Rice University: Li-Ion Components for High-Temperature Aerospace, Industrial Apps


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A toothpaste-like composite with hexagonal boron nitride developed by researchers at Rice University is an effective electrolyte and separator in lithium-ion batteries intended for high-temperature applications in a number of industries, including aerospace and oil and gas. (Source: Jeff Fitlow/Rice University)

One major and dangerous problem with lithium-ion batteries is that they can catch fire when heated to high temperatures, an issue that has caused damage and even death when devices ignited without warning.

Now researchers at Rice University have come up with a solution to this very serious safety problem in the form of a combined electrolyte and separator for rechargeable lithium-ion batteries that supplies energy at usable voltages and in high temperatures. The material is a toothpaste-like composite that is capable of performing well at and withstanding high temperatures without combusting.

The problem with most current lithium-battery chemistries is that they present safety concerns when heated beyond 50C (122F) due to the electrolyte/separator combination used in them, explained Marco-Tulio Rodrigues, a Rice graduate student and one of the authors of a paper on the research published in Advanced Materials Science.

 

“The separator is usually a thin polymer film and may deform at high temperatures, causing a short circuit,” Rodrigues told Design News. “The electrolytes are based on organic solvents, which tend to boil at high temperatures, increasing the internal pressure of the cell. Although commercial batteries implement some protection mechanisms to avoid these problems, any damages to the cell case may potentially lead to ignition, since the electrolyte is also highly flammable.”

 

The work of the Rice team addresses both the issue of developing a separator that will not cause a short circuit and an electrolyte that doesn’t have the tendency to catch fire, he said.

The batteries made with the components they developed functioned as intended in temperatures of 50C (122F) for more than a month without losing efficiency, according to researchers. Moreover, test batteries consistently operated from room temperature to 150C (302F), setting one of the widest temperature ranges ever reported for such devices, they said.

To solve the electrolyte problem, researchers used solutions based on ionic liquids in the electrolytes, which have largely been proposed as substitutes for organic solvents in the electrolyte of lithium-ion batteries because they present a much higher thermal stability, Rodrigues explained.

“These chemicals are basically special salts with a very low melting point, in such a way that they are liquid at room temperatures,” he said. “They are completely nonflammable and they do not evaporate at all until they decompose, which occurs beyond 350C (662F).”

With the electrolyte situation solved, researchers turned their attention to finding a new separator, which they addressed with a material called hexagonal boron nitride, also known as white graphene.

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One-atom switch supercharges fluorescent dyes – Rice University


Rice lab discovers simple technique to make biocompatible ‘turn-on’ dyes

It only took the replacement of one atom for Rice University scientists to give new powers to biocompatible fluorescent molecules.

The Rice lab of chemist Han Xiao reported in the Journal of the American Chemical Society it has developed a single-atom switch to turn fluorescent dyes used in biological imaging on and off at will. The technique will enable high-resolution imaging and dynamic tracking of biological processes in living cells, tissues and animals.

The Rice lab developed a minimally modified probe that can be triggered by a broad range of visible light. The patented process could replace existing photoactivatable fluorophores that may only be activated with ultraviolet light or require toxic chemicals to turn on the fluorescence, characteristics that limit their usefulness.

The researchers took advantage of a phenomenon known as photo-induced electron transfer (PET), which was already known to quench fluorescent signals.

Rice University chemist Han Xiao and his colleagues have discovered a simple method to turn fluorescent tags on and off with visible light by switching one atom. (Credit: Jeff Fitlow/Rice University)

Rice University chemist Han Xiao and his colleagues have discovered a simple method to turn fluorescent tags on and off with visible light by switching one atom. Photo by Jeff Fitlow

They put fluorophores in cages of thiocarbonyl, the moeity responsible for quenching. With one-step organic synthesis, they replaced an oxygen atom in the cage with one of sulfur. That enabled them to induce the PET effect to quench fluorescence.

Triggering the complex again with visible light near the fluorescent molecule’s preferred absorbance oxidized the cage in turn. That knocked out the sulfur and replaced it with an oxygen atom, restoring fluorescence.

“All it takes to make these is a little chemistry and one step,” said Xiao, who joined Rice in 2017 with funding from the Cancer Prevention and Research Institute of Texas  (CPRIT). “We demonstrated in the paper that it works the same for a range of fluorescent dyes. Basically, one reaction solves a lot of problems.”

