/nn406462e Publication Date (Web): January 23, 2014
Copyright © 2014 American Chemical Society

This article is behind a paywall.

One final comment, it took these scientists two years of painstaking work to establish that caps are not the determining factor for chirality. It’s this type of story I find as fascinating, if not more so, as the big breakthroughs because it illustrates the  extraordinary drive it takes to extract even the smallest piece of information. I wish more attention was given to these incremental efforts.

* March 7, 2014 changed ‘while’ to ‘that’.

Buckypaper technology in Florida (US) receives $!.4M grant

Just after suggesting (as per my Nov. 26, 2013 posting) that Florida is quietly becoming a center for nanotechnology efforts in the US, there’s a $1.4M funding announcement for Florida State University’s High-Performance Materials Institute (HPMI. From the Nov. 27, 2013 news item on Nanowerk,

Florida State researchers have been awarded more than $1.4 million from the National Science Foundation to develop a system that will produce large amounts of a state-of-the-art material made from carbon nanotubes that researchers believe could transform everything from the way airplanes are built to how prosthetic limbs fit the human body.

“The goal is clear — to show industry the ability to use this in large-scale quantities,” said Richard Liang, director of FSU’s High-Performance Materials Institute (HPMI) and a professor for the FAMU-FSU College of Engineering. “We’re looking at a more efficient, cost effective way to do this.”

The Nov. 26, 2013 Florida State University (FSU) news release (also on EurekAlert), which originated the news item, provides greater detail about buckypaper, the team’s research work, and the team’s hopes for this grant,

The material, buckypaper, is a feather-light sheet made of carbon nanotubes that is being tested in electronics, energy, medicine, space and transportation.  The aviation industry, for example, is doing tests with buckypaper, and it’s projected that it could replace metal shielding in the Boeing 787, currently made up of 60 miles of cable.

Engineers believe that replacing the cable with buckypaper could reduce the weight of the Boeing 787 by as much as 25 percent.

Florida State researchers have been engaged in other projects with buckypaper as well, including the use of the material in creating more advanced and comfortable prosthetic sockets for amputee patients and multifunctional lightweight composites for aerospace applications.

As revolutionary as buckypaper technology is, a major hurdle for its future use is that it can take two or more hours and can cost as much as $500 to make just a small 7-inch by 7-inch piece.  Companies like Boeing need large amounts of it to use on an aircraft.

However, the current process is neither fast nor cheap.

So, Liang will spend the next four years developing a process to produce large-scale amounts of buckypaper. The process and materials would then be patented and marketed to meet the demands of the industrial partners.

Liang will be joined on the project by Arda Vanli, an HPMI researcher and an assistant professor in the Department of Industrial and Manufacturing Engineering, as well as researchers from Georgia Institute of Technology.

The US National Science Foundation (NSF) webpage listing the award describes the specific research being undertaken and introduces the term ‘Bucky-tapes’,

Award Abstract #1344672
SNM: Roll-to-Roll Manufacturing of High Quality Bucky-tape with Aligned and Crosslinked Carbon Nanotubes Through In-line Sensing and Control

Carbon nanotubes (CNTs) demonstrate amazing properties; however, currently only a fraction of these properties can be transferred into products that can be used by engineers and consumers. To effectively transfer CNTs? properties into useful products requires a method to efficiently align and covalently interconnect the CNTs into tailored architectures at the nanoscale. This project will establish the fundamental understanding and foundation for using CNTs to make thin sheet materials, called Bucky-tapes, which can be rapidly produced in roll form and scaled-up for industrial applications. The proposed method will use a modified die-casting manufacturing process utilizing the self-repelling effects of selected flow media. In-situ ultra-violet (UV) reaction chemistry can covalently interconnect the CNTs rapidly to improve the load transfer and thermal and electronic transport properties of CNT networks. In-line multi-stage stretching of the web could orient the randomly dispersed interconnected CNT networks into specific patterns to provide greater strength and optimized transport properties. In-line Raman spectra monitoring and multistage process models will provide affordable, closed loop quality control and variation reduction methods for a high quality consistent nanomanufacturing process. A prototype will be built to demonstrate the continuous roll-to-roll process for manufacturing strong Bucky-tapes with high electrical and thermal conductivity, and low manufacturing cost.

