Tag Archives: Rice University

Tattoo therapy for chronic disease?

It’s good to wake up to something truly new. In this case, it’s using tattoos and nanoparticles for medical applications. From a Sept. 22, 2016 news item on ScienceDaily,

A temporary tattoo to help control a chronic disease might someday be possible, according to scientists at Baylor College of Medicine [Texas, US] who tested antioxidant nanoparticles created at Rice University [Texas, US].

A Sept. 22, 2016 Rice University news release, which originated the news item, provides more information and some good explanations of the terms used (Note: Links have been removed),

A proof-of-principle study led by Baylor scientist Christine Beeton published today by Nature’s online, open-access journal Scientific Reports shows that nanoparticles modified with polyethylene glycol are conveniently choosy as they are taken up by cells in the immune system.

That could be a plus for patients with autoimmune diseases like multiple sclerosis, one focus of study at the Beeton lab. “Placed just under the skin, the carbon-based particles form a dark spot that fades over about one week as they are slowly released into the circulation,” Beeton said.

T and B lymphocyte cells and macrophages are key components of the immune system. However, in many autoimmune diseases such as multiple sclerosis, T cells are the key players. One suspected cause is that T cells lose their ability to distinguish between invaders and healthy tissue and attack both.

In tests at Baylor, nanoparticles were internalized by T cells, which inhibited their function, but ignored by macrophages. “The ability to selectively inhibit one type of cell over others in the same environment may help doctors gain more control over autoimmune diseases,” Beeton said.

“The majority of current treatments are general, broad-spectrum immunosuppressants,” said Redwan Huq, lead author of the study and a graduate student in the Beeton lab. “They’re going to affect all of these cells, but patients are exposed to side effects (ranging) from infections to increased chances of developing cancer. So we get excited when we see something new that could potentially enable selectivity.” Since the macrophages and other splenic immune cells are unaffected, most of a patient’s existing immune system remains intact, he said.

The soluble nanoparticles synthesized by the Rice lab of chemist James Tour have shown no signs of acute toxicity in prior rodent studies, Huq said. They combine polyethylene glycol with hydrophilic carbon clusters, hence their name, PEG-HCCs. The carbon clusters are 35 nanometers long, 3 nanometers wide and an atom thick, and bulk up to about 100 nanometers in globular form with the addition of PEG. They have proven to be efficient scavengers of reactive oxygen species called superoxide molecules, which are expressed by cells the immune system uses to kill invading microorganisms.

T cells use superoxide in a signaling step to become activated. PEG-HCCs remove this superoxide from the T cells, preventing their activation without killing the cells.

Beeton became aware of PEG-HCCs during a presentation by former Baylor graduate student Taeko Inoue, a co-author of the new study. “As she talked, I was thinking, ‘That has to work in models of multiple sclerosis,’” Beeton said. “I didn’t have a good scientific rationale, but I asked for a small sample of PEG-HCCs to see if they affected immune cells.

“We found they affected the T lymphocytes and not the other splenic immune cells, like the macrophages. It was completely unexpected,” she said.

The Baylor lab’s tests on animal models showed that small amounts of PEG-HCCs injected under the skin are slowly taken up by T lymphocytes, where they collect and inhibit the cell’s function. They also found the nanoparticles did not remain in T cells and dispersed within days after uptake by the cells.

“That’s an issue because you want a drug that’s in the system long enough to be effective, but not so long that, if you have a problem, you can’t remove it,” Beeton said. “PEG-HCCs can be administered for slow release and don’t stay in the system for long. This gives us much better control over the circulating half-life.”

“The more we study the abilities of these nanoparticles, the more surprised we are at how useful they could be for medical applications,” Tour said. The Rice lab has published papers with collaborators at Baylor and elsewhere on using functionalized nanoparticles to deliver cancer drugs to tumors and to quench the overproduction of superoxides after traumatic brain injuries.

Beeton suggested delivering carbon nanoparticles just under the skin rather than into the bloodstream would keep them in the system longer, making them more available for uptake by T cells. And the one drawback – a temporary but visible spot on the skin that looks like a tattoo – could actually be a perk to some.

“We saw it made a black mark when we injected it, and at first we thought that’s going to be a real problem if we ever take it into the clinic,” Beeton said. “But we can work around that. We can inject into an area that’s hidden, or use micropattern needles and shape it.

“I can see doing this for a child who wants a tattoo and could never get her parents to go along,” she said. “This will be a good way to convince them.”

The research was supported by Baylor College of Medicine, the National Multiple Sclerosis Society, National Institutes of Health, the Dan L. Duncan Cancer Center, John S. Dunn Gulf Coast Consortium for Chemical Genomics and the U.S. Army-funded Traumatic Brain Injury Consortium.

That’s an interesting list of funders at the end of the news release.

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

Preferential uptake of antioxidant carbon nanoparticles by T lymphocytes for immunomodulation by Redwan Huq, Errol L. G. Samuel, William K. A. Sikkema, Lizanne G. Nilewski, Thomas Lee, Mark R. Tanner, Fatima S. Khan, Paul C. Porter, Rajeev B. Tajhya, Rutvik S. Patel, Taeko Inoue, Robia G. Pautler, David B. Corry, James M. Tour, & Christine Beeton. Scientific Reports 6, Article number: 33808 (2016) doi:10.1038/srep33808 Published online: 22 September 2016

This paper is open access.

