Using old newspapers to grow carbon nanotubes on a large scale

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A research collaboration between Rice University and the Energy Safety Research Institute (ESRI) at Swansea University has found that old newspapers can be used as a low cost, eco-friendly material on which to grow single walled carbon nanotubes on a large scale.

Carbon nanotubes are tiny molecules with incredible physical properties that can be used in a huge range of things, such as conductive films for touchscreen displays, flexible electronics, fabrics that create energy and antennas for 5G networks.

The new study, published in the MDPI Journal C , details the research experiments carried out in producing carbon nanotubes which could have the potential to solve some of the problems associated with their large scale production such as:-

  • The high cost of preparing a suitable surface for chemical growth.
  • The difficulties in scaling up the process, as only single surface growth processes have been previously available.

The research team discovered that the large surface area of newspapers provided an unlikely but ideal way to chemically grow carbon nanotubes.

Lead researcher Bruce Brinson said: “Newspapers have the benefit of being used in a roll-to-roll process in a stacked form making it an ideal candidate as a low-cost stackable 2D surface to grow carbon nanotubes.”

However, not all newspaper is equally good – only newspaper produced with sizing made from kaolin, which is china clay, resulted in carbon nanotube growth.

Co-author Varun Shenoy Gangoli said: “Many substances including talc, calcium carbonate, and titanium dioxide can be used in sizing in papers which act as a filler to help with their levels of absorption and wear. However it was our observation that kaolin sizing, and not calcium carbonate sizing, showed us how the growth catalyst, which in our case was iron, is affected by the chemical nature of the substrate.”

ESRI Director Andrew Barron, also a professor at Rice University in the USA, said: “While there have been previous research that shows that graphene, carbon nanotubes and carbon dots can be been synthesised on a variety of materials, such as food waste, vegetation waste, animal, bird or insect waste and chemically grown on natural materials, to date, this research has been limited.

“With our new research, we have found a continuous flow system that dramatically reduces the cost of both substrate and post synthesis process which could impact on the future mass manufacture of single walled carbon nanotubes.”

Learn more: RESEARCH SHOWS OLD NEWSPAPERS CAN BE USED TO GROW CARBON NANOTUBES

 

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The blackest black material . . . ever

A 16.78-carat natural yellow diamond from LJ West Diamonds (left), is coated with a new carbon nanotube-based material that is the blackest material on record (the covered diamond, shown at right). The diamond is the subject of The Redemption of Vanity, a work of art created by MIT Center for Art, Science, and Technology artist-in-residence Diemut Strebe, in collaboration with MIT engineer Brian Wardle and his lab, on view at the New York Stock Exchange. Image: R. Capanna, A. Berlato, and A. Pinato

Made from carbon nanotubes, the new coating is 10 times darker than other very black materials.

With apologies to “Spinal Tap,” it appears that black can, indeed, get more black.

MIT engineers report today that they have cooked up a material that is 10 times blacker than anything that has previously been reported. The material is made from vertically aligned carbon nanotubes, or CNTs — microscopic filaments of carbon, like a fuzzy forest of tiny trees, that the team grew on a surface of chlorine-etched aluminum foil. The foil captures at least 99.995 percent* of any incoming light, making it the blackest material on record.

The researchers have published their findings today in the journal ACS-Applied Materials and Interfaces. They are also showcasing the cloak-like material as part of a new exhibit today at the New York Stock Exchange, titled “The Redemption of Vanity.”

The artwork, a collaboration between Brian Wardle, professor of aeronautics and astronautics at MIT, and his group, and MIT Center for Art, Science, and Technology artist-in-residence Diemut Strebe, features a 16.78-carat natural yellow diamond from LJ West Diamonds, estimated to be worth $2 million, which the team coated with the new, ultrablack CNT material. The effect is arresting: The gem, normally brilliantly faceted, appears as a flat, black void.

Wardle says the CNT material, aside from making an artistic statement, may also be of practical use, for instance in optical blinders that reduce unwanted glare, to help space telescopes spot orbiting exoplanets.

