Tag Archives: James M. Tour

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.

Russians offer nanotechnology report at Paris Climate talks

Sadly I cannot find the report presented by the Russians  at the Paris Climate Talks (also known as World Climate Change Conference 2015 [COP21]) but did find this reference to it in a Dec. 7, 2015 article in the New York Times,

One of the surprises of the Paris climate talks was the sudden interest by Russia in appearing as a player in the efforts to reel in greenhouse gases.

The second part occurred on Monday, when an event was added to the schedule of news briefings: “Russia Proposes a New Approach to Climate Change.”

And so Russia did, putting forth a plan — and a report — that in the end seemed largely geared toward promoting a government-funded business, run by a prominent politician.

The Russian Times (rt.com) published a Nov. 30, 2015 article detailing President Vladimir Putin’s address to the conference attendees,

“We have gone beyond the target fixed by the Kyoto Protocol for the period from 1991 to 2012. Russia not only prevented the growth of greenhouse gas emission, by also significantly reduced it,” Putin said.

“Nearly 40 billion tons of carbon dioxide equivalent weren’t released into the atmosphere. As a comparison, the total emissions of all countries in 2012 reached 46 billion tons.”

Russia is planning to keep progressing by bringing breakthrough technologies into practice, “including nanotechnology,” Putin continued saying the country is also open to exchange and share the findings.

Apart from that, Putin has also promised Russia will reduce its polluting emissions by 70 percent by 2030 as compared to base level in 1990.

A Dec. 8, 2015 article by Jasper Nikki De La Cruz for The Science Times provides more detail about the Russian report/proposal (Note: A link has been removed),

Russia proposes a “New Approach” when it comes to dealing with climate change. The proposal focuses on efforts to reduce emissions involving five materials: steel, cement, aluminum, plastic and paper. The proposal is not on the reduction of the production of these materials but rather making these materials lighter, stronger and more efficient. With this approach, nanotechnology is put into the spotlight as the primary technology in making this proposal possible in real-world applications.

Rusnano is a company that is dedicated to nanotechnology. They received $10B of funding from the Russian government. They are pegged to be the frontrunner in research and application of nanotechnology in the production of the mentioned materials.

“Carbon nanotubes have been shown to toughen aluminum, make plastics conductive, extend the life of lithium-ion batteries,” Anatoly B. Chubais, Rusnano founder, said. “So all that is true. Tangentially, that can then lower CO2 emissions, I suppose.”

James Tour, a scientist at Rice University, commented for the New York Times Dec. 7, 2015 article on this suggestion that greater use of carbon nanotubes could reduce emissions,

A report laying out the materials thesis rested heavily on contentions about the use of carbon nanotubes. For a moment that puzzled James M. Tour, a professor of chemistry and materials science at Rice University and an expert on nanomaterials, who was asked about the proposal.

“Carbon nanotubes have been shown to toughen aluminum, make plastics conductive, extend the life of lithium-ion batteries,” he said in an email. “So all that is true. Tangentially, that can then lower CO2 emissions, I suppose.”

But, he added, “All of the above was well known long before Rusnano came around.”

Reporters, too, were confused. When one asked whether the announcement was “a distraction from real action,” Mr. Chubais said the proposal was a means to the same end.

I don’t find the Russian proposal all that outlandish although the emphasis on carbon nanotubes seems a bit outsized (pun intended). In any event, there’s certainly a role for emerging technologies to play in the attempts to change our lifestyles and ameliorate climate change.

A 244-atom submarine powered by light

James Tour lab researchers at Rice University announce in a Nov. 16, 2015 news item on Nanowerk,

Though they’re not quite ready for boarding a lá “Fantastic Voyage,” nanoscale submarines created at Rice University are proving themselves seaworthy.

Each of the single-molecule, 244-atom submersibles built in the Rice lab of chemist James Tour has a motor powered by ultraviolet light. With each full revolution, the motor’s tail-like propeller moves the sub forward 18 nanometers.
And with the motors running at more than a million RPM, that translates into speed. Though the sub’s top speed amounts to less than 1 inch per second, Tour said that’s a breakneck pace on the molecular scale.

“These are the fastest-moving molecules ever seen in solution,” he said.

Expressed in a different way, the researchers reported this month in the American Chemical Society journal Nano Letters that their light-driven nanosubmersibles show an “enhancement in diffusion” of 26 percent. That means the subs diffuse, or spread out, much faster than they already do due to Brownian motion, the random way particles spread in a solution.

While they can’t be steered yet, the study proves molecular motors are powerful enough to drive the sub-10-nanometer subs through solutions of moving molecules of about the same size.