Here’s an image provided by the researchers,

Polyethylene glycol-hydrophilic carbon clusters developed at Rice University were shown to be selectively taken up by T cells, which inhibits their function, in tests at Baylor College of Medicine. The researchers said the nanoparticles could lead to new strategies for controlling autoimmune diseases like multiple sclerosis. (Credit: Errol Samuel/Rice University) - See more at: http://news.rice.edu/2016/09/22/tattoo-therapy-could-ease-chronic-disease/#sthash.sIfs3b0S.dpuf

Polyethylene glycol-hydrophilic carbon clusters developed at Rice University were shown to be selectively taken up by T cells, which inhibits their function, in tests at Baylor College of Medicine. The researchers said the nanoparticles could lead to new strategies for controlling autoimmune diseases like multiple sclerosis. (Credit: Errol Samuel/Rice University)

Carbon capture with asphalt

I wish I could turn back the clock a few years, so I could mention this research from Rice University (Texas, US) on using asphalt for carbon capture (more on why at the end of this post). From a Sept. 13, 2016 news item on Nanowerk (Note: A link has been removed),

Rice University laboratory has improved its method to turn plain asphalt into a porous material that can capture greenhouse gases from natural gas.

In research detailed this month in Advanced Energy Materials (“Ultra-High Surface Area Activated Porous Asphalt for CO2 Capture through Competitive Adsorption at High Pressures”), Rice researchers showed that a new form of the material can sequester 154 percent of its weight in carbon dioxide at high pressures that are common at gas wellheads.

A Sept. 12, 2016 Rice University news release, which originated the news item, further describes the work (Note: Links have been removed),

Raw natural gas typically contains between 2 and 10 percent carbon dioxide and other impurities, which must be removed before the gas can be sold. The cleanup process is complicated and expensive and most often involves flowing the gas through fluids called amines that can soak up and remove about 15 percent of their own weight in carbon dioxide. The amine process also requires a great deal of energy to recycle the fluids for further use.

“It’s a big energy sink,” said Rice chemist James Tour, whose lab developed a technique last year to turn asphalt into a tough, sponge-like substance that could be used in place of amines to remove carbon dioxide from natural gas as it was pumped from ocean wellheads.

Initial field tests in 2015 found that pressure at the wellhead made it possible for that asphalt material to adsorb, or soak up, 114 percent of its weight in carbon at ambient temperatures.

Tour said the new, improved asphalt sorbent is made in two steps from a less expensive form of asphalt, which makes it more practical for industry.

“This shows we can take the least expensive form of asphalt and make it into this very high surface area material to capture carbon dioxide,” Tour said. “Before, we could only use a very expensive form of asphalt that was not readily available.”

The lab heated a common type asphalt known as Gilsonite at ambient pressure to eliminate unneeded organic molecules, and then heated it again in the presence of potassium hydroxide for about 20 minutes to synthesize oxygen-enhanced porous carbon with a surface area of 4,200 square meters per gram, much higher than that of the previous material.

The Rice lab’s initial asphalt-based porous carbon collected carbon dioxide from gas streams under pressure at the wellhead and released it when the pressure was released. The carbon dioxide could then be repurposed or pumped back underground while the porous carbon could be reused immediately.

In the latest tests with its new material, Tours group showed its new sorbent could remove carbon dioxide at 54 bar pressure. One bar is roughly equal to atmospheric pressure at sea level, and the 54 bar measure in the latest experiments is characteristic of the pressure levels typically found at natural gas wellheads, Tour said.

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

Ultra-High Surface Area Activated Porous Asphalt for CO2 Capture through Competitive Adsorption at High Pressures by Almaz S. Jalilov, Yilun Li, Jian Tian, James M. Tour.  Advanced Energy Materials DOI: 10.1002/aenm.201600693  First published [online]: 8 September 2016

This paper is behind a paywall.

Finishing the story I started at the beginning of this post, I was at an early morning political breakfast a few years back when someone seated at our table asked me if there were any nanotechnology applications for carbon sequestration/capture. At the time, I could not bring any such applications to mind. (Sigh) Now I have an answer.

Graphene in the bone

An international team of US, Brazilian, and Indian scientists has developed a graphene-based material they believe could be used in bone implants. From a Sept. 2, 2016 news item on ScienceDaily,

Flakes of graphene welded together into solid materials may be suitable for bone implants, according to a study led by Rice University scientists.

The Rice lab of materials scientist Pulickel Ajayan and colleagues in Texas, Brazil and India used spark plasma sintering to weld flakes of graphene oxide into porous solids that compare favorably with the mechanical properties and biocompatibility of titanium, a standard bone-replacement material.

A Sept. 2, 2016 Rice University news release (also on EurekAlert), which originated the news item, explains the work in more detail,

The researchers believe their technique will give them the ability to create highly complex shapes out of graphene in minutes using graphite molds, which they believe would be easier to process than specialty metals.

“We started thinking about this for bone implants because graphene is one of the most intriguing materials with many possibilities and it’s generally biocompatible,” said Rice postdoctoral research associate Chandra Sekhar Tiwary, co-lead author of the paper with Dibyendu Chakravarty of the International Advanced Research Center for Powder Metallurgy and New Materials in Hyderabad, India. “Four things are important: its mechanical properties, density, porosity and biocompatibility.”

Tiwary said spark plasma sintering is being used in industry to make complex parts, generally with ceramics. “The technique uses a high pulse current that welds the flakes together instantly. You only need high voltage, not high pressure or temperatures,” he said. The material they made is nearly 50 percent porous, with a density half that of graphite and a quarter of titanium metal. But it has enough compressive strength — 40 megapascals — to qualify it for bone implants, he said. The strength of the bonds between sheets keeps it from disintegrating in water.

The researchers controlled the density of the material by altering the voltage that delivers the highly localized blast of heat that makes the nanoscale welds. Though the experiments were carried out at room temperature, the researchers made graphene solids of various density by raising these sintering temperatures from 200 to 400 degrees Celsius. Samples made at local temperatures of 300 C proved best, Tiwary said. “The nice thing about two-dimensional materials is that they give you a lot of surface area to connect. With graphene, you just need to overcome a small activation barrier to make very strong welds,” he said.

