Tag Archives: Rice University

‘Lilliputian’ skyscraper: white graphene for hydrogen storage

This story comes from Rice University (Texas, US). From a March 12, 2018 news item on Nanowerk,

Rice University engineers have zeroed in on the optimal architecture for storing hydrogen in “white graphene” nanomaterials — a design like a Lilliputian skyscraper with “floors” of boron nitride sitting one atop another and held precisely 5.2 angstroms apart by boron nitride pillars.

Caption Thousands of hours of calculations on Rice University’s two fastest supercomputers found that the optimal architecture for packing hydrogen into “white graphene” involves making skyscraper-like frameworks of vertical columns and one-dimensional floors that are about 5.2 angstroms apart. In this illustration, hydrogen molecules (white) sit between sheet-like floors of graphene (gray) that are supported by boron-nitride pillars (pink and blue). Researchers found that identical structures made wholly of boron-nitride had unprecedented capacity for storing readily available hydrogen. Credit Lei Tao/Rice University

A March 12, 2018 Rice University news release (also on EurekAlert), which originated the news item, goes into extensive detail about the work,

“The motivation is to create an efficient material that can take up and hold a lot of hydrogen — both by volume and weight — and that can quickly and easily release that hydrogen when it’s needed,”  [emphasis mine] said the study’s lead author, Rouzbeh Shahsavari, assistant professor of civil and environmental engineering at Rice.

Hydrogen is the lightest and most abundant element in the universe, and its energy-to-mass ratio — the amount of available energy per pound of raw material, for example — far exceeds that of fossil fuels. It’s also the cleanest way to generate electricity: The only byproduct is water. A 2017 report by market analysts at BCC Research found that global demand for hydrogen storage materials and technologies will likely reach $5.4 billion annually by 2021.

Hydrogen’s primary drawbacks relate to portability, storage and safety. While large volumes can be stored under high pressure in underground salt domes and specially designed tanks, small-scale portable tanks — the equivalent of an automobile gas tank — have so far eluded engineers.

Following months of calculations on two of Rice’s fastest supercomputers, Shahsavari and Rice graduate student Shuo Zhao found the optimal architecture for storing hydrogen in boron nitride. One form of the material, hexagonal boron nitride (hBN), consists of atom-thick sheets of boron and nitrogen and is sometimes called white graphene because the atoms are spaced exactly like carbon atoms in flat sheets of graphene.

Previous work in Shahsavari’s Multiscale Materials Lab found that hybrid materials of graphene and boron nitride could hold enough hydrogen to meet the Department of Energy’s storage targets for light-duty fuel cell vehicles.

“The choice of material is important,” he said. “Boron nitride has been shown to be better in terms of hydrogen absorption than pure graphene, carbon nanotubes or hybrids of graphene and boron nitride.

“But the spacing and arrangement of hBN sheets and pillars is also critical,” he said. “So we decided to perform an exhaustive search of all the possible geometries of hBN to see which worked best. We also expanded the calculations to include various temperatures, pressures and dopants, trace elements that can be added to the boron nitride to enhance its hydrogen storage capacity.”

Zhao and Shahsavari set up numerous “ab initio” tests, computer simulations that used first principles of physics. Shahsavari said the approach was computationally intense but worth the extra effort because it offered the most precision.

“We conducted nearly 4,000 ab initio calculations to try and find that sweet spot where the material and geometry go hand in hand and really work together to optimize hydrogen storage,” he said.

Unlike materials that store hydrogen through chemical bonding, Shahsavari said boron nitride is a sorbent that holds hydrogen through physical bonds, which are weaker than chemical bonds. That’s an advantage when it comes to getting hydrogen out of storage because sorbent materials tend to discharge more easily than their chemical cousins, Shahsavari said.

He said the choice of boron nitride sheets or tubes and the corresponding spacing between them in the superstructure were the key to maximizing capacity.

“Without pillars, the sheets sit naturally one atop the other about 3 angstroms apart, and very few hydrogen atoms can penetrate that space,” he said. “When the distance grew to 6 angstroms or more, the capacity also fell off. At 5.2 angstroms, there is a cooperative attraction from both the ceiling and floor, and the hydrogen tends to clump in the middle. Conversely, models made of purely BN tubes — not sheets — had less storage capacity.”

Shahsavari said models showed that the pure hBN tube-sheet structures could hold 8 weight percent of hydrogen. (Weight percent is a measure of concentration, similar to parts per million.) Physical experiments are needed to verify that capacity, but that the DOE’s ultimate target is 7.5 weight percent, and Shahsavari’s models suggests even more hydrogen can be stored in his structure if trace amounts of lithium are added to the hBN.

Finally, Shahsavari said, irregularities in the flat, floor-like sheets of the structure could also prove useful for engineers.

“Wrinkles form naturally in the sheets of pillared boron nitride because of the nature of the junctions between the columns and floors,” he said. “In fact, this could also be advantageous because the wrinkles can provide toughness. If the material is placed under load or impact, that buckled shape can unbuckle easily without breaking. This could add to the material’s safety, which is a big concern in hydrogen storage devices.

“Furthermore, the high thermal conductivity and flexibility of BN may provide additional opportunities to control the adsorption and release kinetics on-demand,” Shahsavari said. “For example, it may be possible to control release kinetics by applying an external voltage, heat or an electric field.”

I may be wrong but this “The motivation is to create an efficient material that can take up and hold a lot of hydrogen — both by volume and weight — and that can quickly and easily release that hydrogen when it’s needed, …”  sounds like a supercapacitor. One other comment, this research appears to be ‘in silico’, i.e., all the testing has been done as computer simulations and the proposed materials themselves have yet to be tested.

