14 Feb 2017
Creating a Life-Saving, Blood-Repellent Super Material – Revolutionizing Medical Implants: Colorado State University
Goodbye Rejection – Implanted medical devices like stents, catheters, and titanium rods are essential, life-saving tools for patients around the world. Still, having a foreign object in the human body does pose its own risks – chiefly, having the body reject the object or increasing the risk of dangerous blood clots. A new collaboration between two distinct scientific disciplines is working toward making those risks a concern of the past.
Biomedical engineers and materials scientists from Colorado State University (CSU) ….
Florida State University College of Engineering Assistant Professor Shangchao Lin has published a new paper in the journal ACS Nano that predicts how an organic-inorganic hybrid material called organometal halide perovskites could be more mechanically flexible than existing silicon and other inorganic materials used for solar cells, thermoelectric devices and light-emitting diodes.
What if every vehicle, home appliance, heating system and light switch were connected to the Internet? Today, that’s not such a stretch of the imagination.
Modern cars, for instance, already have hundreds of sensors and multiple computers connected over an internal network. And that’s just one example of the 6.4 billion connected “things” in use worldwide this year, according to research by Gartner Inc. DHL and Cisco Systems offer even higher estimates—their 2015 Trend Report sets the current number of connected devices at about 15 billion, amidst industry expectations that the tally will increase to 50 billion by 2020.
29 Jan 2017
PEG-PDI, which incorporates a compound long used as a red dye, changes to greenish-blue with the addition of potassium superoxide as it converts the superoxide to dioxygen. Adding more further quenches the reactive oxygen species superoxide, turning the solution purple. Adding hydrogen peroxide in the last step clarifies the liquid, showing that a build-up of excess hydrogen peroxide can deactivate the structure. PEG-PDI, created at Rice University, shows potential as a biological antioxidant. Credit: Tour Group/Rice University
Treated particles of graphene derived from carbon nanotubes have demonstrated remarkable potential as life-saving antioxidants, but as small as they are, something even smaller had to be created to figure out why they work so well.
Researchers at Rice University, the McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth) and Baylor College of Medicine created single-molecule compounds that also quench damaging reactive oxygen species (ROS) but are far easier to analyze using standard scientific tools. The molecules may become the basis for new antioxidant therapies in their own right.
The research appears in the American Chemical Society journal ACS Nano.
The original compounds are hydrophilic carbon clusters functionalized with polyethylene glycol, known as PEG-HCCs and created by Rice and Baylor scientists five years ago. The particles help neutralize ROS molecules overexpressed by the body’s cells in response to an injury before they damage cells or cause mutations.
PEG-HCCs show promise for treating cancer, rebooting blood flow in the brain after traumatic injury and controlling chronic diseases.
The new particles, called PEG-PDI, consist of polyethylene glycol and perylene diimide, a compound used as a dye, the color in red car paint and in solar cells for its light-absorbing properties. Their ability to accept electrons from other molecules makes them functionally similar to PEG-HCCs.
They’re close enough to serve as an analog for experiments, according to Rice chemist James Tour, who led the study with University of Texas biochemist Ah-Lim Tsai.
The researchers wrote that the molecule is not only the first example of a small molecular analogue of PEG-HCCs, but also represents the first successful isolation of a PDI radical anion as a single crystal, which allows its structure to be captured with X-ray crystallography.
“This allows us to see the structure of these active particles,” Tour said. “We can get a view of every atom and the distances between them, and get a lot of information about how these molecules quench destructive oxidants in biological tissue.
“Lots of people get crystal structures for stable compounds, but this is a transient intermediate during a catalytic reaction,” he said. “To be able to crystallize a reactive intermediate like that is amazing.”
Antioxidant compounds mimic effective graphene agents, show potential for therapies
The crystal structure of PEG-PDI is achieved using cobaltocene as a reducing agent and omitting solvents and hydrogen atoms for clarity. Carbon atoms are gray, nitrogens are blue, oxygens red and cobalts purple. The molecules created by scientists at Rice University, the McGovern Medical School at the University of Texas Health Science Center at Houston and Baylor College of Medicine are efficient antioxidants and help scientists understand how larger nanoparticles quench damaging reactive oxygen species in the body. Credit: Tour Group
PEG-HCCs are about 3 nanometers wide and 30 to 40 nanometers long. By comparison, much simpler PEG-PDI molecules are less than a nanometer in width and length.
PEG-PDI molecules are true mimics of superoxide dismutase enzymes, protective antioxidants that break down toxic superoxide radicals into harmless molecular oxygen and hydrogen peroxide. The molecules pull electrons from unstable ROS and catalyze their transformation into less-reactive species.
