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(Image Credit: Moscow Institute of Physics and Technology)

A group of researchers from Russia, Belarus and Spain, including Moscow Institute of Physics and Technology professor Yury Lozovik, have developed a microscopic force sensor based on carbon nanotubes. The scientists proposed using two nanotubes, one of which is a long cylinder with double walls one atom thick. These tubes are placed so that their open ends are opposite to each other. Voltage is then applied to them, and a current of about 10nAflows through the circuit. Carbon tube walls are good conductors, and along the gap between the ends of the nanotubes the current flows thanks to the tunnel effect, which is a quantum phenomenon where electrons pass through a barrier that is considered insurmountable in classical mechanics. This current is called tunneling current and is widely used in practice. There are, for example, tunnel diodes, wherein current flows through the potential barrier of the p-n junction. The researchers used the relationship between the tunneling current and the distance between the ends of the nanotubes to determine the relative position of the carbon nanotubes and thus to find the magnitude of the external force exerted on them. The new sensor allows the position of coaxial cylinders in two-layer nanotubes to be controlled quite accurately. As a result, it is possible to determine the stretch of an n-scale object, to which electrodes are attached. Calculations made by the researchers showed the possibility of recording forces of a few tenths of a nN(10-10newtons). To make it clearer, a single bacterium weighs about 10-14newtons on average, and a mosquito weighs a few dozen mcN (10-5 N).However, the device developed by the physicists may find application beyond micro scales.

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Stanford engineers have developed an improved process for making flexible circuits that use carbon nanotube transistors, a development that paves the way for a new generation of bendable electronic devices. (Bao Lab / Stanford University)

Engineers would love to create flexible electronic devices, such as e-readers that could be folded to fit into a pocket. One approach involves designing circuits based on electronic fibers, known as carbon nanotubes (CNTs), instead of rigid silicon chips. But reliability is essential. Most silicon chips are based on a type of circuit design that allows them to function flawlessly even when the device experiences power fluctuations. However, it is much more challenging to do so with CNT circuits. But now a team at Stanford University has developed a process to create flexible chips that can tolerate power fluctuations in much the same way as silicon circuitry. "This is the first time anyone has designed flexible CNT circuits that have both high immunity to electrical noise and low power consumption, " said Zhenan Bao, a professor of chemical engineering at Stanford. In principle, CNTs should be ideal for making flexible electronic circuitry. These ultra-thin carbon filaments have the physical strength to take the wear and tear of bending and the electrical conductivity to perform any electronic task. But until this recent work from the Stanford team, flexible CNT circuits didn't have the reliability and power-efficiency of rigid silicon chips.

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An electron microscope image shows carbon black nanoparticles modified by adding polyvinyl alcohol for downhole detection of hydrogen sulfide in oil and gas wells. The nanoreporters were created at Rice University. (Credit: Tour Group/Rice University)

Scientists at Rice University have created a nanoscale detector that checks for and reports on the presence of hydrogen sulfide in crude oil and natural gas while they’re still in the ground. The nanoreporter is based on nanometer-sized carbon material developed by a consortium of Rice labs led by chemist James Tour. Limited exposure to hydrogen sulfide causes sore throats, shortness of breath and dizziness, according to the researchers. The human nose quickly becomes desensitized to hydrogen sulfide, leading to an inability to detect higher concentrations. That can be fatal, they said. On the flip side, hydrogen sulfide is also a biologically important signaling molecule in processes that include pain and inflammation. Tour said chemists have synthesized fluorescent probes to detect it in the body. The Rice team capitalized on that work by using the probes to create downhole detectors for oil fields. Crude oil and natural gas inherently contain hydrogen sulfide, which gives off a “rotten egg” smell. Even a 1 percent trace of sulfur turns oil into what’s known as “sour crude,” which is toxic and corrodes pipelines and transportation vessels, Tour said. The extra steps required to turn the sour into “sweet” crude are costly. So it’s important to know the content of what you’re pumping out of the ground, and the earlier the better,” Tour said. Led by Rice professors Tour, Michael Wong and Mason Tomson and researcher Amy Kan, the university has pioneered efforts to gather information from oil fields through the use of nanoreporters. The nanoreporters were designed to detect and report on the presence and amount of oil in a well that might otherwise be hard to assess. Now the same team, joined by chemist Angel Martí, is employing thermally stable, soluble, highly mobile, carbon black-based nanoreporters modified to look for hydrogen sulfide and report results immediately upon their return to the surface.

