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Not a subscriber? Join now.February 10, 2011

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Something for the Alchemist to get his teeth into this week with chiton dental work offering new insights for biomimetic materials. Also, this week a sight unseen with calcite crystals revealing little but their invisibility prowess. Breath tests based on determination of acetone could be useful in sports science and training as well as diabetes monitoring. There's also a pleasant surprise for chocoholics regarding the putative health benefits of their indulgence while materials other than graphene can be made in single-atom thin layers for potential electronic and thermal applications. Finally, the National Science Foundation has given a grant to scientists in California to make the most of their sunshine.

Researchers at Northwestern University have used atom-probe tomography (APT) to take a bite out of the hybrid, organic-inorganic dental structure of the chiton mollusc, Chaetopleura apiculata, which is renowned for its ability to scrape algae from rock. The organism's teeth are outstandingly wear resistant and resilient to fracture. APT quantitatively revealed that the organic fibers, each, also contain either sodium or magnesium ions. However, the APT showed that the fibers were surprisingly heterogeneous, having a previously unsuspected structural hierarchy. This detailed view made possible with APT suggests a possible growth mechanism in which the organism modulates the final chemistry on the nano level.

Specially fabricated calcite crystals are all that is needed to make a so-called "invisibility cloak", a material that renders an otherwise opaque object transparent to visible light. Teams in the UK and in the US and Singapore both recently published details of how calcite can manipulate the path of coherent laser light so that objects beneath the crystals are hidden from view. The US team's approach works under water and can hide an object and big and solid as a paperclip with single-color laser light. The UK researchers avoid the need to submerge their system in water and have also achieved cloaking with incoherent white light rather than lasers. Both approaches side step the composite meta materials used in earlier work that made objects invisible only in wavelengths beyond the visible spectrum.

Breath test diagnostics have been in development for many years, but a recent breakthrough could make the technique much more viable for clinical practice. According to researchers in the UK, trace analytes can be detected in the breath using near infrared Fourier transform broadband cavity enhanced absorption spectroscopy. This could open up a whole new area of medical diagnostics and health research. The team has obtained absorption measurements for various compounds, including isoprene, butadiene, acetone and methane found in simulated breath samples. The detection of acetone could be useful in monitoring the effects of fitness training as well as offering an early diagnostic for diabetes and a non-invasive method of monitoring blood glucose levels.

Another excuse for chocoholics to indulge in their favorite delicacy is the discovery that chocolate contains more polyphenols and flavanols than fruit juice, apparently. Researchers at the Hershey Center for Health & Nutrition in Pennsylvania claim that seeds of the plant Theobroma cacao from which cocoa powder is made deserve "super fruit" status alongside blueberries and other more recognizable fruits. The researchers analyzed various dried powders from a range of seeds and found cocoa powder and chocolate to be higher in the commonly assayed antioxidants used to label other more obviously fruity products their "super" status.

Researchers have found a way to split layered materials into sheets just a single atom thick, the technique could lead to a novel way to make graphene and related materials for future electronic and energy storage technologies. Boron nitride, molybdenum disulfide and bismuth telluride are all amenable to the approach and all have intriguing electronic and physical properties. The materials could be made into devices that generate electricity from waste heat lost from power plants, which lose between 50 and 70 percent of the energy they produce in waste heat. Efficient thermoelectric devices would allow waste heat to be recycled efficiently.

An award of $1.5 million over three years from the National Science Foundation could help an interdisciplinary team from UC Davis and UC Santa Cruz exploit nanoparticles of germanium, silicon and other materials to develop photovoltaic solar cells that are far more efficient than current devices. Conventional solar cells all operate on the same principle of "one photon in, one electron out", which theoretically caps efficiency a little over 30%. But, by constructing solar cells from nanoparticles, the UC researchers hope generate several electrons for each incident photon and so raise maximum efficiency to between 42 and 65 percent. The interdisciplinary nature of the team was crucial to getting the proposal funded as NSF asked for a collaborative effort between materials sciences, chemistry and mathematical sciences.