With the help of colleagues at Hysitron in Minnesota, the researchers measured the load-bearing capacity of thin sheets of two- to five-layer bonded graphene by repeatedly stressing them with a picoindenter attached to a scanning electron microscope and found they were stable up to 70 micronewtons. Colleagues at the University of Texas MD Anderson Cancer Center successfully cultured cells on the material to show its biocompatibility. As a bonus, the researchers also discovered the sintering process has the ability to reduce graphene oxide flakes to pure bilayer graphene, which makes them stronger and more stable than graphene monolayers or graphene oxide.

“This example demonstrates the possible use of unconventional materials in conventional technologies,” Ajayan said. “But these transitions can only be made if materials such as 2-D graphene layers can be scalably made into 3-D solids with appropriate density and strength.

“Engineering junctions and strong interfaces between nanoscale building blocks is the biggest challenge in achieving such goals, but in this case, spark plasma sintering seems to be effective in joining graphene sheets to produce strong 3-D solids,” he said.

The researchers have produced an animation depicting of graphene oxide layers being stacked,

A molecular dynamics simulation shows how graphene oxide layers stack when welded by spark plasma sintering. The presence of oxygen molecules at left prevents the graphene layers from bonding, as they do without oxygen at right. Courtesy of the Ajayan and Galvão groups

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

3D Porous Graphene by Low-Temperature Plasma Welding for Bone Implants by Dibyendu Chakravarty, Chandra Sekhar Tiwary, Cristano F. Woellner, Sruthi Radhakrishnan4, Soumya Vinod, Sehmus Ozden, Pedro Alves da Silva Autreto, Sanjit Bhowmick, Syed Asif, Sendurai A Mani, Douglas S. Galvao, and Pulickel M. Ajayan. Advanced Materials DOI: 10.1002/adma.201603146 Version of Record online: 26 AUG 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Graphene ribbons in solution bending and twisting like DNA

An Aug. 15, 2016 news item on ScienceDaily announces research into graphene nanoribbons and their DNA (deoxyribonucleic acid)-like properties,

Graphene nanoribbons (GNRs) bend and twist easily in solution, making them adaptable for biological uses like DNA analysis, drug delivery and biomimetic applications, according to scientists at Rice University.

Knowing the details of how GNRs behave in a solution will help make them suitable for wide use in biomimetics, according to Rice physicist Ching-Hwa Kiang, whose lab employed its unique capabilities to probe nanoscale materials like cells and proteins in wet environments. Biomimetic materials are those that imitate the forms and properties of natural materials.

An Aug. 15, 2016 Rice University (Texas, US) news release (also on EurekAlert), which originated the news item, describes the ribbons and the research in more detail,

Graphene nanoribbons can be thousands of times longer than they are wide. They can be produced in bulk by chemically “unzipping” carbon nanotubes, a process invented by Rice chemist and co-author James Tour and his lab.

Their size means they can operate on the scale of biological components like proteins and DNA, Kiang said. “We study the mechanical properties of all different kinds of materials, from proteins to cells, but a little different from the way other people do,” she said. “We like to see how materials behave in solution, because that’s where biological things are.” Kiang is a pioneer in developing methods to probe the energy states of proteins as they fold and unfold.

She said Tour suggested her lab have a look at the mechanical properties of GNRs. “It’s a little extra work to study these things in solution rather than dry, but that’s our specialty,” she said.

Nanoribbons are known for adding strength but not weight to solid-state composites, like bicycle frames and tennis rackets, and forming an electrically active matrix. A recent Rice project infused them into an efficient de-icer coating for aircraft.

But in a squishier environment, their ability to conform to surfaces, carry current and strengthen composites could also be valuable.

“It turns out that graphene behaves reasonably well, somewhat similar to other biological materials. But the interesting part is that it behaves differently in a solution than it does in air,” she said. The researchers found that like DNA and proteins, nanoribbons in solution naturally form folds and loops, but can also form helicoids, wrinkles and spirals.

Kiang, Wijeratne [Sithara Wijeratne, Rice graduate now a postdoctoral researcher at Harvard University] and Jingqiang Li, a co-author and student in the Kiang lab, used atomic force microscopy to test their properties. Atomic force microscopy can not only gather high-resolution images but also take sensitive force measurements of nanomaterials by pulling on them. The researchers probed GNRs and their precursors, graphene oxide nanoribbons.

The researchers discovered that all nanoribbons become rigid under stress, but their rigidity increases as oxide molecules are removed to turn graphene oxide nanoribbons into GNRs. They suggested this ability to tune their rigidity should help with the design and fabrication of GNR-biomimetic interfaces.

“Graphene and graphene oxide materials can be functionalized (or modified) to integrate with various biological systems, such as DNA, protein and even cells,” Kiang said. “These have been realized in biological devices, biomolecule detection and molecular medicine. The sensitivity of graphene bio-devices can be improved by using narrow graphene materials like nanoribbons.”

Wijeratne noted graphene nanoribbons are already being tested for use in DNA sequencing, in which strands of DNA are pulled through a nanopore in an electrified material. The base components of DNA affect the electric field, which can be read to identify the bases.

The researchers saw nanoribbons’ biocompatibility as potentially useful for sensors that could travel through the body and report on what they find, not unlike the Tour lab’s nanoreporters that retrieve information from oil wells.

Further studies will focus on the effect of the nanoribbons’ width, which range from 10 to 100 nanometers, on their properties.

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

Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution by Sithara S. Wijeratne, Evgeni S. Penev, Wei Lu, Jingqiang Li, Amanda L. Duque, Boris I. Yakobson, James M. Tour, & Ching-Hwa Kiang. Scientific Reports 6, Article number: 31174 (2016)  doi:10.1038/srep31174 Published online: 09 August 2016

This paper is open access.

