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Elijah Thimsen (Image Credit: Washington University in St. Louis)

One of the reasons solar cells are not used more widely is cost — the materials used to make them most efficient are expensive. Engineers are exploring ways to print solar cells from inks, but the devices don’t work as well. Elijah Thimsen, PhD, assistant professor of energy, environmental & chemical engineering in the School of Engineering & Applied Science at Washington University in St. Louis, and a team of engineers at the University of Minnesota have developed a technique to increase the performance and electrical conductivity of thin films that make up these materials using nanotechnology. Transparent conductors are thin films, which are are simply ultrathin layers of materials deposited on a surface that allow light to pass through and conduct electricity, a process in which electrons flow through a system. Thimsen and his team found by changing the structure of a thin film made of zinc oxide nanoparticles, electrons no longer flowed through the system in a conventional way, but hopped from place to place by a process called tunneling.

The team measured the electronic properties of a thin film made of zinc oxide nanoparticles before and after coating its surface with aluminum oxide. Both the zinc oxide nanoparticles and aluminum oxide are electronic insulators, so only a tiny amount of electricity flows through them. However, when these insulators were combined, the researchers got a surprising result. “The new composite became highly conductive,” Thimsen said. “The composite exhibits fundamentally different behavior than the parent compounds. We found that by controlling the structure of the material, you can control the mechanism by which electrons are transported.” Because the reason behind this is not well understood, Thimsen and the team plan to continue to work to understand the relationship between the structure of the nanoparticle film and the electron transport mechanism, he said.

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A schematic shows the process developed by Rice University scientists to make vertical microsupercapacitors with laser-induced graphene. The flexible devices show potential for use in wearable and next-generation electronics. Click on the image for a larger version. Image Credit: Rice University/Courtesy of the Tour Group.

Rice University scientists advanced their recent development of laser-induced graphene (LIG) by producing and testing stacked, three-dimensional supercapacitors, energy-storage devices that are important for portable, flexible electronics. The Rice lab of chemist James Tour discovered last year that firing a laser at an inexpensive polymer burned off other elements and left a film of porous graphene, the much-studied atom-thick lattice of carbon. The researchers viewed the porous, conductive material as a perfect electrode for supercapacitors or electronic circuits. An electron microscope image shows the cross section of laser-induced graphene burned into both sides of a polyimide substrate. The flexible material created at Rice University has the potential for use in electronics or for energy storage. Click on the image for a larger version.  To prove it, members of the Tour group have since extended their work to make vertically aligned supercapacitors with laser-induced graphene on both sides of a polymer sheet. The sections are then stacked with solid electrolytes in between for a multilayer sandwich with multiple microsupercapacitors. The flexible stacks show excellent energy-storage capacity and power potential and can be scaled up for commercial applications. LIG can be made in air at ambient temperature, perhaps in industrial quantities through roll-to-roll processes, Tour said.

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The nanoreactor works like a virtual chemistry set to discover new reactions and mechanisms. This diagram describes the reaction network for methylcarbamic acid, identifying all the reactions involving it or leading to its production.Image Credit: Stanford University/Courtesy Todd Martinez

In 1952, the famous Urey-Miller experiment mixed together chemicals that were present early in Earth's history, then approximately replicated the environmental conditions on the planet at that time to see if biologically relevant organic molecules would form spontaneously. That experiment produced more than 20 molecules that are important to life, but a team of Stanford University chemists thinks it can do one step better. The group has built a computer model that can not only determine all the possible products of the Urey-Miller experiment, but also detail all the possible chemical reactions that lead to their formation. The nanoreactor, as they call the model, could help scientists discover chemical reactions and mechanisms that improve the efficiency of fuel combustion or batteries, or reveal opportunities for new drugs.

The nanoreactor works something like a virtual chemistry set. Simply enter the structure of some target chemicals into the computer model, set the environmental conditions – such as temperature or pressure – and let it run. Then, algorithms begin to solve the quantum mechanical problems for each electron in the molecules as they interact – where are they likely to move from chemical to chemical, and what mechanisms must occur for those movements to take place? Each step is recorded along the way.

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Graphene is a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice. UC Riverside physicists have found a way to induce magnetism in graphene while also preserving graphene’s electronic properties.Image Credit: SHI LAB, UC RIVERSIDE.