Testing the PEG-PDI molecules can be as simple as putting them in a solution that contains reactive oxygen species molecules like potassium superoxide and watching the solution change color. Further characterization with electron paramagnetic resonance spectroscopy was more complicated, but the fact that it’s even possible makes them powerful tools in resolving mechanistic details, the researchers said.
Tour said adding polyethylene glycol makes the molecules soluble and also increases the amount of time they remain in the bloodstream. “Without PEG, they just go right out of the system through the kidneys,” he said.
When the PEG groups are added, the molecules circulate longer and continue to catalyze reactions.
He said PEG-PDI is just as effective as PEG-HCCs if measured by weight. “Because they have so much more surface area, PEG-HCC particles probably catalyze more parallel reactions per particle,” Tour said. “But if you compare them with PEG-PDI by weight, they are quite similar in total catalytic activity.”
Understanding the structure of PEG-PDI should allow researchers to customize the molecule for applications. “We should have a tremendous ability to modify the molecule’s structure,” he said. “We can add anything we want, exactly where we want, for specific therapies.”
The researchers said PEG-PDI may also be efficient metal- and protein-free catalysts for oxygen reduction reactions used in industry and essential to fuel cells. They are intrinsically more stable than enzymes and can function in much a wider pH range, Tsai said.
Co-author Thomas Kent, a professor of neurology at Baylor who has worked on the project from the start, noted small molecules have a better chance to get on the fast track to approval for therapy by the Food and Drug Administration than nanotube-based agents.
“A small molecule that is not derived from larger nanomaterial may have a better chance of approval to use in humans, assuming it is safe and effective,” he said.
Tour said PEG-PDI serves as a precise model for other graphene derivatives like graphene oxide and permits a more detailed study of graphene-based nanomaterials.
“Making nanomaterials smaller, from well-defined molecules, permits 150 years of synthetic chemistry methods to address the mechanistic questions within nanotechnology,” he said.
More information: Almaz S. Jalilov et al. Perylene Diimide as a Precise Graphene-Like Superoxide Dismutase Mimetic, ACS Nano (2017). DOI: 10.1021/acsnano.6b08211
Provided by: Rice University
29 Jan 2017
Read All The News Here: Genesis Nanotech: “Great Things from Small Things”
29 Jan 2017
A team of researchers at MIT has designed one of the strongest lightweight materials known, by compressing and fusing flakes of graphene, a two-dimensional form of carbon. The new material, a sponge-like configuration with a density of just 5 percent, can have a strength 10 times that of steel.
In its two-dimensional form, graphene is thought to be the strongest of all known materials. But researchers until now have had a hard time translating that two-dimensional strength into useful three-dimensional materials.
The new findings show that the crucial aspect of the new 3-D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.
The findings are being reported today in the journal Science Advances, in a paper by Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering (CEE) and the McAfee Professor of Engineering; Zhao Qin, a CEE research scientist; Gang Seob Jung, a graduate student; and Min Jeong Kang MEng ’16, a recent graduate.
Other groups had suggested the possibility of such lightweight structures, but lab experiments so far had failed to match predictions, with some results exhibiting several orders of magnitude less strength than expected. The MIT team decided to solve the mystery by analyzing the material’s behavior down to the level of individual atoms within the structure. They were able to produce a mathematical framework that very closely matches experimental observations.
Two-dimensional materials—basically flat sheets that are just one atom in thickness but can be indefinitely large in the other dimensions—have exceptional strength as well as unique electrical properties. But because of their extraordinary thinness, “they are not very useful for making 3-D materials that could be used in vehicles, buildings, or devices,” Buehler says. “What we’ve done is to realize the wish of translating these 2-D materials into three-dimensional structures.”
The team was able to compress small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure whose form resembles that of some corals and microscopic creatures called diatoms. These shapes, which have an enormous surface area in proportion to their volume, proved to be remarkably strong. “Once we created these 3-D structures, we wanted to see what’s the limit—what’s the strongest possible material we can produce,” says Qin. To do that, they created a variety of 3-D models and then subjected them to various tests. In computational simulations, which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine, “one of our samples has 5 percent the density of steel, but 10 times the strength,” Qin says.
Buehler says that what happens to their 3-D graphene material, which is composed of curved surfaces under deformation, resembles what would happen with sheets of paper. Paper has little strength along its length and width, and can be easily crumpled up. But when made into certain shapes, for example rolled into a tube, suddenly the strength along the length of the tube is much greater and can support substantial weight. Similarly, the geometric arrangement of the graphene flakes after treatment naturally forms a very strong configuration.