Deriving graphene-like films from salt

This research comes from Russia (mostly). A July 29, 2016 news item on ScienceDaily describes a graphene-like structure derived from salt,

Researchers from Moscow Institute of Physics and Technology (MIPT), Skolkovo Institute of Science and Technology (Skoltech), the Technological Institute for Superhard and Novel Carbon Materials (TISNCM), the National University of Science and Technology MISiS (Russia), and Rice University (USA) used computer simulations to find how thin a slab of salt has to be in order for it to break up into graphene-like layers. Based on the computer simulation, they derived the equation for the number of layers in a crystal that will produce ultrathin films with applications in nanoelectronics. …

Caption: Transition from a cubic arrangement into several hexagonal layers. Credit: authors of the study

Caption: Transition from a cubic arrangement into several hexagonal layers. Credit: authors of the study

A July 29, 2016 Moscow Institute of Physics and Technology press release on EurekAlert, which originated the news item,  provides more technical detail,

From 3D to 2D

Unique monoatomic thickness of graphene makes it an attractive and useful material. Its crystal lattice resembles a honeycombs, as the bonds between the constituent atoms form regular hexagons. Graphene is a single layer of a three-dimensional graphite crystal and its properties (as well as properties of any 2D crystal) are radically different from its 3D counterpart. Since the discovery of graphene, a large amount of research has been directed at new two-dimensional materials with intriguing properties. Ultrathin films have unusual properties that might be useful for applications such as nano- and microelectronics.

Previous theoretical studies suggested that films with a cubic structure and ionic bonding could spontaneously convert to a layered hexagonal graphitic structure in what is known as graphitisation. For some substances, this conversion has been experimentally observed. It was predicted that rock salt NaCl can be one of the compounds with graphitisation tendencies. Graphitisation of cubic compounds could produce new and promising structures for applications in nanoelectronics. However, no theory has been developed that would account for this process in the case of an arbitrary cubic compound and make predictions about its conversion into graphene-like salt layers.

For graphitisation to occur, the crystal layers need to be reduced along the main diagonal of the cubic structure. This will result in one crystal surface being made of sodium ions Na? and the other of chloride ions Cl?. It is important to note that positive and negative ions (i.e. Na? and Cl?)–and not neutral atoms–occupy the lattice points of the structure. This generates charges of opposite signs on the two surfaces. As long as the surfaces are remote from each other, all charges cancel out, and the salt slab shows a preference for a cubic structure. However, if the film is made sufficiently thin, this gives rise to a large dipole moment due to the opposite charges of the two crystal surfaces. The structure seeks to get rid of the dipole moment, which increases the energy of the system. To make the surfaces charge-neutral, the crystal undergoes a rearrangement of atoms.

Experiment vs model

To study how graphitisation tendencies vary depending on the compound, the researchers examined 16 binary compounds with the general formula AB, where A stands for one of the four alkali metals lithium Li, sodium Na, potassium K, and rubidium Rb. These are highly reactive elements found in Group 1 of the periodic table. The B in the formula stands for any of the four halogens fluorine F, chlorine Cl, bromine Br, and iodine I. These elements are in Group 17 of the periodic table and readily react with alkali metals.

All compounds in this study come in a number of different structures, also known as crystal lattices or phases. If atmospheric pressure is increased to 300,000 times its normal value, an another phase (B2) of NaCl (represented by the yellow portion of the diagram) becomes more stable, effecting a change in the crystal lattice. To test their choice of methods and parameters, the researchers simulated two crystal lattices and calculated the pressure that corresponds to the phase transition between them. Their predictions agree with experimental data.

Just how thin should it be?

The compounds within the scope of this study can all have a hexagonal, “graphitic”, G phase (the red in the diagram) that is unstable in 3D bulk but becomes the most stable structure for ultrathin (2D or quasi-2D) films. The researchers identified the relationship between the surface energy of a film and the number of layers in it for both cubic and hexagonal structures. They graphed this relationship by plotting two lines with different slopes for each of the compounds studied. Each pair of lines associated with one compound has a common point that corresponds to the critical slab thickness that makes conversion from a cubic to a hexagonal structure energetically favourable. For example, the critical number of layers was found to be close to 11 for all sodium salts and between 19 and 27 for lithium salts.

Based on this data, the researchers established a relationship between the critical number of layers and two parameters that determine the strength of the ionic bonds in various compounds. The first parameter indicates the size of an ion of a given metal–its ionic radius. The second parameter is called electronegativity and is a measure of the ? atom’s ability to attract the electrons of element B. Higher electronegativity means more powerful attraction of electrons by the atom, a more pronounced ionic nature of the bond, a larger surface dipole, and a lower critical slab thickness.

And there’s more

Pavel Sorokin, Dr. habil., [sic] is head of the Laboratory of New Materials Simulation at TISNCM. He explains the importance of the study, ‘This work has already attracted our colleagues from Israel and Japan. If they confirm our findings experimentally, this phenomenon [of graphitisation] will provide a viable route to the synthesis of ultrathin films with potential applications in nanoelectronics.’

The scientists intend to broaden the scope of their studies by examining other compounds. They believe that ultrathin films of different composition might also undergo spontaneous graphitisation, yielding new layered structures with properties that are even more intriguing.