Researchers worldwide use fluorescent molecules to tag and track cells or elements within cells. Activating the tags with low-powered visible light rather than ultraviolet is much less damaging to the cells being studied, Xiao said, and makes the long exposures of living cells required by super-resolution imaging possible.

Super-resolution experiments by Theodore Wensel, the Robert A. Welch Chair in Chemistry at Baylor College of Medicine, and his team confirmed their abilities, he said.

“We feel this will be a really good probe for living-cell imaging,” Xiao said. “People also use photoactivatable dye to track the dynamics of proteins, to see where and how far and how fast they travel. Our work was to provide a simple, general way to generate this dye.”

At top, a sequence shows the design of thio-caged dyes designed at Rice University to be triggered by visible light. At bottom, confocal and super-resolution imaging of a lipid droplet in living adipocytes incubated with BODIPY (green), SNile Red (red) and Hoechst 33342 (blue), followed by photoactivation using a 561 nm laser. Scale bar: 10 µm. Scale bar for super-resolution image of lipid droplet labeled with SNile Red, bottom right: 1 µm. Courtesy of the Xiao Lab

At top, a sequence shows the design of thio-caged dyes designed at Rice University to be triggered by visible light. At bottom, confocal and super-resolution imaging of a lipid droplet in living adipocytes incubated with BODIPY (green), SNile Red (red) and Hoechst 33342 (blue), followed by photoactivation using a 561-nanometer laser. Scale bar: 10 µm. Scale bar for super-resolution image of lipid droplet labeled with SNile Red, bottom right: 1 µm. Courtesy of the Xiao Lab

The researchers found their technique worked on a wide range of common fluorescent tags and could even be mixed for multicolor imaging of targeted molecules in a single cell.

Rice postdoctoral researcher Juan Tang is lead author of the paper. Co-authors are Rice graduate students Kuan-Lin Wu and Jingqi Pei; postdoctoral fellow Michael Robichaux of Baylor; and graduate student Nhung Nguyen and Yubin Zhou, an assistant professor at the Center for Translational Cancer Research at Texas A&M University. Xiao is the Norman Hackerman-Welch Young Investigator and an assistant professor of chemistry, biosciences, and bioengineering.

CPRIT, the Robert A. Welch Foundation, a Hamill Innovation Award, a John S. Dunn Foundation Collaborative Research Award and the National Institutes of Health supported the research.

“Affairs of the Heart” – Texas Heart Institute & Rice University – Damaged hearts are rewired with Nanotube Fibers


Rice Nano Tube Hearts 7eae23_46bb535810c64757b54ee0fe3f4d8c8c_mv2
Researchers at Texas Heart Institute and Rice University have confirmed that flexible, conductive fibers made of carbon nanotubes can bridge damaged tissue to deliver electrical signals and keep hearts beating despite congestive heart failure or dilated cardiomyopathy or after a heart attack. @ Texas Heart Institute Thin, flexible fibers made of carbon nanotubes have now proven able to bridge damaged heart tissues and deliver the electrical signals needed to keep those hearts beating.

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

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

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

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

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

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

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

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

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

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

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

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

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

In Vivo Restoration of Myocardial Conduction With Carbon Nanotube Fibers

Mark D. McCauley, Flavia Vitale, J. Stephen Yan, Colin C. Young, Brian Greet, Marco Orecchioni, Srikanth Perike, Abdelmotagaly Elgalad, Julia A. Coco, Mathews John, Doris A. Taylor, Luiz C. Sampaio, Lucia G. Delogu, Mehdi Razavi, Matteo Pasquali

Circulation: Arrhythmia and Electrophysiology Vol. 12, No. 8

DOI: 10.1161/CIRCEP.119.007256

Contact information:

Matteo Pasquali

Professor of Chemical and Biomolecular Engineering at Rice University

mp@rice.edu

Phone: 713-348-5830

Pasquali Research Group

Mehdi Razavi

Cardiologist, Associate Professor of Medicine-Cardiology at Baylor College of Medicine and Director of Electrophysiology Clinical Research and Innovations at THI

razavi@bcm.edu

Rice University

Engineers at Rice University boost output of solar desalination system by 50%


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Concentrating the sunlight on tiny spots on the heat-generating membrane exploits an inherent and previously unrecognized nonlinear relationship between photothermal heating and vapor pressure. Credit: Pratiksha Dongare/Rice University

Rice University’s solar-powered approach for purifying salt water with sunlight and nanoparticles is even more efficient than its creators first believed.

