Browsing all articles in Publications
Jun
2

Researchers Develop Plasmonic Amplifier

plasmonResearchers at the University of Iceland, University of Cologne and the Fraunhofer Institute Jena have demonstrated net optical amplification in a plasmonic waveguide. The results of the team, which were published in the journal Nature Photonics, represent an important breakthrough in the field of plasmonics. Optical amplification is the only feasible strategy to make light travel over sizable distances when it is bound in a plasmonic mode. Achieving such a macroscopic propagation of surface plasma waves is critical for many applications of the emerging plasmonics technology, which range from compact communication devices and optical computing to the detection and characterization of cells, virus particles or even single molecules.

A surface plasmon is a collective excitation involving all conducting electrons in a metallic layer moving relatively to the static positive ions of the metal as shown in the diagram. Research on plasmonics, a relatively new branch of optics, has received an increasing level of international attention over the last decade. This interest is mainly driven by the fact that surface plasmons, travelling along the interface between a metal and a dielectric, allow confining optical energy to volumes that are significantly smaller than those accessible with conventional dielectric waveguiding structures such as optical fibers.

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May
18

Quantum entanglement in real biological system

green plantsThe future of clean green solar power may well hinge on scientists being able to unravel the mysteries of photosynthesis, the process by which green plants convert sunlight into electrochemical energy. To this end, researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) have recorded the first observation and characterization of a critical physical phenomenon behind photosynthesis known as quantum entanglement.

Previous experiments led by Graham Fleming, a physical chemist, pointed to quantum mechanical effects as the key to the ability of green plants, through photosynthesis, to almost instantaneously transfer solar energy from molecules in light harvesting complexes to molecules in electrochemical reaction centres. Now a new collaborative team that includes Fleming have identified entanglement as a natural feature of these quantum effects. Their work is published in the Nature Physics journal. When two quantum-sized particles, for example a pair of electrons, are entangled, any change to one will be instantly reflected in the other, no matter how far apart they might be. Though physically separated, the two particles act as a single entity.

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May
6

Analysis of graphene via atomic moire interferometry

moire patternsIn a groundbreaking series of experiments, scientists in the United States managed to develop a new method of analyzing how graphene sheets are stacked on top of each other. The technique is also suitable for determining which areas of the compound are subjected to most strain, when the material is placed inside more complex structures. All of this can be inferred using moire patterns, which are interference patterns that appear at an atomic scale, when two layers of atoms are placed on top of each other imperfectly, as in slightly askew (image courtesy of NIST).

The research team that conducted the new investigation features physicists from the US National Institutes of Standards and Technology (NIST) and the Georgia Institute of Technology (Georgia Tech). The experts say that the moire patterns can also be used on multiple grids or atom arrays, not only on two. They add that using “atomic moire interferometry” can also help scientists determine the rotational orientation of the graphene sheets used in a variety of technological applications. Their work is published in the Physical Review B journal.

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Apr
26

New prospects for solar cells

new solar cellsThe most efficient solar cells, composed of a semiconductor material such as silicon, have been developed in Switzerland in the early 90s. As in the case of conventional electrochemical batteries, solar cells consist of a cathode, a platinum-based catalyst, and an anode, a porous layer formed from titanium dioxide nanoparticles and coated with a dye absorbs sunlight. A conductive liquid, the electrolyte is placed between two electrodes.

Despite the use of materials for the most inexpensive, easy to manufacture and flexible, large-scale commercialization of these batteries confronts two major obstacles. The electrolyte is very corrosive, causing a deficiency in sustainability. It is also very colorful, preventing light from entering and effectively limiting the photo-voltage of 0.7 volts. Moreover, platinum is an expensive material, non-transparent and rare.

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Apr
14

Energy dissipation and transport in nanoscale devices

microelectronicsUnderstanding energy dissipation and transport in nanoscale structures is of great importance for the design of energy-efficient circuits and energy-conversion systems. This is also a rich domain for fundamental discoveries at the intersection of electron, lattice (phonon), and optical (photon) interactions. A review article published in NanoResearch presents the recent progress in understanding and manipulation of energy dissipation and transport in nanoscale solid-state structures.

Some of the greatest challenges of modern society are related to energy consumption, dissipation, and waste. Among these, present and future technologies based on nanoscale materials and devices hold great potential for improved energy conservation, conversion, or harvesting. A prominent example is that of integrated electronics, where power dissipation issues have recently become one of its greatest challenges. Power dissipation limits the performance of electronics from handheld devices (~10–3 W) to massive data centres (~109 W), all primarily based on silicon micro/nanotechnology.

