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Category: nanotechnology – Page 194

On the electromagnetic spectrum, terahertz light is located between infrared radiation and microwaves. It holds enormous potential for tomorrow’s technologies: Among other things, it might succeed 5G by enabling extremely fast mobile communications connections and wireless networks. The bottleneck in the transition from gigahertz to terahertz frequencies has been caused by insufficiently efficient sources and converters. A German-Spanish research team with the participation of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now developed a material system to generate terahertz pulses much more effectively than before. It is based on graphene, i.e., a super-thin carbon sheet, coated with a metallic lamellar structure. The research group presented its results in the journal ACS Nano.

Some time ago, a team of experts working on the HZDR accelerator ELBE were able to show that graphene can act as a frequency multiplier: When the two-dimensional carbon is irradiated with light pulses in the low terahertz frequency range, these are converted to higher frequencies. Until now, the problem has been that extremely strong input signals, which in turn could only be produced by a full-scale particle accelerator, were required to generate such terahertz pulses efficiently.“This is obviously impractical for future technical applications,” explains the study’s primary author Jan-Christoph Deinert of the Institute of Radiation Physics at HZDR. “So, we looked for a material system that also works with a much less violent input, i.e., with lower field strengths.”

For this purpose, HZDR scientists, together with colleagues from the Catalan Institute of Nanoscience and Nanotechnology (ICN2), the Institute of Photonic Sciences (ICFO), the University of Bielefeld, TU Berlin and the Mainz-based Max Planck Institute for Polymer Research, came up with a new idea: the frequency conversion could be enhanced enormously by coating the graphene with tiny gold lamellae, which possess a fascinating property: “They act like antennas that significantly amplify the incoming terahertz radiation in graphene,” explains project coordinator Klaas-Jan Tielrooij from ICN2. “As a result, we get very strong fields where the graphene is exposed between the lamellae. This allows us to generate terahertz pulses very efficiently.”

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Hydrogen is a sustainable source of clean energy that avoids toxic emissions and can add value to multiple sectors in the economy including transportation, power generation, metals manufacturing, among others. Technologies for storing and transporting hydrogen bridge the gap between sustainable energy production and fuel use, and therefore are an essential component of a viable hydrogen economy. But traditional means of storage and transportation are expensive and susceptible to contamination. As a result, researchers are searching for alternative techniques that are reliable, low-cost and simple. More-efficient hydrogen delivery systems would benefit many applications such as stationary power, portable power, and mobile vehicle industries.

Now, as reported in the journal Proceedings of the National Academy of Sciences, researchers have designed and synthesized an effective material for speeding up one of the limiting steps in extracting from alcohols. The material, a , is made from tiny clusters of nickel anchored on a 2-D substrate. The team led by researchers at Lawrence Berkeley National Laboratory’s (Berkeley Lab) Molecular Foundry found that the catalyst could cleanly and efficiently accelerate the reaction that removes hydrogen atoms from a liquid chemical carrier. The material is robust and made from earth-abundant metals rather than existing options made from precious metals, and will help make hydrogen a viable energy source for a wide range of applications.

“We present here not merely a catalyst with higher activity than other nickel catalysts that we tested, for an important renewable energy fuel, but also a broader strategy toward using affordable metals in a broad range of reactions,” said Jeff Urban, the Inorganic Nanostructures Facility director at the Molecular Foundry who led the work. The research is part of the Hydrogen Materials Advanced Research Consortium (HyMARC), a consortium funded by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cell Technologies Office (EERE). Through this effort, five national laboratories work towards the goal to address the scientific gaps blocking the advancement of solid hydrogen storage materials. Outputs from this work will directly feed into EERE’s H2@Scale vision for affordable hydrogen production, storage, distribution and utilization across multiple sectors in the economy.

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One step closer to a light into matter molecular synthesizer: 3.

Molecular machine-track conjugate 1 (Figure 1) was designed to use iterative Wittig reactions to form carbon-carbon double bonds between a macrocycle and building blocks abstracted one at a time and in sequence from a track. The Wittig reaction 24, 25, 26 was chosen as it is robust and structurally tolerant, lending itself to exploitation in a range of contexts, including dynamic DNA-template synthesis.9 Our machine is based on a rotaxane architecture, in which the macrocycle has a reactive aldehyde attachment and the axle has the building-block sequence encoded as phosphonium salts during its synthesis. The 2, 2-diphenylpropane phosphonium units act both to restrict the position of the ring on the track and, upon deprotonation, as reactive ylide functionalities. Each ylide is large enough to block the passage of the macrocycle, trapping the ring within a compartment defined by the bulky stopper at the terminus of original threading and the next ylide along the track. Once a reactive building block can be reached by the macrocycle-appended aldehyde, it can be removed from the track through a Wittig reaction that adds it to the terminus of the growing chain. Each barrier also contains an aldehyde unit, so that once the building block is added to the end of the chain, it is able to react with the next barrier on the track that the macrocycle can access, enabling the alkene-connected oligomer to grow through successive Wittig reactions.

The specific size and constitution of the 2, 2-diphenylpropane motif of the building blocks proved important for successful machine operation. Early track designs in which the ylide and aldehyde were attached to the same aromatic ring or extended conjugated system proved insufficiently reactive (see Section S7 for a brief discussion of initial designs). Embedding the phosphorus atoms within the vector of the track allowed synthetically accessible triaryl phosphines to be the basis of the track design, expediting the synthesis (see Sections S2 and S3). The phenyl substituent at each phosphorus center (e.g., 4a–4D) also proved important: when a tolyl (4-methylphenyl) linking group was investigated, it proved difficult to develop macrocycles that could both thread during the rotaxane-forming reaction and, subsequently, pass over the phosphine oxide in the track formed from the Wittig reaction.