This project can transform CNT thin films networks from a lab-scale demonstration material into commercially viable products with superior properties potentially surpassing the state-of-the-art carbon fiber material. The continuous Bucky-tapes can lead to new materials applications in aerospace, electronics, energy, medicine, and transportation. For example, continuous Bucky-tape could replace metal shielding of 60 miles of cables in the Boeing 787 and reduce cable weight by 25%. The education and outreach plan will expose especially under-represented students to molecular design, nanomanufacturing process development and quality control, structure-property relationship studies. Application oriented materials-by-design and nanomanufacturing process development will motivate students into nanotechnology, manufacturing and new materials development.

I had mentioned this team’s work on buckypaper (or are they now calling it Bucky-tape?) in an Oct. 4, 2011 posting which features a video about buckypaper and in which I noted the possible applications for buckypaper closely mirror those for CNC (cellulose nanocrystals) or, as it’s also known,  NCC (nanocrystalline cellulose).

You can check out Florida State University’s High Performance Materials Institute here.

Ballooning with carbon nanotubes on behalf of climate science

What a gorgeous picture!

Scientific balloon launched from New Mexico in September 2013 carrying an experimental instrument designed to collect and measure the energy of light emitted by the Sun, with the help of NIST chips coated with carbon nanotubes. Credit: LASP

Scientific balloon launched from New Mexico in September 2013 carrying an experimental instrument designed to collect and measure the energy of light emitted by the Sun, with the help of NIST chips coated with carbon nanotubes.
Credit: LASP

US National Institute of Standards and Technology (NIST) researchers made the carbon nanotube chips which help the instruments in the pictured balloon (above) to collect data about light. From the Oct. 24, 2013 news item on Nanowerk,,

A huge plastic balloon floated high in the skies over New Mexico on Sept. 29, 2013, carrying instruments to collect climate-related test data with the help of carbon nanotube chips made by the National Institute of Standards and Technology (NIST).

The onboard instrument was an experimental spectrometer designed to collect and measure visible and infrared wavelengths of light ranging from 350 to 2,300 nanometers. Simpler, lighter and less expensive than conventional counterparts, the spectrometer was tested to determine how accurately it can measure the relative energy of light emitted by the Sun and subsequently reflected or scattered by the Earth and Moon.

The Oct. 22, 2013 NIST news release, which originated the news item, provides some additional detail (Note: Footnotes have been removed),

Researchers at NIST’s Boulder, Colo., campus made the spectrometer’s “slit,” a high-precision chip that selected the entering light. The device was made under a recent agreement between NIST and the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics (LASP). The slit was then calibrated at NIST’s Gaithersburg, Md., headquarters.

For nearly a decade, NIST Boulder researchers have been using carbon nanotubes, the darkest material on Earth, to make coatings for laser power detectors. Nanotubes efficiently absorb nearly all light across a broad span of wavelengths, a useful feature for reducing internal scatter in the balloon imager. NIST also has facilities for, and expertise in, pairing nanotubes with micromachined silicon chips.

The Oct. 1, 2013 LASP (University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics) news release about the project offers information about the climate change data the researchers are hoping to collect and about the spectrometer being used for that purpose,

The instrument, funded by a $4.7 million NASA Earth Science Technology Office Instrument Incubator Program contract, is intended to acquire extremely accurate radiometric measurements of Earth relative to the incident sunlight. Over time, such measurements can tell scientists about changes in land-use, vegetation, urban landscape use, and atmospheric conditions on our planet. Such long-term radiometric measurements from the HyperSpectral Imager for Climate Science (HySICS) instrument can then help scientists identify the drivers of climate change.

Greg Kopp, HySICS Principal Investigator and CU-LASP research scientist, said, “HySICS allows us to acquire an accurate baseline of current Earth conditions so that we can monitor changes that are so relevant to society. This high altitude balloon flight was the first of two to demonstrate the instrument’s potential space capabilities needed to extend the measurements around the globe and over longer times.”

The instrument relies on precise measurements of the Sun for on-orbit calibrations. These solar measurements provide calibrations of the Earth measurements against this well-measured solar reference that other high accuracy space assets provide. Based on accurate solar calibrations, the HySICS radiometric measurements of the Earth can thus establish a long-term data record that is ten times more accurate than any current measurements.

