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Current materials-related news gathered from around the Web that is frequently updated. Visit this page regularly to keep in touch with the latest in materials research. Please note that some external websites may require registration for access.

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• Spin injection with half-metals: A perfect match
  (Physics)

  
  Credit: Physics

  A new report discusses an important development in spin injection using Heusler alloys, some of which have long been predicted to be half-metals. Half-metals, which are extremely rare in nature, have 100% spin polarization at the Fermi level, and therefore only pass a current in which the electrons are polarized either “up” or “down.” Up to now, attempts to use Heusler alloys as spin injectors have not been promising because the alloy becomes disordered at the interface with the semiconductor and the spin polarization is greatly reduced. By better understanding the alloy-semiconductor interface, the researchers were able to reach a spin injection efficiency of at least 50% from Co₂FeSi into GaAs. This is the highest efficiency achieved so far with a Heusler alloy. Co₂FeSi is unusual in many respects—there are indications that it indeed might be half-metallic, it remains ferromagnetic up to 1100 K and has the largest magnetic moment among the Heusler compounds. Most importantly, it has a crystal structure that matches perfectly with that of III-V semiconductors, which allows for fabrication of high-quality interfaces.
  [New Class of Materials: Half-Metallic Ferromagnets, Phys. Rev. Lett. 50, 2024 - 2027 (1983)]
  (September 26, 2008)

• Quench in superconducting magnets shuts down LHC
  (Science)

  When physicists first sent particles racing through the world's biggest atom smasher on 10 September, the Large Hadron Collider (LHC) at the European particle physics laboratory, CERN, near Geneva, Switzerland, the gargantuan machine purred like a kitten. However, 9 days later, some of the 1232 main superconducting dipole magnets, which keep the beams on their circular trajectories, abruptly overheated in an event known as a "quench." The incident ruptured the plumbing that carries liquid helium through the magnets to chill them to 2 kelvin--2 degrees above absolute zero. A quench occurs when part of a superconducting magnet overheats and acts like an ordinary wire. The hot bit serves as an electric heater that can trigger a runaway reaction, toasting the rest of the magnet and converting the energy in its field to heat.
  [Incident in LHC sector 3-4, CERN press release]
  (September 26, 2008)

• DNA templates for nanomachinery
  (Science)

  The precise and complementary base pair matching in DNA has increasingly led to its use as a building or templating material in the assembly of nanoscale objects such as particles or wires, or for the decoration of particles and wires with metals or other molecules. A new report has reviewed recent developments in the use of DNA as a precise positional tool for complex material assembly. Developments have moved from simple one-dimensional templating to two and three dimensions, with scope for dynamically changing the shape or size of an object, or the fabrication of nanomachines.
  [Assembling Materials with DNA as the Guide, Science 26 September 2008: Vol. 321. no. 5897, pp. 1795 - 1799, DOI: 10.1126/science.1154533]
  (September 26, 2008)

• Nanoparticles hide behind protein cloak
  (Royal Society of Chemistry)

  Polymer nanoparticles suspended in human blood become cloaked in plasma proteins, new research shows. The composition of the protein cloak depends not only on the surface properties of the nanoparticle, but also, surprisingly, on its size. The findings suggest that when a nanoparticle enters the blood it soon acquires a new identity based on proteins, and it is these, rather than the nanoparticle per se, that are likely to be recognised at, say, a cell surface. The findings have implications for scientists' understanding of nanoparticle toxicity, but also on nanoparticle-based targeted therapies.
  [Nanoparticle size and surface properties determine the protein corona with possible implications for biological impacts, PNAS September 23, 2008 vol. 105 no. 38 14265-14270]
  (September 25, 2008)

• Copper future for dye-sensitized solar cells
  (Royal Society of Chemistry)

  Rare ruthenium complexes that are a key component of dye-sensitised solar cells could in future be replaced by molecules based on copper, say researchers of a new study. Dye-sensitised solar cells (which use absorbent dyes to convert sunlight into photoelectrons and a separate semiconductor to generate a current) are promising candidates to replace conventional silicon solar panels, since they are cheaper and more flexible - though not yet as efficient. Though only small amounts of a ruthenium-based dye are required in the solar cell, ruthenium is one of the rarest metals on Earth, so the team is hoping to switch to complexes of a more common metal. They showed that complexes of copper(I) can interact with light in a similar way to ruthenium. The key, they revealed, is to keep copper in the +1 oxidation state, which is achieved by 6,6'-disubstituted 2,2'-bipyridine ligands that grip the copper ion tightly, preventing it from oxidising into copper(II).
  [An element of surprise—efficient copper-functionalized dye-sensitized solar cells, Chem. Commun., 2008, 3717 - 3719, DOI: 10.1039/b808491b]
  (September 24, 2008)

• "Smoothest ever"surface created
  (Science Daily)

  
  Credit: Advanced Materials

  A research team has created the “quantum stabilized atom mirror,” the smoothest surface ever, according to the researchers. The mirror resembles a curved wafer. It is made up of a thin silicon crystal with a thickness of 50 microns, and covered with a very fine layer of lead, 1 or 2 nanometres thick. To study the reflection on this metal, the scientists used helium atoms. Until now mirrors made solely from silicon reflected 1% of helium atoms, but by adding the layer of lead they have managed to achieve a reflection of up to 67%. This is already being used in the design of the world's first atomic microscope.
  [A Quantum-Stabilized Mirror for Atoms. Advanced Materials, 20 (18): 3492. September 2008]
  (September 23, 2008)

• How colloidal dispersions relax under stress
  (Physics)

  
  Credit: Physics. Illustration by Alan Stonebraker

  Of the many physical systems that we can study, colloids and colloid dispersions may well be one of the most prevalent in our daily lives. Inks, paints, clays, emulsions, and milk, as well as surfactant aggregates (micelles) and nanoparticle suspensions are all colloid dispersions. The rheology of these dispersions and other complex liquids is essentially a problem of nonequilibrium statistical mechanics that must account for many-body interactions. The response of colloid dispersions to a shear force is often nonlinear and can result in interesting physical phenomena. Predicting how a colloid dispersion responds to an external stress and connecting this relationship to the microscopic interactions between the dispersed particles is a key goal of theoretical rheology. A new paper now reports the development of a rheological constitutive equation for dense colloidal suspensions and glasses (here, constitutive refers to the stress-response relationship). The work links a highly successful microscopic theory, which describes how colloidal particles become arrested at the glass transition of a colloid, to a formal description of suspension rheology. Although this is not the first effort in this direction, this paper is an important contribution because it applies to both colloidal dispersion and glasses, can describe the response for nonlinear, arbitrary deformation fields, and satisfies the criterion that the stresses should be invariant for different reference frames.
  [First-Principles Constitutive Equation for Suspension Rheology, Phys. Rev. Lett. 101, 138301 (2008), doi:10.1103/PhysRevLett.101.138301]
  (September 23, 2008)

• Frictional duality in nanoparticle sliding
  (Physical Review Focus)