Each phosphorus center is attached to a methylene group bearing a diarylpropane building block derivatized with a different pair of substituents (H, Ph, C6H4CH2CHMe2, or C6H4OMe). These provide different sidechains in the machine product, the same role that different amino acids play in proteins. However, two (identical) sidechains are present per monomer using this artificial molecular machine design compared with one sidechain per amino acid in proteins. This was chosen partly to illustrate how artificial machines and their products are not subject to the same constraints as biomolecular synthesizers but, conveniently, the symmetry of the building blocks also makes their synthesis more straightforward. Each phosphonium moiety is separated from the next by rigid spacers that prevent folding of the track and so ensure that the phosphonium salts can only react with the aldehyde group at the end of the chain attached to the macrocycle rather than others on the track.

Continue reading “A Track-Based Molecular Synthesizer that Builds a Single-Sequence Oligomer through Iterative Carbon-Carbon Bond Formation” | >

How electrons move together as a group inside cylindrical nanoparticles?

Scientists from the University of Exeter seems to find out the answer to this question. They even have made a breakthrough in the field of electromagnetism, with perspectives for metamaterials research.

In collaboration with the University of Strasbourg, scientists hypothesized how electrons move collectively in tiny metal nanoparticles shaped like cylinders.

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Graphene, one of the most important nanomaterials developed so far, continues to surprise the scientific community. This time, thanks to the extraordinary phenomena found by a group of physicists from the University of Arkansas. We are talking specifically about the capacity to use the thermal motion of atoms in graphene as a source of energy!

In this recent work, published in Physical Review E under the title Fluctuation-induced current from freestanding graphene, the team of researchers have successfully developed a circuit capable of capturing graphene’s thermal motion and converting it into an electrical current.

As it is said in this article : “The idea of harvesting energy from graphene is controversial because it refutes physicist Richard Feynman’s well-known assertion that the thermal motion of atoms, known as Brownian motion, cannot do work. Thibado’s team found that at room temperature the thermal motion of graphene does in fact induce an alternating current (AC) in a circuit, an achievement thought to be impossible.”

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Emerging and reemerging infections present an ever-increasing challenge to global health. Here, we report a nanoparticle-enabled smartphone (NES) system for rapid and sensitive virus detection. The virus is captured on a microchip and labeled with specifically designed platinum nanoprobes to induce gas bubble formation in the presence of hydrogen peroxide. The formed bubbles are controlled to make distinct visual patterns, allowing simple and sensitive virus detection using a convolutional neural network (CNN)-enabled smartphone system and without using any optical hardware smartphone attachment. We evaluated the developed CNN-NES for testing viruses such as hepatitis B virus (HBV), HCV, and Zika virus (ZIKV). The CNN-NES was tested with 134 ZIKV-and HBV-spiked and ZIKV-and HCV-infected patient plasma/serum samples. The sensitivity of the system in qualitatively detecting viral-infected samples with a clinically relevant virus concentration threshold of 250 copies/ml was 98.97% with a confidence interval of 94.39 to 99.97%.

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Smartphone systems can also benefit from the recent unprecedented advancements in nanotechnology to develop diagnostic approaches. Catalysis can be considered as one of the popular applications of nanoparticles because of their large surface-to-volume ratio and high surface energy (11–16). So far, numerous diagnostic platforms for cancer and infectious diseases have been developed by substituting enzymes, such as catalase, oxidase, and peroxidase with nanoparticle structures (17–20). Here, we adopted the intrinsic catalytic properties of platinum nanoparticles (PtNPs) for gas bubble formation to detect viruses on-chip using a convolutional neural network (CNN)–enabled smartphone system.

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Super-fast quantum computers and communication devices could revolutionize countless aspects of our lives—but first, researchers need a fast, efficient source of the entangled pairs of photons such systems use to transmit and manipulate information. Researchers at Stevens Institute of Technology have done just that, not only creating a chip-based photon source 100 times more efficient that previously possible, but bringing massive quantum device integration within reach.

“It’s long been suspected that this was possible in theory, but we’re the first to show it in practice,” said Yuping Huang, Gallagher associate professor of physics and director of the Center for Quantum Science and Engineering.

To create , researchers trap light in carefully sculpted nanoscale microcavities; as light circulates in the cavity, its photons resonate and split into entangled pairs. But there’s a catch: at present, such systems are extremely inefficient, requiring a torrent of incoming laser light comprising hundreds of millions of photons before a single entangled photon pair will grudgingly drip out at the other end.

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Circa 2007

Robocops could soon leave the realm of science fiction thanks to a new bullet-proof material proposed by engineers in Australia. According to computer simulations done by the team, bullets would be no match for vests made of the material, and would simply bounce off owing to the high elasticity of the nanotubes. The researchers claim that the material, which has not been made yet, would be a great improvement on existing anti-ballistic clothing that stop bullets from penetrating by spreading the bullet’s force — something that can still cause serious injury (Nanotechnology 18 475701).

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Circa 2006 o.,o.

Researchers at the National Institute of Standards and Technology and the University of Colorado at Boulder have designed a carbon nanotube knife that, in theory, would work like a tight-wire cheese slicer.

In a paper presented this month at the 2006 International Mechanical Engineering Congress and Exposition, the research team announced a prototype nanoknife that could, in the future, become a tabletop tool of biology, allowing scientists to cut and study cells more precisely than they can today.

For years, biologists have wrestled with conventional diamond or glass knives, which cut frozen cell samples at a large angle, forcing the samples to bend and sometimes later crack. Because carbon nanotubes are extremely strong and slender in diameter, they make ideal materials for thinly cutting precise slivers of cells. In particular, scientists might use the nanoknife to make 3D images of cells and tissues for electron tomography, which requires samples less than 300 nanometers thick.

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