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Nanoblocks and spheres are coated with complementary DNA tethers so the two dissimilar shapes attract and bind to one another. (Image Credit: Brookhaven National Lab)

Taking child's play with building blocks to a whole new level—the nanometer scale—scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have constructed 3D "superlattice" multicomponent nanoparticle arrays where the arrangement of particles is driven by the shape of the tiny building blocks. The method uses linker molecules made of complementary strands of DNA to overcome the blocks' tendency to pack together in a way that would separate differently shaped components. The results are an important step on the path toward designing predictable composite materials for applications in catalysis, other energy technologies, and medicine. "If we want to take advantage of the promising properties of nanoparticles, we need to be able to reliably incorporate them into larger-scale composite materials for real-world applications," explained Brookhaven physicist Oleg Gang, who led the research at Brookhaven's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility.

The research builds on the team's experience linking nanoparticles together using strands of synthetic DNA. Like the molecule that carries the genetic code of living things, these synthetic strands have complementary bases known by the genetic code letters G, C, T, and A, which bind to one another in only one way (G to C; T to A). Gang has previously used complementary DNA tethers attached to nanoparticles to guide the assembly of a range of arrays and structures. The new work explores particle shape as a means of controlling the directionality of these interactions to achieve long-range order in large-scale assemblies and clusters.

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The particles are delivered into the sebaceous gland by the ultrasound, and are heated by the laser. The heat deactivates the gland.(Photo Credit: UC Santa Barbara, Peter Allen Illustration)

Acne, a scourge of adolescence, may be about to meet its ultra high-tech match. By using a combination of ultrasound, gold-covered particles and lasers, researchers from UC Santa Barbara and the private medical device company Sebacia have developed a targeted therapy that could potentially lessen the frequency and intensity of breakouts, relieving acne sufferers the discomfort and stress of dealing with severe and recurring pimples. “Through this unique collaboration, we have essentially established the foundation of a novel therapy,” said Samir Mitragotri, professor of chemical engineering at UCSB.

The new technology builds on Mitragotri’s specialties in targeted therapy and transdermal drug delivery. Using low-frequency ultrasound, the therapy pushes gold-coated silica particles through the follicle into the sebaceous glands. Postdoctoral research associate Byeong Hee Hwang, now an assistant professor at Incheon National University, conducted research at UCSB. According to the research, this protocol would have several benefits over conventional treatments. Called selective photothermolysis, the method does not irritate or dry the skin’s surface. In addition, it poses no risk of resistance or long-term side effects that can occur with antibiotics or other systemic treatments.

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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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Grain boundaries are rows of defects that disrupt the electronic properties of two-dimensional materials like graphene, but new theory by scientists at Rice University shows no such effects in atomically flat phosphorus. That may make the material ideal for nano-electronic applications. (Image Credit: Evgeni Penev/Rice University)

Defects damage the ideal properties of many two-dimensional materials, like carbon-based graphene. Phosphorus just shrugs. That makes it a promising candidate for nano-electronic applications that require stable properties, according to new research by Rice University theoretical physicist Boris Yakobson and his colleagues. The Rice team analyzed the properties of elemental bonds between semiconducting phosphorus atoms in 2-D sheets. Two-dimensional phosphorus is not theoretical; it was recently created through exfoliation from black phosphorus. The researchers compared their findings to 2-D metal dichalcogenides like molybdenum disulfide; these metal compounds have also been considered for electronics because of their inherent semiconducting properties. In pristine dichalcogenides, atoms of the two elements alternate in lockstep. But wherever two atoms of the same element bond, they create a point defect. Think of it as a temporary disturbance in the force that could slow electrons down, Yakobson said.

Semiconductors are the basic element of modern electronics that direct and control how electrons move through a circuit. But when a disturbance deepens a band gap, the semiconductor is less stable. When chaos reigns in the form of multiple point defects or grain boundaries — where sheets of a 2-D material merge at angles, forcing like atoms to bond – the materials become far less useful. The Yakobson lab’s calculations show phosphorus has no such problem. Even when point defects or grain boundaries exist, the material’s semiconducting properties are stable. Like perfect graphene – but unlike imperfect graphene — it performs as expected.

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An international team led by researchers at SLAC National Accelerator Laboratory and Stanford University joined two offbeat carbon molecules – diamondoids, the square cages at left, and buckyballs, the soccer-ball shapes at right – to create “buckydiamondoids,” center. These hybrid molecules function as rectifiers, conducting electrons in only one direction, and could help pave the way to molecular electronic devices. (Image Credit: Manoharan Lab/Stanford University)

Scientists have married two unconventional forms of carbon – one shaped like a soccer ball, the other a tiny diamond – to make a molecule that conducts electricity in only one direction. This tiny electronic component, known as a rectifier, could play a key role in shrinking chip components down to the size of molecules to enable faster, more powerful devices. “We wanted to see what new, emergent properties might come out when you put these two ingredients together to create a ‘buckydiamondoid,’” said Hari Manoharan of the Stanford Institute for Materials and Energy Sciences (SIMES) at the Department of Energy’s SLAC National Accelerator Laboratory. “What we got was a basically a one-way valve for conducting electricity – clearly more than the sum of its parts.”  The research team included scientists from Stanford University, Belgium, Germany and Ukraine.