  
  Credit: D. Dietzel & A. Schirmeisen/Univ. of Münster

  It's no surprise that a block sliding across a table is slowed by friction, but for sufficiently small crystals, theory and a few experiments suggest that frictionless motion may be the norm. Now, a team of researchers pushing nanometer-sized metal blocks across an ultra-clean graphite surface reports that some of them skate freely, while others resist. They did this by spraying atoms of antimony onto an ultra-clean graphite surface, where they formed "islands" as large as 300,000 square nanometers. They then measured the force needed for their AFM tip to push different-sized antimony islands across the graphite surface. The results support a theory that friction arises only when extra atoms get trapped between the surfaces. This insight into the origins of friction may be important for researchers developing nanoscale machines that include sliding parts.
  [Frictional Duality Observed during Nanoparticle Sliding, Phys. Rev. Lett. 101, 125505 (issue of 19 September 2008)]
  (September 23, 2008)

• Self-assembled gradient concentric rings of carbon nanotubes
  (Advanced Functional Materials)

  
  Credit: Advanced Functional Materials

  Researchers have recently demonstrated a simple and straightforward method to create gradient concentric rings of carbon nanotubes over very large surface areas by combining two consecutive self-assembly processes. Hundreds of gradient concentric polymer rings with remarkable regularity were spontaneously formed on Si substrates via evaporation-induced self-assembly of polymer in a confined geometry consisting of a sphere on a flat Si substrate. The concentric polymer rings on the Si were then exploited as a chemically patterned surface to guide the formation of multiwalled carbon nanotube (MWNT) rings (i.e., directed self-assembly). Specifically, a drop of water-dispersed MWNTs mixed with poly (diallyl dimethylammonium) chloride (PDDA) was cast on the surface of the template polymer rings. The periodically alternating hydrophobic polymer rings and hydrophilic Si substrate (i.e., Si rings) provided different wettabilities for the MWNT/PDDA solution. As water evaporated, the MWNT solution dewetted the polymer rings while forming MWNT rings on the Si rings. The combination of spontaneous evaporation-induced self-assembly and subsequent directed self-assembly offers a new means of patterning microscopic CNT rings over large areas. This method is fast and cost-effective, eliminating the need for multistage lithography and externally applied forces.
  [Directed Self-Assembly of Gradient Concentric Carbon Nanotube Rings, Advanced Functional Materials, Volume 18 Issue 14, (2008) Pages 2114 - 2122]
  (September 22, 2008)

• Unlocking the secret of the Kondo Effect
  (University College, London/Nature Physics)

  The Kondo effect, one of the few examples in physics where many particles collectively behave as one object (a single quantum-mechanical body), has intrigued scientists for decades. When a single magnetic atom is located inside a metal, the free electrons of the metal ‘screen’ the atom. That way, a cloud of many electrons around the atom becomes magnetized. Sometimes, if the metal is cooled down to very low temperatures, the atomic spin enters a so-called ‘quantum superposition’ state. In this state its north-pole points in two opposite directions at the same time. As a result, the entire electron cloud around the spin will also be simultaneously magnetized in two directions. Now, using a technique that was developed earlier by the same team, researchers have shown that it is possible to predict when the Kondo effect will occur – and to understand why. The key turns out to be in the geometry of a magnetic atom’s immediate surroundings. By carefully studying how this geometry influences the magnetic moment (or “spin”) of the atom, the emergence of the Kondo effect can now be predicted and understood.
  [The role of magnetic anisotropy in the Kondo effect, Nature Physics, Published online: 21 September 2008 | doi :10.1038/nphys1072 ]
  (September 22, 2008)

• Shape changes of catalytic Rh nanoparticles during oxidation, reduction
  (Science)

  
  Credit: Nolte et al., Science

  Heterogeneous catalysts often consist of metal nanoparticles absorbed on oxide supports, and the size and shape of these nanoparticles are likely to be affected by conditions in the reactor such as temperature and oxidation state. However, such changes are not readily observed experimentally because many methods require vacuum conditions. A research team was able to examine the changes to rhodium nanoparticles on a MgO surface using high-resolution in situ x-ray diffraction, as well as transmission election microscopy. At elevated temperatures (570 K), these pyramid-shaped nanoparticles became flatter upon exposure to oxygen, which causes the formation of a surface oxide. The nanoparticles returned to their original shape after exposure to CO, which causes reduction of the surface.
  [Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles, Science 19 September 2008:
  Vol. 321. no. 5896, pp. 1654 - 1658 DOI: 10.1126/science.1160845]
  (September 19, 2008)

• New architecture for single-electron devices allows CMOS-compatible fabrication
  (Nano Werk)

  For single-electron devices to become practical, they need to move from the highly individual and customized fabrication process typically found in laboratories to an automated, high-throughput and industrial-scale production environment. The reason this hasn't happened yet is that the various nanoscale pattern definition techniques used today – such as e-beam lithography, mechanically controllable break junctions, electromigration, electrodeposition, nanoscale oxidation, and scanning tunneling microscopy – generally are not suitable for large-scale parallel processing. The fabrication of single-electron devices requires nanoscale geometrical arrangement of device components, that is, source and drain electrodes and Coulomb islands. A new study now demonstrates that this can be done with complete parallel processing using CMOS-compatible processes and materials. Furthermore, these single-electron devices can operate at room temperature, an essential requirement for practical implementations. According to the Authors, they have demonstrated chip-level fabrication of room-temperature single-electron devices that does not use any of the sophisticated nanoscale pattern definition techniques that generally have intrinsic limitations for large-scale processing, and except for electrical measurements at the end, at no time was any device treated individually.
  [CMOS-compatible fabrication of room-temperature single-electron devices, Nature Nanotechnology, Published online: 14 September 2008 | doi:10.1038/nnano.2008.267]
  (September 19, 2008)

• Replicating the compound eye of a fruit fly
  (Nanotechnology)

  
  Credit: Nanotechnology (IOP)

  In the field of biomimetics, compound eyes found in nature are of interest for replication because of their unique optical schemes. In a new study, researchers have successfully replicated and created a biotemplate of the compound eye of the fruit fly, by rapidly rotating it and using an oblique angle deposition technique. The researchers have named this the conformal evaporated- film-by-rotation (CEFR) technique. It allowed for replication at both the micro- and nanoscales and of the curvature. Chalcogenide glasses were used in the present work for the replication because of their infrared optical properties as well as their excellent chemical and mechanical properties. The researchers were able to use the technique to replicate even more complex biological structures such as the head of the fly and its wings, which is not possible using conventional thin-film deposition techniques.
  [Replication of fly eyes by the conformal-evaporated-film-by-rotation technique, Nanotechnology 19 355704 (2008) doi: 10.1088/0957-4484/19/35/355704]
  (September 18, 2008)

• Patterning of core-shell microgel nanoparticles
  (North Carolina State University)

