Molecular trick alters rules of attraction for non-magnetic metals

In a study led by the University of Leeds and published in the journal ("Beating the Stoner criterion using molecular interfaces"), researchers detail a way of altering the quantum interactions of matter in order to "fiddle the numbers" in a mathematical equation that determines whether elements are magnetic, called the Stoner Criterion. Co-lead author Fatma Al Ma'Mari, from the School of Physics & Astronomy at the University of Leeds, said: "Being able to generate magnetism in materials that are not naturally magnetic opens new paths to devices that use abundant and hazardless elements, such as carbon and copper." Magnets are used in many industrial and technological applications, including power generation in wind turbines, memory storage in hard disks and in medical imaging. "Future technologies, such as quantum computers, will require a new breed of magnets with additional properties to increase storage and processing capabilities. Our research is a step towards creating such 'magnetic metamaterials' that can fulfil this need," said Al Ma'Mari. Yet, despite their widespread use, at room temperature only three elements are ferromagnetic -- meaning they have high susceptibility to becoming and remaining magnetic in the absence of a field, as opposed to paramagnetic substances, which are only weakly attracted to the poles of a magnet and do not retain any magnetism on their own. These ferromagnetic elements are the metals iron, cobalt and nickel. Copper buckyballs. (Image: University of Leeds) Co-lead author Tim Moorsom, also from the University's School of Physics & Astronomy, said: "Having such a small variety of magnetic materials limits our ability to tailor magnetic systems to the needs of applications without using very rare or toxic materials. Having to build devices with only the three magnetic metals naturally available to us is rather like trying to build a skyscraper using only wrought iron. Why not add a little carbon and make steel?" The condition that determines whether a substance is ferromagnetic is called the Stoner Criterion. It explains why iron is ferromagnetic while manganese is not, even though the elements are found side-by-side in the periodic table. The Stoner Criterion was formulated by Professor Edmund Clifton Stoner, a theoretical physicist who worked at the University of Leeds from the 1930s until the 60s. At its heart, it analyses the distribution of electrons in an atom and the strength of the interaction between them. It states that for an element to be ferromagnetic, when you multiply the number of different states that electrons are allowed to occupy in orbitals around the nucleus of an atom -- called the Density of States (DOS) -- by something called the 'exchange interaction', the result must be greater than one. The exchange interaction refers to the magnetic interaction between electrons within an atom, which is determined by the orientation of each electron's magnetic 'spin' -- a quantum mechanical property to describe the intrinsic angular momentum carried by elementary particles, with only two options, either 'up' or 'down'. In the new study, the researchers have shown how to change the exchange interaction and DOS in non-magnetic materials by removing some electrons using an interface coated with a thin layer of the carbon molecule C60, which is also called a 'buckyball'. The movement of electrons between the metal and the molecules allows the non-magnetic material to overcome the Stoner Criterion. Dr Oscar Cespedes, principal investigator of the project, also from the University's School of Physics & Astronomy, said: "We and other researchers had noticed that creating a molecular interface changed how magnets behave. For us, the next step was to test if molecules could also be used to bring magnetic ordering into non-magnetic metals." The researchers say that the study has successfully demonstrated the technique, but that further work is needed to make these synthetic magnets stronger. "Currently, you wouldn't be able to stick one of these magnets to your fridge. But we are confident that applying the technique to the right combination of elements will yield a new form of designer magnets for current and future technologies," said Dr Cespedes.

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Researchers identify movement of droplets on soft surfaces

Researchers from the University of Twente have succeeded in clearly identifying why droplets on soft, squishy surfaces react differently than on hard surfaces. A water droplet, for example, moves very differently over jelly than over glass, but the science of how this works has never been investigated. Better understanding of this phenomenon is of importance for a variety of applications where droplets come into contact with extremely soft, deformable materials, as is the case in 3D printing, soft contact lenses or sauces such as mayonnaise. The result was published in the renowned scientific journal ("Droplets move over viscoelastic substrates by surfing a ridge"). Due to the surface tension in the liquid, minuscule 'ridges' arise at the edge of the droplet on the soft, jellylike surface. "That little ridge is always there, even if the droplet is motionless", explains UT researcher Stefan Karpitschka. "Surface tension is a force in the liquid surface, which makes droplets and bubbles spherical. This force is also the reason why insects are able to walk on a water surface. Normally the force of the surface tension is much too weak to deform the areas under the droplet. However, for very soft materials, this effect is suddenly very important, especially for the sliding movement of the droplets. This is because the friction caused by the movement of the little ridge in the gel is much larger than the internal friction in the liquid."

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3D printing, contact lenses and mayonnaise The most important application for this fundamental research lies in the field of inkjet printing. In this case molten materials are printed in the form of droplets, which then harden into 2D images or 3D structures. Current research shows how the molten droplets can distort the partially solidified materials and how this affects the droplet motion. Other applications where materials are deformed under the influence of surface tension are, for example, contact lenses, mayonnaise, and the manufacture of nano-structures on microchips.