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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. 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. The platform builds the fibrils by combining the properties of the nanotube with a synthetic peptide fragment that is placed inside the cylinder. The resulting fibril-filled nanotubes can then be organized into two-dimensional structures through a series of DNA-DNA hybridization interactions.

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Professor Jonathan Coleman, AMBER. (Image Credit: AMBER)

Researchers in AMBER, the Science Foundation Ireland funded materials science centre headquartered at Trinity College Dublin have, for the first time, developed a new method of producing industrial quantities of high quality graphene. Described as a wonder material, graphene is a single-atom thick sheet of carbon. It is extremely light and stronger than steel, yet incredibly flexible and extremely electrically conductive. The discovery will change the way many consumer and industrial products are manufactured. The materials will have a multitude of potential applications including advanced food packaging; high strength plastics; foldable touch screens for mobile phones and laptops; super-protective coatings for wind turbines and ships; faster broadband and batteries with dramatically higher capacity than anything available today. Until now, researchers have been unable to produce graphene of high quality in large enough quantities. The subject of on-going international research, the research undertaken by AMBER is the first to perfect a large-scale production of pristine graphene materials and has been highlighted by the highly prestigious Nature Materials publication as a global breakthrough. Professor Coleman and his team used a simple method for transforming flakes of graphite into defect-free graphene using commercially available tools, such as high-shear mixers. They demonstrated that not only could graphene-containing liquids be produced in standard lab-scale quantities of a few 100 millilitres, but the process could be scaled up to produce 100s of litres and beyond.

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The particles were designed to release doxorubicin when exposed to ultraviolet light. Here, ovarian cancer cells turn red as the doxorubicin is released over time. (Image Source: MIT; Image courtesy of Erik Dreaden and Kevin Shopsowitz)

Delivering chemotherapy drugs in nanoparticle form could help reduce side effects by targeting the drugs directly to the tumors. In recent years, scientists have developed nanoparticles that deliver one or two chemotherapy drugs, but it has been difficult to design particles that can carry any more than that in a precise ratio. Now MIT chemists have devised a new way to build such nanoparticles, making it much easier to include three or more different drugs. The researchers showed that they could load their particles with three drugs commonly used to treat ovarian cancer. “We think it’s the first example of a nanoparticle that carries a precise ratio of three drugs and can release those drugs in response to three distinct triggering mechanisms,” says Jeremiah Johnson, an assistant professor of chemistry at MIT. Such particles could be designed to carry even more drugs, allowing researchers to develop new treatment regimens that could better kill cancer cells while avoiding the side effects of traditional chemotherapy. Johnson and colleagues demonstrated that the triple-threat nanoparticles could kill ovarian cancer cells more effectively than particles carrying only one or two drugs, and they have begun testing the particles against tumors in animals.

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The illustration shows the nanofibers in white and the virus in green. (Image Source: Uppsala University; Photograph Credit: Björn Syse)

Researchers at the Division of Nanotechnology and Functional Materials, Uppsala University have developed a paper filter, which can remove virus particles with an efficiency matching that of the best industrial virus filters. The paper filter consists of 100 percent high purity cellulose nanofibers, directly derived from nature. The research was carried out in collaboration with virologists from the Swedish University of Agricultural Sciences/Swedish National Veterinary Institute. Virus particles are very peculiar objects- tiny (about thousand times thinner than a human hair) yet mighty. Viruses can only replicate in living cells but once the cells become infected the viruses can turn out to be extremely pathogenic. Viruses can actively cause diseases on their own or even transform healthy cells to malignant tumors. ‘Viral contamination of biotechnological products is a serious challenge for production of therapeutic proteins and vaccines. Because of the small size, virus removal is a non-trivial task, and, therefore, inexpensive and robust virus removal filters are highly demanded’, says Albert Mihranyan, Associate Professor at the Division of Nanotechnology and Functional Materials, Uppsala University, who heads the study.