  
  Credit: Nano Letters, ACS

  Researchers have shown that core-shell microgels, in which the core of a cross-linked, or networked, polymer is surrounded by a shell of a different polymer, when heated to the proper temperature, bob to the surface of a layer of a thin polymer film and then can reversibly recede below the surface when heated a second time. This could be used to form controllable surface patterns of the nanoparticles, with possible applications as reusable nano-bar codes, or fluorescent nano-sensors.
  [Autophobicity-Driven Surface Segregation and Patterning of Core-Shell Microgel Nanoparticles, Nano Letters 8 ( 9 ), 3010 – 3016 , 2008 . 10.1021/nl802109x]
  (September 17, 2008)

• High-temperature superconductivity in composite systems
  (Physics)

  
  Credit: Physics. Illustration by Alan Stonebraker

  In the past twenty years, two families of superconducting materials with transition temperature above 50 K have been discovered: the cuprates and more recently, the iron-pnictides. Many believe that some cuprate compounds should be very high temperature superconductors (that is, with a Tc~200 K) were it not for the fact that the superconducting carriers, the Cooper pairs, have a low mobility [3]. A new report turns this logic around and suggests that making contact between a nominally low-mobility superconductor and a high-mobility metal will increase the mobility of Cooper pairs in the superconductor and raise Tc.
  [Route to high-temperature superconductivity in composite systems, Phys. Rev. B 78, 094509 (2008) – Published September 15, 2008]
  (September 17, 2008)

• Quantitative understanding of phase transition via nucleation
  (Journal of Applied Physics)

  Nucleation induced phase transformation is a fundamental process in materials science. In 1950, David Turnbull reported that in the case of homogeneous solidification, the liquid needs to be undercooled to a specific extent below the melting point (Tmp) before nucleation occurred and this was approximately 0.18 Tmp. This was established empirically using experimental measurements. However, it has so far not been possible to quantitatively predict the extent of this undercooling needed using classical nucleation theory (CNT). A new study now reports that the magnitude of undercooling for metallic liquids can indeed be predicted from CNT, so long as the excess volume due to the density difference between the solid and liquid is accounted for. The study also shows that there is a universal character in the minimum nucleation barrier energy for the formation of a stable microscopic nucleus of the new phase in the existing phase. Thus, thermodynamics in conjunction with CNT can yield quantitative information about the energetics of homogeneous nucleation and solidification, according to this new report.
  [Nucleation energetics during homogeneous solidification in elemental metallic liquids, J. Appl. Phys . 104, 033506 (2008); DOI:10.1063/1.2961329]
  (September 15, 2008)

• Quantum limits in plasmonic devices
  (Science Daily)

  For a number of years, so-called plasmonic components have proven to be a possible way around the dilemma of electronics and photonics. By combining photonics and electronics, scientists have shown that information can be transferred with the help of so-called plasmons. Plasmons are surface waves, like waves in the ocean, but here consisting of electrons, which can spread at extremely high speeds in metals. New findings now show that difficulties arise when the size of such components is reduced to the nanometer level. At that point it turns out that the dual nature of electrons makes itself felt: the electrons no longer act like particles but rather have a diffuse character, with their location and movement no longer being clearly defined. This elusive personality leads to the energy of the plasmon being dissipated and lost in the transfer of information. For nanocomponents, this consequence is devastating, entailing the loss of all information before it can be transferred.
  [New quantum limits in plasmonic devices, Europhysics Letters, to be published]
  (September 15, 2008)

• New method to slice thin Ge wafers
  (Univ. of Utah)

  Brass-coated, steel-wire saws are currently used to slice round wafers of germanium from cylindrical single-crystal ingots. But the brittle chemical element cracks easily, requiring broken pieces to be recycled, and the width of the saws means a significant amount of germanium is lost during the cutting process. The sawing method was originally developed for silicon wafers, which are roughly 100 times stronger. A new method for slicing solar cell wafers – known as wire electrical discharge machining (WEDM) – is being refined for this task now. It wastes less germanium and produces more wafers by cutting even thinner wafers with less waste and cracking. The method uses an extremely thin molybdenum wire with an electrical current running through it. It has been used previously for machining metals during tool-making. The new study found that the "kerf" – which is the amount of germanium wasted during the slicing process – was 22 percent less when a 75-micron diameter electrified Mo wire was used to cut the wafers, compared with the conventional wire saw method. The researchers cut 2.6-inch-diameter wafers with a thickness of 350 microns.
  [To be published in Journal of Materials Processing Technology]
  (September 15, 2008)

• New helium ion microscope better than conventional SEM?
  (NIST)

  
  Credit: NIST

  A new microscope technology uses helium ions to generate the signal used to image extremely small objects, a technique analogous to electrons in scanning electron microscopes. Paradoxically, although helium ions are far larger than electrons, they can provide higher resolution images with higher contrast. The depth of field is much better with the new technology too, so more of the image is in focus. Ions have larger mass and shorter wavelength than electrons, and they could be better for imaging. According to the researchers, the images appear almost three-dimensional, revealing details smaller than a nanometer—the distance spanned by only three atoms in the silicon crystal.
  (September 12, 2008)

• Snapshot of nanoscale transformation
  (Lawrence Livermore National Lab)

  Researchers have been able to obtain high-resolution snapshots of the transformation of nanoscale structures. Using a new Dynamic Transmission Electron Microscope (DTEM), they were able to observe the microstructure and properties of reactive multilayer foils (also known as nanolaminates) with 15-nanosecond-scale resolution. Time-resolved images of nanolaminates show a brief change in structure with a short cellular phase separation during cooling. The ability to directly observe and characterize short-lived complex events can lead to a fundamental understanding of properties such as reactivity, stability and strength, and help in the design of new and improved materials and devices.
  [Imaging of Transient Structures Using Nanosecond in Situ TEM, Science 12 September 2008: Vol. 321. no. 5895, pp. 1472 - 1475 DOI: 10.1126/science.1161517]
  (September 12, 2008)

• 'Tree on a chip' mimics water transport in plants
  (Nature News)

  
  Credit: Tobias Wheeler, Cornell Univ.

  A 'microtree' created from a synthetic gel used to make contact lenses has replicated water transport in plants. The design could be tweaked to improve extraction of water from dry soils, or to create more efficient cooling systems, according to the researchers. They made the water channels from a hydrogel based on poly(hydroxyethyl methacrylate) that contains tiny, homogeneous pores. The system generates a continuous negative pressure that pulls in water from a vapor via the 'roots' and transports it as a liquid along hydrogel channels to the 'leaves', from which the water is evaporated.
  [Nature 455 , 209–212 (2008)]
  (September 11, 2008)

• Prototype superconductor for Tokamak fusion reactor proves successful
  (Science Daily)

  
  Credit: Japan Atomic Energy Agency

  Fusion for Energy (F4E) with the support of the European Commission, Japan Atomic Energy Agency (JAEA) and ITER Organisation have successfully tested a prototype superconductor for the ITER Poloidal Field coils made of Niobium(Nb)-Titanium(Ti) reaching a stable operation at 52 kA in a magnetic field of 6.4 Tesla. Poloidal Field coils will be used to maintain the plasma equilibrium and shape inside the ITER Tokamak reactor. The results gave scientists complete confidence that this conductor would fulfill the extremely demanding performance required for ITER.
  (September 10, 2008)

