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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Mar
9

Chemically driven thermopower waves

nanotube conducting heatA team of scientists at MIT have discovered a previously unknown phenomenon that can cause powerful waves of energy to shoot through minuscule wires known as carbon nanotubes. The discovery could lead to a new way of producing electricity, the researchers say.

The phenomenon, described as thermopower waves, “opens up a new area of energy research, which is rare,” says Michael Strano, who was the senior author of a paper describing the new findings that appeared in Nature Materials. The lead author was Wonjoon Choi, a doctoral student in mechanical engineering.

A carbon nanotube (shown in the illustration made by Christine Daniloff) can produce a very rapid wave of power when it is coated by a layer of fuel and ignited, so that heat travels along the tube. Like a collection of flotsam propelled along the surface by waves travelling across the ocean, it turns out that a thermal wave — a moving pulse of heat — travelling along a microscopic wire can drive electrons along, creating an electrical current.

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Mar
8

Physicists find a way to see through opaque materials

Materials such as paper, paint, and biological tissue are opaque because the light that passes through them is scattered in complicated and seemingly random ways. A new experiment conducted by researchers at the City of Paris Industrial Physics and Chemistry Higher Educational Institution (ESPCI ParisTech) has shown that it’s possible to focus light through opaque materials and detect objects hidden behind them, provided you know enough about the material. The experiment is reported in Physical Review Letters.

seeing_through_opaque_materials

Knowing enough about the way light is scattered through materials would allow physicists to see through opaque substances, such as the sugar cube on the right. In addition, physicists could use information characterizing an opaque material to put it to work as a high quality optical component, comparable to the glass lens shown on the left.

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Mar
5

Iron-Clad Fibers: A Metal-Based Biological Strategy for Hard Flexible Coatings

Researchers at the Max Planck Institute of Colloids and Interfaces and collaborators at the University of California at Santa Barbara and the University of Chicago believe they have uncovered the basis how marine mussels use the byssus, a bundle of tough and extensible fibres, to fasten securely to wave-swept rocky coastlines.

mussel_fibres

(I) Mussels attach to hard surfaces in the marine intertidal zone with the byssus. (II) Byssal threads are extensible fibers with a hard and rough-textured protective cuticle (scanning electron microscopy). The knobby morphology of the cuticle originates from granular inclusions embedded in a continuous matrix. (III) The amount of dopa-iron complexes was found to be much higher in the granules than the matrix, which likely leads to their differences in mechanical performance during stretching. (Image: Matt Harrington, Max Planck Institute of Colloids and Interfaces)

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