“This is akin to a person walking across a basketball court with 1,000 people throwing basketballs at him,” Tour said.

A Nov. 16, 2015 Rice University news release (also on EurekAlert), which originated the news item, provides context and details about the research,

Tour’s group has extensive experience with molecular machines. A decade ago, his lab introduced the world to nanocars, single-molecule cars with four wheels, axles and independent suspensions that could be “driven” across a surface.

Tour said many scientists have created microscopic machines with motors over the years, but most have either used or generated toxic chemicals. He said a motor that was conceived in the last decade by a group in the Netherlands proved suitable for Rice’s submersibles, which were produced in a 20-step chemical synthesis.

“These motors are well-known and used for different things,” said lead author and Rice graduate student Victor García-López. “But we were the first ones to propose they can be used to propel nanocars and now submersibles.”

The motors, which operate more like a bacteria’s flagellum than a propeller, complete each revolution in four steps. When excited by light, the double bond that holds the rotor to the body becomes a single bond, allowing it to rotate a quarter step. As the motor seeks to return to a lower energy state, it jumps adjacent atoms for another quarter turn. The process repeats as long as the light is on.

For comparison tests, the lab also made submersibles with no motors, slow motors and motors that paddle back and forth. All versions of the submersibles have pontoons that fluoresce red when excited by a laser, according to the researchers. (Yellow, sadly, was not an option.)

“One of the challenges was arming the motors with the appropriate fluorophores for tracking without altering the fast rotation,” García-López said.

Once built, the team turned to Gufeng Wang at North Carolina State University to measure how well the nanosubs moved.

“We had used scanning tunneling microscopy and fluorescence microscopy to watch our cars drive, but that wouldn’t work for the submersibles,” Tour said. “They would drift out of focus pretty quickly.”

The North Carolina team sandwiched a drop of diluted acetonitrile liquid containing a few nanosubs between two slides and used a custom confocal fluorescence microscope to hit it from opposite sides with both ultraviolet light (for the motor) and a red laser (for the pontoons).

The microscope’s laser defined a column of light in the solution within which tracking occurred, García-López said. “That way, the NC State team could guarantee it was analyzing only one molecule at a time,” he said.

Rice’s researchers hope future nanosubs will be able to carry cargoes for medical and other purposes. “There’s a path forward,” García-López said. “This is the first step, and we’ve proven the concept. Now we need to explore opportunities and potential applications.”

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

Unimolecular Submersible Nanomachines. Synthesis, Actuation, and Monitoring by Víctor García-López, Pinn-Tsong Chiang, Fang Chen, Gedeng Ruan, Angel A. Martí, Anatoly B. Kolomeisky, Gufeng Wang, and James M. Tour. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.5b03764 Publication Date (Web): November 5, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

There is an illustration of the 244-atom submersible,

Rice University scientists have created light-driven, single-molecule submersibles that contain just 244 atoms. Illustration by Loïc Samuel

Rice University scientists have created light-driven, single-molecule submersibles that contain just 244 atoms. Illustration by Loïc Samuel

Graphene gains metallic powers after laser-burning

Rice University (Texas, US) researchers have developed a technique for embedding metallic nanoparticles in graphene with the hope of one day replacing platinum catalysts in fuel cells. From an August 20, 2015 news item on ScienceDaily,

Laser-induced graphene, created by the Rice lab of chemist James Tour last year, is a flexible film with a surface of porous graphene made by exposing a common plastic known as polyimide to a commercial laser-scribing beam. The researchers have now found a way to enhance the product with reactive metals.

An August 20, 2015 Rice University news release (also on EurekAlert), which originated the news item, provides further description,

With the discovery, the material that the researchers call “metal oxide-laser induced graphene” (MO-LIG) becomes a new candidate to replace expensive metals like platinum in catalytic fuel-cell applications in which oxygen and hydrogen are converted to water and electricity.

“The wonderful thing about this process is that we can use commercial polymers, with simple inexpensive metal salts added,” Tour said. “We then subject them to the commercial laser scriber, which generates metal nanoparticles embedded in graphene. So much of the chemistry is done by the laser, which generates graphene in the open air at room temperature.

“These composites, which have less than 1 percent metal, respond as ‘super catalysts’ for fuel-cell applications. Other methods to do this take far more steps and require expensive metals and expensive carbon precursors.”

Initially, the researchers made laser-induced graphene with commercially available polyimide sheets. Later, they infused liquid polyimide with boron to produce laser-induced graphene with a greatly increased capacity to store an electrical charge, which made it an effective supercapacitor.

For the latest iteration, they mixed the liquid and one of three concentrations containing cobalt, iron or molybdenum metal salts. After condensing each mixture into a film, they treated it with an infrared laser and then heated it in argon gas for half an hour at 750 degrees Celsius.