• Effects of disorder harnessed in magnetic sensors
  (University of Chicago)

  In silver selenide and silver telluride, the magnetic response disappears at room temperature, which limits their technological applications. But researchers have now used two methods to recreate the effect at much higher temperatures in indium antimonide. Disordering the material—simply grinding it up and fusing it with heat—produces the effect. So does introducing impurities of just a few parts per million. This could be used to make magnetic sensors capable of operating at the high temperatures that ceramic engines in cars and aircraft of the future will require.
  [Classical and quantum routes to linear magnetoresistance, Nature Materials 7, 697 - 700 (2008)]
  (September 10, 2008)

• New gecko-inspired adhesive shakes off dirt
  (University of California, Berkeley)

  
  Credit: Langmuir, ACS

  Researchers have created the first adhesive that cleans itself after each use without the need for water or chemicals, much like the remarkable hairs found on the gecko lizard's toes. They designed the adhesive with microfibers made from stiff polymers. Using microspheres that were 3 to 10 micrometers in diameter to simulate contaminants, the researchers were able to show that the microfibers pushed the microsphere particles toward the fiber tips when the adhesive was not in contact with a surface. This is based on the fact that a gecko keeps its feet sticky but clean by shedding dirt particles with every step.
  [Contact Self-Cleaning of Synthetic Gecko Adhesive from Polymer Microfibers, Langmuir, ASAP Article, 10.1021/la8021485
  Web Release Date: September 10, 2008]
  (September 10, 2008)

• Metamaterial nano-optical lens demonstrated
  (Nature Research Highlights)

  It would be very useful make lenses from metamaterials — structures that can have a negative refractive index. Such lenses would tightly focus light over short distances with little or no distortion. A research team now reports that they have built a two-dimensional metamaterials lens from a semiconductor crystal. The lens was made by carving a lattice into a layered indium gallium arsenic phosphide wafer. It can focus infrared light of the same wavelength as that used in common devices to a spot just 12 micrometres away from its surface. The researchers say that the work could lead to smaller, more efficient digital cameras and sensors.
  [Nano-optical microlens with ultrashort focal length using negative refraction, Appl. Phys. Lett. 93, 053111 (2008); DOI: 10.1063/1.2968873]
  (September 9, 2008)

• Switchable bio-adhesion for thermoresponsive polymer
  (Science Daily)

  
  Credit: Fraunhofer-Gesellschaft

  A new type of property-changing polymer has been developed: It is water-repellent at 37°C, which makes it an ideal culture substrate for biological cells. On the other hand, at room temperature it attracts water, allowing the cells to be detached easily from the substrate. This is not the first thermoresponsive polymer. The big difference is that it is based on polyethylene glycol (PEG), which unlike other materials of this type is biocompatible. It is thus an ideal substrate for cell cultures. The new material has the added advantage of being water-soluble and non-toxic.
  (September 9, 2008)

• Electron irradiation induced reversible metal-to-insulator transition in carbon nanotubes
  (Nature Nanotechnology)

  
  Credit: ACS

  Researchers have demonstrated reversible metal-to-insulator changes in single-walled carbon nanotubes through electron-beam irradiation. Individual nanotubes were positioned between palladium electrodes, formed on doped silicon with an oxide layer, and placed in an SEM. Irradiation of a section of the nanotube by an electron beam with a diameter of 2–3 nm induced a decrease of three orders of magnitude in the electrical conduction. A large voltage applied to the nanotube returned it to its original metallic state. The researchers suggest that the observed changes are due to charges that get trapped in the substrate during irradiation.
  [Reversible Metal−Insulator Transitions in Metallic Single-Walled Carbon Nanotubes, ASAP Nano Lett., ASAP Article, August 14, 2008, 10.1021/nl801288d]
  (September 8, 2008)

• Nanolithography breaks new record
  (NanotechWeb)

  
  Credit: Nature Nanotechnology

  Researchers claim to have developed the most precise nanolithography technique ever. They have used the method, which employs the tip of a scanning tunnelling microscope, to pattern tiny nanostructures (ribbons) into a graphene sheet. The group made the nanostructures by bombarding a graphene sheet with electrons emitted from an atomically sharp tip positioned just a few angstroms above the surface of the material. This "local access" ensures that the technique is precise. By moving the tip along a given geometry, different shapes can be patterned. A big advantage of the technique is that it allows in-situ atomic-scale resolution imaging of the sample immediately after it has been shaped.
  (September 8, 2008)

• Amplitude spectroscopy sheds light on artificial atoms
  (Physics World)

  
  Credit: S.O. Valenzuela & W.D. Oliver, MIT

  Researchers have turned the idea of atomic spectroscopy on its head by inventing a new technique that works by shining radiation of a fixed frequency on a sample, while sweeping the amplitude of the radiation up and down, termed aplitude spectrocopy. They say the new method works particularly well on “artificial atoms”. One problem with conventional spectroscopy is that it can be tricky to carry out with microwaves and millimetre waves (at frequencies of 10–300 GHz). This has been bad news for researchers studying artificial atoms, which exhibit properties of ordinary atoms, including discrete energy levels. The snag in using artificial atoms as putative quantum-information systems is that the gaps between the levels tend to be in the tricky millimetre and microwave region. The new technique shows great promise for studying, and possibly even controlling, artificial atoms. The team’s artificial atom is a “superconducting qubit”, which is a tiny loop of niobium about 16 µm across that is cooled to about 20 mK. A superconducting current flows around the loop and its energy levels are quantized much like the energy levels of electrons orbiting an atomic nucleus.
  [Amplitude spectroscopy of a solid-state artificial atom, Nature 455, 51-57 (4 September 2008); doi:10.1038/nature07262]
  (September 5, 2008)

• Understanding nanogold's catalytic prowess for CO oxidation
  (Eurekalert/NIST)

  It is known that gold nanoparticles measuring less than 5 nanometers in diameter possess a high level of catalytic activity when they are deposited on metal-oxide supports. In particular, they are effective at catalyzing the critical conversion of toxic carbon monoxide (CO) into more benign carbon dioxide (CO2) at room temperature and even at temperatures as low as -76 degrees C. Scientists have sought to determine exactly how gold nanoparticles function as catalysts. A research team now reports that they have pinpointed the active species at which the critical oxidation reaction occurs when gold is supported on iron oxide. According to the new study, bilayer clusters measuring about one-half nanometer in diameter and containing only about 10 gold atoms are responsible for triggering the CO oxidation reaction. The researchers, using aberration-corrected transmission electron microscopy capable of resolving single gold atoms, also report that a simple change in preparation – the drying of the catalyst in flowing rather than static air – helps impart to the gold its catalytic capability.
  [Identification of Active Gold Nanoclusters on Iron Oxide Supports for CO Oxidation, Science, 5 September 2008: Vol. 321. no. 5894, pp. 1331 - 1335, DOI: 10.1126/science.1159639]
  (September 5, 2008)