Researchers in Rice’s Laboratory for Nanophotonics (LANP) this week showed they could boost the efficiency of their solar-powered desalination system by more than 50% simply by adding inexpensive plastic lenses to concentrate sunlight into “hot spots.” The results are available online in the Proceedings of the National Academy of Sciences.

“The typical way to boost performance in solar-driven systems is to add solar concentrators and bring in more light,” said Pratiksha Dongare, a graduate student in applied physics at Rice’s Brown School of Engineering and co-lead author of the paper. “The big difference here is that we’re using the same amount of light. We’ve shown it’s possible to inexpensively redistribute that power and dramatically increase the rate of purified  production.”

In conventional membrane distillation, hot, salty water is flowed across one side of a sheetlike membrane while cool, filtered water flows across the other. The temperature difference creates a difference in  that drives water vapor from the heated side through the membrane toward the cooler, lower-pressure side. Scaling up the technology is difficult because the  across the membrane—and the resulting output of clean water—decreases as the size of the membrane increases. Rice’s “nanophotonics-enabled solar membrane distillation” (NESMD) technology addresses this by using light-absorbing nanoparticles to turn the membrane itself into a solar-driven .

'Hot spots' increase efficiency of solar desalination

Rice University researchers (from left) Pratiksha Dongare, Alessandro Alabastri and Oara Neumann showed that Rice’s ‘nanophotonics-enabled solar membrane distillation’ (NESMD) system was more efficient when the size of the device was scaled up and light was concentrated in ‘hot spots.’ Credit: Jeff Fitlow/Rice University

Dongare and colleagues, including study co-lead author Alessandro Alabastri, coat the top layer of their membranes with low-cost, commercially available nanoparticles that are designed to convert more than 80% of sunlight energy into heat. The solar-driven nanoparticle heating reduces production costs, and Rice engineers are working to scale up the technology for applications in  that have no access to electricity.

The concept and particles used in NESMD were first demonstrated in 2012 by LANP director Naomi Halas and research scientist Oara Neumann, who are both co-authors on the new study. In this week’s study, Halas, Dongare, Alabastri, Neumann and LANP physicist Peter Nordlander found they could exploit an inherent and previously unrecognized nonlinear relationship between incident light intensity and vapor pressure.

Alabastri, a physicist and Texas Instruments Research Assistant Professor in Rice’s Department of Electrical and Computer Engineering, used a simple mathematical example to describe the difference between a linear and nonlinear relationship. “If you take any two numbers that equal 10—seven and three, five and five, six and four—you will always get 10 if you add them together. But if the process is nonlinear, you might square them or even cube them before adding. So if we have nine and one, that would be nine squared, or 81, plus one squared, which equals 82. That is far better than 10, which is the best you can do with a linear relationship.”

In the case of NESMD, the nonlinear improvement comes from concentrating sunlight into tiny spots, much like a child might with a magnifying glass on a sunny day. Concentrating the light on a tiny spot on the membrane results in a linear increase in heat, but the heating, in turn, produces a nonlinear increase in vapor pressure. And the increased pressure forces more purified steam through the membrane in less time.

'Hot spots' increase efficiency of solar desalination
Researchers from Rice University’s Laboratory for Nanophotonics found they could boost the efficiency of their solar-powered desalination system by more than 50% by adding inexpensive plastic lenses to concentrate sunlight into “hot spots.” . Credit: Pratiksha Dongare/Rice University

“We showed that it’s always better to have more photons in a smaller area than to have a homogeneous distribution of photons across the entire ,” Alabastri said.

Halas, a chemist and engineer who’s spent more than 25 years pioneering the use of light-activated nanomaterials, said, “The efficiencies provided by this nonlinear optical process are important because water scarcity is a daily reality for about half of the world’s people, and efficient solar distillation could change that.

“Beyond water purification, this nonlinear optical effect also could improve technologies that use solar heating to drive chemical processes like photocatalysis,” Halas said.

For example, LANP is developing a copper-based nanoparticle for converting ammonia into hydrogen fuel at ambient pressure.

Halas is the Stanley C. Moore Professor of Electrical and Computer Engineering, director of Rice’s Smalley-Curl Institute and a professor of chemistry, bioengineering, physics and astronomy, and materials science and nanoengineering.

