Articles in 2012

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  • The interaction between spins in magnetic materials gives rise to a number of interesting effects. An example is the discovery of an unusual magnetic state based on a long-range ordering force between magnetic domain walls that is analogous to the interaction between protons and neutrons in atomic nuclei.

    • Sergey Artyukhin
    • Maxim Mostovoy
    • Dimitri N. Argyriou
    Article
  • The spatial organization of porous coordination-polymer crystals into higher-order structures is critical for their integration in heterogeneous catalysts, separation systems and electrochemical devices. A method for spatially controlling the nucleation site leading to the formation of mesoscopic architecture in porous coordination polymers, in both two and three dimensions, is now demonstrated.

    • Julien Reboul
    • Shuhei Furukawa
    • Susumu Kitagawa
    Article
  • Elemental barium at high pressure presents many complex crystal structures that have yet to be determined. The most complex of these crystal structures (phase Ba-IVc at 19 GPa) has now been solved and consists of a commensurate host–guest structure with 768 atoms in the basic unit, where the relative alignment of the guest-atom chains can be represented as a two-dimensional pattern with repeating interlocking motifs.

    • I. Loa
    • R. J. Nelmes
    • M. I. McMahon
    Article
  • The selective capture of carbon dioxide in porous materials has potential for the storage and purification of fuel gases, but strategies to enhance carbon dioxide–host selectivity are required. A partially interpenetrated metal–organic framework that undergoes dramatic phase transition on desolvation and exhibits temperature-dependent selective hysteretic sorption of carbon dioxide is now reported.

    • Sihai Yang
    • Xiang Lin
    • Martin Schröder
    Article
  • Magnetic cooling could be a radically different energy solution that could replace conventional vapour compression refrigeration in the future. It is now shown that a Heusler-type magnetocaloric alloy exhibits a remarkable cooling capability due to the effect of a sharp structural transformation at a specific temperature. The finding may be of relevance beyond Heusler alloys and represents an important step towards the implementation of cooling systems based on magnetocaloric materials.

    • Jian Liu
    • Tino Gottschall
    • Oliver Gutfleisch
    Article
  • The spreading and differentiation of stem cells is influenced by the mechanical properties—in particular by the stiffness—of the extracellular matrix. Now, experiments on epidermal stem cells cultured on substrates with a covalently attached collagen coating show that stem cells sense the stiffness of the substrate through the anchoring density of collagen fibres.

    • Britta Trappmann
    • Julien E. Gautrot
    • Wilhelm T. S. Huck
    Article
  • Developing capture materials and processes that reduce the energy required to separate carbon dioxide from flue gas in power plants is an important area of research. A computational approach to rank adsorbents for their performance in carbon dioxide capture and storage is now proposed, which will enable hundreds of thousands of zeolitic structures to be screened.

    • Li-Chiang Lin
    • Adam H. Berger
    • Berend Smit
    Article
  • Most materials expand along the direction of an external pulling force, but there are no materials that compress instead. The proposal of mechanical metamaterials that show such negative compressibility promises new artificial materials with designed functionalities.

    • Zachary G. Nicolaou
    • Adilson E. Motter
    Article
  • Topological insulators exhibit intriguing electronic properties that originate from protected metallic states on their surface. Experimental studies so far are based on a limited number of materials. A high-throughput approach now shows how to search for topological insulators in a variety of unexplored classes of materials.

    • Kesong Yang
    • Wahyu Setyawan
    • Stefano Curtarolo
    Article
  • Graphene oxide could potentially be used for numerous applications, particularly in electronics. Understanding its structural stability in an ambient atmosphere is essential for the realization of devices. A new study shows that multilayer graphene oxide is in fact metastable at room temperature.