That process produced robust MO-LIGs with metallic, 10-nanometer particles spread evenly through the graphene. Tests showed their ability to catalyze oxygen reduction, an essential chemical reaction in fuel cells. Further doping of the material with sulfur allowed for hydrogen evolution, another catalytic process that converts water into hydrogen, Tour said.

“Remarkably, simple treatment of the graphene-molybdenum oxides with sulfur, which converted the metal oxides to metal sulfides, afforded a hydrogen evolution reaction catalyst, underscoring the broad utility of this approach,” he said.

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

In situ Formation of Metal Oxide Nanocrystals Embedded in Laser-Induced Graphene by Ruquan Ye, Zhiwei Peng, Tuo Wang, Yunong Xu, Jibo Zhang, Yilun Li, Lizanne G. Nilewski, Jian Lin, and James M. Tour. ACS Nano, Just Accepted Manuscript DOI: 10.1021/acsnano.5b04138 Publication Date (Web): August 18, 2015
Copyright © 2015 American Chemical Society

This paper is open access provided you have an ACS ID, which is a free registration. ACS is the American Chemical Society.

Nanoscale antioxidants

A Feb. 10, 2015 news item on Azonano features injectable nanoparticles that act as antioxidants useful in case of injury, in particular, brain injury,

Injectable nanoparticles that could protect an injured person from further damage due to oxidative stress have proven to be astoundingly effective in tests to study their mechanism.

Scientists at Rice University, Baylor College of Medicine and the University of Texas Health Science Center at Houston (UTHealth) Medical School designed methods to validate their 2012 discovery that combined polyethylene glycol-hydrophilic carbon clusters — known as PEG-HCCs — could quickly stem the process of overoxidation that can cause damage in the minutes and hours after an injury.

A Feb. 9, 2015 Rice University news release (also on EurekAlert), which originated the news item, describe the benefits in more detail,

The tests revealed a single nanoparticle can quickly catalyze the neutralization of thousands of damaging reactive oxygen species molecules that are overexpressed by the body’s cells in response to an injury and turn the molecules into oxygen. These reactive species can damage cells and cause mutations, but PEG-HCCs appear to have an enormous capacity to turn them into less-reactive substances.

The researchers hope an injection of PEG-HCCs as soon as possible after an injury, such as traumatic brain injury or stroke, can mitigate further brain damage by restoring normal oxygen levels to the brain’s sensitive circulatory system.

“Effectively, they bring the level of reactive oxygen species back to normal almost instantly,” said Rice chemist James Tour. “This could be a useful tool for emergency responders who need to quickly stabilize an accident or heart attack victim or to treat soldiers in the field of battle.” Tour led the new study with neurologist Thomas Kent of Baylor College of Medicine and biochemist Ah-Lim Tsai of UTHealth.

The news release goes on to describe the antioxidant particles and previous research,

PEG-HCCs are about 3 nanometers wide and 30 to 40 nanometers long and contain from 2,000 to 5,000 carbon atoms. In tests, an individual PEG-HCC nanoparticle can catalyze the conversion of 20,000 to a million reactive oxygen species molecules per second into molecular oxygen, which damaged tissues need, and hydrogen peroxide while quenching reactive intermediates.

Tour and Kent led the earlier research that determined an infusion of nontoxic PEG-HCCs may quickly stabilize blood flow in the brain and protect against reactive oxygen species molecules overexpressed by cells during a medical trauma, especially when accompanied by massive blood loss.

Their research targeted traumatic brain injuries, after which cells release an excessive amount of the reactive oxygen species known as a superoxide into the blood. These toxic free radicals are molecules with one unpaired electron that the immune system uses to kill invading microorganisms. In small concentrations, they contribute to a cell’s normal energy regulation. Generally, they are kept in check by superoxide dismutase, an enzyme that neutralizes superoxides.

But even mild traumas can release enough superoxides to overwhelm the brain’s natural defenses. In turn, superoxides can form such other reactive oxygen species as peroxynitrite that cause further damage.

“The current research shows PEG-HCCs work catalytically, extremely rapidly and with an enormous capacity to neutralize thousands upon thousands of the deleterious molecules, particularly superoxide and hydroxyl radicals that destroy normal tissue when left unregulated,” Tour said.

“This will be important not only in traumatic brain injury and stroke treatment, but for many acute injuries of any organ or tissue and in medical procedures such as organ transplantation,” he said. “Anytime tissue is stressed and thereby oxygen-starved, superoxide can form to further attack the surrounding good tissue.”