NESMD is in development at the Rice-based Center for Nanotechnology Enabled Water Treatment (NEWT) and won research and development funding from the Department of Energy’s Solar Desalination program in 2018.


Explore further

Freshwater from salt water using only solar energy: Modular, off-grid desalination technology


More information: Pratiksha D. Dongare et al, Solar thermal desalination as a nonlinear optical process, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1905311116

Provided by Rice University

Chemists build a better cancer-killing drill: Rice University designs molecular motors with an upgrade for activation with near-infrared light


Houston, TX | Posted on May 29th, 2019

Researchers at Rice University, Durham (U.K.) University and North Carolina State University reported their success at activating the motors with precise two-photon excitation via near-infrared light. Unlike the ultraviolet light they first used to drive the motors, the new technique does not damage adjacent, healthy cells.

The team’s results appear in the American Chemical Society journal ACS Nano.

The research led by chemists James Tour of Rice, Robert Pal of Durham and Gufeng Wang of North Carolina may be best applied to skin, oral and gastrointestinal cancer cells that can be reached for treatment with a laser. 

In a 2017 Nature paper, the same team reported the development of molecular motors enhanced with small proteins that target specific cancer cells.

Once in place and activated with light, the paddlelike motors spin up to 3 million times a second, allowing the molecules to drill through the cells’ protective membranes and killing them in minutes.

Since then, researchers have worked on a way to eliminate the use of damaging ultraviolet light. In two-photon absorption, a phenomenon predicted in 1931 and confirmed 30 years later with the advent of lasers, the motors absorb photons in two frequencies and move to a higher energy state, triggering the paddles.

A video produced in 2017 explains the basic concept of cell death via molecular motors. Video produced by Brandon Martin/Rice University.

“Multiphoton activation is not only more biocompatible but also allows deeper tissue penetration and eliminates any unwanted side effects that may arise with the previously used UV light,” Pal said. 

The researchers tested their updated motors on skin, breast, cervical and prostate cancer cells in the lab. Once the motors found their targets, lasers activated them with a precision of about 200 nanometers.

In most cases, the cells were dead within three minutes, they reported. They believe the motors also drill through chromatin and other components of the diseased cells, which could help slow metastasis.

Because the motors target specific cells, Tour said work is underway to adapt them to kill antibiotic-resistant bacteria as well.

“We continue to perfect the molecular motors, aiming toward ones that will work with visible light and provide even higher efficacies of kill toward the cellular targets,” he said.

Rice postdoctoral researcher Dongdong Liu is lead author of the paper. Co-authors are Rice alumni Victor Garcia-López, Lizanne Nilewski and Amir Aliyan, visiting research scientist Richard Gunasekera, and senior research scientist Lawrence Alemany and graduate student Tao Jin of North Carolina State.

Wang is an assistant professor of chemistry at North Carolina State. Pal is an assistant professor of chemistry at Durham. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice.

The Royal Society, the United Kingdom’s Engineering and Physical Sciences Research Council, the Discovery Institute, the Pensmore Foundation and North Carolina State supported the research.

About Rice University
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,962 undergraduates and 3,027 graduate students, Rice’s undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 2 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance.

Follow Rice News and Media Relations via Twitter @RiceUNews.

Copyright © Rice University

Rice University – Flexible insulator offers high strength and superior thermal conduction – Applications for Flexible Electronics and Energy Storage


 

flexible insulator offers high strength and superior thermal conduction
Rice University research scientist M.M. Rahman holds a flexible dielectric made of a polymer nanofiber layer and boron nitride. The new material stands up to high temperatures and could be ideal for flexible electronics, energy storage and electric devices where heat is a factor. Credit: Jeff Fitlow/Rice University

A nanocomposite invented at Rice University’s Brown School of Engineering promises to be a superior high-temperature dielectric material for flexible electronics, energy storage and electric devices.

The nanocomposite combines one-dimensional  nanofibers and two-dimensional  nanosheets. The nanofibers reinforce the self-assembling material while the “white graphene” nanosheets provide a thermally conductive network that allows it to withstand the heat that breaks down common dielectrics, the polarized insulators in batteries and other devices that separate positive and negative electrodes.

The discovery by the lab of Rice  scientist Pulickel Ajayan is detailed in Advanced Functional Materials.