The new configurations have been made in the lab using a high-resolution, multimaterial 3-D printer. They were mechanically tested for their tensile and compressive properties, and their mechanical response under loading was simulated using the team’s theoretical models. The results from the experiments and simulations matched accurately.
The new, more accurate results, based on atomistic computational modeling by the MIT team, ruled out a possibility proposed previously by other teams: that it might be possible to make 3-D graphene structures so lightweight that they would actually be lighter than air, and could be used as a durable replacement for helium in balloons. The current work shows, however, that at such low densities, the material would not have sufficient strength and would collapse from the surrounding air pressure.
But many other possible applications of the material could eventually be feasible, the researchers say, for uses that require a combination of extreme strength and light weight. “You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals,” Buehler says, to gain similar advantages of strength combined with advantages in cost, processing methods, or other material properties (such as transparency or electrical conductivity).
“You can replace the material itself with anything,” Buehler says. “The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”
The unusual geometric shapes that graphene naturally forms under heat and pressure look something like a Nerf ball—round, but full of holes. These shapes, known as gyroids, are so complex that “actually making them using conventional manufacturing methods is probably impossible,” Buehler says. The team used 3-D-printed models of the structure, enlarged to thousands of times their natural size, for testing purposes.
For actual synthesis, the researchers say, one possibility is to use the polymer or metal particles as templates, coat them with graphene by chemical vapor deposit before heat and pressure treatments, and then chemically or physically remove the polymer or metal phases to leave 3-D graphene in the gyroid form. For this, the computational model given in the current study provides a guideline to evaluate the mechanical quality of the synthesis output.
The same geometry could even be applied to large-scale structural materials, they suggest. For example, concrete for a structure such a bridge might be made with this porous geometry, providing comparable strength with a fraction of the weight. This approach would have the additional benefit of providing good insulation because of the large amount of enclosed airspace within it.
Because the shape is riddled with very tiny pore spaces, the material might also find application in some filtration systems, for either water or chemical processing. The mathematical descriptions derived by this group could facilitate the development of a variety of applications, the researchers say.
More information: “The mechanics and design of a lightweight three-dimensional graphene assembly,” Science Advances, DOI: 10.1126/sciadv.1601536 , advances.sciencemag.org/content/3/1/e1601536
29 Jan 2017
The University Institute for Advanced Materials Research at the Universitat Jaume I (UJI) has participated in the European Project Sunflower, whose objective has been the development of organic photovoltaic materials less toxic and viable for industrial production.
A consortium of 17 research and business institutions has carried out this European project in the field of nanotechnology for four years and with an overall budget of 14.2 million euros, with funding of 10.1 million euros from the Seventh Framework Programme of the European Commission.
An introduction to Sunflower
Researchers at Sunflower have carried out several studies, among the most successful of which there are the design of an organic photovoltaic cell that can be printed and, consequently, has great versatility. In short, “we can assure that, thanks to these works, progress has been made in the achievement of solar cells with a good performance, low cost and very interesting architectural characteristics”, states the director of the University Institute for Advanced Materials Research (INAM) Juan Bisquert.
The goals of Sunflower were very ambitious, according to Antonio Guerrero, researcher at the Department of Physics integrated in the INAM, since it was intended “not only to improve the stability and efficiency of the photovoltaic materials, but also to reduce their costs of production”.
In fact, according to Guerrero, “the processes for making the leap from the laboratory to the industrial scale have been improved because, among others, non-halogenated solvents have been used that are compatible with industrial production methods and that considerably reduce the toxic loading of halogenates”.
“The involvement of our institute in these projects has a great interest because one of our priority lines of research is the new materials to develop renewable energies,” says Bisquert, who is also professor of Applied Physics. In addition, these consortia involve the work of academia and industry. According to the researcher, “the transfer of knowledge to society is favoured and, in this case, we demonstrate that organic materials investigated for twenty years are already close to become viable technologies”.
Change of use of plastic materials
The participation of UJI researchers at Sunflower has focused on “improving the aspect of chemical reactivity of materials or structural compatibility”, says Germà García, professor of Applied Physics and member of INAM.
“We have worked to move from the concepts of inorganic electronics to photovoltaic cells to the part of organic electronics,” he adds. The researchers wanted to take advantage of the faculties of absorption and conduction of plastic materials and to verify its capacity of solar production, an unusual use because normally they are used as an electrical insulation.
At UJI laboratories, they have studied the organic materials, very complex devices because they have up to eight nanometric layers. “We have made advanced electrical measurements to see where the energy losses were and thus to inform producers of materials and devices in order to improve the stability and efficiency of solar cells,” explains Guerrero.