For anyone interested in a more technical description of the device, the NIST news release has this,

For the balloon spectrometer, known as HySICS (HyperSpectral Imager for Climate Science), NIST made two types of custom chips that were stacked together in a sandwich. In the middle were aperture chips, coated with aluminum to block light transmission through the silicon, with small rectangular openings etched into the chip to allow light into the instrument.

A precision spectrometer must ensure that it only gathers light coming directly from its target, so the two outer layers of the sandwich were masking chips—larger openings etched at an angle and coated with tall, thin carbon nanotubes. These VANTAs (“vertically aligned nanotube arrays”) act as superefficient sponges to absorb scattered or stray light across the entire spectral range of the Sun.

While the balloon was in flight, the spectrometer scanned the slit across the Sun to measure solar irradiance. Spectral filters were calibrated by scanning the slit across the Moon and making measurements with and without filters in the beam path. The spectrometer also imaged light emitted from the Earth using the Sun as a reference light source.

For the information junkies amongst us, the Oct. 22, 2013 NIST news release offers links to more information about carbon nanotubes, etc. while the Oct. 1, 2013 LASP news release offers contact information for lead researcher, Greg Kopp.

Super-black nanotechnology, space exploration, and carbon nanotubes grown by atomic layer deposition (ALD)

Super-black in this context means that very little light is reflected by the carbon nanotubes that a team at the US National Aeronautics and Space Administration (NASA) have produced. From a July 17, 2013 NASA news release (also here on EurekAlert),

A NASA engineer has achieved yet another milestone in his quest to advance an emerging super-black nanotechnology that promises to make spacecraft instruments more sensitive without enlarging their size.

A team led by John Hagopian, an optics engineer at NASA’s Goddard Space Flight Center in Greenbelt, Md., has demonstrated that it can grow a uniform layer of carbon nanotubes through the use of another emerging technology called atomic layer deposition or ALD. The marriage of the two technologies now means that NASA can grow nanotubes on three-dimensional components, such as complex baffles and tubes commonly used in optical instruments.

“The significance of this is that we have new tools that can make NASA instruments more sensitive without making our telescopes bigger and bigger,” Hagopian said. “This demonstrates the power of nanoscale technology, which is particularly applicable to a new class of less-expensive tiny satellites called Cubesats that NASA is developing to reduce the cost of space missions.”

(It’s the first time I’ve seen atomic layer deposition (ALD) described as an emerging technology; I’ve always thought of it as well established.)  Here’s a 2010 NASA video, which  provides a good explanation of this team’s work,

With the basic problem being less data due to light reflection from the instruments used to make the observations in space, the researchers determined that ALD might provide carbon nanotubes suitable for super-black instrumentation for space exploration. From the NASA news release,

To determine the viability of using ALD to create the catalyst layer, while Dwivedi [NASA Goddard co-investigator Vivek Dwivedi, University of Maryland] was building his new ALD reactor, Hagopian engaged through the Science Exchange the services of the Melbourne Centre for Nanofabrication (MCN), Australia’s largest nanofabrication research center. The Science Exchange is an online community marketplace where scientific service providers can offer their services. The NASA team delivered a number of components, including an intricately shaped occulter used in a new NASA-developed instrument for observing planets around other stars.

Through this collaboration, the Australian team fine-tuned the recipe for laying down the catalyst layer — in other words, the precise instructions detailing the type of precursor gas, the reactor temperature and pressure needed to deposit a uniform foundation. “The iron films that we deposited initially were not as uniform as other coatings we have worked with, so we needed a methodical development process to achieve the outcomes that NASA needed for the next step,” said Lachlan Hyde, MCN’s expert in ALD.

The Australian team succeeded, Hagopian said. “We have successfully grown carbon nanotubes on the samples we provided to MCN and they demonstrate properties very similar to those we’ve grown using other techniques for applying the catalyst layer. This has really opened up the possibilities for us. Our goal of ultimately applying a carbon-nanotube coating to complex instrument parts is nearly realized.”

For anyone who’d like a little more information about the Science Exchange, I posted about this scientific markeplace both on Sept. 2, 2011 after it was launched in August of that year and later on Dec. 19, 2011 in a followup about a specific nano project.