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

Ionic Graphitization of Ultrathin Films of Ionic Compounds by A. G. Kvashnin, E. Y. Pashkin, B. I. Yakobson, and P. B. Sorokin. J. Phys. Chem. Lett., 2016, 7 (14), pp 2659–2663 DOI: 10.1021/acs.jpclett.6b01214 Publication Date (Web): June 23, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

A de-icer and a preventative for airplane wings from Rice University

I last mentioned this graphene-based work (from James Tour at Rice University in Texas, US) on de-icing not just airplane wings but also windshields, skyscrapers and more in a Sept. 17, 2014 posting. The latest study indicates the technology could be used as a preventative according to a May 23, 2016 news item on phys.org,

Rice University scientists have advanced their graphene-based de-icer to serve a dual purpose. The new material still melts ice from wings and wires when conditions get too cold. But if the air is above 7 degrees Fahrenheit, ice won’t form at all.

A May 23, 2016 Rice University news release (also on EurekAlert), which originated the news item, goes on to describe the work in more detail,

The Rice lab of chemist James Tour gave its de-icer superhydrophobic (water-repelling) capabilities that passively prevent water from freezing above 7 degrees. The tough film that forms when the de-icer is sprayed on a surface is made of atom-thin graphene nanoribbons that are conductive, so the material can also be heated with electricity to melt ice and snow in colder conditions.

The material can be spray-coated, making it suitable for large applications like aircraft, power lines, radar domes and ships, according to the researchers. …

“We’ve learned to make an ice-resistant material for milder conditions in which heating isn’t even necessary, but having the option is useful,” Tour said. “What we now have is a very thin, robust coating that can keep large areas free of ice and snow in a wide range of conditions.”

Tour, lead authors Tuo Wang, a Rice graduate student, and Yonghao Zheng, a Rice postdoctoral researcher, and their colleagues tested the film on glass and plastic.

Materials are superhydrophobic if they have a water-contact angle larger than 150 degrees. The term refers to the angle at which the surface of the water meets the surface of the material. The greater the beading, the higher the angle. An angle of 0 degrees is basically a puddle, while a maximum angle of 180 degrees defines a sphere just touching the surface.

The Rice films use graphene nanoribbons modified with a fluorine compound to enhance their hydrophobicity. They found that nanoribbons modified with longer perfluorinated chains resulted in films with a higher contact angle, suggesting that the films are tunable for particular conditions, Tour said.

Warming test surfaces to room temperature and cooling again had no effect on the film’s properties, he said.

The researchers discovered that below 7 degrees, water would condense within the structure’s pores, causing the surface to lose both its superhydrophobic and ice-phobic properties. At that point, applying at least 12 volts of electricity warmed them enough to retain its repellant properties.

Applying 40 volts to the film brought it to room temperature, even if the ambient temperature was 25 degrees below zero. Ice allowed to form at that temperature melted after 90 seconds of resistive heating.

The researchers found that while effective, the de-icing mode did not remove water completely, as some remained trapped in the pores between linked nanoribbon bundles. Adding a lubricant with a low melting point (minus 61 degrees F) to the film made the surface slippery, sped de-icing and saved energy.

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

Passive Anti-icing and Active Deicing Films by Tuo Wang, Yonghao Zheng, Abdul-Rahman O. Raji, Yilun Li, William K.A. Sikkema, and James M. Tour. ACS Appl. Mater. Interfaces, Just Accepted Manuscript DOI: 10.1021/acsami.6b03060 Publication Date (Web): May 18, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Teslaphoresis; self-assembling materials from a distance

Getting carbon nanotubes to self-assemble from a distance is possible according to an April 14, 2016 news item on ScienceDaily,

Scientists at Rice University have discovered that the strong force field emitted by a Tesla coil causes carbon nanotubes to self-assemble into long wires, a phenomenon they call “Teslaphoresis.”

An April 14, 2016 Rice University (US) news release, (also on EurekAlert) which originated the news item, expands on the theme,

Cherukuri [Rice chemist Paul Cherukuri] sees this research as setting a clear path toward scalable assembly of nanotubes from the bottom up.

The system works by remotely oscillating positive and negative charges in each nanotube, causing them to chain together into long wires. Cherukuri’s specially designed Tesla coil even generates a tractor beam-like effect as nanotube wires are pulled toward the coil over long distances.

This force-field effect on matter had never been observed on such a large scale, Cherukuri said, and the phenomenon was unknown to Nikola Tesla, who invented the coil in 1891 with the intention of delivering wireless electrical energy.

“Electric fields have been used to move small objects, but only over ultrashort distances,” Cherukuri said. “With Teslaphoresis, we have the ability to massively scale up force fields to move matter remotely.”

The researchers discovered that the phenomenon simultaneously assembles and powers circuits that harvest energy from the field. In one experiment, nanotubes assembled themselves into wires, formed a circuit connecting two LEDs and then absorbed energy from the Tesla coil’s field to light them.

Cherukuri realized a redesigned Tesla coil could create a powerful force field at distances far greater than anyone imagined. His team observed alignment and movement of the nanotubes several feet away from the coil. “It is such a stunning thing to watch these nanotubes come alive and stitch themselves into wires on the other side of the room,” he said.

Nanotubes were a natural first test material, given their heritage at Rice, where the HiPco production process was invented. But the researchers envision many other nanomaterials can be assembled as well.

Lindsey Bornhoeft, the paper’s lead author and a biomedical engineering graduate student at Texas A&M University, said the directed force field from the bench-top coil at Rice is restricted to just a few feet. To examine the effects on matter at greater distances would require larger systems that are under development. Cherukuri suggested patterned surfaces and multiple Tesla coil systems could create more complex self-assembling circuits from nanoscale-sized particles.

Cherukuri and his wife, Tonya, also a Rice alum and a co-author of the paper, noted that their son Adam made some remarkable observations while watching videos of the experiment. “I was surprised that he noticed patterns in nanotube movements that I didn’t see,” Cherukuri said. “I couldn’t make him an author on the paper, but both he and his little brother John are acknowledged for helpful discussions.”