These details about the research are also noted in the news release,

The researchers used an electron paramagnetic resonance spectroscopy technique that gets direct structure and rate information for superoxide radicals by counting unpaired electrons in the presence or absence of PEG-HCC antioxidants. Another test with an oxygen-sensing electrode, peroxidase and a red dye confirmed the particles’ ability to catalyze superoxide conversion.

“In sharp contrast to the well-known superoxide dismutase, PEG-HCC is not a protein and does not have metal to serve the catalytic role,” Tsai said. “The efficient catalytic turnover could be due to its more ‘planar,’ highly conjugated carbon core.”

The tests showed the number of superoxides consumed far surpassed the number of possible PEG-HCC bonding sites. The researchers found the particles have no effect on important nitric oxides that keep blood vessels dilated and aid neurotransmission and cell protection, nor was the efficiency sensitive to pH changes.

“PEG-HCCs have enormous capacity to convert superoxide to oxygen and the ability to quench reactive intermediates while not affecting nitric oxide molecules that are beneficial in normal amounts,” Kent said. “So they hold a unique place in our potential armamentarium against a range of diseases that involve loss of oxygen and damaging levels of free radicals.”

The study also determined PEG-HCCs remain stable, as batches up to 3 months old performed as good as new.

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

Highly efficient conversion of superoxide to oxygen using hydrophilic carbon clusters by Errol L. G. Samuel, Daniela C. Marcano, Vladimir Berka, Brittany R. Bitner, Gang Wu, Austin Potter, Roderic H. Fabian, Robia G. Pautler, Thomas A. Kent, Ah-Lim Tsai, and James M. Tour. Published online before print February 9, 2015, doi: 10.1073/pnas.1417047112 PNAS February 9, 2015

This paper is behind a paywall.

De-icing film for radar domes adapted for use on glass

Interesting to see that graphene is in use for de-icing. From a Sept. 16, 2014 news item  on ScienceDaily,

Rice University scientists who created a deicing film for radar domes have now refined the technology to work as a transparent coating for glass.

The new work by Rice chemist James Tour and his colleagues could keep glass surfaces from windshields to skyscrapers free of ice and fog while retaining their transparency to radio frequencies (RF).

A Sept. 16, 2014 Rice University news release on EurekAlert, which originated the news item, describes the technology and its new application in more detail,

The material is made of graphene nanoribbons, atom-thick strips of carbon created by splitting nanotubes, a process also invented by the Tour lab. Whether sprayed, painted or spin-coated, the ribbons are transparent and conduct both heat and electricity.

Last year the Rice group created films of overlapping nanoribbons and polyurethane paint to melt ice on sensitive military radar domes, which need to be kept clear of ice to keep them at peak performance. The material would replace a bulky and energy-hungry metal oxide framework.

The graphene-infused paint worked well, Tour said, but where it was thickest, it would break down when exposed to high-powered radio signals. “At extremely high RF, the thicker portions were absorbing the signal,” he said. “That caused degradation of the film. Those spots got so hot that they burned up.”

The answer was to make the films more consistent. The new films are between 50 and 200 nanometers thick – a human hair is about 50,000 nanometers thick – and retain their ability to heat when a voltage is applied. The researchers were also able to preserve their transparency. The films are still useful for deicing applications but can be used to coat glass and plastic as well as radar domes and antennas.

In the previous process, the nanoribbons were mixed with polyurethane, but testing showed the graphene nanoribbons themselves formed an active network when applied directly to a surface. They were subsequently coated with a thin layer of polyurethane for protection. Samples were spread onto glass slides that were then iced. When voltage was applied to either side of the slide, the ice melted within minutes even when kept in a minus-20-degree Celsius environment, the researchers reported.

“One can now think of using these films in automobile glass as an invisible deicer, and even in skyscrapers,” Tour said. “Glass skyscrapers could be kept free of fog and ice, but also be transparent to radio frequencies. It’s really frustrating these days to find yourself in a building where your cellphone doesn’t work. This could help alleviate that problem.”

Tour noted future generations of long-range Wi-Fi may also benefit. “It’s going to be important, as Wi-Fi becomes more ubiquitous, especially in cities. Signals can’t get through anything that’s metallic in nature, but these layers are so thin they won’t have any trouble penetrating.”

He said nanoribbon films also open a path toward embedding electronic circuits in glass that are both optically and RF transparent.

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

Functionalized Graphene Nanoribbon Films as a Radiofrequency and Optically Transparent Material by Abdul-Rahman O. Raji, Sydney Salters, Errol L. G. Samuel, Yu Zhu, Vladimir Volman, and James M. Tour. ACS Appl. Mater. Interfaces, Article ASAP DOI: 10.1021/am503478w Publication Date (Web): September 4, 2014
Copyright © 2014 American Chemical Society

This paper is behind a paywall.