Solar energy in everyday objects
“The potential applications of organic photovoltaic technology (OPV) are numerous, ranging from mobile consumer electronics to architecture,” says the project coordinator Giovanni Nisato, from the Swiss Centre for Electronics and Microtechnology (CSEM).
“Thanks to the results we have obtained, printed organic photovoltaics will become part of our daily lives, and will allow us to use renewable energy and respect the environment with a positive impact on our quality of life,” according to Nisato.
The European Sunflower project has been developed over 48 months with the main objective of extending the life and cost-efficiency of organic photovoltaic technology through better process control and understanding of materials. In addition, in the opinion of those responsible, the results of this research could double the share of renewable energy in its energy matrix, from 14% in 2012 to 27-30% by 2030. In fact, Sunflower has facilitated a significant increase in the use of solar energy incorporated in everyday objects.
The Sunflower consortium consists of 17 partners from across Europe: CSEM (Switzerland), DuPont Teijin Films UK Ltd (UK), Amcor Flexibles Kreuzlingen AG (Switzerland), Agfa-Gevaert NV (Belgium), Fluxim AG (Switzerland), University of Antwerp (Belgium), SAES Getters SpA (Italy), Consiglio Nazionale delle Ricerche-ISMN-Bologna (Italy), Hochschule für Life Sciences FHNW (Switzerland), Chalmers Tekniska Hoegskola AB (Sweden), Fraunhofer Institut der angewandten Forschung zur Foerderung @EV (Germany), Linköpings Universitet (Sweden), Universitat Jaume I (Spain), Genes’Ink (France), National Centre for Scientific Research (France), Belectric OPV GmbH (Germany) and Merck KGaA (Germany).
Meanwhile, the main lines of research at the INAM focus on new types of materials for clean energy devices, solar cells based on low cost compounds, such as perovskite and other organic compounds. Furthermore, INAM studies the production of fuels from sunlight, breaking water molecules and producing hydrogen and other catalytic materials in the chemical aspect, all of great importance in the context of international research.
02 Dec 2014
First developed in China in about the year A.D. 150, paper has many uses, the most common being for writing and printing upon. Indeed, the development and spread of civilization owes much to paper’s use as writing material.
According to some surveys, 90 percent of all information in businesses today is retained on paper, even though the bulk of this printed paper is discarded after just one-time use.
Such waste of paper (and ink cartridges)—not to mention the accompanying environmental problems such as deforestation and chemical pollution to air, water and land—could be curtailed if the paper were “rewritable,” that is, capable of being written on and erased multiple times.
Chemists at the University of California, Riverside have now fabricated in the lab just such novel rewritable paper, one that is based on the color switching property of commercial chemicals called redox dyes. The dye forms the imaging layer of the paper. Printing is achieved by using ultraviolet light to photobleach the dye, except the portions that constitute the text on the paper. The new rewritable paper can be erased and written on more than 20 times with no significant loss in contrast and resolution.
Yadong Yin’s lab at the University of California, Riverside has fabricated novel rewritable paper, one that is based on the color switching property of commercial chemicals called redox dyes. Credit: Yin Lab, UC Riverside.
“This rewritable paper does not require additional inks for printing, making it both economically and environmentally viable,” said Yadong Yin, a professor of chemistry, whose lab led the research. “It represents an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental conservation.”
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The rewritable paper is essentially rewritable media in the form of glass or plastic film to which letters and patterns can be repeatedly printed, retained for days, and then erased by simple heating.
The paper comes in three primary colors: blue, red and green, produced by using the commercial redox dyes methylene blue, neutral red and acid green, respectively. Included in the dye are titania nanocrystals (these serve as catalysts) and the thickening agent hydrogen cellulose (HEC). The combination of the dye, catalysts and HEC lends high reversibility and repeatability to the film.
During the writing phase, ultraviolet light reduces the dye to its colorless state. During the erasing phase, re-oxidation of the reduced dye recovers the original color; that is, the imaging material recovers its original color by reacting with ambient oxygen. Heating at 115 C can speed up the reaction so that the erasing process is often completed in less than 10 minutes.
“The printed letters remain legible with high resolution at ambient conditions for more than three days – long enough for practical applications such as reading newspapers,” Yin said. “Better still, our rewritable paper is simple to make, has low production cost, low toxicity and low energy consumption.”
His lab is currently working on a paper version of the rewritable paper.
“Even for this kind of paper, heating to 115 C poses no problem,” Yin said. “In conventional laser printers, paper is already heated to 200 C in order to get toner particles to bond to the paper surface.”