Getting back to super-black nanotechnology, here’s what the NASA team produced, from the news release,

During the research, Hagopian tuned the nano-based super-black material, making it ideal for this application, absorbing on average more than 99 percent of the ultraviolet, visible, infrared and far-infrared light that strikes it — a never-before-achieved milestone that now promises to open new frontiers in scientific discovery. The material consists of a thin coating of multi-walled carbon nanotubes about 10,000 times thinner than a strand of human hair.

Once a laboratory novelty grown only on silicon, the NASA team now grows these forests of vertical carbon tubes on commonly used spacecraft materials, such as titanium, copper and stainless steel. Tiny gaps between the tubes collect and trap light, while the carbon absorbs the photons, preventing them from reflecting off surfaces. Because only a small fraction of light reflects off the coating, the human eye and sensitive detectors see the material as black.

Before growing this forest of nanotubes on instrument parts, however, materials scientists must first deposit a highly uniform foundation or catalyst layer of iron oxide that supports the nanotube growth. For ALD, technicians do this by placing a component or some other substrate material inside a reactor chamber and sequentially pulsing different types of gases to create an ultra-thin film whose layers are literally no thicker than a single atom. Once applied, scientists then are ready to actually grow the carbon nanotubes. They place the component in another oven and heat the part to about 1,832  F (750 C). While it heats, the component is bathed in carbon-containing feedstock gas.

Congratulations to the team, I gather they’ve been working on this light absorption project for quite a while.

You probably can’t poison yourself by eating too many nanoparticles

Researchers, Ingrid Bergin in the Unit for Laboratory Animal Medicine, at the University of Michigan in Ann Arbor and Frank Witzmann in the Department of Cellular and Integrative Physiology, at Indiana University School of Medicine, in Indianapolis, have stated that ingesting food and beverage (translated by me from the more scientific description) with nanoparticles (at today’s current levels) is unlikely to prove toxic. A June 26, 2013 Inderscience news release on EurekAlert describes the researchers’ research and their conclusions,

Writing in a forthcoming issue of the International Journal of Biomedical Nanoscience and Nanotechnology, researchers have compared existing laboratory and experimental animal studies pertaining to the toxicity of nanoparticles most likely to be intentionally or accidentally ingested. Based on their review, the researchers determined ingestion of nanoparticles at likely exposure levels is unlikely to cause health problems, at least with respect to acute toxicity. Furthermore, in vitro laboratory testing, which often shows toxicity at a cellular level, does not correspond well with in vivo testing, which tends to show less adverse effects.

Ingrid Bergin in the Unit for Laboratory Animal Medicine, at the University of Michigan in Ann Arbor and Frank Witzmann in the Department of Cellular and Integrative Physiology, at Indiana University School of Medicine, in Indianapolis, explain that the use of particles that are in the nano size range (from 1 billionth to 100 billionths of a meter in diameter, 1-100 nm, other thereabouts) are finding applications in consumer products and medicine. These include particles such as nano-silver, which is increasingly used in consumer products and dietary supplements for its purported antimicrobial properties. Nanoparticles can have some intriguing and useful properties because they do not necessarily behave in the same chemical and physical ways as non-nanoparticle versions of the same material.

Nanoparticles are now used as natural flavor enhancers in the form of liposomes and related materials, food pigments and in some so-called “health supplements”. They are also used in antibacterial toothbrushes coated with silver nanoparticles, for instance in food and drink containers and in hygienic infant feeding equipment. They are also used to carry pharmaceuticals to specific disease sites in the body to reduce side effects. Nanoparticles actually encompass a very wide range of materials from pure metals and alloys, to metal oxide nanoparticles, and carbon-based and plastic nanoparticles. Because of their increasing utilization in consumer products, there has been concern over whether these small scale materials could have unique toxicity effects when compared to more traditional versions of the same materials.

Difficulties in assessing the health risks of nanoparticles include the fact that particles of differing materials and shapes can have different properties. Furthermore, the route of exposure (e.g. ingestion vs. inhalation) affects the likelihood of toxicity. The U.S. researchers evaluated the current literature specifically with respect to toxicity of ingested nanoparticles. They point out that, in addition to intentional ingestion as with dietary supplements, unintentional ingestion can occur due to nanoparticle presence in water or as a breakdown product from coated consumer goods. Inhaled nanoparticles also represent an ingestion hazard since they are coughed up, swallowed, and eliminated through the intestinal tract.