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

Merger of Energetic Affinity and Optimal Geometry Provides New Class of Boron Nitride Based Sorbents with Unprecedented Hydrogen Storage Capacity by Rouzbeh Shahsavari and Shuo Zhao. Small Vol. 14 Issue 10 DOI: 10.1002/smll.201702863 Version of Record online: 8 MAR 2018

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Flat gallium (gallenene) and nanoelectronics

Another day, another 2D material. A March 9, 2018 news item on ScienceDaily announced the latest thin material from Rice university,

Scientists at Rice University and the Indian Institute of Science, Bangalore, have discovered a method to make atomically flat gallium that shows promise for nanoscale electronics.

The Rice lab of materials scientist Pulickel Ajayan and colleagues in India created two-dimensional gallenene, a thin film of conductive material that is to gallium what graphene is to carbon.

Extracted into a two-dimensional form, the novel material appears to have an affinity for binding with semiconductors like silicon and could make an efficient metal contact in two-dimensional electronic devices, the researchers said.

A March 9, 2018 Rice University news release (also on EurekAlert), which originated the news item, describes the process for creating gallenene,

Gallium is a metal with a low melting point; unlike graphene and many other 2-D structures, it cannot yet be grown with vapor phase deposition methods. Moreover, gallium also has a tendency to oxidize quickly. And while early samples of graphene were removed from graphite with adhesive tape, the bonds between gallium layers are too strong for such a simple approach.

So the Rice team led by co-authors Vidya Kochat, a former postdoctoral researcher at Rice, and Atanu Samanta, a student at the Indian Institute of Science, used heat instead of force.

Rather than a bottom-up approach, the researchers worked their way down from bulk gallium by heating it to 29.7 degrees Celsius (about 85 degrees Fahrenheit), just below the element’s melting point. That was enough to drip gallium onto a glass slide. As a drop cooled just a bit, the researchers pressed a flat piece of silicon dioxide on top to lift just a few flat layers of gallenene.

They successfully exfoliated gallenene onto other substrates, including gallium nitride, gallium arsenide, silicone and nickel. That allowed them to confirm that particular gallenene-substrate combinations have different electronic properties and to suggest that these properties can be tuned for applications.

“The current work utilizes the weak interfaces of solids and liquids to separate thin 2-D sheets of gallium,” said Chandra Sekhar Tiwary, principal investigator on the project he completed at Rice before becoming an assistant professor at the Indian Institute of Technology in Gandhinagar, India. “The same method can be explored for other metals and compounds with low melting points.”

Gallenene’s plasmonic and other properties are being investigated, according to Ajayan. “Near 2-D metals are difficult to extract, since these are mostly high-strength, nonlayered structures, so gallenene is an exception that could bridge the need for metals in the 2-D world,” he said.

Co-authors of the paper are graduate student Yuan Zhang and Associate Research Professor Robert Vajtai of Rice; Anthony Stender, a former Rice postdoctoral researcher and now an assistant professor at Ohio University; Sanjit Bhowmick, Praveena Manimunda and Syed Asif of Bruker Nano Surfaces, Minneapolis; and Rice alumnus Abhishek Singh of the Indian Institute of Science. Ajayan is chair of Rice’s Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry.

The Air Force Office of Scientific Research sponsored the research, with additional support from the Indo-US Science and Technology Forum, the government of India and a Rice Center for Quantum Materials/Smalley-Curl Postdoctoral Fellowship in Quantum Materials.

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

Atomically thin gallium layers from solid-melt exfoliation by Vidya Kochat, Atanu Samanta, Yuan Zhang, Sanjit Bhowmick, Praveena Manimunda, Syed Asif S. Asif, Anthony S. Stender, Robert Vajtai, Abhishek K. Singh, Chandra S. Tiwary, and Pulickel M. Ajayan. Science Advances 09 Mar 2018: Vol. 4, no. 3, e1701373 DOI: 10.1126/sciadv.1701373

This paper appears to be open access.

Do you want that coffee with some graphene on toast?

These scientists are excited:

For those who prefer text, here’s the Rice University Feb. 13, 2018 news release (received via email and available online here and on EurekAlert here) Note: Links have been removed),

Rice University scientists who introduced laser-induced graphene (LIG) have enhanced their technique to produce what may become a new class of edible electronics.

The Rice lab of chemist James Tour, which once turned Girl Scout cookies into graphene, is investigating ways to write graphene patterns onto food and other materials to quickly embed conductive identification tags and sensors into the products themselves.

“This is not ink,” Tour said. “This is taking the material itself and converting it into graphene.”

The process is an extension of the Tour lab’s contention that anything with the proper carbon content can be turned into graphene. In recent years, the lab has developed and expanded upon its method to make graphene foam by using a commercial laser to transform the top layer of an inexpensive polymer film.

The foam consists of microscopic, cross-linked flakes of graphene, the two-dimensional form of carbon. LIG can be written into target materials in patterns and used as a supercapacitor, an electrocatalyst for fuel cells, radio-frequency identification (RFID) antennas and biological sensors, among other potential applications.

The new work reported in the American Chemical Society journal ACS Nano demonstrated that laser-induced graphene can be burned into paper, cardboard, cloth, coal and certain foods, even toast.

“Very often, we don’t see the advantage of something until we make it available,” Tour said. “Perhaps all food will have a tiny RFID tag that gives you information about where it’s been, how long it’s been stored, its country and city of origin and the path it took to get to your table.”

He said LIG tags could also be sensors that detect E. coli or other microorganisms on food. “They could light up and give you a signal that you don’t want to eat this,” Tour said. “All that could be placed not on a separate tag on the food, but on the food itself.”

Multiple laser passes with a defocused beam allowed the researchers to write LIG patterns into cloth, paper, potatoes, coconut shells and cork, as well as toast. (The bread is toasted first to “carbonize” the surface.) The process happens in air at ambient temperatures.

“In some cases, multiple lasing creates a two-step reaction,” Tour said. “First, the laser photothermally converts the target surface into amorphous carbon. Then on subsequent passes of the laser, the selective absorption of infrared light turns the amorphous carbon into LIG. We discovered that the wavelength clearly matters.”