    • Suenne Kim
    • Si Zhou
    • Elisa Riedo
    Article
  • Efficient electrochemical transformation of water to molecular hydrogen and of hydroxyl ions to oxygen in alkaline environments is important for reducing energy losses in water–alkali electrolysers. Insight into the activities of hydr(oxy)oxides on platinum catalyst surfaces for hydrogen and oxygen evolution reactions should prove significant for designing practical alkaline electrocatalysts.

    • Ram Subbaraman
    • Dusan Tripkovic
    • Nenad M. Markovic
    Article
  • Studying electrochemical equilibria at interfaces on the atomic scale is crucial for understanding physicochemical processes, but such investigations are currently limited by phase instabilities and instrumentation. A small amount of electron donors in a solid electrolyte is now shown to enable scanning tunnelling microscope measurements and atomically resolved imaging.

    • Ilia Valov
    • Ina Sapezanskaia
    • Rainer Waser
    Article
  • Magnetoelectric composite materials are of interest for sensitive magnetic-field sensors. The realization of a magnetoelectric composite that does not require an applied external magnetic field, but instead relies on internal bias via exchange coupling, promises sensitive sensors even for small magnetic fields.

    • Enno Lage
    • Christine Kirchhof
    • Dirk Meyners
    Article
  • Molecular orientation, which critically influences the properties of organic materials, could until now only be characterized if the sample exhibited sufficient crystallinity. Resonant scattering of polarized soft X-rays by aromatic carbon bonds has now been used to probe non-crystalline ordering and molecular orientation in thin films with a resolution down to 20 nm.

    • B. A. Collins
    • J. E. Cochran
    • H. Ade
    Article
  • Coherent diffractive imaging is a powerful numerical technique that can reconstruct and enhance images. The demonstration of this technique with subwavelength resolution now exhibits the possibility of new applications such as single-shot imaging of ultrafast events with ultrahigh resolution.

    • A. Szameit
    • Y. Shechtman
    • M. Segev
    Article
  • Metamaterials have enabled many different photonic technologies. Now, the realization of holographic information storage promises new types of applications, in particular when combined with other metamaterials functionality.

    • Stéphane Larouche
    • Yu-Ju Tsai
    • David R. Smith
    Article
  • The headgroup of phospholipids in eukaryotic cell membranes contains phosphatidyl choline (PC). Now, branched polyglycerols decorated with the 'PC-inverse' choline phosphate (CP) are shown to behave as 'universal' biomembrane adhesives, binding electrostatically to cell membranes and to PC-containing liposomes. Binding can be reversed by exposure to PC-containing polymers. These adhesives may find use as tissue sealants and as drug-delivery vehicles.

    • Xifei Yu
    • Zonghua Liu
    • Donald E. Brooks
    Article
  • Although materials used in electrochemical devices for energy applications would benefit from the precise structural control that can be achieved by using silica sol–gel chemistry, such synthetic approaches typically result in insulating porous materials. Now, a simple approach based on a multifunctional sol–gel precursor allows the synthesis of porous nanocomposites with metallic percolation networks exhibiting high electrical conductivity.

    • Scott C. Warren
    • Matthew R. Perkins
    • Ulrich Wiesner
    Article
  • The plausible existence of a liquid–liquid transition (LLT) pre-empted by crystallization in supercooled water has long been debated. So far, indications of such a ‘hidden’ LLT have been found in nanoconfined water and in the amorphous polymorphism of ice. Now, the finding of an isocompositional LLT in a water–glycerol mixture where glycerol prevents water crystallization suggests a new link to an elusive LLT in pure water.

    • Ken-ichiro Murata
    • Hajime Tanaka
    Article
  • Although (Ga,Mn)As is considered the model ferromagnetic semiconductor, the electronic structure of the charges — holes in this case — and its connection with the Curie temperature (TC) are still unclear. Experiments now provide a direct link between TC and the existence of an impurity band for the holes. Clarifying this issue is essential to designing other materials with potentially higher TC.

    • M. Dobrowolska
    • K. Tivakornsasithorn
    • W. Walukiewicz
    Article