De-icing is a matter of some interest in the airlines industry as I noted in my Nov. 19, 2012 posting about de-icing airplane wings.

Better RRAM memory devices in the short term

Given my recent spate of posts about computing and the future of the chip (list to follow at the end of this post), this Rice University [Texas, US] research suggests that some improvements to current memory devices might be coming to the market in the near future. From a July 12, 2014 news item on Azonano,

Rice University’s breakthrough silicon oxide technology for high-density, next-generation computer memory is one step closer to mass production, thanks to a refinement that will allow manufacturers to fabricate devices at room temperature with conventional production methods.

A July 10, 2014 Rice University news release, which originated the news item, provides more detail,

Tour and colleagues began work on their breakthrough RRAM technology more than five years ago. The basic concept behind resistive memory devices is the insertion of a dielectric material — one that won’t normally conduct electricity — between two wires. When a sufficiently high voltage is applied across the wires, a narrow conduction path can be formed through the dielectric material.

The presence or absence of these conduction pathways can be used to represent the binary 1s and 0s of digital data. Research with a number of dielectric materials over the past decade has shown that such conduction pathways can be formed, broken and reformed thousands of times, which means RRAM can be used as the basis of rewritable random-access memory.

RRAM is under development worldwide and expected to supplant flash memory technology in the marketplace within a few years because it is faster than flash and can pack far more information into less space. For example, manufacturers have announced plans for RRAM prototype chips that will be capable of storing about one terabyte of data on a device the size of a postage stamp — more than 50 times the data density of current flash memory technology.

The key ingredient of Rice’s RRAM is its dielectric component, silicon oxide. Silicon is the most abundant element on Earth and the basic ingredient in conventional microchips. Microelectronics fabrication technologies based on silicon are widespread and easily understood, but until the 2010 discovery of conductive filament pathways in silicon oxide in Tour’s lab, the material wasn’t considered an option for RRAM.

Since then, Tour’s team has raced to further develop its RRAM and even used it for exotic new devices like transparent flexible memory chips. At the same time, the researchers also conducted countless tests to compare the performance of silicon oxide memories with competing dielectric RRAM technologies.

“Our technology is the only one that satisfies every market requirement, both from a production and a performance standpoint, for nonvolatile memory,” Tour said. “It can be manufactured at room temperature, has an extremely low forming voltage, high on-off ratio, low power consumption, nine-bit capacity per cell, exceptional switching speeds and excellent cycling endurance.”

In the latest study, a team headed by lead author and Rice postdoctoral researcher Gunuk Wang showed that using a porous version of silicon oxide could dramatically improve Rice’s RRAM in several ways. First, the porous material reduced the forming voltage — the power needed to form conduction pathways — to less than two volts, a 13-fold improvement over the team’s previous best and a number that stacks up against competing RRAM technologies. In addition, the porous silicon oxide also allowed Tour’s team to eliminate the need for a “device edge structure.”

“That means we can take a sheet of porous silicon oxide and just drop down electrodes without having to fabricate edges,” Tour said. “When we made our initial announcement about silicon oxide in 2010, one of the first questions I got from industry was whether we could do this without fabricating edges. At the time we could not, but the change to porous silicon oxide finally allows us to do that.”

Wang said, “We also demonstrated that the porous silicon oxide material increased the endurance cycles more than 100 times as compared with previous nonporous silicon oxide memories. Finally, the porous silicon oxide material has a capacity of up to nine bits per cell that is highest number among oxide-based memories, and the multiple capacity is unaffected by high temperatures.”

Tour said the latest developments with porous silicon oxide — reduced forming voltage, elimination of need for edge fabrication, excellent endurance cycling and multi-bit capacity — are extremely appealing to memory companies.

“This is a major accomplishment, and we’ve already been approached by companies interested in licensing this new technology,” he said.

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

Nanoporous Silicon Oxide Memory by Gunuk Wang, Yang Yang, Jae-Hwang Lee, Vera Abramova, Huilong Fei, Gedeng Ruan, Edwin L. Thomas, and James M. Tour. Nano Lett., Article ASAP DOI: 10.1021/nl501803s Publication Date (Web): July 3, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

As for my recent spate of posts on computers and chips, there’s a July 11, 2014 posting about IBM, a 7nm chip, and much more; a July 9, 2014 posting about Intel and its 14nm low-power chip processing and plans for a 10nm chip; and, finally, a June 26, 2014 posting about HP Labs and its plans for memristive-based computing and their project dubbed ‘The Machine’.