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Apr
7

Enzyme in white blood cells can break down carbon nanotubes

nanotube toxicityAn EU-funded study of carbon nanotubes by scientists in Ireland, Sweden and the US has shown that these extraordinarily strong molecules can be broken down into carbon and water by an enzyme found in white blood cells. The discovery, published in the journal Nature Nanotechnology, offers hope that this new material may be exploited safely in medicine and industry.

The findings are an outcome of the NANOMMUNE (‘Comprehensive assessment of hazardous effects of engineered nanomaterials on the immune system’) project, financed under the NMP (‘Nanosciences, nanotechnologies, materials and new production’) theme of the EU’s Seventh Framework Programme (FP7).

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Mar
31

Study of symmetries in colloidal monolayers

Nature likes some symmetries, but dislikes others. Ordered solids often display a so-called 6-fold rotation symmetry. To achieve this kind of symmetry, the atoms in a plane surround themselves with six neighbours in an arrangement similar to that found in a honeycomb. As opposed to this, ordered materials with 7-fold, 9-fold or 11-fold symmetries do not appear to arise in nature.

Researchers from the Max Planck Institute for Metals Research, the University of Stuttgart and the Technische Universität Berlin discovered the reason for this when they tried to impose a 7-fold symmetry on a layer of charged colloid particles using strong laser fields: the emergence of ordered structures requires the presence of nuclei to which the atoms with the corresponding symmetry can attach. Such nuclei can be found in large numbers in the symmetries for which nature shows a preference. However, they only arise sporadically in patterns with 7-fold symmetry.

symmetries in monolayer colloids

The researchers generate light patterns like the ones shown in the picture above by superimposing several laser beams (Image: Jules Mikhael, University of Stuttgart). Flower-shaped structures form in the laser reliefs which act as a nucleus for the order (top left: 5-fold; top right: 6-fold; bottom left: 7-fold; bottom right: 8-fold).

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Mar
26

Lock and key mecanism for particle self-assembly

Physicists at the New York University Center for Soft Matter Research have created “handshaking” colloid particles that link together based on their shape rather than randomly. Their work, reported in Nature, marks the first time scientists have succeeded in programming colloid particles to join in this manner and offers a type of architecture that could enhance the creation of synthetic materials.

handshaking particles

The graphic above shows how the researchers developed a “lock and key” mechanism that allows specific particles to join together (image courtesy of Nature). “We expect these interactions to offer unprecedented opportunities for engineering smart composite particles, new functional materials, and microscopic machinery with mobile parts,” wrote the researchers.

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Mar
18

The crystallographic secrets of red coral

red coralAn international team of scientists has shown for the first time that living organisms are able to manufacture biominerals with organization of up to eight levels. The research focused on the skeleton of Mediterranean red coral. This coral, shown on the photography made by Joaquim Garrabou, has a crystalline order that is almost perfect at nanometric scale and could help in the development of new materials.

“This research into red coral shows for the first time that biominerals (minerals synthesised by living beings) display a crystalline order made up of up to eight hierarchical levels of modules”, explains Joaquim Garrabou, co-author of the study and a biologist at the CSIC Institute of Marine Sciences, “each module is made up of other smaller ones, and is in turn a component of other larger ones”.

The study, published in the journal American Mineralogist, was led by researchers from the Marseilles Interdisciplinary Nanoscience Centre (France), with collaboration from the California Institute of Technology (United States). The work focuses on red coral (corallium rubrum), an invertebrate that lives in the rocky depths of the Mediterranean and Western Atlantic.

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Mar
12

A polymer material that could dissipate heat

Most polymers — materials made of long, chain-like molecules — are very good insulators for both heat and electricity. But an MIT team has found a way to transform the most widely used polymer, polyethylene, into a material that conducts heat just as well as most metals, yet remains an electrical insulator.

thermoconductive polymer

The illustration to the left displays the tangled nature of the polymer filaments, with heat-stopping voids indicated as dark blobs. When drawn and heated into a thin thread (illustration to the right), the molecules line up and the voids are compressed, making the material a good conductor (illustrations courtesy of Gang Chen).

The new process causes the polymer to conduct heat very efficiently in just one direction, unlike metals, which conduct equally well in all directions. This may make the new material especially useful for applications where it is important to draw heat away from an object, such as a computer processor chip. The work is described in a paper published in Nature Nanotechnology.

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