Cherukuri knows the value of youthful observation — and imagination — since he started designing Tesla coils as a teen. “I would have never thought, as a 14-year-old kid building coils, that it was going to be useful someday,” he said.

Cherukuri and his team self-funded the work, which he said made it more meaningful for the group. “This was one of the most exciting projects I’ve ever done, made even more so because it was an all-volunteer group of passionate scientists and students. But because Rice has this wonderful culture of unconventional wisdom, we were able to make an amazing discovery that pushes the frontiers of nanoscience.”

The teammates look forward to seeing where their research leads. “These nanotube wires grow and act like nerves, and controlled assembly of nanomaterials from the bottom up may be used as a template for applications in regenerative medicine,” Bornhoeft said.

“There are so many applications where one could utilize strong force fields to control the behavior of matter in both biological and artificial systems,” Cherukuri said. “And even more exciting is how much fundamental physics and chemistry we are discovering as we move along. This really is just the first act in an amazing story.”

Rice University has produced a video featuring the research and the researchers,

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

Teslaphoresis of Carbon Nanotubes by Lindsey R. Bornhoeft, Aida C. Castillo, Preston R. Smalley, Carter Kittrell, Dustin K. James, Bruce E. Brinson, Thomas R. Rybolt, Bruce R. Johnson, Tonya K. Cherukuri†, and Paul Cherukuri. ACS Nano, Article ASAP DOI: 10.1021/acsnano.6b02313 Publication Date (Web): April 13, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

The Tesla coil was created by Nikola Tesla, a renowned Serbian-American scientist and engineer.

2-D boron as a superconductor

A March 31, 2016 news item on ScienceDaily highlights some research into 2D (two-dimensional) boron at Rice University (Texas, US),

Rice University scientists have determined that two-dimensional boron is a natural low-temperature superconductor. In fact, it may be the only 2-D material with such potential.

Rice theoretical physicist Boris Yakobson and his co-workers published their calculations that show atomically flat boron is metallic and will transmit electrons with no resistance. …

The hitch, as with most superconducting materials, is that it loses its resistivity only when very cold, in this case between 10 and 20 kelvins (roughly, minus-430 degrees Fahrenheit). But for making very small superconducting circuits, it might be the only game in town.

A March 30, 2016 Rice University news release (also on EurekAlert but dated March 31, 2016), which originated the news item, expands on the theme,

The basic phenomenon of superconductivity has been known for more than 100 years, said Evgeni Penev, a research scientist in the Yakobson group, but had not been tested for its presence in atomically flat boron.

“It’s well-known that the material is pretty light because the atomic mass is small,” Penev said. “If it’s metallic too, these are two major prerequisites for superconductivity. That means at low temperatures, electrons can pair up in a kind of dance in the crystal.”

“Lower dimensionality is also helpful,” Yakobson said. “It may be the only, or one of very few, two-dimensional metals. So there are three factors that gave the initial motivation for us to pursue the research. Then we just got more and more excited as we got into it.”

Electrons with opposite momenta and spins effectively become Cooper pairs; they attract each other at low temperatures with the help of lattice vibrations, the so-called “phonons,” and give the material its superconducting properties, Penev said. “Superconductivity becomes a manifestation of the macroscopic wave function that describes the whole sample. It’s an amazing phenomenon,” he said.

It wasn’t entirely by chance that the first theoretical paper establishing conductivity in a 2-D material appeared at roughly the same time the first samples of the material were made by laboratories in the United States and China. In fact, an earlier paper by the Yakobson group had offered a road map for doing so.

That 2-D boron has now been produced is a good thing, according to Yakobson and lead authors Penev and Alex Kutana, a postdoctoral researcher at Rice. “We’ve been working to characterize boron for years, from cage clusters to nanotubes to planer sheets, but the fact that these papers appeared so close together means these labs can now test our theories,” Yakobson said.

“In principle, this work could have been done three years ago as well,” he said. “So why didn’t we? Because the material remained hypothetical; okay, theoretically possible, but we didn’t have a good reason to carry it too far.

“But then last fall it became clear from professional meetings and interactions that it can be made. Now those papers are published. When you think it’s coming for real, the next level of exploration becomes more justifiable,” Yakobson said.

Boron atoms can make more than one pattern when coming together as a 2-D material, another characteristic predicted by Yakobson and his team that has now come to fruition. These patterns, known as polymorphs, may allow researchers to tune the material’s conductivity “just by picking a selective arrangement of the hexagonal holes,” Penev said.

He also noted boron’s qualities were hinted at when researchers discovered more than a decade ago that magnesium diborite is a high-temperature electron-phonon superconductor. “People realized a long time ago the superconductivity is due to the boron layer,” Penev said. “The magnesium acts to dope the material by spilling some electrons into the boron layer. In this case, we don’t need them because the 2-D boron is already metallic.”

Penev suggested that isolating 2-D boron between layers of inert hexagonal boron nitride (aka “white graphene”) might help stabilize its superconducting nature.

Without the availability of a block of time on several large government supercomputers, the study would have taken a lot longer, Yakobson said. “Alex did the heavy lifting on the computational work,” he said. “To turn it from a lunchtime discussion into a real quantitative research result took a very big effort.”

The paper is the first by Yakobson’s group on the topic of superconductivity, though Penev is a published author on the subject. “I started working on superconductivity in 1993, but it was always kind of a hobby, and I hadn’t done anything on the topic in 10 years,” Penev said. “So this paper brings it full circle.”

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

Can Two-Dimensional Boron Superconduct? by Evgeni S. Penev, Alex Kutana, and Boris I. Yakobson. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.6b00070 Publication Date (Web): March 22, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Dexter Johnson has published an April 5, 2016 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) about this latest Rice University work on 2D boron that includes comments from his email interview with Penev.