Carbon capture with nanoporous material in the oilfields

Researchers at Rice University (Texas) have devised a new technique for carbon capture according to a June 3, 2014 news item on Nanowerk,

Rice University scientists have created an Earth-friendly way to separate carbon dioxide from natural gas at wellheads.

A porous material invented by the Rice lab of chemist James Tour sequesters carbon dioxide, a greenhouse gas, at ambient temperature with pressure provided by the wellhead and lets it go once the pressure is released. The material shows promise to replace more costly and energy-intensive processes.

A June 3, 2014 Rice University news release, which originated the news item, provides a general description of how carbon dioxide is currently removed during fossil fuel production and adds a few more details about the new technology,

Natural gas is the cleanest fossil fuel. Development of cost-effective means to separate carbon dioxide during the production process will improve this advantage over other fossil fuels and enable the economic production of gas resources with higher carbon dioxide content that would be too costly to recover using current carbon capture technologies, Tour said. Traditionally, carbon dioxide has been removed from natural gas to meet pipelines’ specifications.

The Tour lab, with assistance from the National Institute of Standards and Technology (NIST), produced the patented material that pulls only carbon dioxide molecules from flowing natural gas and polymerizes them while under pressure naturally provided by the well.

When the pressure is released, the carbon dioxide spontaneously depolymerizes and frees the sorbent material to collect more.

All of this works in ambient temperatures, unlike current high-temperature capture technologies that use up a significant portion of the energy being produced.

The news release mentions current political/legislative actions in the US and the implications for the oil and gas industry while further describing the advantages of this new technique,

“If the oil and gas industry does not respond to concerns about carbon dioxide and other emissions, it could well face new regulations,” Tour said, noting the White House issued its latest National Climate Assessment last month [May 2014] and, this week [June 2, 2014], set new rules to cut carbon pollution from the nation’s power plants.

“Our technique allows one to specifically remove carbon dioxide at the source. It doesn’t have to be transported to a collection station to do the separation,” he said. “This will be especially effective offshore, where the footprint of traditional methods that involve scrubbing towers or membranes are too cumbersome.

“This will enable companies to pump carbon dioxide directly back downhole, where it’s been for millions of years, or use it for enhanced oil recovery to further the release of oil and natural gas. Or they can package and sell it for other industrial applications,” he said.

This is an epic (Note to writer: well done) news release as only now is there a technical explanation,

The Rice material, a nanoporous solid of carbon with nitrogen or sulfur, is inexpensive and simple to produce compared with the liquid amine-based scrubbers used now, Tour said. “Amines are corrosive and hard on equipment,” he said. “They do capture carbon dioxide, but they need to be heated to about 140 degrees Celsius to release it for permanent storage. That’s a terrible waste of energy.”

Rice graduate student Chih-Chau Hwang, lead author of the paper, first tried to combine amines with porous carbon. “But I still needed to heat it to break the covalent bonds between the amine and carbon dioxide molecules,” he said. Hwang also considered metal oxide frameworks that trap carbon dioxide molecules, but they had the unfortunate side effect of capturing the desired methane as well and they are far too expensive to make for this application.

The porous carbon powder he settled on has massive surface area and turns the neat trick of converting gaseous carbon dioxide into solid polymer chains that nestle in the pores.

“Nobody’s ever seen a mechanism like this,” Tour said. “You’ve got to have that nucleophile (the sulfur or nitrogen atoms) to start the polymerization reaction. This would never work on simple activated carbon; the key is that the polymer forms and provides continuous selectivity for carbon dioxide.”

Methane, ethane and propane molecules that make up natural gas may try to stick to the carbon, but the growing polymer chains simply push them off, he said.

The researchers treated their carbon source with potassium hydroxide at 600 degrees Celsius to produce the powders with either sulfur or nitrogen atoms evenly distributed through the resulting porous material. The sulfur-infused powder performed best, absorbing 82 percent of its weight in carbon dioxide. The nitrogen-infused powder was nearly as good and improved with further processing.

Tour said the material did not degrade over many cycles, “and my guess is we won’t see any. After heating it to 600 degrees C for the one-step synthesis from inexpensive industrial polymers, the final carbon material has a surface area of 2,500 square meters per gram, and it is enormously robust and extremely stable.”

Apache Corp., a Houston-based oil and gas exploration and production company, funded the research at Rice and licensed the technology. Tour expected it will take time and more work on manufacturing and engineering aspects to commercialize.

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

Capturing carbon dioxide as a polymer from natural gas by Chih-Chau Hwang, Josiah J. Tour, Carter Kittrell, Laura Espinal, Lawrence B. Alemany, & James M. Tour. Nature Communications 5, Article number: 3961 doi:10.1038/ncomms4961 Published 03 June 2014

This paper is behind a paywall.