• Bottoms up: Better organic semiconductors for printable electronics
  (Eurekalert)

  
  Credit: Yoon, SNU, Talbott, NIST

  Researchers have learned how to tweak a new class of polymer-based semiconductors to better control the location and alignment of the components of the blend. Their recent results—how to move the top to the bottom—could enable the design of practical, large-scale manufacturing techniques for a wide range of printable, flexible electronic displays and other devices. They used a neutron imaging technique that allowed them to observe, with nanometer resolution, how the distribution of small organic semiconductor molecules embedded in polymer films changed with depth—the films are less than 100 nanometers thick.
  [Structure and Properties of Small Molecule−Polymer Blend Semiconductors for Organic Thin Film Transistors, ASAP J. Am. Chem. Soc.10.1021/ja804013n]
  (September 4, 2008)

• 'Powdered methane' created
  (Nature News)

  
  Credit: A. Cooper et al., ACS

  Methane and natural gas are usually shipped around in pressurized pipelines and canisters. But researchers have now developed a new way to transport the gases: in the form of a powder. They found that they can trap methane in a bizarre material dubbed 'dry water', which is a mixture of silica and water that looks and acts like a fine white powder. The methane reacts with the water to produce crystalline methane gas hydrate, in which individual methane molecules sit inside ice-like cages of water molecules. In principle, this could offer a way to store methane conveniently for use as a vehicle fuel.
  [Methane Storage in Dry Water Gas Hydrates, J. Am. Chem. Soc., 130 ( 35 ), 11608 – 11609 , 2008. 10.1021/ja8048173]
  (September 4, 2008)

• 2-D "nanonet" of Si and Ti wires grown
  (Eurekalert)

  
  Credit: Angewandte Chemie International

  Researchers have produced "nanonets", a flexible webbing of nano-scale wires that multiplies surface area critical to improving the performance of the wires in electronics and energy applications. They grew wires from titanium and silicon into a two-dimensional network of branches that resemble flat, rectangular netting. By creating nanonets, the team conquered a longstanding engineering challenge in nanotechnology: creating a material that is extremely thin yet maintains its complexity, a structural design large or long enough to efficiently transfer an electrical charge. The nanonets grew spontaneously from the bottom-up through simple chemical reactions, unprovoked by a catalyst.
  [Spontaneous Growth of Highly Conductive Two-Dimensional Single-Crystalline TiSi₂ Nanonets, Angewandte Chemie International Edition, Early View, Published Online: 2 Sep 2008, DOI 10.1002/anie.200802744]
  (September 3, 2008)

• Ceramic material revs up microwaving
  (e! Science News/Penn State Univ.)

  Materials are transparent to microwaves because the microwaves do not interact with the molecules in standard tableware. With liquids like water, the microwaves cause the molecules to move back and forth creating heat. Researchers have now developed a ceramic from petalite and magnetite sintered together that heats up in the microwave without causing equipment problems the way most metals do. Petalite is a commonly occurring mineral that contains lithium, aluminum and silicon and is often used to make thermal shock resistant ceramics because it expands very little when heated. When the petalite and magnetite are fired together, the magnetite converts to an iron oxide that heats up when placed in a microwave.
  [Novel Energy-Saving Materials for Microwave Heating, Chem. Mater., 20 (15), 4803–4807, 2008. 10.1021/cm801138n]
  (September 2, 2008)

• Process for creating DNA tubes with programmable sizes
  (Eurekalert/CalTech)

  Scientists have developed a simple process for mass producing molecular tubes of identical--and precisely programmable--circumferences. The technological feat may allow the use of the molecular tubes in a number of nanotechnology applications. The molecular tubes are composed of wound-up strands of DNA. They designed a series of flexible, single-stranded DNA molecules, called single-stranded DNA tiles. Each single-stranded tile is exactly 42 bases long and contains four modular binding sites. By pairing up the complementary binding sites, these single-stranded tiles bind with each other in a particular orientation like Lego pieces snapped together, forming a tube composed of parallel DNA helices.The circumference of the resulting tube is determined by the number of different 42-base pieces used in its construction.
  [Programming DNA Tube Circumferences, Science 8 August 2008: Vol. 321. no. 5890, pp. 824 - 826, DOI: 10.1126/science.1157312]
  (September 2, 2008)

• Catalyst breaks apart C-F bonds
  (Royal Society of Chemistry)

  
  Credit: O. V. Ozerov

  A research team has developed a new catalyst that is able to prise apart the highly unreactive carbon-fluorine bond at room temperature, potentially paving the way to the efficient disposal of hydrofluorocarbons (HFCs) - highly stable and long-lived greenhouse gases. They have been able to successfully reduce aliphatic fluorocarbons at room temperature using a silylium-carborane catalyst - with conversion rates of greater than 97 per cent and high turnover numbers. The catalyst is made up of a strong Lewis acid, Et₃Si+, and a stable halogenated carborane anion. The highly active Et₃Si+ species, which is able to pluck fluorine atoms from the carbon framework, is regenerated in a reaction with Et₃SiH to complete the catalytic cycle.
  [Hydrodefluorination of Perfluoroalkyl Groups Using Silylium-Carborane Catalysts, Science 29 August 2008: Vol. 321. no. 5893, pp. 1188 - 1190 DOI: 10.1126/science.1159979]
  (September 2, 2008)

• Artificial bone blends into tendons
  (e! Science News/Georgia Tech)

  
  Credit: Andres Garcia, Georgia Tech

  Researchers have used skin cells to create artificial bones that mimic the ability of natural bone to blend into other tissues such as tendons or ligaments. The artificial bones display a gradual change from bone to softer tissue rather than the sudden shift of previously developed artificial tissue, providing better integration with the body and allowing them to handle weight more successfully. One of the biggest challenges in regenerative medicine is to have a graded continuous interface, because anatomically that's how the majority of tissues appear and there are studies that strongly suggest that the graded interface provides better integration and load transfer. The researchers were not only able to create artificial bone that melds into softer tissues, but were also able to implant the technology in vivo for several weeks.
  [Engineering graded tissue interfaces, PNAS August 26, 2008 vol. 105 no. 34 12170-12175 ]
  (August 29, 2008)

• Pulling DNA through a pore
  (Science - Editor's Choice)

  Many studies have probed the force required to pull apart double-stranded DNA. Given the interest in using pore structures to sequence nucleic acids, a research group has now measured the force needed to separate hairpins in a self-attracted single strand of DNA as it is pulled through such a pore, in this case a β-cyclodextrin ring. The ring was attached to an atomic force microscope tip and threaded onto a surface-immobilized polyethylene glycol molecule, to which a single strand of DNA that could form a hairpin was then linked at the free end. The force needed to pull the β-cyclodextrin ring through the hairpin was about 40 times greater than that typically needed to pull double-stranded DNA apart directly. The authors note that the transition state for destabilizing the hairpin occurs over a much smaller distance, and so more force must be applied.
  [An AFM/Rotaxane Molecular Reading Head for Sequence-Dependent DNA Structures, Small, DOI
  10.1002/smll.200800233 (2008)]
  (August 29, 2008)