His lab also is working on increasing the cycling number (the number of times the rewritable paper can be printed and erased), with a target of 100, to reduce overall cost. His research team is exploring ways to extend the legibility of the printed texts or images for more than three days to expand their potential uses.
“One way is to develop new photocatalyst nanoparticles that become highly reductive when irradiated by ultraviolet light,” Yin said. “We are exploring, too, the possibility of multi-color printing. The design principle can be extended to various commercial redox dyes to produce rewritable paper capable of showing prints of different colors. All these efforts will help increase the practical applications of the technology.”
He was joined in the study by UC Riverside’s Wenshou Wang (first author of the research paper), Ning Xie and Le He. Wang and Yin conceived and designed the experiments. Wang performed the experiments. Xie and He contributed to sample analysis. Wang and Yin analyzed the results.
The research was funded by a grant to Yin from the U.S. Department of Energy.
This technology has been disclosed and assigned UC case number 2015-250. A provisional patent has been filed and the UCR Office of Technology Commercialization is actively seeking a company to license the technology.
Yin’s lab has recently synthesized colloidal titania nanoparticle catalyst doped with barium ions that enables reversible light-responsive color switching with excellent cycling performance and considerably high switching rate.
“The improved performance is attributed to the more effective removal of the photogenerated oxidative holes that results from barium doping. This leaves more electrons for promoting the reduction of redox dyes,” Yin said.
The finding was recently reported in Angewandte Chemie.
Explore further: Paper electronics could make health care more accessible
Study results appear online today (Dec. 2) in Nature Communications.
11 Nov 2014
The Rice lab of chemist James Tour has turned molybdenum disulfide’s two-dimensional form into a nanoporous film that can catalyze the production of hydrogen or be used for energy storage.
The versatile chemical compound classified as a dichalcogenide is inert along its flat sides, but previous studies determined the material’s edges are highly efficient catalysts for hydrogen evolution reaction (HER), a process used in fuel cells to pull hydrogen from water.
Tour and his colleagues have found a cost-effective way to create flexible films of the material that maximize the amount of exposed edge and have potential for a variety of energy-oriented applications.
The Rice research appears in the journal Advanced Materials.
A new material developed at Rice University based on molybdenum disulfide exposes as much of the edge as possible, making it efficient as both a catalyst for hydrogen production and for energy storage. Credit: Tour Group/Rice University
Molybdenum disulfide isn’t quite as flat as graphene, the atom-thick form of pure carbon, because it contains both molybdenum and sulfur atoms. When viewed from above, it looks like graphene, with rows of ordered hexagons. But seen from the side, three distinct layers are revealed, with sulfur atoms in their own planes above and below the molybdenum.
This crystal structure creates a more robust edge, and the more edge, the better for catalytic reactions or storage, Tour said.
“So much of chemistry occurs at the edges of materials,” he said. “A two-dimensional material is like a sheet of paper: a large plain with very little edge. But our material is highly porous. What we see in the images are short, 5- to 6-nanometer planes and a lot of edge, as though the material had bore holes drilled all the way through.”
The new film was created by Tour and lead authors Yang Yang, a postdoctoral researcher; Huilong Fei, a graduate student; and their colleagues. It catalyzes the separation of hydrogen from water when exposed to a current. “Its performance as a HER generator is as good as any molybdenum disulfide structure that has ever been seen, and it’s really easy to make,” Tour said.
While other researchers have proposed arrays of molybdenum disulfide sheets standing on edge, the Rice group took a different approach. First, they grew a porous molybdenum oxide film onto a molybdenum substrate through room-temperature anodization, an electrochemical process with many uses but traditionally employed to thicken natural oxide layers on metals.
The film was then exposed to sulfur vapor at 300 degrees Celsius (572 degrees Fahrenheit) for one hour. This converted the material to molybdenum disulfide without damage to its nano-porous sponge-like structure, they reported.
The films can also serve as supercapacitors, which store energy quickly as static charge and release it in a burst. Though they don’t store as much energy as an electrochemical battery, they have long lifespans and are in wide use because they can deliver far more power than a battery. The Rice lab built supercapacitors with the films; in tests, they retained 90 percent of their capacity after 10,000 charge-discharge cycles and 83 percent after 20,000 cycles.
“We see anodization as a route to materials for multiple platforms in the next generation of alternative energy devices,” Tour said. “These could be fuel cells, supercapacitors and batteries. And we’ve demonstrated two of those three are possible with this new material.”
Explore further: Harnessing an unusual ‘valley’ quantum property of electrons