The researchers turned to multiple lasing and defocusing when they discovered that simply turning up the laser’s power didn’t make better graphene on a coconut or other organic materials. But adjusting the process allowed them to make a micro supercapacitor in the shape of a Rice “R” on their twice-lased coconut skin.

Defocusing the laser sped the process for many materials as the wider beam allowed each spot on a target to be lased many times in a single raster scan. That also allowed for fine control over the product, Tour said. Defocusing allowed them to turn previously unsuitable polyetherimide into LIG.

“We also found we could take bread or paper or cloth and add fire retardant to them to promote the formation of amorphous carbon,” said Rice graduate student Yieu Chyan, co-lead author of the paper. “Now we’re able to take all these materials and convert them directly in air without requiring a controlled atmosphere box or more complicated methods.”

The common element of all the targeted materials appears to be lignin, Tour said. An earlier study relied on lignin, a complex organic polymer that forms rigid cell walls, as a carbon precursor to burn LIG in oven-dried wood. Cork, coconut shells and potato skins have even higher lignin content, which made it easier to convert them to graphene.

Tour said flexible, wearable electronics may be an early market for the technique. “This has applications to put conductive traces on clothing, whether you want to heat the clothing or add a sensor or conductive pattern,” he said.

Rice alumnus Ruquan Ye is co-lead author of the study. Co-authors are Rice graduate student Yilun Li and postdoctoral fellow Swatantra Pratap Singh and Professor Christopher Arnusch of Ben-Gurion University of the Negev, Israel. 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 Air Force Office of Scientific Research supported the research.

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

Laser-Induced Graphene by Multiple Lasing: Toward Electronics on Cloth, Paper, and Food by Yieu Chyan, Ruquan Ye†, Yilun Li, Swatantra Pratap Singh, Christopher J. Arnusch, and James M. Tour. ACS Nano DOI: 10.1021/acsnano.7b08539 Publication Date (Web): February 13, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

h/t Feb. 13, 2018 news item on Nanowerk

How small can a carbon nanotube get before it stops being ‘electrical’?

Research, which began as an attempt to get reproducible electronics (?) measurements, yielded some unexpected results according ta January 3, 2018 news item on phys.org,

Carbon nanotubes bound for electronics not only need to be as clean as possible to maximize their utility in next-generation nanoscale devices, but contact effects may limit how small a nano device can be, according to researchers at the Energy Safety Research Institute (ESRI) at Swansea University [UK] in collaboration with researchers at Rice University [US].

ESRI Director Andrew Barron, also a professor at Rice University in the USA, and his team have figured out how to get nanotubes clean enough to obtain reproducible electronic measurements and in the process not only explained why the electrical properties of nanotubes have historically been so difficult to measure consistently, but have shown that there may be a limit to how “nano” future electronic devices can be using carbon nanotubes.

Swansea University Issued a January 3, 2018 press release (also on EurekAlert), which originated the news item, explains the work in more detail,

Like any normal wire, semiconducting nanotubes are progressively more resistant to current along their length. But conductivity measurements of nanotubes over the years have been anything but consistent. The ESRI team wanted to know why.

“We are interested in the creation of nanotube based conductors, and while people have been able to make wires their conduction has not met expectations. We were interested in determining the basic sconce behind the variability observed by other researchers.”

They discovered that hard-to-remove contaminants — leftover iron catalyst, carbon and water — could easily skew the results of conductivity tests. Burning them away, Barron said, creates new possibilities for carbon nanotubes in nanoscale electronics.

The new study appears in the American Chemical Society journal Nano Letters.

The researchers first made multiwalled carbon nanotubes between 40 and 200 nanometers in diameter and up to 30 microns long. They then either heated the nanotubes in a vacuum or bombarded them with argon ions to clean their surfaces.

They tested individual nanotubes the same way one would test any electrical conductor: By touching them with two probes to see how much current passes through the material from one tip to the other. In this case, their tungsten probes were attached to a scanning tunneling microscope.

In clean nanotubes, resistance got progressively stronger as the distance increased, as it should. But the results were skewed when the probes encountered surface contaminants, which increased the electric field strength at the tip. And when measurements were taken within 4 microns of each other, regions of depleted conductivity caused by contaminants overlapped, further scrambling the results.

“We think this is why there’s such inconsistency in the literature,” Barron said.

“If nanotubes are to be the next generation lightweight conductor, then consistent results, batch-to-batch, and sample-to-sample, is needed for devices such as motors and generators as well as power systems.”

Annealing the nanotubes in a vacuum above 200 degrees Celsius (392 degrees Fahrenheit) reduced surface contamination, but not enough to eliminate inconsistent results, they found. Argon ion bombardment also cleaned the tubes, but led to an increase in defects that degrade conductivity.

Ultimately they discovered vacuum annealing nanotubes at 500 degrees Celsius (932 Fahrenheit) reduced contamination enough to accurately measure resistance, they reported.

To now, Barron said, engineers who use nanotube fibers or films in devices modify the material through doping or other means to get the conductive properties they require. But if the source nanotubes are sufficiently decontaminated, they should be able to get the right conductivity by simply putting their contacts in the right spot.

“A key result of our work was that if contacts on a nanotube are less than 1 micron apart, the electronic properties of the nanotube changes from conductor to semiconductor, due to the presence of overlapping depletion zones” said Barron, “this has a potential limiting factor on the size of nanotube based electronic devices – this would limit the application of Moore’s law to nanotube devices.”

Chris Barnett of Swansea is lead author of the paper. Co-authors are Cathren Gowenlock and Kathryn Welsby, and Rice alumnus Alvin Orbaek White of Swansea. Barron is the Sêr Cymru Chair of Low Carbon Energy and Environment at Swansea and the Charles W. Duncan Jr.–Welch Professor of Chemistry and a professor of materials science and nanoengineering at Rice.