Many electronic circuits have three basic components: a material that conducts electrons; rectifiers, which commonly take the form of diodes, to steer that flow in a single direction; and transistors to switch the flow on and off. Scientists combined two offbeat ingredients – buckyballs and diamondoids – to create the new diode-like component. Buckyballs – short for buckminsterfullerenes – are hollow carbon spheres whose 1985 discovery earned three scientists a Nobel Prize in chemistry. Diamondoids are tiny carbon cages bonded together as they are in diamonds, but weighing less than a billionth of a billionth of a carat. Both are subjects of a lot of research aimed at understanding their properties and finding ways to use them. In 2007, a team led by researchers from SLAC and Stanford discovered that a single layer of diamondoids on a metal surface can efficiently emit a beam of electrons. Manoharan and his colleagues wondered: What would happen if they paired an electron-emitting diamondoid with another molecule that likes to grab electrons? Buckyballs are just that sort of electron-grabbing molecule. For this study, diamondoids were produced in the SLAC laboratory of SIMES researchers Jeremy Dahl and Robert Carlson, who are world experts in extracting the tiny diamonds from petroleum. They were then shipped to Germany, where chemists at Justus-Liebig University figured out how to attach them to buckyballs.

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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.(Image 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. The Caltech researchers explain that 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. "Ceramics have always been thought to be heavy and brittle," says Greer, a professor of materials science and mechanics in the Division of Engineering and Applied Science at Caltech. "We're showing that in fact, they don't have to be either. This very clearly demonstrates that if you use the concept of the nanoscale to create structures and then use those nanostructures like LEGO to construct larger materials, you can obtain nearly any set of properties you want. You can create materials by design."

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Nisarg J. Shah (left) and Stephen W. Morton collaborate on research to improve bone implants and cancer treatments. Shah holds a 3-D-printed implantable polymer scaffold, while Morton holds a jar of nanoparticles for targeting triple-negative breast cancer cells.(Image Credit: MIT/Denis Paiste/Materials Processing Center)

Personalized cancer treatments and better bone implants could grow from techniques demonstrated by graduate students Stephen W. Morton and Nisarg J. Shah, who are both working in chemical engineering professor Paula Hammond's lab at MIT. Morton's work focuses on developing drug-carrying nanoparticles to target hard-to-treat cancers — such as triple-negative breast cancer (TNBC) — while Shah develops coatings that promote better adhesion for bone implants. Their work shares a materials-based approach that uses layer-by-layer assembly of nanoparticles and coatings. This approach provides controlled release of desirable components from chemotherapy drugs to bone growth factors. Use of natural materials promises to reduce harmful side effects. "We have all of these different areas in which we are seeking to address different problems related to human health, certainly in the context of cancer research which is a very big part of the lab now," Shah says. "In addition to that we are also looking at how we can improve ways in which various patient diseases and injuries are managed in a way that will improve current clinical standards."

However it could take from five to seven years to move from preclinical success in lab animals through human clinical trials to public availability. "Layer-by-layer allows us to introduce very specific materials on the surface of various substrates, be it a nanoparticle, be it an implant, right from the nanoscale to the macroscale," Shah explains. "We were able to introduce all kinds of different properties by depositing very specific materials on substrates, modifying their surface properties and eventually having them do very specific things in the context of applications."

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Dr Nair with a graphene membrane. (Image Credit: The University of Manchester)

A thin layer of graphene paint can make impermeable and chemically resistant coatings which could be used for packaging to keep food fresh for longer and protect metal structures against corrosion, new findings from The University of Manchester in the UK show. The surface of graphene, a one atom thick sheet of carbon, can be randomly decorated with oxygen to create graphene oxide; a form of graphene that could have a significant impact on the chemical, pharmaceutical and electronic industries. Applied as paint, it could provide an ultra-strong, non-corrosive coating for a wide range of industrial applications. Graphene oxide solutions can be used to paint various surfaces ranging from glass to metals to even conventional bricks. After a simple chemical treatment, the resulting coatings behave like graphite in terms of chemical and thermal stability but become mechanically nearly as tough as graphene, the strongest material known to man.

The team led by Dr Rahul Nair and Nobel laureate Sir Andre Geim demonstrated previously that multilayer films made from graphene oxide are vacuum tight under dry conditions but, if expose to water or its vapour, act as molecular sieves allowing passage of small molecules below a certain size. Those findings could have huge implications for water purification. This contrasting property is due to the structure of graphene oxide films that consist of millions of small flakes stacked randomly on top of each other but leave nano-sized capillaries between them. Water molecules like to be inside these nanocapillaries and can drag small atoms and molecules along. The University of Manchester team now shows that it is possible to tightly close those nanocapillaries using simple chemical treatments, which makes graphene films even stronger mechanically as well as completely impermeable to everything: gases, liquids or strong chemicals. For example, the researchers demonstrate that glassware or copper plates covered with graphene paint can be used as containers for strongly corrosive acids. The exceptional barrier properties of graphene paint have already attracted interest from many companies who now collaborate with The University of Manchester on development of new protective and anticorrosion coatings

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