Research scientist M.M. Rahman and postdoctoral researcher Anand Puthirath of the Ajayan lab led the study to meet the challenge posed by next-generation electronics: Dielectrics must be thin, tough, flexible and able to withstand .

“Ceramic is a very good dielectric, but it is mechanically brittle,” Rahman said of the common material. “On the other hand, polymer is a good dielectric with good mechanical properties, but its thermal tolerance is very low.”

Boron  is an electrical insulator, but happily disperses heat, he said. “When we combined the polymer nanofiber with boron nitride, we got a material that’s mechanically exceptional, and thermally and chemically very stable,” Rahman said.

A lab video shows how quickly heat disperses from a composite of a polymer nanoscale fiber layer and boron nitride nanosheets. When exposed to light, both materials heat up, but the plain polymer nanofiber layer on the left retains the heat far longer than the composite at right. Credit: Ajayan Research Group/Rice University

The 12-to-15-micron-thick material acts as an effective heat sink up to 250 degrees Celsius (482 degrees Fahrenheit), according to the researchers. Tests showed the polymer nanofibers-boron nitride combination dispersed heat four times better than the polymer alone.

In its simplest form, a single layer of polyaramid nanofibers binds via van der Waals forces to a sprinkling of boron nitride flakes, 10% by weight of the final product. The flakes are just dense enough to form a heat-dissipating network that still allows the composite to retain its flexibility, and even foldability, while maintaining its robustness. Layering polyaramid and boron nitride can make the material thicker while still retaining flexibility, according to the researchers.

“The 1D polyaramid  has many interesting properties except thermal conductivity,” Rahman said. “And  nitride is a very interesting 2-D material right now. They both have different independent properties, but when they are together, they make something very unique.”

Rahman said the material is scalable and should be easy to incorporate into manufacturing.


Explore further

New material to pave the way for more efficient electronic devices


More information: Muhammad M. Rahman et al. Fiber Reinforced Layered Dielectric Nanocomposite, Advanced Functional Materials (2019). DOI: 10.1002/adfm.201900056

Journal information: Advanced Functional Materials
Provided by Rice University

MIT Review: Borophene (not graphene) is the new wonder material that’s got everyone excited


Stronger and more flexible than graphene, a single-atom layer of boron could revolutionize sensors, batteries, and catalytic chemistry.

Not so long ago, graphene was the great new wonder material. A super-strong, atom-thick sheet of carbon “chicken wire,” it can form tubes, balls, and other curious shapes.

And because it conducts electricity, materials scientists raised the prospect of a new era of graphene-based computer processing and a lucrative graphene chip industry to boot. The European Union invested €1 billion to kick-start a graphene industry.

This brave new graphene-based world has yet to materialize. But it has triggered an interest in other two-dimensional materials. And the most exciting of all is borophene: a single layer of boron atoms that form various crystalline structures.

The reason for the excitement is the extraordinary range of applications that borophene looks good for. Electrochemists think borophene could become the anode material in a new generation of more powerful lithium-ion batteries.

Read More: Borophene Discoveries at Rice University

Chemists are entranced by its catalytic capabilities. And physicists are testing its abilities as a sensor to detect numerous kinds of atoms and molecules.

Today, Zhi-Qiang Wang at Xiamen University in China and a number of colleagues review the remarkable properties of borophene and the applications they might lead to.

Borophene has a short history. Physicists first predicted its existence in the 1990s using computer simulations to show how boron atoms could form a monolayer.

But this exotic substance wasn’t synthesized until 2015, using chemical vapor deposition. This is a process in which a hot gas of boron atoms condenses onto a cool surface of pure silver.

The regular arrangement of silver atoms forces boron atoms into a similar pattern, each binding to as many as six other atoms to create a flat hexagonal structure. However, a significant proportion of boron atoms bind only with four or five other atoms, and this creates vacancies in the structure. The pattern of vacancies is what gives borophene crystals their unique properties.

Since borophene’s synthesis, chemists have been eagerly characterizing its properties. Borophene turns out to be stronger than graphene, and more flexible. It a good conductor of both electricity and heat, and it also superconducts. These properties vary depending on the material’s orientation and the arrangement of vacancies. This makes it “tunable,” at least in principle. That’s one reason chemists are so excited.