The Welsh Government Sêr Cymru National Research Network in Advanced Engineering and Materials, the Sêr Cymru Chair Program, the Office of Naval Research and the Robert A. Welch Foundation supported the research.

Rice University has published a January 4, 2018 Rice University news release (also on EurekAlert), which is almost (95%) identical to the press release from Swansea. That’s a bit unusual as collaborating institutions usually like to focus on their unique contributions to the research, hence, multiple news/press releases.

Dexter Johnson, in a January 11, 2018 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website,  adds a detail or two while writing in an accessible style.

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

Spatial and Contamination-Dependent Electrical Properties of Carbon Nanotubes by Chris J. Barnett, Cathren E. Gowenlock, Kathryn Welsby, Alvin Orbaek White, and Andrew R. Barron. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.7b03390 Publication Date (Web): December 19, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

Resizing viral peptides for nanoscale drug delivery system

A January 9, 2018 news item on Nanowerk sheds some light on the research (Note: A link has been removed),

By chipping away at a viral protein, Rice University scientists have discovered a path toward virus-like, nanoscale devices that may be able to deliver drugs to cells.

The protein is one of three that make up the protective shell, called the capsid, of natural adeno-associated viruses (AAV). By making progressively smaller versions of the protein, the researchers made capsids with unique abilities and learned a great deal about AAV’s mechanisms.

The research appears in the American Chemical Society journal ACS Nano (“Reprogramming the Activatable Peptide Display Function of Adeno-Associated Virus Nanoparticles”).
programmable adeno-associated viruses

Rice University bioengineers have developed programmable adeno-associated viruses by modifying one of three proteins that assemble into a tough shell called a capsid. In this illustration, blue subunits in the capsid represent the protein VP3 and green subunits represent a truncated mutant of VP2.

Here’s an image illustrating the work,

Rice University bioengineers have developed programmable adeno-associated viruses by modifying one of three proteins that assemble into a tough shell called a capsid. In this illustration, blue subunits in the capsid represent the protein VP3 and green subunits represent a truncated mutant of VP2. From top to bottom: a VP3-only capsid that does not display any peptides; a mosaic capsid with a majority of VP3 and small amount of the VP2 mutant that shows a low level of activable peptide display; a mosaic capsid with equal amounts of VP3 and VP2 mutant that shows a high level of activable peptide display; and a homomeric VP2 mutant capsid with a high level of constant, brush-like peptide display. For a larger version, click on the image. Illustration by Nicole Thadani Courtesy: Rice University

A January 8, 2018 Rice University news release (also on EurekAlert), which originated the news item, expands on the story,

Rice bioengineer Junghae Suh studies the manipulation of nondisease-causing AAVs to deliver helpful cargoes like chemotherapy drugs. Her research has led to the development of viruses that can be triggered by light or by extracellular proteases associated with certain diseases.

AAVs are small — about 25 nanometers — and contain a single strand of DNA inside tough capsids that consist of a mosaic of proteins known as VP1, VP2 and VP3. AAVs have been used to deliver gene-therapy payloads, but nobody has figured out how AAV capsids physically reconfigure themselves when triggered by external stimuli, Suh said. That was the starting point for her lab.

“This virus has intrinsic peptide (small protein) domains hidden inside the capsid,” she said. “When the virus infects a cell, it senses the low pH and other endosomal factors, and these peptide domains pop out onto the surface of the virus capsid.

“This conformational change, which we termed an ‘activatable peptide display,’ is important for the virus because the externalized domains break down the endosomal membrane and allow the virus to escape into the cytoplasm,” Suh said. “In addition, nuclear localization sequences in those domains allow the virus to transit into the nucleus. We believed we could replace that functionality with something else.”

Suh and lead author and Rice graduate student Nicole Thadani think their mutant AAVs can become “biocomputing nanoparticles” that detect and process environmental inputs and produce controllable outputs. Modifying the capsid is the first step.

Of the three natural capsid proteins, only VP1 and VP2 can be triggered to expose their functional peptides, but neither can make a capsid on its own. Shorter VP3s can form capsids by themselves, but do not display peptides. In natural AAVs, VP3 proteins outnumber each of their compadres 10-to-1.

That limits the number of peptides that can be exposed, so Suh, Thadani and their co-authors set out to change the ratio. That led them to truncate VP2 and synthesize mosaic capsids with VP3, resulting in successful alteration of the number of exposed peptides. Based on previous research, they inserted a common hexahistidine tag that made it easy to monitor the surface display of the peptide region.

“We wanted to boost the protein’s activable property beyond what occurs in the native virus capsid,” Thadani said. “Rather than displaying just five copies of the peptide per capsid, now we may be able to display 20 or 30 and get more of the bioactivity that we want.”

They then made a truncated VP2 able to form a capsid on its own. “The results were quite surprising, and not obvious to us,” Suh said. “We chopped down that VP2 component enough to form what we call a homomeric capsid, where the entire capsid is made up of just that mutant subunit. That gave us viruses that appear to have peptide ‘brushes’ that are always on the surface.

“A viral structure like that has never been seen in nature,” she said. “We got a particle with this peptide brush, with loose ends everywhere. Now we want to know if we can use these loose ends to attach other things or carry out other functions.”

Homomeric AAVs display as many as 60 peptides, while mosaic AAVs could be programmed to respond to stimuli specific to particular cells or tissues and display a smaller desired number of peptides, the researchers said.

“Viruses have evolved to invade cells very effectively,” Suh said. “We want to use our virus as a nanoparticle platform to deliver protein- or peptide-based therapeutics more efficiently into cells. We want to harness what nature has already created, tweak it a little bit and use it for our purposes.”