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Gold nanoparticles make better catalysts for CO2 recycling than bulk gold metal. Size is crucial though, since edges produce more desired results than corners (red points, above). Nanoparticles of 8 nm appear to have a better edge-to-corner ratio than 4 nm, 6 nm, or 10 nm nanoparticles. Credit: Sun lab/Brown University

By tuning gold nanoparticles to just the right size, researchers from Brown University have developed a catalyst that selectively converts carbon dioxide (CO2) to carbon monoxide (CO), an active carbon molecule that can be used to make alternative fuels and commodity chemicals. “Our study shows potential of carefully designed gold nanoparticles to recycle CO2 into useful forms of carbon,” said Shouheng Sun, professor of chemistry and one of the study’s senior authors. “The work we’ve done here is preliminary, but we think there’s great potential for this technology to be scaled up for commercial applications.” The idea of recycling CO2 — a greenhouse gas the planet current has in excess — is enticing, but there are obstacles. CO2 is an extremely stable molecule that must be reduced to an active form like CO to make it useful. CO is used to make synthetic natural gas, methanol, and other alternative fuels. Converting CO2 to CO isn’t easy. Prior research has shown that catalysts made of gold foil are active for this conversion, but they don’t do the job efficiently. The gold tends to react both with the CO2 and with the water in which the CO2 is dissolved, creating hydrogen byproduct rather than the desired CO. The Brown experimental group, led by Sun and Wenlei Zhu, a graduate student in Sun’s group, wanted to see if shrinking the gold down to nanoparticles might make it more selective for CO2. They found that the nanoparticles were indeed more selective, but that the exact size of those particles was important. Eight nanometer particles had the best selectivity, achieving a 90-percent rate of conversion from CO2 to CO. Other sizes the team tested — four, six, and 10 nanometers — didn’t perform nearly as well.

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Northwestern researchers have developed a “recipe” for using nanomaterials as atoms, DNA as bonds and a little heat to form tiny crystals. An electron microscope image (left) shows a faceted single crystal consisting of nanoparticles brought together using DNA interactions. A schematic (right) illustrates how the lattice of nanoparticles is held together by DNA, taken from a simulation used to model the system. The observed crystal shape is a rhombic dodecahedron, a 12-sided polyhedron made up of congruent rhombic faces. (Image Credit: Northwestern University)

Nature builds flawless diamonds, sapphires and other gems. Now a Northwestern University research team is the first to build near-perfect single crystals out of nanoparticles and DNA, using the same structure favored by nature. “Single crystals are the backbone of many things we rely on -- diamonds for beauty as well as industrial applications, sapphires for lasers and silicon for electronics,” said nanoscientist Chad A. Mirkin. “The precise placement of atoms within a well-defined lattice defines these high-quality crystals. “Now we can do the same with nanomaterials and DNA, the blueprint of life,” Mirkin said. “Our method could lead to novel technologies and even enable new industries, much as the ability to grow silicon in perfect crystalline arrangements made possible the multibillion-dollar semiconductor industry.” His research group developed the “recipe” for using nanomaterials as atoms, DNA as bonds and a little heat to form tiny crystals. This single-crystal recipe builds on superlattice techniques Mirkin’s lab has been developing for nearly two decades. In this recent work, Mirkin, an experimentalist, teamed up with Monica Olvera de la Cruz, a theoretician, to evaluate the new technique and develop an understanding of it. Given a set of nanoparticles and a specific type of DNA, Olvera de la Cruz showed they can accurately predict the 3-D structure, or crystal shape, into which the disordered components will self-assemble.

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A carbon nanotube-coated paper triangle placed on an ionization source charged by a small battery is held in front of a mass spectrometer. Researchers at Purdue University and the Indian Institute of Technology Madras studied the use of carbon nanotubes to advance ambient ionization techniques. (Purdue University photo/Courtesy of Thalappil Pradeep)

Nanotechnology is advancing tools likened to Star Trek's "tricorder" that perform on-the-spot chemical analysis for a range of applications including medical testing, explosives detection and food safety. Researchers found that when paper used to collect a sample was coated with carbon nanotubes, the voltage required was 1,000 times reduced, the signal was sharpened and the equipment was able to capture far more delicate molecules. A team of researchers from Purdue University and the Indian Institute of Technology Madras performed the study. "This is a big step in our efforts to create miniature, handheld mass spectrometers for the field," said R. Graham Cooks, Purdue's Henry B. Hass Distinguished Professor of Chemistry. "The dramatic decrease in power required means a reduction in battery size and cost to perform the experiments. The entire system is becoming lighter and cheaper, which brings it that much closer to being viable for easy, widespread use." "Taking science to the people is what is most important," Pradeep said. "Mass spectrometry is a fantastic tool, but it is not yet on every physician's table or in the pocket of agricultural inspectors and security guards. Great techniques have been developed, but we need to hone them into tools that are affordable, can be efficiently manufactured and easily used."

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