Graphene, a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice, has any desirable properties. Magnetism alas is not one of them. Magnetism can be induced in graphene by doping it with magnetic impurities, but this doping tends to disrupt graphene’s electronic properties. Now a team of physicists at the University of California, Riverside has found an ingenious way to induce magnetism in graphene while also preserving graphene’s electronic properties. They have accomplished this by bringing a graphene sheet very close to a magnetic insulator – an electrical insulator with magnetic properties.

“This is the first time that graphene has been made magnetic this way,” said Jing Shi, a professor of physics and astronomy, whose lab led the research. “The magnetic graphene acquires new electronic properties so that new quantum phenomena can arise. These properties can lead to new electronic devices that are more robust and multi-functional.”
The finding has the potential to increase graphene’s use in computers, as in computer chips that use electronic spin to store data.

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The MIT researchers' wireless chemical sensor. (Image Credit: MIT; Photo: Melanie Gonick)

MIT chemists have devised a new way to wirelessly detect hazardous gases and environmental pollutants, using a simple sensor that can be read by a smartphone. These inexpensive sensors could be widely deployed, making it easier to monitor public spaces or detect food spoilage in warehouses. Using this system, the researchers have demonstrated that they can detect gaseous ammonia, hydrogen peroxide, and cyclohexanone, among other gases. “The beauty of these sensors is that they are really cheap. You put them up, they sit there, and then you come around and read them. There’s no wiring involved. There’s no power,” says Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT. For several years, Swager’s lab has been developing gas-detecting sensors based on devices known as chemiresistors, which consist of simple electrical circuits modified so that their resistance changes when exposed to a particular chemical. Measuring that change in resistance reveals whether the target gas is present. The new sensors are made from modified near-field communication (NFC) tags. These tags, which receive the little power they need from the device reading them, function as wirelessly addressable barcodes and are mainly used for tracking products such as cars or pharmaceuticals as they move through a supply chain, such as in a manufacturing plant or warehouse.

NFC tags can be read by any smartphone that has near-field communication capability, which is included in many newer smartphone models. These phones can send out short pulses of magnetic fields at radio frequency (13.56 megahertz), inducing an electric current in the circuit on the tag, which relays information to the phone. To adapt these tags for their own purposes, the MIT team first disrupted the electronic circuit by punching a hole in it. Then, they reconnected the circuit with a linker made of carbon nanotubes that are specialized to detect a particular gas. In this case, the researchers added the carbon nanotubes by “drawing” them onto the tag with a mechanical pencil they first created in 2012, in which the usual pencil lead is replaced with a compressed powder of carbon nanotubes. The team refers to the modified tags as CARDs: chemically actuated resonant devices.

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This sequence shows how the Greer Lab's three-dimensional, ceramic nanolattices can recover after being compressed by more than 50 percent. Clockwise, from left to right, an alumina nanolattice before compression, during compression, fully compressed, and recovered following compression.Credit: Lucas Meza/Caltech

Imagine a balloon that could float without using any lighter-than-air gas. Instead, it could simply have all of its air sucked out while maintaining its filled shape. Such a vacuum balloon, which could help ease the world's current shortage of helium, can only be made if a new material existed that was strong enough to sustain the pressure generated by forcing out all that air while still being lightweight and flexible. Caltech materials scientist Julia Greer and her colleagues are on the path to developing such a material and many others that possess unheard-of combinations of properties. For example, they might create a material that is thermally insulating but also extremely lightweight, or one that is simultaneously strong, lightweight, and nonbreakable—properties that are generally thought to be mutually exclusive. Greer's team has developed a method for constructing new structural materials by taking advantage of the unusual properties that solids can have at the nanometer scale, where features are measured in billionths of meters. In a paper, the Caltech researchers explain how they used the method to produce a ceramic (e.g., a piece of chalk or a brick) that contains about 99.9 percent air yet is incredibly strong, and that can recover its original shape after being smashed by more than 50 percent.