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

Reprogramming the Activatable Peptide Display Function of Adeno-Associated Virus Nanoparticles by Nicole N. Thadani, Christopher Dempsey, Julia Zhao, Sonya M. Vasquez, and Junghae Suh. ACS Nano, Article ASAP DOI: 10.1021/acsnano.7b07804 Publication Date (Web): December 26, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

Carbon nanotubes for enhanced wheat growth?

It’s been a long time (Oct. 22, 2009 posting; scroll down about 20% of the way) since I’ve written about carbon nanotubes and their possible use in agriculture but now a December 6, 2017 news item on ScienceDaily raises the topic again,

The introduction of purified carbon nanotubes appears to have a beneficial effect on the early growth of wheatgrass, according to Rice University scientists. But in the presence of contaminants, those same nanotubes could do great harm.

The Rice lab of chemist Andrew Barron grew wheatgrass in a hydroponic garden to test the potential toxicity of nanoparticles on the plant. To their surprise, they found one type of particle dispersed in water helped the plant grow bigger and faster.

They suspect the results spring from nanotubes’ natural hydrophobic (water-avoiding) nature that in one experiment apparently facilitated the plants’ enhanced uptake of water.

The research appears in the Royal Society of Chemistry journal Environmental Science: Nano.

A December 6, 2017 Rice University news release (also on EurekAlert), which originated the news item, expands on the theme,

The lab mounted the small-scale study with the knowledge that the industrial production of nanotubes will inevitably lead to their wider dispersal in the environment. The study cited rapid growth in the market for nanoparticles in drugs, cosmetic, fabrics, water filters and military weapons, with thousands of tons produced annually.

Despite their widespread use, Barron said few researchers have looked at the impact of environmental nanoparticles — whether natural or man-made — on plant growth.

The researchers planted wheatgrass seeds in multiple replicates in cotton wool and fed them with dispersions that contained raw single-walled or multi-walled nanotubes, purified single-walled nanotubes or iron oxide nanoparticles that mimicked leftover catalyst often attached to nanotubes. The solutions were either water or tetrahydrofuran (THF), an industrial solvent. Some of the seeds were fed pure water or THF as a control.

Rice University researchers tested the effects of carbon nanotubes on the growth of wheatgrass. While some showed no effect, purified single-walled nanotubes in water (5) enhanced the plants' growth, while the same nanotubes in a solvent (6) retarded their development. The photos at left show the plants after four days and at right after eight days, with odd-numbered plants growing in water and evens in a solvent. Numbers 1 and 2 are controls without nanotubes; 3-4 contain raw single-walled tubes; 5-6 purified single-walled tubes; 7-8 raw multi-walled tubes; 9-10 low-concentration iron-oxide nanoparticles and 11-12 high-concentration iron-oxide nanoparticles.

Rice University researchers tested the effects of carbon nanotubes on the growth of wheatgrass. While some showed no effect, purified single-walled nanotubes in water (5) enhanced the plants’ growth, while the same nanotubes in a solvent (6) retarded their development. The photos at left show the plants after four days and at right after eight days, with odd-numbered plants growing in water and evens in a solvent. Numbers 1 and 2 are controls without nanotubes; 3-4 contain raw single-walled tubes; 5-6 purified single-walled tubes; 7-8 raw multi-walled tubes; 9-10 low-concentration iron-oxide nanoparticles and 11-12 high-concentration iron-oxide nanoparticles. Click on the image for a larger version. Photos by Seung Mook Lee

After eight days, the plantings showed that purified single-walled nanotubes in water enhanced the germination rate and shoot growth of wheatgrass, which grew an average of 13 percent larger than plants in plain water. Raw single- and multi-walled nanotubes and particles in either solution had little effect on the plants’ growth, they found.

However, purified single-walled nanotubes in THF retarded plant development by 45 percent compared to single-walled nanotubes in water, suggesting the nanotubes act as a carrier for the toxic substance.

The concern, Barron said, is that if single-walled nanotubes combine with organic pollutants like pesticides, industrial chemicals or solvents in the environment, they may concentrate and immobilize the toxins and enhance their uptake by plants.

Nothing seen in the limited study indicated whether carbon nanotubes in the environment, and potentially in plants, will rise up the food chain and be harmful to humans, he said.

On the other hand, the researchers said it may be worth looking at whether hydrophobic substrates that mimic the positive effects observed in single-walled nanotubes could be used for high-efficiency channeling of water to seeds.

“Our work confirms the importance of thinking of nanomaterials as part of a system rather in isolation,” Barron said. “It is the combination with other compounds that is important to understand.”

Seung Mook Lee, a former visiting student research assistant from Memorial High School in Houston and now an undergraduate student at the University of California, Berkeley, is lead author of the paper. Co-authors are Rice research scientist Pavan Raja and graduate student Gibran Esquenazi. Barron is the Charles W. Duncan Jr.–Welch Professor of Chemistry and a professor of materials science and nanoengineering at Rice and the Sêr Cymru Chair of Low Carbon Energy and Environment at Swansea University, Wales (UK).

The Welsh Government Sêr Cymru Program and the Robert A. Welch Foundation supported the research.

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

Effect of raw and purified carbon nanotubes and iron oxide nanoparticles on the growth of wheatgrass prepared from the cotyledons of common wheat (triticum aestivum) by Seung Mook Lee, Pavan M. V. Raja, Gibran L. Esquenazi, and Andrew R. Barron. Environ. Sci.: Nano, 2018, Advance Article DOI: 10.1039/C7EN00680B First published on 09 Nov 2017

This paper appears to be behind a paywall.

Using only sunlight to desalinate water

The researchers seem to believe that this new desalination technique could be a game changer. From a June 20, 2017 news item on Azonano,

An off-grid technology using only the energy from sunlight to transform salt water into fresh drinking water has been developed as an outcome of the effort from a federally funded research.

The desalination system uses a combination of light-harvesting nanophotonics and membrane distillation technology and is considered to be the first major innovation from the Center for Nanotechnology Enabled Water Treatment (NEWT), which is a multi-institutional engineering research center located at Rice University.