Based on their review, the team concludes that, “Ingested nanoparticles appear unlikely to have acute or severe toxic effects at typical levels of exposure.” Nevertheless, they add that the current literature is inadequate to assess whether nanoparticles can accumulate in tissues and have long-term effects or whether they might cause subtle alterations in gut microbial populations. The researchers stress that better methods are needed for correlating particle concentrations used for cell-based assessment of toxicity with the actual likely exposure levels to body cells. Such methods may lead to better predictive value for laboratory in vitro testing, which currently over-predicts toxicity of ingested nanoparticles as compared to in vivo testing.

The researchers focused specifically on ingestion via the gastrointestinal tract which I take to mean that they focused largely on nanoparticles in food (eaten) and liquid (swallowed).

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

Nanoparticle toxicity by the gastrointestinal route: evidence and knowledge gaps by Ingrid L. Bergin; Frank A. Witzmann.  Int. J. of Biomedical Nanoscience and Nanotechnology, 2013 Vol.3, No.1/2, pp.163 – 210.  DOI: 10.1504/IJBNN.2013.054515

I think the abstract further helps to understand the research focus,

The increasing interest in nanoparticles for advanced technologies, consumer products, and biomedical applications has led to great excitement about potential benefits but also concern over the potential for adverse human health effects. The gastrointestinal tract represents a likely route of entry for many nanomaterials, both directly through intentional ingestion or indirectly via nanoparticle dissolution from food containers or by secondary ingestion of inhaled particles. Additionally, increased utilisation of nanoparticles may lead to increased environmental contamination and unintentional ingestion via water, food animals, or fish. The gastrointestinal tract is a site of complex, symbiotic interactions between host cells and the resident microbiome. Accordingly, evaluation of nanoparticles must take into consideration not only absorption and extraintestinal organ accumulation but also the potential for altered gut microbes and the effects of this perturbation on the host. The existing literature was evaluated for evidence of toxicity based on these considerations. Focus was placed on three categories of nanomaterials: nanometals and metal oxides, carbon-based nanoparticles, and polymer/dendrimers with emphasis on those particles of greatest relevance to gastrointestinal exposures.

The article is behind a paywall.

I last mentioned Frank Witzmann here in a May 8, 2013 posting titled, US multicenter (Nano GO Consortium) study of engineered nanomaterial toxicology.

No more carbon nanotubes from Bayer MaterialScience

A May 8, 2013 news item on Nanowerk proclaims,

Bayer MaterialScience intends to focus its development activities more intently on topics that are closely linked to its core business. For that reason the company will bring its work on carbon nanotubes (CNTs) to a close. Precisely how the research results and know-how for the production and application CNT will be used further will be determined shortly.

Researchers from Bayer MaterialScience had collaborated with external partners in recent years to resolve complex issues related to the safe production of specific carbon nanotubes. [emphasis mine] Methods for scaling up the production processes were developed, as were new generations of catalysts and new types of products.

The timing for this announcement from Bayer MateriaScience is interesting given that the US National Institute of Occupational Health and Safety (NIOSH) just announced some stringent recommendations (almost zero) for occupational exposure to carbon nanofibers and carbon nanotubes (my Apr. 28, 2013 posting).

The May 8, 2013 Bayer MaterialScience news release, which originated the news item, provides more detail about the business decision,

Much of the knowledge gleaned over recent years was made available to other companies and research institutions within the Innovation Alliance Carbon Nanotubes (Inno.CNT), which counts Bayer MaterialScience among its roughly 90 members.

“We remain convinced that carbon nanotubes have huge potential,” says Patrick Thomas, Chief Executive Officer of Bayer MaterialScience. It has been found, however, that the potential areas of application that once seemed promising from a technical standpoint are currently either very fragmented or have few overlaps with the company’s core products and their application spectrum.

“For Bayer MaterialScience, groundbreaking applications for the mass market relating to our own portfolio and therefore comprehensive commercialization are not likely in the foreseeable future,” says Thomas. Nonetheless, this know-how provides an important basis for a possible later use of CNT, for example in the optimization of lithium ion batteries, Thomas says. “We are currently in contact with potential interested parties regarding the specific application of the know-how generated,” Thomas adds.