“There are optical and space science applications for very black materials, and of course, artists have been interested in black, going back well before the Renaissance,” Wardle says. “Our material is 10 times blacker than anything that’s ever been reported, but I think the blackest black is a constantly moving target. Someone will find a blacker material, and eventually we’ll understand all the underlying mechanisms, and will be able to properly engineer the ultimate black.”

Wardle’s co-author on the paper is former MIT postdoc Kehang Cui, now a professor at Shanghai Jiao Tong University.

Into the void

Wardle and Cui didn’t intend to engineer an ultrablack material. Instead, they were experimenting with ways to grow carbon nanotubes on electrically conducting materials such as aluminum, to boost their electrical and thermal properties.

But in attempting to grow CNTs on aluminum, Cui ran up against a barrier, literally: an ever-present layer of oxide that coats aluminum when it is exposed to air. This oxide layer acts as an insulator, blocking rather than conducting electricity and heat. As he cast about for ways to remove aluminum’s oxide layer, Cui found a solution in salt, or sodium chloride.

At the time, Wardle’s group was using salt and other pantry products, such as baking soda and detergent, to grow carbon nanotubes. In their tests with salt, Cui noticed that chloride ions were eating away at aluminum’s surface and dissolving its oxide layer.

“This etching process is common for many metals,” Cui says. “For instance, ships suffer from corrosion of chlorine-based ocean water. Now we’re using this process to our advantage.”

Cui found that if he soaked aluminum foil in saltwater, he could remove the oxide layer. He then transferred the foil to an oxygen-free environment to prevent reoxidation, and finally, placed the etched aluminum in an oven, where the group carried out techniques to grow carbon nanotubes via a process called chemical vapor deposition.

By removing the oxide layer, the researchers were able to grow carbon nanotubes on aluminum, at much lower temperatures than they otherwise would, by about 100 degrees Celsius. They also saw that the combination of CNTs on aluminum significantly enhanced the material’s thermal and electrical properties — a finding that they expected.

What surprised them was the material’s color.

“I remember noticing how black it was before growing carbon nanotubes on it, and then after growth, it looked even darker,” Cui recalls. “So I thought I should measure the optical reflectance of the sample.

“Our group does not usually focus on optical properties of materials, but this work was going on at the same time as our art-science collaborations with Diemut, so art influenced science in this case,” says Wardle.

Wardle and Cui, who have applied for a patent on the technology, are making the new CNT process freely available to any artist to use for a noncommercial art project.

“Built to take abuse”

Cui measured the amount of light reflected by the material, not just from directly overhead, but also from every other possible angle. The results showed that the material absorbed at least 99.995 percent of incoming light, from every angle. In other words, it reflected 10 times less light than all other superblack materials, including Vantablack. If the material contained bumps or ridges, or features of any kind, no matter what angle it was viewed from, these features would be invisible, obscured in a void of black.

The researchers aren’t entirely sure of the mechanism contributing to the material’s opacity, but they suspect that it may have something to do with the combination of etched aluminum, which is somewhat blackened, with the carbon nanotubes. Scientists believe that forests of carbon nanotubes can trap and convert most incoming light to heat, reflecting very little of it back out as light, thereby giving CNTs a particularly black shade.

“CNT forests of different varieties are known to be extremely black, but there is a lack of mechanistic understanding as to why this material is the blackest. That needs further study,” Wardle says.

The material is already gaining interest in the aerospace community. Astrophysicist and Nobel laureate John Mather, who was not involved in the research, is exploring the possibility of using Wardle’s material as the basis for a star shade — a massive black shade that would shield a space telescope from stray light.

“Optical instruments like cameras and telescopes have to get rid of unwanted glare, so you can see what you want to see,” Mather says. “Would you like to see an Earth orbiting another star? We need something very black. … And this black has to be tough to withstand a rocket launch. Old versions were fragile forests of fur, but these are more like pot scrubbers — built to take abuse.”

*An earlier version of this story stated that the new material captures more than 99.96 percent of incoming light. That number has been updated to be more precise; the material absorbs at least 99.995 of incoming light.