• Quantum 'traffic jam' in high-temperature superconductors
  (Eurekalert)

  A new study has uncovered the first experimental evidence for why the transition temperature of high-temperature superconductors cannot simply be elevated by increasing the electrons' binding energy. The research demonstrates how, as electron-pair binding energy increases, the electrons' tendency to get caught in a quantum mechanical "traffic jam" overwhelms the interactions needed for the material to act as a superconductor -- a freely flowing fluid of electron pairs. Understanding the detailed mechanism for how quantum traffic jams (technically referred to as "Mottness" after the late Sir Neville Mott) impact superconductivity in cuprates may point scientists toward new materials that can be made to act as superconductors at significantly higher temperatures suitable for real-world applications.
  [How Cooper pairs vanish approaching the Mott insulator in Bi₂Sr₂CaCu₂O_8+delta, Nature 454, 1072-1078 (28 August 2008) | doi:10.1038/nature07243]
  (August 28, 2008)

• Research shows proteins have controlled motions
  (Iowa State University)

  Research now shows that proteins have controlled motions. Most biochemists traditionally believe proteins have many random, uncontrolled movements. The research conducted over a 10-year period shows that not only are protein motions more restricted, but also that these restricted, controlled motions are part of the function of the proteins. Using as an example a protein from HIV virus,the researchers used a simple model and tested to see how the proteins moved. The large number of reported structures show exactly the motions that are required for their function, and exactly the same motions as computed by a model.
  (August 28, 2008)

• Nanoparticles stick a perfect landing
  (Physical Review Focus)

  
  Credit: T. Dumitricã, Univ. of Minnesota

  A research team is designing super-hard, wear-resistant coatings for machine tools. In their patented technique, a spray of particles--each a few nanometers across and containing silicon or some combination of chemicals--strikes a target substrate, such as a silicon surface, with velocities between 1 and 2 kilometers per second. The lumpy coating is built up as these nanoparticles stick to the surface.To investigate where the energy goes, they ran computer simulations of a hypersonic nanoparticle. They found that for speeds less than 1.2 kilometers per second, the nanoparticle bounces off the surface like a basketball. But at higher speeds, some of the nanoparticle undergoes a phase transition to a compressed state called β-tin, where each atom bonds to six neighbors. This transition is surprising because the collision energy is not high enough to induce a phase transition in a macroscopic object. However, the impact force is applied over a few square nanometers, so the pressure inside the nanoparticle is extremely large--around 200,000 atmospheres, which is more than enough to cause the phase transition.
  [Efficient sticking of surface-passivated Si nanospheres via phase-transition plasticity, Phys. Rev. B 78, 081405(R) (2008)]
  (August 28, 2008)

• CNT growth imaged in real-time
  (NanotechWeb)

  
  Credit: Puretzky et al., ORNL

  In situ time-lapse photography and pulsed laser irradiation were used to investigate the growth kinetics of vertically aligned carbon nanotubes (CNTs). During the study, the research team found that the laser-ablated CNT arrays subsequently grew faster – more than compensating for the initial loss in length.
  [Real-time imaging of vertically aligned carbon nanotube array growth kinetics, Nanotechnology 19 (2008) 055605]
  (August 27, 2008)

• New 'nano-positioners' may have atomic-scale precision
  (Purdue University)

  
  Credit: Birck Nanotechnology Center
  Purdue University

  A tiny motorized positioning device hasa been developed that has twice the dexterity of similar devices for applications that include biological sensors and more compact, powerful computer hard drives. The device, called a monolithic comb drive, might be used as a "nanoscale manipulator" that precisely moves or senses movement and forces. The devices also can be used in watery environments for probing biological molecules. The monolithic comb drives could make it possible to improve a class of probe-based sensors that detect viruses and biological molecules. The sensors detect objects using two different components: A probe is moved while at the same time the platform holding the specimen is positioned. The new technology would replace both components with a single one - the monolithic comb drive.
  (August 26, 2008)

• Spin-flip speed is pushed to the limit
  (Physics World)

  Researchers have devised an extremely fast way of changing the value of a magnetic data bit using a current of spin-polarized electrons. The technique could be used to create magnetic random access memories (MRAMs) that are as fast as conventional memory chips and have storage densities that are just as high. Most MRAMs use a tiny magnetic coil near to the nanopillar to switch the direction of its magnetization and so flip the bit from, say, "0" to "1". However, it is a tricky business making coils small enough to achieve MRAM chips with bit densities as high as those found in DRAM or SRAM. One solution is to forget about having a bulky coil and instead flip the nanopillar by passing a pulse of spin-polarized electrons through it. Most spins in such a pulse point in a specific direction (up or down) and their magnetic moment exerts a “spin torque” on the magnetization of the nanopillar. Researchers have now shown that by carefully controlling the temporal shape and length of the pulse — and by applying a small constant magnetic field — a nanopillar can be flipped in just 1 ns.
  [Biased Quasiballistic Spin Torque Magnetization Reversal, Phys. Rev. Lett. 101, 087201 (2008)]
  (August 26, 2008)

• Double bonding with silicon
  (Royal Society of Chemistry)

  
  Credit: Science

  Researchers have reported the first stable silicon (0) compound to contain a silicon-silicon double bond. The disilicon molecule (Si=Si) is far too reactive to exist in isolation. Disilenes (R₂Si=SiR₂) and disilynes do exist, but the cores in these compounds are no longer in the elemental, highly active, zero oxidation state; their silicon atoms have lost their lone pairs by combining with other molecular fragments. The researchers managed to synthesise a dark red crystal complex whose core effectively has the properties of a diatomic silicon unit. They stabilized the electron-deficient core with a bulky carbene - a coordinating ligand that the group has previously used to isolate diborene. The unusual molecule could kickstart the development of new reaction strategies using highly reactive silicon compounds.
  [A Stable Silicon(0) Compound with a Si=Si Double Bond, Science, Vol. 321. no. 5892, pp. 1069 - 1071, DOI: 10.1126/science.1160768]
  (August 26, 2008)

• Exotic oscillating reaction moves matter
  (Chemical & Engineering News)

  
  Credit: Shingo Maeda, Waseda University

  The oscillating Belousov-Zhabotinsky (BZ) reaction, well-known for producing dazzling color-changing patterns, is now also finding use as a novel way to move matter. Researchers have designed a polymer gel that undulates with a peristaltic motion similar to the way cilia or intestinal muscles pulse with rhythmical, directional contractions. As the gel undergoes the BZ reaction, a ruthenium catalyst periodically changes its oxidation state back and forth, generating chemical waves that propagate outward, causing the gel to shrink and swell.
  [Peristaltic Motion of Polymer Gels, Angewandte Chemie International Edition, Volume 47 Issue 35, Pages 6690 - 6693]
  (August 25, 2008)

• Nanocapacitors increase memory storage
  (NanotechWeb)