The researchers have made an illustration of the material available,

 Illustration by Tanyia Johnson/Rice University

Illustration by Tanyia Johnson/Rice University

This morning, Azonano posted a June 6, 2014 news item about a patent for carbon capture,

CO2 Solutions Inc. ( the “Corporation”), an innovator in the field of enzyme-enabled carbon capture technology, today announced it has received a Notice of Allowance from the U.S. Patent and Trademark Office for its patent application No. 13/264,294 entitled Process for CO2 Capture Using Micro-Particles Comprising Biocatalysts.

One might almost think these announcements were timed to coincide with the US White House’s moves.

As for CO2 Solutions, this company is located in Québec, Canada.  You can find out more about the company here (you may want to click on the English language button).

Like water for graphene nanoribbons

Reference to magical realism and fiction aside (Like Water for Chocolate by Laura Esquivel), it turns out that water is integral to the formation of very long, very thin graphene nanoribbons. A July 30, 2011 Rice University news release describes the phenomenon, a two year research odyssey, and the scientific ‘accident’ which led researchers to the discovery,

New research at Rice University shows how water makes it practical to form long graphene nanoribbons less than 10 nanometers wide.

And it’s unlikely that many of the other labs currently trying to harness the potential of graphene, a single-atom sheet of carbon, for microelectronics would have come up with the technique the Rice researchers found while they were looking for something else.

The discovery by lead author Vera Abramova and co-author Alexander Slesarev, both graduate students in the lab of Rice chemist James Tour, appears online this month in the American Chemical Society journal ACS Nano.

A bit of water adsorbed from the atmosphere was found to act as a mask in a process that begins with the creation of patterns via lithography and ends with very long, very thin graphene nanoribbons. The ribbons form wherever water gathers at the wedge between the raised pattern and the graphene surface.

The water formation is called a meniscus; it is created when the surface tension of a liquid causes it to curve [in a convex or concave manner]. In the Rice process, the meniscus mask protects a tiny ribbon of graphene from being etched away when the pattern is removed.

Tour said any method to form long wires only a few nanometers wide should catch the interest of microelectronics manufacturers as they approach the limits of their ability to miniaturize circuitry. “They can never take advantage of the smallest nanoscale devices if they can’t address them with a nanoscale wire,” he said. “Right now, manufacturers can make small features, or make big features and put them where they want them. But to have both has been difficult. To be able to pattern a line this thin right where you want it is a big deal because it permits you to take advantage of the smallness in size of nanoscale devices.”

Tour said water’s tendency to adhere to surfaces is often annoying, but in this case it’s essential to the process. “There are big machines that are used in electronics research that are often heated to hundreds of degrees under ultrahigh vacuum to drive off all the water that adheres to the inside surfaces,” he said. “Otherwise there’s always going to be a layer of water. In our experiments, water accumulates at the edge of the structure and protects the graphene from the reactive ion etching (RIE). So in our case, that residual water is the key to success.

Abramova and Slesarev had set out to fabricate nanoribbons by inverting a method developed by another Rice lab to make narrow gaps in materials. The original method utilized the ability of some metals to form a native oxide layer that expands and shields material just on the edge of the metal mask. The new method worked, but not as expected.

“We first suspected there was some kind of shadowing,” Abramova said. But other metals that didn’t expand as much, if at all, showed no difference, nor did varying the depth of the pattern. “I was basically looking for anything that would change something.”

It took two years to develop and test the meniscus theory, during which the researchers also confirmed its potential to create sub-10-nanometer wires from other kinds of materials, including platinum. They also constructed field-effect transistors to check the electronic properties of graphene nanoribbons.

To be sure that water does indeed account for the ribbons, they tried eliminating its effect by first drying the patterns by heating them under vacuum, and then by displacing the water with acetone to eliminate the meniscus. In both cases, no graphene nanoribbons were created.

The researchers are working to better control the nanoribbons’ width, and they hope to refine the nanoribbons’ edges, which help dictate their electronic properties.

“With this study, we figured out you don’t need expensive tools to get these narrow features,” Tour said. “You can use the standard tools [;] a fab line already has to make features that are smaller than 10 nanometers.”

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

Meniscus-Mask Lithography for Narrow Graphene Nanoribbons by Vera Abramova, Alexander S. Slesarev, and James M. Tour. ACS Nano, Article ASAP DOI: 10.1021/nn403057t Publication Date (Web): July 23, 2013
Copyright © 2013 American Chemical Society

This paper is behind a paywall.

Dexter Johnson in his July30, 2013 posting on the Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers]) notes that this use of water is counter-intuitive,

In [an] ironic twist, the water that most lithography processes try avoid and eliminate at great cost is the same water that makes this new lithography process work.

