Nature Materials 8, 1 (2009). doi:10.1038/nmat2352

The financial crisis teaches us about the consequences of ignoring risks. We cannot afford to repeat the same mistakes for the continuing crises in energy and climate.

Nature Materials 8, 3 (2009). doi:10.1038/nmat2351

Joseph Michels, a managing director at One Equity Partners, talks to Nature Materials about making private equity investments in high-tech companies in times of recession.

Nature Materials 8, 7 (2009). doi:10.1038/nmat2350

Authors: Alejandro L. Briseno & Peidong Yang

Using self-assembly and electrodeposition, complementary organic and inorganic building blocks are combined to form a lamellar hybrid that is an efficient photoconductor.

Nature Materials 8, 11 (2009). doi:10.1038/nmat2347

Authors: Yen Cu & W. Mark Saltzman

Mucus presents a formidable barrier to nanoparticle drug-delivery systems, but adding a coating of polymer molecules helps them sneak through the net.

Nature Materials 8, 9 (2009). doi:10.1038/nmat2348

Authors: Stephen Ducharme & Alexei Gruverman

A simple nanoimprinting method creates arrays of ferroelectric polymer structures suitable for low-cost, non-volatile memories.

Nature Materials 8, 8 (2009). doi:10.1038/nmat2349

Author: Jacek Kossut

In semiconductor quantum dots, the electronic wave functions are squeezed into small areas. Stretching them in a controllable yet simple way profoundly affects their properties and can give them characteristics important for practical applications.

Nature Materials 8, 47 (2009). doi:10.1038/nmat2335

Authors: J. Biener, A. Wittstock, L. A. Zepeda-Ruiz, M. M. Biener, V. Zielasek, D. Kramer, R. N. Viswanath, J. Weissmüller, M. Bäumer & A. V. Hamza

Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first. Here, we demonstrate that surface-chemistry-driven actuation can be realized in high-surface-area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes of the order of a few tenths of a per cent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress, and can be used to convert chemical energy directly into a mechanical response, thus opening the door to surface-chemistry-driven actuator and sensor technologies.

Nature Materials 8, 35 (2009). doi:10.1038/nmat2342

Authors: David A. Bussian, Scott A. Crooker, Ming Yin, Marcin Brynda, Alexander L. Efros & Victor I. Klimov

Magnetic doping of semiconductor nanostructures is actively pursued for applications in magnetic memory and spin-based electronics. Central to these efforts is a drive to control the interaction strength between carriers (electrons and holes) and the embedded magnetic atoms. In this respect, colloidal nanocrystal heterostructures provide great flexibility through growth-controlled ‘engineering’ of electron and hole wavefunctions in individual nanocrystals. Here, we demonstrate a widely tunable magnetic sp–d exchange interaction between electron–hole excitations (excitons) and paramagnetic manganese ions using ‘inverted’ core–shell nanocrystals composed of Mn2+-doped ZnSe cores overcoated with undoped shells of narrower-gap CdSe. Magnetic circular dichroism studies reveal giant Zeeman spin splittings of the band-edge exciton that, surprisingly, are tunable in both magnitude and sign. Effective exciton g-factors are controllably tuned from −200 to +30 solely by increasing the CdSe shell thickness, demonstrating that strong quantum confinement and wavefunction engineering in heterostructured nanocrystal materials can be used to manipulate carrier–Mn2+ wavefunction overlap and the sp–d exchange parameters themselves.

Nature Materials 8, 52 (2009). doi:10.1038/nmat2338

Authors: Anthony J. Kim, Raynaldo Scarlett, Paul L. Biancaniello, Talid Sinno & John C. Crocker

DNA is the premier material for directing nanoscale self-assembly, having been used to produce many complex forms. Recently, DNA has been used to direct colloids and nanoparticles into novel crystalline structures, providing a potential route to fabricating meta-materials with unique optical properties. Although theory has sought the crystal phases that minimize total free energy, kinetic barriers remain essentially unstudied. Here we study interfacial equilibration in a DNA-directed microsphere self-assembly system and carry out corresponding detailed simulations. We introduce a single-nucleotide difference in the DNA strands on two mixed microsphere species, which generates a free-energy penalty for inserting ‘impurity’ spheres into a ‘host’ sphere crystal, resulting in a reproducible segregation coefficient. Comparison with simulation reveals that, under our experimental conditions, particles can equilibrate only with a few nearest neighbours before burial by the growth front, posing a potential impediment to the growth of complex structures.