What robots and humans?

I have two robot news bits for this posting. The first probes the unease currently being expressed (pop culture movies, Stephen Hawking, the Cambridge Centre for Existential Risk, etc.) about robots and their increasing intelligence and increased use in all types of labour formerly and currently performed by humans. The second item is about a research project where ‘artificial agents’ (robots) are being taught human values with stories.

Human labour obsolete?

‘When machines can do any job, what will humans do?’ is the question being asked in a presentation by Rice University computer scientist, Moshe Vardi, for the American Association for the Advancement of Science (AAAS) annual meeting held in Washington, D.C. from Feb. 11 – 15, 2016.

Here’s more about Dr. Vardi’s provocative question from a Feb. 14, 2016 Rice University news release (also on EurekAlert),

Rice University computer scientist Moshe Vardi expects that within 30 years, machines will be capable of doing almost any job that a human can. In anticipation, he is asking his colleagues to consider the societal implications. Can the global economy adapt to greater than 50 percent unemployment? Will those out of work be content to live a life of leisure?

“We are approaching a time when machines will be able to outperform humans at almost any task,” Vardi said. “I believe that society needs to confront this question before it is upon us: If machines are capable of doing almost any work humans can do, what will humans do?”

Vardi addressed this issue Sunday [Feb. 14, 2016] in a presentation titled “Smart Robots and Their Impact on Society” at one of the world’s largest and most prestigious scientific meetings — the annual meeting of the American Association for the Advancement of Science in Washington, D.C.

“The question I want to put forward is, Does the technology we are developing ultimately benefit mankind?” Vardi said. He asked the question after presenting a body of evidence suggesting that the pace of advancement in the field of artificial intelligence (AI) is increasing, even as existing robotic and AI technologies are eliminating a growing number of middle-class jobs and thereby driving up income inequality.

Vardi, a member of both the National Academy of Engineering and the National Academy of Science, is a Distinguished Service Professor and the Karen Ostrum George Professor of Computational Engineering at Rice, where he also directs Rice’s Ken Kennedy Institute for Information Technology. Since 2008 he has served as the editor-in-chief of Communications of the ACM, the flagship publication of the Association for Computing Machinery (ACM), one of the world’s largest computational professional societies.

Vardi said some people believe that future advances in automation will ultimately benefit humans, just as automation has benefited society since the dawn of the industrial age.

“A typical answer is that if machines will do all our work, we will be free to pursue leisure activities,” Vardi said. But even if the world economic system could be restructured to enable billions of people to live lives of leisure, Vardi questioned whether it would benefit humanity.

“I do not find this a promising future, as I do not find the prospect of leisure-only life appealing. I believe that work is essential to human well-being,” he said.

“Humanity is about to face perhaps its greatest challenge ever, which is finding meaning in life after the end of ‘In the sweat of thy face shalt thou eat bread,’” Vardi said. “We need to rise to the occasion and meet this challenge” before human labor becomes obsolete, he said.

In addition to dual membership in the National Academies, Vardi is a Guggenheim fellow and a member of the American Academy of Arts and Sciences, the European Academy of Sciences and the Academia Europa. He is a fellow of the ACM, the American Association for Artificial Intelligence and the Institute for Electrical and Electronics Engineers (IEEE). His numerous honors include the Southeastern Universities Research Association’s 2013 Distinguished Scientist Award, the 2011 IEEE Computer Society Harry H. Goode Award, the 2008 ACM Presidential Award, the 2008 Blaise Pascal Medal for Computer Science by the European Academy of Sciences and the 2000 Goedel Prize for outstanding papers in the area of theoretical computer science.

Vardi joined Rice’s faculty in 1993. His research centers upon the application of logic to computer science, database systems, complexity theory, multi-agent systems and specification and verification of hardware and software. He is the author or co-author of more than 500 technical articles and of two books, “Reasoning About Knowledge” and “Finite Model Theory and Its Applications.”

In a Feb. 5, 2015 post, I rounded up a number of articles about our robot future. It provides a still useful overview of the thinking on the topic.

Teaching human values with stories

A Feb. 12, 2016 Georgia (US) Institute of Technology (Georgia Tech) news release (also on EurekAlert) describes the research,

The rapid pace of artificial intelligence (AI) has raised fears about whether robots could act unethically or soon choose to harm humans. Some are calling for bans on robotics research; others are calling for more research to understand how AI might be constrained. But how can robots learn ethical behavior if there is no “user manual” for being human?

Researchers Mark Riedl and Brent Harrison from the School of Interactive Computing at the Georgia Institute of Technology believe the answer lies in “Quixote” — to be unveiled at the AAAI [Association for the Advancement of Artificial Intelligence]-16 Conference in Phoenix, Ariz. (Feb. 12 – 17, 2016). Quixote teaches “value alignment” to robots by training them to read stories, learn acceptable sequences of events and understand successful ways to behave in human societies.

“The collected stories of different cultures teach children how to behave in socially acceptable ways with examples of proper and improper behavior in fables, novels and other literature,” says Riedl, associate professor and director of the Entertainment Intelligence Lab. “We believe story comprehension in robots can eliminate psychotic-appearing behavior and reinforce choices that won’t harm humans and still achieve the intended purpose.”

Quixote is a technique for aligning an AI’s goals with human values by placing rewards on socially appropriate behavior. It builds upon Riedl’s prior research — the Scheherazade system — which demonstrated how artificial intelligence can gather a correct sequence of actions by crowdsourcing story plots from the Internet.

Scheherazade learns what is a normal or “correct” plot graph. It then passes that data structure along to Quixote, which converts it into a “reward signal” that reinforces certain behaviors and punishes other behaviors during trial-and-error learning. In essence, Quixote learns that it will be rewarded whenever it acts like the protagonist in a story instead of randomly or like the antagonist.