Graphene and radioactive waste

In fact, the material in question is graphene oxide and researchers at Rice University (Texas) and Lomonosov Moscow State University have found that it can rapidly remove radioactive material from water  From the Jan. 8, 2013 news item on ScienceDaily,

A collaborative effort by the Rice lab of chemist James Tour and the Moscow lab of chemist Stepan Kalmykov determined that microscopic, atom-thick flakes of graphene oxide bind quickly to natural and human-made radionuclides and condense them into solids. The flakes are soluble in liquids and easily produced in bulk.

The Rice University Jan. 8, 2013 news release, which originated the news item, was written by Mike Williams and provides additional insight and quotes from the researchers (Note: Links have been removed),

The discovery, Tour said, could be a boon in the cleanup of contaminated sites like the Fukushima nuclear plants damaged by the 2011 earthquake and tsunami. It could also cut the cost of hydraulic fracturing (“fracking”) for oil and gas recovery and help reboot American mining of rare earth metals, he said.

Graphene oxide’s large surface area defines its capacity to adsorb toxins, Kalmykov said. “So the high retention properties are not surprising to us,” he said. “What is astonishing is the very fast kinetics of sorption, which is key.”

“In the probabilistic world of chemical reactions where scarce stuff (low concentrations) infrequently bumps into something with which it can react, there is a greater likelihood that the ‘magic’ will happen with graphene oxide than with a big old hunk of bentonite,” said Steven Winston, a former vice president of Lockheed Martin and Parsons Engineering and an expert in nuclear power and remediation who is working with the researchers. “In short, fast is good.”

Here’s how it works (from the news release; Note: Links have been removed),

The researchers focused on removing radioactive isotopes of the actinides  and lanthanides  – the 30 rare earth elements in the periodic table – from liquids, rather than solids or gases. “Though they don’t really like water all that much, they can and do hide out there,” Winston said. “From a human health and environment point of view, that’s where they’re least welcome.”

Naturally occurring radionuclides are also unwelcome in fracking fluids that bring them to the surface in drilling operations, Tour said. “When groundwater comes out of a well and it’s radioactive above a certain level, they can’t put it back into the ground,” he said. “It’s too hot. Companies have to ship contaminated water to repository sites around the country at very large expense.” The ability to quickly filter out contaminants on-site would save a great deal of money, he said.

He sees even greater potential benefits for the mining industry. Environmental requirements have “essentially shut down U.S. mining of rare earth metals, which are needed for cell phones,” Tour said. “China owns the market because they’re not subject to the same environmental standards. So if this technology offers the chance to revive mining here, it could be huge.”

Tour said that capturing radionuclides does not make them less radioactive, just easier to handle. “Where you have huge pools of radioactive material, like at Fukushima, you add graphene oxide and get back a solid material from what were just ions in a solution,” he said. “Then you can skim it off and burn it. Graphene oxide burns very rapidly and leaves a cake of radioactive material you can then reuse.”

The low cost and biodegradable qualities of graphene oxide should make it appropriate for use in permeable reactive barriers, a fairly new technology for in situ groundwater remediation, he said.

Romanchuk, Slesarev, Kalmykov and Tour are co-authors of the paper with Dmitry Kosynkin, a former postdoctoral researcher at Rice, now with Saudi Aramco. Kalmykov is radiochemistry division head and a professor at Lomonosov Moscow State University. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science at Rice.

Here’s a ‘before’ shot of solution with graphene oxide and an ‘after’ shot where radionuclides have been added and begun to clump,

A new method for removing radioactive material from solutions is the result of collaboration between Rice University and Lomonosov Moscow State University. The vial at left holds microscopic particles of graphene oxide in a solution. At right, graphene oxide is added to simulated nuclear waste, which quickly clumps for easy removal. Image by Anna Yu. Romanchuk/Lomonosov Moscow State University

A new method for removing radioactive material from solutions is the result of collaboration between Rice University and Lomonosov Moscow State University. The vial at left holds microscopic particles of graphene oxide in a solution. At right, graphene oxide is added to simulated nuclear waste, which quickly clumps for easy removal. Image by Anna Yu. Romanchuk/Lomonosov Moscow State University

As noted in the ScienceDaily news item, the research has been published in the Royal Society’s Physical Chemistry Chemical Physics journal,

Anna Yu. Romanchuk, Alexander Slesarev, Stepan N. Kalmykov, Dmitry Kosynkin, James M Tour. Graphene Oxide for Effective Radionuclide Removal. Physical Chemistry Chemical Physics, 2012; DOI: 10.1039/C2CP44593J

This article is behind a paywall.