Learn more: MIT engineers develop “blackest black” material to date

 

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Nanotube fibers can rewire damaged hearts

Illustration by James Philpot/Texas Heart Institute

Texas Heart doctors confirm Rice-made, conductive carbon threads are electrical bridges

Thin, flexible fibers made of carbon nanotubes have now proven able to bridge damaged heart tissues and deliver the electrical signals needed to keep those hearts beating.

Scientists at Texas Heart Institute (THI) report they have used biocompatible fibers invented at Rice University in studies that showed sewing them directly into damaged tissue can restore electrical function to hearts.

“Instead of shocking and defibrillating, we are actually correcting diseased conduction of the largest major pumping chamber of the heart by creating a bridge to bypass and conduct over a scarred area of a damaged heart,” said Dr. Mehdi Razavi, a cardiologist and director of Electrophysiology Clinical Research and Innovations at THI, who co-led the study with Rice chemical and biomolecular engineer Matteo Pasquali.

“Today there is no technology that treats the underlying cause of the No. 1 cause of sudden death, ventricular arrhythmias,” Razavi said. “These arrhythmias are caused by the disorganized firing of impulses from the heart’s lower chambers and are challenging to treat in patients after a heart attack or with scarred heart tissue due to such other conditions as congestive heart failure or dilated cardiomyopathy.”

Results of the studies on preclinical models appear as an open-access Editor’s Pick in the American Heart Association’s Circulation: Arrhythmia and Electrophysiology. The association helped fund the research with a 2015 grant.

The research springs from the pioneering 2013 invention by Pasquali’s lab of a method to make conductive fibers out of carbon nanotubes. The lab’s first threadlike fibers were a quarter of the width of a human hair, but contained tens of millions of microscopic nanotubes. The fibers are also being studied for electrical interfaces with the brain, for use in cochlear implants, as flexible antennas and for automotive and aerospace applications.

The experiments showed the nontoxic, polymer-coated fibers, with their ends stripped to serve as electrodes, were effective in restoring function during monthlong tests in large preclinical models as well as rodents, whether the initial conduction was slowed, severed or blocked, according to the researchers. The fibers served their purpose with or without the presence of a pacemaker, they found.

In the rodents, they wrote, conduction disappeared when the fibers were removed.

“The reestablishment of cardiac conduction with carbon nanotube fibers has the potential to revolutionize therapy for cardiac electrical disturbances, one of the most common causes of death in the United States,” said co-lead author Mark McCauley, who carried out many of the experiments as a postdoctoral fellow at THI. He is now an assistant professor of clinical medicine at the University of Illinois College of Medicine.

“Our experiments provided the first scientific support for using a synthetic material-based treatment rather than a drug to treat the leading cause of sudden death in the U.S. and many developing countries around the world,” Razavi added.

Many questions remain before the procedure can move toward human testing, Pasquali said. The researchers must establish a way to sew the fibers in place using a minimally invasive catheter, and make sure the fibers are strong and flexible enough to serve a constantly beating heart over the long term. He said they must also determine how long and wide fibers should be, precisely how much electricity they need to carry and how they would perform in the growing hearts of young patients.

“Flexibility is important because the heart is continuously pulsating and moving, so anything that’s attached to the heart’s surface is going to be deformed and flexed,” said Pasquali, who has appointments at Rice’s Brown School of Engineering and Wiess School of Natural Sciences.

“Good interfacial contact is also critical to pick up and deliver the electrical signal,” he said. “In the past, multiple materials had to be combined to attain both electrical conductivity and effective contacts. These fibers have both properties built in by design, which greatly simplifies device construction and lowers risks of long-term failure due to delamination of multiple layers or coatings.”

Razavi noted that while there are many effective antiarrhythmic drugs available, they are often contraindicated in patients after a heart attack. “What is really needed therapeutically is to increase conduction,” he said. “Carbon nanotube fibers have the conductive properties of metal but are flexible enough to allow us to navigate and deliver energy to a very specific area of a delicate, damaged heart.”

Learn more: Damaged hearts rewired with nanotube fibers

 

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Directly converting carbon fibers and nanotubes into diamond fibers at ambient temperature and pressure

High-resolution scanning electron microscopy images of (a) a carbon nano fiber (CNF) before pulsed laser annealing (PLA) technique, (b) CNF after PLA showing the conversion of carbon nano fibers into diamond nano fibers.