For example, if a robot is tasked with picking up a prescription for a human as quickly as possible, the robot could a) rob the pharmacy, take the medicine, and run; b) interact politely with the pharmacists, or c) wait in line. Without value alignment and positive reinforcement, the robot would learn that robbing is the fastest and cheapest way to accomplish its task. With value alignment from Quixote, the robot would be rewarded for waiting patiently in line and paying for the prescription.

Riedl and Harrison demonstrate in their research how a value-aligned reward signal can be produced to uncover all possible steps in a given scenario, map them into a plot trajectory tree, which is then used by the robotic agent to make “plot choices” (akin to what humans might remember as a Choose-Your-Own-Adventure novel) and receive rewards or punishments based on its choice.

The Quixote technique is best for robots that have a limited purpose but need to interact with humans to achieve it, and it is a primitive first step toward general moral reasoning in AI, Riedl says.

“We believe that AI has to be enculturated to adopt the values of a particular society, and in doing so, it will strive to avoid unacceptable behavior,” he adds. “Giving robots the ability to read and understand our stories may be the most expedient means in the absence of a human user manual.”

So there you have it, some food for thought.

Graphene-boron nitride material research from Rice University (US) and Polytechnique Montréal (Canada)

A Jan. 13, 2016 Rice University news release (also on EurekAlert) highlights computational research on hybrid material (graphene-boron nitride),

Developing novel materials from the atoms up goes faster when some of the trial and error is eliminated. A new Rice University and Montreal Polytechnic study aims to do that for graphene and boron nitride hybrids.

Rice materials scientist Rouzbeh Shahsavari and Farzaneh Shayeganfar, a postdoctoral researcher at Montreal Polytechnic (also known as École Polytechnique de Montréal or Polytechnique de Montréal), designed computer simulations that combine graphene, the atom-thick form of carbon, with either carbon or boron nitride nanotubes.

Their hope is that such hybrids can leverage the best aspects of their constituent materials. Defining the properties of various combinations would simplify development for manufacturers who want to use these exotic materials in next-generation electronics. The researchers found not only electronic but also magnetic properties that could be useful.

Shahsavari’s lab studies materials to see how they can be made more efficient, functional and environmentally friendly. They include macroscale materials like cement and ceramics as well as nanoscale hybrids with unique properties.

“Whether it’s on the macro- or microscale, if we can know specifically what a hybrid will do before anyone goes to the trouble of fabricating it, we can save cost and time and perhaps enable new properties not possible with any of the constituents,” Shahsavari said.

His lab’s computer models simulate how the intrinsic energies of atoms influence each other as they bond into molecules. For the new work, the researchers modeled hybrid structures of graphene and carbon nanotubes and of graphene and boron nitride nanotubes.

“We wanted to investigate and compare the electronic and potentially magnetic properties of different junction configurations, including their stability, electronic band gaps and charge transfer,” he said. “Then we designed three different nanostructures with different junction geometry.”

Two were hybrids with graphene layers seamlessly joined to carbon nanotubes. The other was similar but, for the first time, they modeled a hybrid with boron nitride nanotubes. How the sheets and tubes merged determined the hybrid’s properties. They also built versions with nanotubes sandwiched between graphene layers.

Graphene is a perfect conductor when its atoms align as hexagonal rings, but the material becomes strained when it deforms to accommodate nanotubes in hybrids. The atoms balance their energies at these junctions by forming five-, seven- or eight-member rings. These all induce changes in the way electricity flows across the junctions, turning the hybrid material into a valuable semiconductor.

The researchers’ calculations allowed them to map out a number of effects. For example, it turned out the junctions of the hybrid system create pseudomagnetic fields.

“The pseudomagnetic field due to strain was reported earlier for graphene, but not these hybrid boron nitride and carbon nanostructures where strain is inherent to the system,” Shahsavari said. He noted the effect may be useful in spintronic and nano-transistor applications.

“The pseudomagnetic field causes charge carriers in the hybrid to circulate as if under the influence of an applied external magnetic field,” he said. “Thus, in view of the exceptional flexibility, strength and thermal conductivity of hybrid carbon and boron nitride systems, we propose the pseudomagnetic field may be a viable way to control the electronic structure of new materials.”

All the effects serve as a road map for nanoengineering applications, Shahsavari said.

“We’re laying the foundations for a range of tunable hybrid architectures, especially for boron nitride, which is as promising as graphene but much less explored,” he said. “Scientists have been studying all-carbon structures for years, but the development of boron nitride and other two-dimensional materials and their various combinations with each other gives us a rich set of possibilities for the design of materials with never-seen-before properties.”

Shahsavari is an assistant professor of civil and environmental engineering and of materials science and nanoengineering.


Rice supported the research, and computational resources were provided by Calcul Quebec and Compute Canada.

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

Electronic and pseudomagnetic properties of hybrid carbon/boron-nitride nanomaterials via ab-initio calculations and elasticity theory by Farzaneh Shayeganfar and Rouzbeh Shahsavari. Carbon Volume 99, April 2016, Pages 523–532 doi:10.1016/j.carbon.2015.12.050

This paper is behind a paywall.

Here’s an image illustrating the hybrid material,

Caption: The calculated properties of a three-dimensional hybrid of graphene and boron nitride nanotubes would have pseudomagnetic properties, according to researchers at Rice University and Montreal Polytechnic. Credit: Shahsavari Lab/Rice University

Caption: The calculated properties of a three-dimensional hybrid of graphene and boron nitride nanotubes would have pseudomagnetic properties, according to researchers at Rice University and Montreal Polytechnic. Credit: Shahsavari Lab/Rice University