Nature Materials 8, 30 (2009). doi:10.1038/nmat2340

Authors: D. Ma, A. D. Stoica & X.-L. Wang

The atomic structure of metallic glasses has been a long-standing scientific problem. Unlike crystalline metals, where long-range ordering is established by periodic stacking of fundamental building blocks known as unit cells, a metallic glass has no long-range translational or orientational order, although some degrees of short- and medium-range order do exist. Previous studies have identified solute- (minority atom)-centred clusters as the fundamental building blocks or short-range order in metallic glasses. Idealized cluster packing schemes, such as efficient cluster packing on a cubic lattice and icosahedral packing as in a quasicrystal, have been proposed and provided first insights on the medium-range order in metallic glasses. However, these packing schemes break down beyond a length scale of a few clusters. Here, on the basis of neutron and X-ray diffraction experiments, we propose a new packing scheme—self-similar packing of atomic clusters. We show that the medium-range order has the characteristics of a fractal network with a dimension of 2.31, and is described by a power-law correlation function over the medium-range length scale. Our finding provides a new perspective of order in disordered materials and has broad implications for understanding their structure–property relationship, particularly those involving a change in length scales.

Nature Materials 8, 25 (2009). doi:10.1038/nmat2343

Authors: T. Tallinen, J. A. Åström & J. Timonen

Crumpling a thin sheet of material into a small volume requires energy for creating a network of deformations such as vertices and ridges. Scaling properties of a single elastic vertex or ridge have been analysed theoretically, and crumpling of a sheet by numerical simulations. Real materials are however elasto-plastic and large local strains induce irreversible plastic deformations. Hence, a numerical model that can be purely elastic or elasto-plastic is introduced. In crumpled elastic sheets, the ridge patterns are found to be similar, independent of the width to thickness (L/h) ratio of the sheet, and the fractal dimension of crumpled sheets is given by scaling properties of the energy and average length of ridges. In crumpled elasto-plastic sheets, such a similarity does not appear as the L/h ratio affects the deformations, and the fractal dimension (Dpl) is thereby reduced. Evidence is also found of Dpl not being universal but dependent on the plastic yield point of the material.

Nature Materials 8, 41 (2009). doi:10.1038/nmat2332

Authors: Nunzio Tuccitto, Violetta Ferri, Marco Cavazzini, Silvio Quici, Genady Zhavnerko, Antonino Licciardello & Maria Anita Rampi

One of the main goals of molecular electronics is to achieve electronic functions from devices consisting of tailored organic molecules connecting two metal electrodes. The fabrication of nanometre-scale spaced electrodes still results in expensive, and often scarcely reproducible, devices. On the other hand, the ‘conductance’ of long organic molecules—generally dominated by the tunnelling mechanism—is very poor. Here, we show that by incorporating a large number of metal centres into rigid molecular backbones we can obtain very long (up to 40 nm) and highly ‘conductive’ molecular wires. The metal-centre molecular wires are assembled in situ on metal surfaces via a sequential stepwise coordination of metal ions by terpyridine-based ligands. They form highly ordered molecular films of elevated mechanical robustness. The electrical properties, characterized by a junction based on Hg electrodes, indicate that the ‘conductance’ of these metal-centre molecular wires does not decrease significantly even for very long molecular wires, and depends on the nature of the incorporated redox centre. The outstanding electrical and mechanical characteristics of these easy-to-assemble molecular systems open the door to a new generation of molecular wires, able to bridge large-gap electrodes, and to form robust films for organic electronics.

Nature Materials 8, 62 (2009). doi:10.1038/nmat2339

Authors: Zhijun Hu, Mingwen Tian, Bernard Nysten & Alain M. Jonas

Nature Materials 8, 56 (2009). doi:10.1038/nmat2341

Authors: Georg M. Müller, Jakob Walowski, Marija Djordjevic, Gou-Xing Miao, Arunava Gupta, Ana V. Ramos, Kai Gehrke, Vasily Moshnyaga, Konrad Samwer, Jan Schmalhorst, Andy Thomas, Andreas Hütten, Günter Reiss, Jagadeesh S. Moodera & Markus Münzenberg

Nature Materials 8, 68 (2009). doi:10.1038/nmat2336

Authors: Marina Sofos, Joshua Goldberger, David A. Stone, Jonathan E. Allen, Qing Ma, David J. Herman, Wei-Wen Tsai, Lincoln J. Lauhon & Samuel I. Stupp

Nature Materials 8, 76 (2009). doi:10.1038/nmat2317

Authors: Xinchen Wang, Kazuhiko Maeda, Arne Thomas, Kazuhiro Takanabe, Gang Xin, Johan M. Carlsson, Kazunari Domen & Markus Antonietti