Research from North Carolina State University has demonstrated a new technique that converts carbon fibers and nanotubes into diamond fibers at ambient temperature and pressure in air using a pulsed laser method.

The conversion method involves melting the carbon using nanosecond laser pulses and then quenching, or rapidly cooling, the material.

These diamond fibers could find uses in nanoscale devices with functions ranging from quantum computing, sensing and communication to diamond brushes and field-emission displays. The method can also be used to create diamond-seeded carbon fibers that can be used to grow larger diamond structures using hot-filament chemical vapor deposition and plasma-enhanced chemical vapor deposition techniques. These larger diamond structures could find uses as tool coatings for oil and gas exploration as well as deep-sea drilling, and for diamond jewelry.

Previous methods used to convert non-diamond carbon to diamond have involved using extreme heat and pressure at great expense with a limited yield. Melting the carbon with laser pulses and then undercooling it with a substrate made of sapphire, glass or a plastic polymer are the two keys to the discovery, said Dr. Jagdish Narayan, John C. Fan Distinguished Chair Professor in the Department of Materials Science and Engineering at NC State and corresponding author of a paper describing the work.

“Without undercooling, you cannot convert carbon into diamond this way,” Narayan said.

When heated, carbon normally goes from a solid state to a gas. Using a substrate restricts heat flow from the laser pulse enough that the carbon does not change phases.

The laser, similar to those used for Lasik eye surgery, is used for only 100 nanoseconds and heats the carbon to a temperature of 4,000 Kelvin, about 3,727 degrees Celsius.

NC State has filed for a patent licensing the technology.

Learn more: New Method Allows Direct Conversion of Carbon Fibers and Nanotubes Into Diamond Fibers

 

 

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Artificial cells and hybrid systems that combine biological cells and man-made components come closer

An artist’s rendition of a carbon nanotube porin embedded in a cell membrane with a single strand of DNA passing through it. Image by Adam Gardner

Proteins in lipid membranes are one of the fundamental building blocks of biological functionality. Lawrence Livermore researchers have figured out how to mimic their role using carbon nanotube porins.

Using high-speed, atomic force microscopy (HS-AFM), the team showed that a new type of biomimetic channel — carbon nanotube porins (CNTPs) — also is laterally mobile in supported lipid membranes, mirroring biological protein behavior.

The research opens the door to use CNTPs as models to study membrane protein physics, as well as versatile and mobile components for artificial cells and hybrid systems that combine biological cells and man-made components.

Lipid membranes represent one the fundamental components of the architecture of life because they provide a versatile matrix for a variety of membrane proteins that can perform a variety of tasks including molecular recognition and signal transduction, metabolite transport and membrane remodeling.

The 2D fluid nature of the lipid membrane not only allows it to adapt to a variety of shapes, but also permits membrane proteins to diffuse within this 2D plane, enabling many important biological processes.

“To understand the fundamental physics of protein motion in the lipid membrane, we needed an approach that would combine simple and robust membrane protein models with imaging and tracking approaches that can follow membrane motion on the relevant length and time scales,” said Yuliang Zhang, an LLNL postdoctoral researcher and lead author of a paper in the journal, Philosophical Transactions of the Royal Society B.

The team created simple and versatile artificial membrane pore equivalents — CNTPs —that are made of short segments of single-wall carbon nanotubes that can self-insert into the lipid membrane and form a transmembrane pore. These very simple objects show a wealth of behaviors similar to membrane protein pores: they can transport water, ions and protons across the membrane.

“We found that the CNTPS were able to reproduce another key property of membrane proteins — their ability to diffuse in the lipid membrane,” said Alex Noy, LLNL scientist and the principal investigator on the CNTP project. “High-speed AFM imaging can capture real-time dynamics of CNTP motion in the supported lipid bi-layer membrane.”

Zhang said the study demonstrates that the similarities between CNTPs and biological membrane pores include not only similar transport properties, but also the ability to move laterally in the membrane.

Learn more: Carbon nanotubes mimic biology

 

 

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