NEWT’s “nanophotonics-enabled solar membrane distillation” technology (NESMD) integrates tried-and-true water treatment methods with cutting-edge nanotechnology capable of transforming sunlight to heat. …

A June 19, 2017 Rice University news release, which originated the news item, expands on the theme,

More than 18,000 desalination plants operate in 150 countries, but NEWT’s desalination technology is unlike any other used today.

“Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water,” said Rice scientist and water treatment expert Qilin Li, a corresponding author on the study. “This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities.”

The oldest method for making freshwater from salt water is distillation. Salt water is boiled, and the steam is captured and run through a condensing coil. Distillation has been used for centuries, but it requires complex infrastructure and is energy inefficient due to the amount of heat required to boil water and produce steam. More than half the cost of operating a water distillation plant is for energy.

An emerging technology for desalination is membrane distillation, where hot salt water is flowed across one side of a porous membrane and cold freshwater is flowed across the other. Water vapor is naturally drawn through the membrane from the hot to the cold side, and because the seawater need not be boiled, the energy requirements are less than they would be for traditional distillation. However, the energy costs are still significant because heat is continuously lost from the hot side of the membrane to the cold.

“Unlike traditional membrane distillation, NESMD benefits from increasing efficiency with scale,” said Rice’s Naomi Halas, a corresponding author on the paper and the leader of NEWT’s nanophotonics research efforts. “It requires minimal pumping energy for optimal distillate conversion, and there are a number of ways we can further optimize the technology to make it more productive and efficient.”

NEWT’s new technology builds upon research in Halas’ lab to create engineered nanoparticles that harvest as much as 80 percent of sunlight to generate steam. By adding low-cost, commercially available nanoparticles to a porous membrane, NEWT has essentially turned the membrane itself into a one-sided heating element that alone heats the water to drive membrane distillation.

“The integration of photothermal heating capabilities within a water purification membrane for direct, solar-driven desalination opens new opportunities in water purification,” said Yale University ‘s Menachem “Meny” Elimelech, a co-author of the new study and NEWT’s lead researcher for membrane processes.

In the PNAS study, researchers offered proof-of-concept results based on tests with an NESMD chamber about the size of three postage stamps and just a few millimeters thick. The distillation membrane in the chamber contained a specially designed top layer of carbon black nanoparticles infused into a porous polymer. The light-capturing nanoparticles heated the entire surface of the membrane when exposed to sunlight. A thin half-millimeter-thick layer of salt water flowed atop the carbon-black layer, and a cool freshwater stream flowed below.

Li, the leader of NEWT’s advanced treatment test beds at Rice, said the water production rate increased greatly by concentrating the sunlight. “The intensity got up 17.5 kilowatts per meter squared when a lens was used to concentrate sunlight by 25 times, and the water production increased to about 6 liters per meter squared per hour.”

Li said NEWT’s research team has already made a much larger system that contains a panel that is about 70 centimeters by 25 centimeters. Ultimately, she said, NEWT hopes to produce a modular system where users could order as many panels as they needed based on their daily water demands.

“You could assemble these together, just as you would the panels in a solar farm,” she said. “Depending on the water production rate you need, you could calculate how much membrane area you would need. For example, if you need 20 liters per hour, and the panels produce 6 liters per hour per square meter, you would order a little over 3 square meters of panels.”

Established by the National Science Foundation in 2015, NEWT aims to develop compact, mobile, off-grid water-treatment systems that can provide clean water to millions of people who lack it and make U.S. energy production more sustainable and cost-effective. NEWT, which is expected to leverage more than $40 million in federal and industrial support over the next decade, is the first NSF Engineering Research Center (ERC) in Houston and only the third in Texas since NSF began the ERC program in 1985. NEWT focuses on applications for humanitarian emergency response, rural water systems and wastewater treatment and reuse at remote sites, including both onshore and offshore drilling platforms for oil and gas exploration.

There is a video but it is focused on the NEWT center rather than any specific water technologies,

For anyone interested in the technology, here’s a link to and a citation for the researchers’ paper,

Nanophotonics-enabled solar membrane distillation for off-grid water purification by Pratiksha D. Dongare, Alessandro Alabastri, Seth Pedersen, Katherine R. Zodrow, Nathaniel J. Hogan, Oara Neumann, Jinjian Wu, Tianxiao Wang, Akshay Deshmukh,f, Menachem Elimelech, Qilin Li, Peter Nordlander, and Naomi J. Halas. PNAS {Proceedings of the National Academy of Sciences] doi: 10.1073/pnas.1701835114 June 19, 2017

This paper appears to be open access.

Mussels to muscles for biocompatible fibres

Mussels and barnacles in the intertidal near Newquay, Cornwall, England.
Wilson44691 at English Wikipedia – Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster

I love puns and word play so I was happy to see this in a June 9, 2017 news item on ScienceDaily,

Rice University chemists can thank the mussel for putting the muscle into their new macroscale scaffold fibers.

A June 9, 2017 Rice University news release (also on EurekAlert), which originated the news item, provides more details about the research,

The Rice lab of chemist Jeffrey Hartgerink had already figured out how to make biocompatible nanofibers out of synthetic peptides. In new work, the lab is using an amino acid found in the sticky feet of mussels to make those fibers line up into strong hydrogel strings.

Hartgerink and Rice graduate student I-Che Li introduced their room-temperature method this month in an open-access paper in the Journal of the American Chemical Society.

The hydrogel strings can be picked up and moved with tweezers, and Li said he expects they will help labs gain better control over the growth of cell cultures.

“Usually when cells grow on a surface, they spread randomly,” he said. “There are a lot of biomaterials we want to grow in a specific direction. With the hydrogel scaffold aligned, we can expect cells to grow the way we want them to. One example would be neuron cells, which we want to grow head-to-tail to aid nerve regeneration.

