Articles in 2009

Coherent X-ray diffraction spectroscopy has recently emerged as a powerful tool for imaging strain at the nanoscale. Developments in both fabrication and experimental techniques have now enabled all nine components of the strain tensor in a nanorod to be determined, demonstrating the ability of coherent X-ray diffraction spectroscopy to yield measurements of strain in three dimensions with a resolution of a few tens of nanometres.

One of the more promising uses of metamaterials is in imaging, where the capability to control the propagation of light could lead to new applications. In particular, the realization of a broadband metamaterial lens that has an almost complete hemispherical field of view that is focused on a flat plane represents a significant step towards such new uses.

Surfaces with physicochemical properties that can be modulated using external stimuli offer great promise for designing responsive or adaptive materials. Now, biocompatible dynamic scaffolds based on thin hydrogel coatings that reversibly hide and display surface chemical patterns in response to temperature changes have been fabricated.

Electrostatic control of spin polarization is a promising route for developing efficient spintronic devices, but is challenging for materials with a small spin–orbit interaction. It is now shown that an electric field can be used to vary the spin polarization in a silicon quantum well by exploiting the discrete nature of the energy levels. This route may work for other inorganic and organic materials.

The existence of topological conducting surfaces on insulators has been demonstrated by angular photoemission spectroscopy, but the number of transport experiments on these systems have so far been scarce. Transport evidence of topological surface states is now shown in Bi₂Se₃ nanoribbons through the observation of Aharonov–Bohm oscillations.

Surface-enhanced Raman scattering has been widely used for chemical sensing, even though the large nonlinearity of the effect makes reproducible sensing difficult. A DNA-based assembly technique now offers a means of precise engineering of gap distances in nanoparticle dumbbells for a robust surface-enhanced Raman sensing of DNA and RNA molecules.

Demagnetization in metals occurs on very different timescales depending on the material. It is now shown that electron–phonon-mediated spin scattering describes the process of demagnetization well in every case, and the differences in timescale are mainly determined by the ratio between Curie temperature and the atomic magnetic moment.

An important challenge in medicine is the efficient delivery of drugs in the body using non-toxic nanocarriers. Porous metal–organic frameworks with imaging properties are now used as nanoscale carriers for the controlled delivery of antitumour and retroviral drugs against cancer and AIDS.

Surface plasmon polaritons allow the control of light on a scale much smaller than its wavelength, and thus are important for nanophotonic applications. The demonstration of an electrical source of surface plasmon polaritons compatible with silicon electronics takes a step towards such integrated plasmonic circuits.

Chiral nematic liquid-crystal phases consist of rod-shaped molecules that have a preference to twist. However, applied fields force them to exist without the twist. Introducing particle-like twists, so called torons, using laser light relieves this frustration by facilitating the reappearance of the twist. The presence of torons could extend the use of liquid crystals in electro-optic and photonic devices.

The morphology and structure of polymer blends is central to charge-carrier, exciton and photon management in organic light-emitting diodes, transistors and solar cells. A broadly applicable approach, based on mixing a photocrosslinkable moiety into semiconducting polymers, enables the simple formation of heterostructured blends with control of morphology and structure for use in all types of device.

An acoustic hyperlens that is able to magnify and image objects much smaller than the probing wavelength promises new applications in sonar imaging.

The degree of atomic ordering in magnetic nanoparticles decreases strongly with the particles' size. The origin of such a phenomenon has been determined by high-resolution transmission electron microscopy and tomography, which shows how correct heat treatment can lead to atomic order also in very small nanoparticles.

At present, when intervertebral discs fail, the only existing treatments are fusion of neighbouring vertebrae or polymer and metal implants. A tissue-engineering approach using an electrospun-fibre laminated scaffold could provide functional equivalence with native tissues in both construction form and strength.

Hybrid materials based on block copolymers and nanoparticles are a promising class of nanocomposites. Tailoring the block copolymer properties by using supramolecular chemistry allows control of the particle spatial organization and resulting composite properties.

Virtual worlds such as Second Life have been perceived as a social meeting point for a small following of devotees. A number of serious emerging mainstream applications may fundamentally alter this perception.

Artificial photosynthesis is an appealing strategy for producing sustainable fuels, if we can find the right materials to make it work efficiently. Scientists of all backgrounds are coming together to see if we can beat nature at her own game.