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Carbon-60 molecules, also known as buckyballs, were combined with amines in a compound that absorbs a fifth of its weight in carbon dioxide. It shows potential as an environmentally friendly material for capturing carbon from natural gas wells and industrial plants. (Courtesy of the Barron Research Group/Rice University)

Rice University scientists have discovered an environmentally friendly carbon-capture method that could be equally adept at drawing carbon dioxide emissions from industrial flue gases and natural gas wells. The Rice lab of chemist Andrew Barron revealed in a proof-of-concept study that amine-rich compounds are highly effective at capturing the greenhouse gas when combined with carbon-60 molecules. “We had two goals,” Barron said. “One was to make the compound 100 percent selective between carbon dioxide and methane at any pressure and temperature. The other was to reduce the high temperature needed by other amine solutions to get the carbon dioxide back out again. We’ve been successful on both counts.” Carbon-60, the soccer ball-shaped molecule also known as buckminsterfullerene (or the “buckyball”) was discovered at Rice by Nobel Prize laureates Richard Smalley, Robert Curl and Harold Kroto in 1985. The ultimate curvature of buckyballs may make them the best possible way to bind amine molecules that capture carbon dioxide but allow desirable methane to pass through.

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(Image Credit: University of Oregon)

Scientists, including University of Oregon chemist Geraldine Richmond, have tapped oil and water to create scaffolds of self-assembling, synthetic proteins called peptoid nanosheets that mimic complex biological mechanisms and processes. The accomplishment is expected to fuel an alternative design of the two-dimensional peptoid nanosheets that can be used in a broad range of applications. Among them could be improved chemical sensors and separators, and safer, more effective drug-delivery vehicles. Study co-author Ronald Zuckermann of the Molecular Foundry at Lawrence Berkeley National Laboratory (LBNL) first developed these ultra-thin nanosheets in 2010 using an air-and-water combination.

"We often think of oil on water as something that is environmentally bad when, in fact, my group over the past 20 years has been studying the unique properties of the junction between water and oil as an interesting place for molecules to assemble in unique ways — including for soaps and oil dispersants," said Richmond, who holds a UO presidential chair. "This study shows it is also a unique platform for making nanosheets." To create the new version of the nanosheets, the research team used vibrational sum frequency spectroscopy to probe the molecular interactions between the peptoids as they assemble at the oil-water interface. The work showed that peptoid polymers adsorbed to the interface are highly ordered in a way that is influenced by interactions between neighboring molecules.

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Pieces of Kimsooja's "Needle Woman" artwork during fabrication in Shanghai show the polymer film developed by Cornell researchers. (Image Credit: Cornell University/Jaeho Chong)

For her newest work, Korean artist Kimsooja wanted to explore a “shape and perspective that reveals the invisible as visible, physical as immaterial, and vice versa.” As artist-in-residence for the Cornell Council for the Arts’ (CCA) 2014 Biennial, she has realized that objective with “A Needle Woman: Galaxy was a Memory, Earth is a Souvenir,” one of several installations on campus for the semesterlong biennial, “Intimate Cosmologies: The Aesthetics of Scale in an Age of Nanotechnology.” The biennial, which runs through December 21, is a deep survey of artistic and scientific exploration, framing changes in 21st-century culture, art practice and nanoscale technology through collaborative research-based projects by faculty and students and guest artists. Kimsooja’s 46-foot-tall structure features an iridescent polymer film developed at Cornell, reflecting light with structural colors similar to those in a butterfly’s wings. Creating it involved some diligent problem-solving by materials scientists in the lab of Uli Wiesner, the Spencer T. Olin Professor of Engineering.

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Scientists at New York University and the University of Melbourne have developed a method using DNA origami to turn one-dimensional nano materials into two dimensions. Their breakthrough offers the potential to enhance fiber optics and electronic devices by reducing their size and increasing their speed. “We can now take linear nano-materials and direct how they are organized in two dimensions, using a DNA origami platform to create any number of shapes,” explains NYU Chemistry Professor Nadrian Seeman, the paper’s senior author, who founded and developed the field of DNA nanotechnology, now pursued by laboratories around the globe, three decades ago.

Seeman’s collaborator, Sally Gras, an associate professor at the University of Melbourne, says, “We brought together two of life’s building blocks, DNA and protein, in an exciting new way. We are growing protein fibers within a DNA origami structure.” DNA origami employs approximately two hundred short DNA strands to direct longer strands in forming specific shapes. In their work, the scientists sought to create, and then manipulate the shape of, amyloid fibrils—rods of aggregated proteins, or peptides, that match the strength of spider’s silk. To do so, they engineered a collection of 20 DNA double helices to form a nanotube big enough (15 to 20 nanometers—just over one-billionth of a meter—in diameter) to house the fibrils.

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