“Basically, this could allow us to direct cell growth from here to there,” he said. “That’s why this material is so exciting.”

In previous research Hartgerink’s lab had developed synthetic hydrogels that could be injected into the body to serve as scaffolds for tissue growth. The hydrogels contained hydrophobic peptides that self-assembled into fibers about 6 nanometers wide and up to several microns long. However, because the fibers did not interact with one other, they generally appeared in microscope images as a tangled mass.

Experiments showed the fibers could be coaxed into alignment with the application of shear forces, in the same way that playing cards are aligned during shuffling by pushing on both the top and bottom of the deck.

Hartgerink and Li decided to try pushing the fibers through a needle to force them into alignment, a process that would be easier if the material was water soluble. So they added a chain of amino acids known as DOPA to the sides of the fibers to allow them to remain water-soluble in the syringe, Li said.

DOPA — short for 3,4-dihydroxyphenylalanine — is the compound that lets mussels stick to just about anything. Hartgerink and Li found that the combination of DOPA and shear stress from passing through the needle prompted the fibers to form visible, rope-like bundles.

They also found that DOPA promoted chemical cross-linking reactions that helped the bundles hold their shape. “DOPA is really sensitive to oxidizing agents,” Li said. “Even exposing DOPA to air oxidizes it, and that aids in cross-linking the fibers.”

As a bonus, the aligned fibers also proved to have a curious and useful optical property called “uniform birefringence,” or double-refraction. Li said this could allow researchers to use polarized light to see exactly where the aligned fibers are, even if they’re covered by cells.

“This will be an important technique for us to make sure of the long-range order of fiber alignment when we are testing directed cell growth,” he said.

The researchers expect the aligned fibers can be used for macroscale medical applications but with nanoscale control over the structures.

“Self-assembly is basically the ability of a molecule to make ordered structure from chaos, and what I-Che has done is push this organization to a new level with his aligned strings,” said Hartgerink, a professor of chemistry and of bioengineering. “With this material, we are excited to see if we can impose this organization onto the growth of cells that interact with it.”

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

Covalent Capture of Aligned Self-Assembling Nanofibers by I-Che Li and Jeffrey D. Hartgerink. J. Am. Chem. Soc., Article ASAP DOI: 10.1021/jacs.7b04655 Publication Date (Web): June 5, 2017

Copyright © 2017 American Chemical Society

This paper is open access.

Gently measuring electrical signals in small animals with nano-SPEARs

This work comes from Rice University (Texas, US) according to an April 17, 2017 news item on Nanowerk,

Microscopic probes developed at Rice University have simplified the process of measuring electrical activity in individual cells of small living animals. The technique allows a single animal like a worm to be tested again and again and could revolutionize data-gathering for disease characterization and drug interactions.

The Rice lab of electrical and computer engineer Jacob Robinson has invented “nanoscale suspended electrode arrays” — aka nano-SPEARs — to give researchers access to electrophysiological signals from the cells of small animals without injuring them. Nano-SPEARs replace glass pipette electrodes that must be aligned by hand each time they are used.”

An April 17, 2017 Rice University news release (also on EurekAltert), which originated the news item, details the work,

“One of the experimental bottlenecks in studying synaptic behavior and degenerative diseases that affect the synapse is performing electrical measurements at those synapses,” Robinson said. “We set out to study large groups of animals under lots of different conditions to screen drugs or test different genetic factors that relate to errors in signaling at those synapses.”

Robinson’s early work at Rice focused on high-quality, high-throughput electrical characterization of individual cells. The new platform adapts the concept to probe the surface cells of nematodes, worms that make up 80 percent of all animals on Earth.

Most of what is known about muscle activity and synaptic transmission in the worms comes from the few studies that successfully used manually aligned glass pipettes to measure electrical activity from individual cells, Robinson said. However, this patch clamp technique requires time-consuming and invasive surgery that could negatively affect the data that is gathered from small research animals.

The platform developed by Robinson’s team works something like a toll booth for traveling worms. As each animal passes through a narrow channel, it is temporarily immobilized and pressed against one or several nano-SPEARS that penetrate its body-wall muscle and record electrical activity from nearby cells. That animal is then released, the next is captured and measured, and so on. Robinson said the device proved much faster to use than traditional electrophysiological cell measurement techniques.

The nano-SPEARs are created using standard thin-film deposition procedures and electron-beam or photolithography and can be made from less than 200 nanometers to more than 5 microns thick, depending on the size of animal to be tested. Because the nano-SPEARs can be fabricated on either silicon or glass, the technique easily combines with fluorescence microscopy, Robinson said.

The animals suitable for probing with a nano-SPEAR can be as large as several millimeters, like hydra, cousins of the jellyfish and the subject of an upcoming study. But nematodes known as Caenorhabditis elegans were practical for several reasons: First, Robinson said, they’re small enough to be compatible with microfluidic devices and nanowire electrodes. Second, there were a lot of them down the hall at the lab of Rice colleague Weiwei Zhong, who studies nematodes as transparent, easily manipulated models for signaling pathways that are common to all animals.

“I used to shy away from measuring electrophysiology because the conventional method of patch clamping is so technically challenging,” said Zhong, an assistant professor of biochemistry and cell biology and co-author of the paper. “Only a few graduate students or postdocs can do it. With Jacob’s device, even an undergraduate student can measure electrophysiology.”

“This meshes nicely with the high-throughput phenotyping she does,” Robinson said. “She can now correlate locomotive phenotypes with activity at the muscle cells. We believe that will be useful to study degenerative diseases centered around neuromuscular junctions.”

In fact, the labs have begun doing so. “We are now using this setup to profile worms with neurodegenerative disease models such as Parkinson’s and screen for drugs that reduce the symptoms,” Zhong said. “This would not be possible using the conventional method.”