  
  Credit: Nature Nanotechnology

  Ferroelectric materials are promising alternatives to magnetic and dielectric materials for non-volatile data storage. However, the problem is that ferroelectrics are easily damaged by conventional lithographic techniques. A different approach, called stencil patterning, that was recently reported could be a solution. The research team has used their stencilling method to create a high-density array of ferroelectric nanocapacitors with a density of 176 Gb/inch² – a record for this material. The technique does not damage the sensitive ferroelectric structures, unlike existing "top-down" lithography.
  [Nature Nanotechnology, to be published]
  (August 25, 2008)

• Air-purifying stained glass windows early use of nanotechnology
  (e! Science News)

  Stained glass windows that are painted with gold purify the air when they are lit up by sunlight, according to a new study. Numerous church windows across Europe were decorated with glass coloured in gold nanoparticles. Glaziers in medieval forges were thus early nanotechnologists who produced colors with gold nanoparticles of different sizes, suggest the researchers involved in the study. The tiny particles of gold, energized by the sun, are able to destroy air-borne pollutants like volatile organic chemicals which often come from new furniture, carpets and paint.
  (August 25, 2008)

• Investigation finds building fires caused collapse of World Trade Center building 7
  (NIST)

  
  Credit: NIST

  The fall of the 47-story World Trade Center building 7 (WTC 7) in New York City late in the afternoon of Sept. 11, 2001, was primarily due to fires, according to a new report following an extensive, three-year scientific and technical building and fire safety investigation. This was the first known instance of fire causing the total collapse of a tall building. "Heating of floor beams and girders caused a critical support column to fail, initiating a fire-induced progressive collapse that brought the building down." According to the report, a key factor leading to the eventual collapse of WTC 7 was thermal expansion of long-span floor systems at temperatures "hundreds of degrees below those typically considered in current practice for fire resistance ratings." The report included 13 recommendations for improving building and fire safety.
  [Link to Final Report on the Collapse of World Trade Center Building 7]
  (August 22, 2008)

• Gold's magic number for catalysis
  (Royal Society of Chemistry)

  
  Credit: Nature

  A new gold catalyst can catalyse hydrocarbon oxidation, using O₂ as the only oxidant. But catalyst particle size is critical - above 2nm diameter, the catalyst loses all activity. The researchers used styrene oxidation as a test reaction. The catalyst consists of 55-atom gold clusters, which form nanometre-sized particles on inert supports. The Au55 particles are so-called 'magic number' clusters that contain exactly the right number of atoms for very stable geometries, making them ideally suited to catalysis. However, the particle size of the catalyst is critical. While 1.4nm diameter particles were effective and robust catalysts, particles 2nm or larger have no catalytic activity.
  [Selective oxidation with dioxygen by gold nanoparticle catalysts derived from 55-atom clusters, Nature 454 , 981-983 (21 August 2008) | doi :10.1038/nature07194]
  (August 21, 2008)

• Creating an unconventional metal by doping a semiconductor
  (Eurekalert)

  
  Credit: UCL, London Centre for Nanotechnology

  Researchers report that they have combined silicon with iron with a small amount of manganese to create a new material which is neither a magnet nor an ordinary semiconductor. The new material exists in a quantum halfway house between magnet and semiconductor - in the same way that much more complex materials such as ceramics which exhibit high temperature superconductivity exist in quantum halfway houses between metals and magnetic insulators. The research is of fundamental importance because it demonstrates, for the first time, a simple recipe for reaching this halfway house, whilst also suggesting new mechanisms for controlling electrical currents and magnetism in semiconductor devices.
  [Doping a semiconductor to create an unconventional metal, Nature 454 , 976-980 (21 August 2008) | doi :10.1038/nature07137]
  (August 21, 2008)

• Light transmitted through opaque materials
  (Physorg.com)

  
  Credit: Mosk and Vellekoop. University of Twente

  Opaque materials scatter rather than absorb light. Theorists have predicted that no matter how disordered opaque scattering materials are, they still contain open channels that light could conceivably fit through. Researchers have now shown how to find these open channels, and how to control the shape of incoming light waves so that they can make their way through. Until now, manipulating the light so that the open channels could actually be found has been too complex. They focused a laser beam onto an opaque layer of white zinc oxide (a material used by painters such as Van Gogh). With a digital camera, they measured the light emerging from the other side, and used this information to control the shape of the incoming light wave with a computerized feedback loop. To change the light wave´s shape, the scientists slowed parts of the wave with a liquid crystal display. These delayed parts interfered with other parts of the same wave, and ultimately increased the amount of light reaching the camera by at least 44% compared with the initial unshaped wave.
  [Universal optimal transmission of light through disordered materials, arXiv:0804.2412v2]
  (August 20, 2008)

• Stable and highly pure helical peptide arrays created
  (Eurekalert)

  
  Credit: Julia Laskin, Pacific Northwest National Laboratory

  Scientists have succeeded in making a layer of tiny protein coils attached to a surface, much like miniature bedsprings in a frame. This thin film made of stable and very pure helices can help researchers develop molecular electronics or solar cells, or to divine the biology of proteins. They pulled off this design trick using a "soft-landing" technique that disperses the tiny protein coils onto a waiting surface. The small proteins called peptides are of a variety that normally take the shape of a coiled spring or helix in gas phase. The method used delivered ultra-pure helical peptides to the surface and trapped them there.
  [Helical Peptide Arrays on Self-Assembled Monolayer Surfaces through Soft and Reactive Landing of Mass-Selected Ions, Angewandte Chemie International Edition, Volume 47 Issue 35, Pages 6678 - 6680]
  (August 20, 2008)

• More efficient catalyst for making hydrogen from ethanol
  (Ohio State University)

  A new catalyst that makes hydrogen from ethanol with 90 percent yield, at a workable temperature, and using inexpensive ingredients has been reported. Conventionally, precious metals, such as platinum or rhodium are used as catalysts for this purpose. The new catalyst powder is made from tiny granules of cerium oxide -- a common ingredient in ceramics -- and calcium, covered with even smaller particles of cobalt. It produces hydrogen with 90 percent efficiency at 660 degrees Fahrenheit (around 350 degrees Celsius) -- a low temperature by industrial standards.
  (August 20, 2008)

• Nanowire sensors and electronics integrated on a chip
  (Technology Review)

  
  Credit: Ali Javey, Univ. California, Berkeley

  Nanowires make good sensors because their small dimensions enhance their sensitivity. Nanowire-based light sensors, for example, can detect just a few photons. But to be useful in practical devices, the sensors have to be integrated with electronics that can amplify and process such small signals. Researchers have now created the first integrated circuit that uses nanowires as both sensors and electronic components. With a simple printing technique, the group was able to fabricate large arrays of uniform circuits, which could serve as image sensors.
  (August 19, 2008)

• Al passivates sidewall oxide layers in magnetic nanoparticles
  (NanotechWeb)