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FDA issues guidance on the use of nanomaterials in food for animals

The U.S. Food and Drug Administration has issued a final guidance for industry, 'Use of Nanomaterials in Food for Animals' (pdf), which is intended to assist industry and other stakeholders in identifying potential issues related to safety or regulatory status of food for animals containing nanomaterials or otherwise involving the application of nanotechnology. This guidance is applicable to food ingredients intended for use in animal food which (1) consist entirely of nanomaterials, (2) contain nanomaterials as a component or (3) otherwise involve the application of nanotechnology. This final guidance addresses the legal framework for adding nanomaterial substances to food for animals and includes recommendations for submitting a Food Additive Petition (FAP) for a nanomaterial animal food ingredient. This guidance also recommends manufacturers consult with FDA early in the development of their nanomaterial animal food ingredient and before submitting an FAP. At this time, we are not aware of any animal food ingredient engineered on the nanometer scale for which there is generally available safety data sufficient to serve as the foundation for a determination that the use of such an animal food ingredient is generally recognized as safe (GRAS). Nanotechnology is an emerging technology that allows scientists to create, explore, and manipulate materials on a scale measured in nanometers – particles so small that they cannot be seen with a regular microscope. These particles can have chemical, physical, and biological properties that differ from those of their larger counterparts, and nanotechnology has a broad range of potential applications. Guidance documents represent the FDA’s current thinking on particular topics, policies, and regulatory issues. While “guidance for industry” documents are prepared primarily for industry, they also are used by FDA staff and other stakeholders to understand the agency’s interpretation of laws and policies. Although this guidance has been finalized, you can submit comments at any time. To submit comments to the docket by mail, use the following address. Be sure to include docket number FDA-2013-D-1009 on each page of your written comments.

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New benchmarks for molecular spectroscopy

Researchers at Tsinghua University in Beijing have recently used a technique called zero-kinetic energy photoelectron spectroscopy to obtain a list in unprecedented detail of the quantum energy levels of the cyanoacetylene cation, a linear, five-atom molecule that exhibits nuclear and electronic coupling effects and is found in interstellar clouds and in the atmosphere of Saturn's largest moon Titan. When describing molecular motion, scientists generally assume that vibrational motion in the nucleus doesn't have an effect on an atom's electronic states due to the significant size disparity between electrons and particles in the nucleus -- this is known as the Born-Oppenheimer approximation, and is a cornerstone of chemical physics. However, the approximation isn't sufficient to describe the changes in energetic states for a number of photo-induced processes involving cyanoacetylene. By interrogating the energy structures of cyanoacetylene and a number of similar organic molecules, the Chinese researchers aim to contribute to a better understanding of these processes. The spectrum with theoretical assignments shows the vibrational energy levels of HCCCN+, which is the first reported one for linear five-atomic molecule. (Image: YMO/Tsinghua). (click on image to enlarge) "[It] is an ideal tool to study the energy structure of the cation," said Yuxiang Mo, a physics professor at Tsinghua University in Beijing, and primary investigator on the project. "At the present, there is no other experimental tool that can accomplish this task." His group's paper appears this week in , from AIP Publishing ("The Renner-Teller effect in HCCCN+(X2π) studied by zero-kinetic energy photoelectron spectroscopy and theoretical calculations"). Exceptions to the Born-Oppenheimer approximation occur in linear, symmetric molecules with degenerate electronic states, such as cyanoacetylene (one hydrogen, one nitrogen, and three carbon atoms). Here, the nuclear and electronic motions are vibronically coupled, meaning a change in one will affect the other. This is known as the Renner-Teller effect. In their setup, the researchers used a tunable, nanosecond, pulsed vacuum ultraviolet laser to pump the sample cyanoacetylene molecules to highly electronically excited Rydberg states. The ions were consequently ionized by a very small, pulsed electric field, allowing them to be detected. The vacuum ultraviolet laser consisted of two laser beams focused on to a pulsed jet of xenon gas, a technique also known as the four-wave mixing method. By scanning the frequency of the vacuum ultraviolet laser -- standard spectroscopic practice -- they then obtained the energy levels of the ions. This technique, known as zero-kinetic energy photoelectron, or ZEKE, spectroscopy, is well suited for measuring vibrational energy of cations. It has given the researchers a full, high-resolution readout of the energy levels for cations from their vibrational ground state to excited states several thousand wavenumbers, or magnitudes of frequency, higher, furthering their understanding of the coupled vibrations in the Renner-Teller effect. The researchers found the ions' energy levels to be in good agreement with the theoretical vibronic energy levels of the cyanoacetylene cation they obtained from a diabatic model, which are used to describe the electron and nuclear coupling effects in a quantum system. They also obtained a list of spin-vibronic energy levels for fluoromethane, chloromethane, and monochloroacetylene cations, which are highly symmetric or linear molecules that also have strong electron and nuclear coupling effects. "From these results, it seems that now we understand the main physics of the vibronic coupling for these benchmark molecules," Mo said. Future work for Mo and his colleagues includes measuring the vibronic energy levels in more general situations, such as the accidental crossing of electronic potential energy surfaces.

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