Initial tests on C. elegans models for amyotrophic lateral sclerosis and Parkinson’s disease revealed for the first time clear differences in electrophysiological responses between the two, the researchers reported.

Testing the efficacy of drugs will be helped by the new ability to study small animals for long periods. “What we can do, for the first time, is look at electrical activity over a long period of time and discover interesting patterns of behavior,” Robinson said.

Some worms were studied for up to an hour, and others were tested on multiple days, said lead author Daniel Gonzales, a Rice graduate student in Robinson’s lab who took charge of herding nematodes through the microfluidic devices.

“It was in some way easier than working with isolated cells because the worms are larger and fairly sturdy,” Gonzales said. “With cells, if there’s too much pressure, they die. If they hit a wall, they die. But worms are really sturdy, so it was just a matter of getting them up against the electrodes and keeping them there.”

The team constructed microfluidic arrays with multiple channels that allowed testing of many nematodes at once. In comparison with patch-clamping techniques that limit labs to studying about one animal per hour, Robinson said his team measured as many as 16 nematodes per hour.

“Because this is a silicon-based technology, making arrays and producing recording chambers in high numbers becomes a real possibility,” he said.

A scanning electron micrograph shows a nano-SPEAR suspended midway between layers of silicon (grey) and photoresist material (pink) that form a recording chamber for immobilized nematodes. The high-throughput technology developed at Rice University can be adapted for other small animals and could enhance data-gathering for disease characterization and drug interactions. Courtesy of the Robinson Lab

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

Scalable electrophysiology in intact small animals with nanoscale suspended electrode arrays by Daniel L. Gonzales, Krishna N. Badhiwala, Daniel G. Vercosa, Benjamin W. Avants, Zheng Liu, Weiwei Zhong, & Jacob T. Robinson. Nature Nanotechnology (2017) doi:10.1038/nnano.2017.55 Published online 17 April 2017

This paper is behind a paywall.

Recycle electronic waste by crushing it into nanodust

Given the issues with e-waste this work seems quite exciting. From a March 21, 2017 Rice University news release (also on EurekAlert), Note: Links have been removed,

Researchers at Rice University and the Indian Institute of Science have an idea to simplify electronic waste recycling: Crush it into nanodust.

Specifically, they want to make the particles so small that separating different components is relatively simple compared with processes used to recycle electronic junk now.

Chandra Sekhar Tiwary, a postdoctoral researcher at Rice and a researcher at the Indian Institute of Science in Bangalore, uses a low-temperature cryo-mill to pulverize electronic waste – primarily the chips, other electronic components and polymers that make up printed circuit boards (PCBs) — into particles so small that they do not contaminate each other.

Then they can be sorted and reused, he said.

Circuit boards from electronics, like computer mice, can be crushed into nanodust by a cryo-mill, according to researchers at Rice and the Indian Institute of Science. The dust can then be easily separated into its component elements for recycling.

Circuit boards from electronics, like computer mice, can be crushed into nanodust by a cryo-mill, according to researchers at Rice and the Indian Institute of Science. The dust can then be easily separated into its component elements for recycling. Courtesy of the Ajayan Research Group

The process is the subject of a Materials Today paper by Tiwary, Rice materials scientist Pulickel Ajayan and Indian Institute professors Kamanio Chattopadhyay and D.P. Mahapatra. 

The researchers intend it to replace current processes that involve dumping outdated electronics into landfills, or burning or treating them with chemicals to recover valuable metals and alloys. None are particularly friendly to the environment, Tiwary said.

“In every case, the cycle is one way, and burning or using chemicals takes a lot of energy while still leaving waste,” he said. “We propose a system that breaks all of the components – metals, oxides and polymers – into homogenous powders and makes them easy to reuse.”

The researchers estimate that so-called e-waste will grow by 33 percent over the next four years, and by 2030 will weigh more than a billion tons. Nearly 80 to 85 percent of often-toxic e-waste ends up in an incinerator or a landfill, Tiwary said, and is the fastest-growing waste stream in the United States, according to the Environmental Protection Agency.

The answer may be scaled-up versions of a cryo-mill designed by the Indian team that, rather than heating them, keeps materials at ultra-low temperatures during crushing.

Cold materials are more brittle and easier to pulverize, Tiwary said. “We take advantage of the physics. When you heat things, they are more likely to combine: You can put metals into polymer, oxides into polymers. That’s what high-temperature processing is for, and it makes mixing really easy.

A transparent piece of epoxy, left, compared to epoxy with e-waste reinforcement at right. A cryo-milling process developed at Rice University and the Indian Institute of Science simplifies the process of separating and recycling electronic waste.

A transparent piece of epoxy, left, compared to epoxy with e-waste reinforcement at right. A cryo-milling process developed at Rice University and the Indian Institute of Science simplifies the process of separating and recycling electronic waste. Courtesy of the Ajayan Research Group

“But in low temperatures, they don’t like to mix. The materials’ basic properties – their elastic modulus, thermal conductivity and coefficient of thermal expansion – all change. They allow everything to separate really well,” he said.

The test subjects in this case were computer mice – or at least their PCB innards. The cryo-mill contained argon gas and a single tool-grade steel ball. A steady stream of liquid nitrogen kept the container at 154 kelvins (minus 182 degrees Fahrenheit).

When shaken, the ball smashes the polymer first, then the metals and then the oxides just long enough to separate the materials into a powder, with particles between 20 and 100 nanometers wide. That can take up to three hours, after which the particles are bathed in water to separate them.

“Then they can be reused,” he said. “Nothing is wasted.”

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

Electronic waste recycling via cryo-milling and nanoparticle beneficiation by C.S. Tiwary, S. Kishore, R. Vasireddi, D.R. Mahapatra, P.M. Ajayan, K. Chattopadhyay. Materials Today         http://dx.doi.org/10.1016/j.mattod.2017.01.015 Available online 20 March 2017

This paper is behind a paywall.