The conclusion of the nano projects has no impact on the headcount. All 30 people employed in this sector will be transferred to other suitable positions within the Group.

I”m glad to hear no one will lose their job.

Finally, I recall reading somewhere that there was a glut of carbon nanotube production and taking that with the recent NIOSH recommendation and Bayer’s claim of poor prospects for commercialization, it seems like one of those decisions that made itself.

ETA May 20, 2013: Dexter Johnson provides some insight into carbon nanotube production and the glut in his May 18, 2013 posting on Nanoclast (on the IEEE [Institute of Electrical and Electronics Engineers] website),

This [Bayer MaterialScience decision] is no surprise since there was a huge glut of product resulting in industry utilization rates that must have been in the single digits. This oversupplied market was the result of a MWNT [multi-walled nanotube] capacity arms race that started in the mid-2000s.

I recommend reading the rest of the posting where Dexter goes on to describe how pricing dropped precipitously from 2006 to 2009  and the resultant efforts to develop markets for the product.

US National Institute of Occupational Health and Safety sets recommendations for workplace exposure to carbon nanofibers/nanotubes

Earlier this week, the US National Institute of Occupational Health and Safety (NIOSH) set recommendations for workplace exposure to carbon nanotubes and carbon nanofibers. According to the Apr. 24, 2013 media advisory from the US Centers for Disease Control and Prevention (NIOSH’s parent agency), the recommendations have been issued in the new Current Intelligence Bulletin (CIB) no. 65. From CIB No. 65,

NIOSH is the leading federal agency conducting research and providing guidance on the occupational safety and health implications and applications of nanotechnology. As nanotechnology continues to expand into every industrial sector, workers will be at an increased risk of exposure to new nanomaterials. Today, nanomaterials are found in hundreds of products, ranging from cosmetics, to clothing, to industrial and biomedical applications. These nanoscale-based products are typically called “first generation” products of nanotechnology. Many of these nanoscale-based products are composed of engineered nanoparticles, such as metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes (buckyballs), among others. Early scientific studies have indicated that some of these nanoscale particles may pose a greater health risk than the larger bulk form of these materials.

Results from recent animal studies indicate that carbon nanotubes (CNT) and carbon nanofibers (CNF) may pose a respiratory hazard. CNTs and CNFs are tiny, cylindrical, large aspect ratio, manufactured forms of carbon. There is no single type of carbon nanotube or nanofiber; one type can differ from another in shape, size, chemical composition (from residual metal catalysts or functionalization of the CNT and CNF) and other physical and chemical characteristics. Such variations in composition and size have added to the complexity of understanding their hazard potential. Occupational exposure to CNTs and CNFs can occur not only in the process of manufacturing them, but also at the point of incorporating these materials into other products and applications. A number of research studies with rodents have shown adverse lung effects at relatively low-mass doses of CNT and CNF, including pulmonary inflammation and rapidly developing, persistent fibrosis. Although it is not known whether similar adverse health effects occur in humans after exposure to CNT and CNF, the results from animal research studies indicate the need to minimize worker exposure.

This NIOSH CIB, (1) reviews the animal and other toxicological data relevant to assessing the potential non-malignant adverse respiratory effects of CNT and CNF, (2) provides a quantitative risk assessment based on animal dose-response data, (3) proposes a recommended exposure limit (REL) of 1 μg/m3 elemental carbon as a respirable mass 8-hour time-weighted average (TWA) concentration, [emphasis mine] and (4) describes strategies for controlling workplace exposures and implementing a medical surveillance program. The NIOSH REL is expected to reduce the risk for pulmonary inflammation and fibrosis. However, because of some residual risk at the REL and uncertainty concerning chronic health effects, including whether some types of CNTs may be carcinogenic, continued efforts should be made to reduce exposures as much as possible.

The recommended exposure, for those of us who can’t read the technical notation, translates to one microgram per cubic meter per eight-hour workday.  In other words, almost zero. Note that this is a recommendation and not a regulation. H/T Apr. 26, 2013 article by Elizabeth Wiese for USA Today

My Mar. 12, 2013 posting highlights some of the NIOSH research which preceded this recommendation.