  
  Credit: Intel

  The thermal stability of magnetic nanoparticles – crucial for making good spin-based data storage devices – can be improved by depositing a thin layer of aluminum onto the particles, according to a new report. Nanomagnetic particles develop an antiferromagnetic sidewall oxide layer during processing in oxygen. This layer has detrimental effects on the particles, including reduced thermal stability at room temperature and anomalously high magnetic damping at low temperatures. Damping is a key parameter in determining the magnetic reversal time in memory devices. The researchers say that one way to overcome this problem is to passivate the sidewall oxide layers by depositing a thin aluminum layer onto the nanoparticles. They do this using an ion-beam deposition technique at very low pressures, which allows a uniform coating to be applied. The technique results in almost full recovery of the expected intrinsic magnetic properties of the material, together with a 100% improvement in the thermal stability of the nanoparticles and decreased magnetic damping.
  [Nature Materials, to be published]
  (August 19, 2008)

• Virus helps to build micro-battery
  (Nature News)

  
  Credit: Nam et al., PNAS

  Scientists have designed a quick method to build a microbattery that relies on a genetically-engineered virus called M13. They first made a template from polydimethylsiloxane (PDMS). After coating it with alternating layers of positive and negative electrolytes, they added the virus. The virus was designed to have negatively charged amino acids at its surface, so that it stuck to the template, and an affinity for cobalt — a favoured material for batteries. Each virus is a semi-rigid fiber a few nanometres in diameter and about a micrometer long, which tends to pack tightly into a whorl that looks similar to a fingerprint. The whole assembly was dipped into a solution of cobalt ions, which coated the viruses to create a very large surface area that could store charge. Stamping the template onto a platinum layer and peeling off the PDMS left behind an array of small dots of the prepared material, cobalt-side down, which formed the heart of an effective battery.
  [Proc. Natl. Acad. Sci. USA (2008) advance online publication, doi:10.1073/pnas.0711620105]
  (August 19, 2008)

• Two new metamaterials bend light backwards
  (Science News)

  
  Credit: Valentine et al./Nature

  Two new metamaterials that bend light backward have been reported, suggesting the possibility of invisibility cloaks, which has been widely reported in the general press. In the first report, the authors describe a film made of about 20 alternating layers, each just tens of nanometers thick, of silver and magnesium fluoride. Holes about 800 nanometers apart penetrate all the layers, creating a fishnet appearance. As light rays fall on the material, the light’s electric fields induce a small displacement in the electrons of both types of layers. The electrons’ displacement itself produces electric fields, which add up to those of light and help turn the waves at an opposite angle. In the second study, researchers created a new kind of material by embedding 60-nanometer-thick silver wires in an aluminum-oxide sheet just one-hundredth of a millimeter thick. The wires were all aligned with one another and cut through the sheet at a perpendicular angle. Light displaces electrons in the silver nanowires and bends backward, while the aluminum oxide keeps the material transparent — to a degree. The 10-micrometer-thick sheets still appear almost black to the eye, and the material does work for visible light. However, neither material is yet ready for full-fledged cloaking status.
  [Three-dimensional optical metamaterial with a negative refractive index, Nature advance online publication 11 August 2008 | doi:10.1038/nature07247; Optical Negative Refraction in Bulk Metamaterials of Nanowires, Science 15 August 2008:
  Vol. 321. no. 5891, p. 930, DOI: 10.1126/science.1157566]
  (August 18, 2008)

• Observing optically induced transient structures in graphite
  (Physical Review Focus)

  There is currently no way to convert the graphite form of carbon to the diamond structure in thin films. However, if a focused laser beam could do such a conversion, it could "write" a nanoscale electronic circuit in a thin graphite layer, exploiting the strength and insulating properties of diamond in some areas and the semiconductive nature of graphite in other areas. A research team has taken a step toward this by showing a specific structural change in graphite resulting from laser light. The team illuminated a graphite target with 45-femtosecond pulses from a near-infrared laser. Synchronized with the light pulses were short bursts of an electron beam that allowed the team to probe the carbon atoms' positions using electron diffraction. Within 14 picoseconds following the laser pulse, many atoms were observed to form inter-layer bonds similar in some ways to those in diamond. 30 picoseconds later, these bonds had disappeared.
  [Direct Observation of Optically Induced Transient Structures in Graphite Using Ultrafast Electron Crystallography, Phys. Rev. Lett. 101, 077401 (2008)]
  (August 18, 2008)

• Beijing Olympic logo mass-produced on the micro-scale
  (Northwestern University)

  
  Credit: Chad Mirkin, Northwestern Univ.

  The 2008 Summer Olympics logo has been mass-produced and printed 15,000 times covering only one square centimeter of total space. Researchers printed the logos as well as an integrated gold circuit using a new printing technique called Polymer Pen Lithography (PPL) that can write on three different length scales using only one device. Polymer Pen Lithography uses arrays of tiny pens made of polymers to print over large areas with nanoscopic through macroscopic resolution. By simply changing contact pressure (and the amount the pens deform), as well as the time of delivery, dots of various diameters can be produced. In the case of the Olympic logo, the researchers started with a bitmap image of the logo and uniformly printed 15,000 replicas onto a gold substrate using an “ink” of the molecule 16-mercaptohexadecanoic acid. The ink is a mere one molecule thick.
  [Polymer Pen Lithography, Science, Published Online August 14, 2008 DOI: 10.1126/science.1162193 ]
  (August 15, 2008)

• Added nanotubes yield stretchy, high-quality elastic conductors
  (Technology Review)

  
  Credit: Science/AAAS

  By adding carbon nanotubes to a stretchy polymer, researchers have made a conductive material that they used to connect organic transistors in a stretchable electronic circuit. The measured conductivity records the world's highest value among soft materials, according to the authors. They report a conductivity of 57 siemens per centimeter, which is lower than that of copper, but two orders of magnitude higher than that of previously reported polymer-carbon-nanotube composites. The material is able to stretch up to about 134 percent of its original shape without significant damage.
  [A Rubberlike Stretchable Active Matrix Using Elastic Conductors, Science, Published Online August 7, 2008, DOI: 10.1126/science.1160309]
  (August 15, 2008)

• Novel self-assembly method could break size barrier
  (MIT)

  Using a novel system based on block copolymers that can assemble themselves into precise patterns, researchers have come up with a way of beating size limitations that would otherwise crimp improvements in data-storage media and electronic microchips. Such self-assembling block copolymers have been known for many years, but the problem was that the regular patterns they produced were well-ordered only over very small areas. The researchers found a way to combine this self-assembly with conventional lithographic chip-making technology, so that the lithographic patterns provide a set of "anchors" to hold the structure in place, while the self-assembling molecules fill in the fine detail between the anchors.
  [Graphoepitaxy of Self-Assembled Block Copolymers on Two-Dimensional Periodic Patterned Templates, Science 15 August 2008: Vol. 321. no. 5891, pp. 939 - 943, DOI: 10.1126/science.1159352]
  (August 15, 2008)

• Former MRS President Harry John Leamy III Passes Away
  Leamy (67) was President of MRS in 1983.
  (August 5, 2008)