Borophene is also light and fairly reactive. That makes it a good candidate for storing metal ions in batteries. “Borophene is a promising anode material for Li, Na, and Mg ion batteries due to high theoretical specific capacities, excellent electronic conductivity and outstanding ion transport properties,” say Wang and co.

Hydrogen atoms also stick easily to borophene’s single-layer structure, and this adsorption property, combined with the huge surface area of atomic layers, makes borophene a promising material for hydrogen storage. Theoretical studies suggest borophene could store over 15% of its weight in hydrogen, significantly outperforming other materials.

Then there is borophene’s ability to catalyze the breakdown of molecular hydrogen into hydrogen ions, and water into hydrogen and oxygen ions.

“Outstanding catalytic performances of borophene have been found in hydrogen evolution reaction, oxygen reduction reaction, oxygen evolution reaction, and CO2 electroreduction reaction,” say the team. That could usher in a new era of water-based energy cycles.

Nevertheless, chemists have some work to do before borophene can be more widely used. For a start, they have yet to find a way to make borophene in large quantities.

And the material’s reactivity means it is vulnerable to oxidation, so it needs to be carefully protected. Both factors make borophene expensive to make and hard to handle. So there is work ahead.

But chemists have great faith. Borophene may just become the next wonder material to entrance the world.

Ref: arxiv.org/abs/1903.11304 : Review of borophene and its potential applications

From MIT Technology Review March 2019

 

Using Nanotechnology to Clean Water: A Conversation with Pedro Alvarez of Rice University (NEWT – Nano Enabled Water Treatment)


silver-nano-p-clean-drinking-water-india (1)

In this special anniversary episode of Stories from the NNI, Dr. Lisa Friedersdorf, Director of NNCO, talks to Prof. Pedro Alvarez, of Rice University. Pedro and Lisa discuss the role nanotechnology plays in water security, exciting research results and applications, and his thoughts on the NNI.

 

 

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Read More: How Can Graphene Be Used in Desalination?

Update Rice University – Researchers develop a method to make atom-flat sensors that seamlessly integrate with devices – technique will make active sensors or devices possible for telecommunication and bio-sensing, plasmonics


Rice U Flat Atom structure DuEfkhxWwAAfEGTRice University engineers have developed a method to transfer complete, flexible, two-dimensional circuits from their fabrication platforms to curved and other smooth surfaces. Such circuits are able to couple with near-field …more

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by  scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices to report on what they perceive.

Electronically active 2-D materials have been the subject of much research since the introduction of graphene in 2004. Even though they are often touted for their strength, they’re difficult to move to where they’re needed without destroying them.Nano Sensor 1 FANG

The Ajayan and Lou groups, along with the lab of Rice engineer Jacob Robinson, have a new way to keep the materials and their associated circuitry, including electrodes, intact as they’re moved to curved or other smooth surfaces.

The results of their work appear in the American Chemical Society journal ACS Nano.

Rice logo_rice3The Rice team tested the concept by making a 10-nanometer-thick indium selenide photodetector with gold electrodes and placing it onto an . Because it was so close, the near-field sensor effectively coupled with an evanescent field—the oscillating electromagnetic wave that rides the surface of the fiber—and accurately detected the flow of information inside.

The benefit is that these sensors can now be imbedded into such fibers where they can monitor performance without adding weight or hindering the signal flow.

“This paper proposes several interesting possibilities for applying 2-D devices in real applications,” Lou said. “For example, optical fibers at the bottom of the ocean are thousands of miles long, and if there’s a problem, it’s hard to know where it occurred. If you have these sensors at different locations, you can sense the damage to the fiber.”

Lou said labs have gotten good at transferring the growing roster of 2-D materials from one surface to another, but the addition of electrodes and other components complicates the process. “Think about a transistor,” he said. “It has source, drain and gate electrodes and a dielectric (insulator) on top, and all of these have to be transferred intact. That’s a very big challenge, because all of those materials are different.”

Raw 2-D materials are often moved with a layer of polymethyl methacrylate (PMMA), more commonly known as Plexiglas, on top, and the Rice researchers make use of that technique. But they needed a robust bottom layer that would not only keep the circuit intact during the move but could also be removed before attaching the device to its target. (The PMMA is also removed when the circuit reaches its destination.)

The ideal solution was poly-dimethyl-glutarimide (PMGI), which can be used as a device fabrication platform and easily etched away before transfer to the target. “We’ve spent quite some time to develop this sacrificial layer,” Lou said. PMGI appears to work for any 2-D material, as the researchers experimented successfully with molybdenum diselenide and other materials as well.

Nano sensors 2 electronics_vision_10-11-17

The Rice labs have only developed passive sensors so far, but the researchers believe their technique will make active  or devices possible for telecommunication, biosensing, plasmonics and other applications.

 Explore further: Fluorine flows in, makes material metal

More information: Zehua Jin et al, Near-Field Coupled Integrable Two-Dimensional InSe Photosensor on Optical Fiber, ACS Nano (2018). DOI: 10.1021/acsnano.8b07159

 

Scientists develop Lithium Metal batteries that charge faster, last longer with 10X times more energy by volume than Li-Ion Batteries – BIG potential for Our EV / AV Future


 

October 25, 2018

Rice University scientists are counting on films of carbon nanotubes to make high-powered, fast-charging lithium metal batteries a logical replacement for common lithium-ion batteries.

The Rice lab of chemist James Tour showed thin nanotube films effectively stop dendrites that grow naturally from unprotected lithium metal anodes in batteries. Over time, these tentacle-like dendrites can pierce the battery’s electrolyte core and reach the cathode, causing the battery to fail.

That problem has both dampened the use of lithium metal in commercial applications and encouraged researchers worldwide to solve it.

img_0837-1Rice University graduate student Gladys López-Silva holds a lithium metal anode with a film of carbon nanotubes. Once the film is attached, it becomes infiltrated by lithium ions and turns red. Photo by Jeff Fitlow

Lithium metal charges much faster and holds about 10 times more energy by volume than the lithium-ion electrodes found in just about every electronic device, including cellphones and electric cars.

 

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“One of the ways to slow dendrites in lithium-ion batteries is to limit how fast they charge,” Tour said. “People don’t like that. They want to be able to charge their batteries quickly.”

The Rice team’s answer, detailed in Advanced Materials, is simple, inexpensive and highly effective at stopping dendrite growth, Tour said.

“What we’ve done turns out to be really easy,” he said. “You just coat a lithium metal foil with a multiwalled carbon nanotube film. The lithium dopes the nanotube film, which turns from black to red, and the film in turn diffuses the lithium ions.”

“Physical contact with lithium metal reduces the nanotube film, but balances it by adding lithium ions,” said Rice postdoctoral researcher Rodrigo Salvatierra, co-lead author of the paper with graduate student Gladys López-Silva. “The ions distribute themselves throughout the nanotube film.”

img_0835An illustration shows how lithium metal anodes developed at Rice University are protected from dendrite growth by a film of carbon nanotubes. Courtesy of the Tour Group

When the battery is in use, the film discharges stored ions and the underlying lithium anode refills it, maintaining the film’s ability to stop dendrite growth.

The tangled-nanotube film effectively quenched dendrites over 580 charge/discharge cycles of a test battery with a sulfurized-carbon cathode the lab developed in previous experiments.

The researchers reported the full lithium metal cells retained 99.8 percent of their coulombic efficiency, the measure of how well electrons move within an electrochemical system.

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Rice University scientists have discovered that a film of multiwalled carbon nanotubes quenches the growth of dendrites in lithium metal-based batteries. Courtesy of the Tour Group

Co-authors of the paper are Rice alumni Almaz Jalilov of the King Fahd University of Petroleum and Minerals, Saudi Arabia; Jongwon Yoon, a senior researcher at the Korea Basic Science Institute; and Gang Wu, an instructor, and Ah-Lim Tsai, a professor of hematology, both at the McGovern Medical School at the University of Texas Health Science Center at Houston.

Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice.

The research was supported by the Air Force Office of Scientific Research, the National Institutes of Health, the National Council of Science and Technology, Mexico; the National Council for Scientific and Technological Development, Ministry of Science, Technology and Innovation and Coordination for the Improvement of Higher Education Personnel, Brazil; and Celgard, LLC.

1028_DENDRITE-5-rn-18fsg2wRice University chemist James Tour, left, graduate student Gladys López-Silva and postdoctoral researcher Rodrigo Salvatierra use a film of carbon nanotubes to prevent dendrite growth in lithium metal batteries, which charge faster and hold more power than current lithium-ion batteries. Photo by Jeff Fitlow.

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