Articles in 2008

The low thermal conductivity of some thermoelectric materials is commonly attributed to rattlers — atoms trapped in oversized cages. Two independent studies now show that rattlers indeed reduce thermal conductivity to glass-like values.

Smart windows and switchable displays require electrochomic materials that change their optical properties on electron transfer. Organic polymers offer further benefits including high contrast, greater colour variety and flexible substrates, but their use has remained challenging. Now, a donor–acceptor approach has yielded the first neutral black polymeric electrochrome.

The presence of guest atoms—known as rattlers—in the cages of some clathrate structures is considered to be responsible for the low thermal conductivity of the materials. Neutron spectroscopy provides important evidence regarding the actual phonon dispersion in the material, and the precise way in which this is influenced by rattlers.

The low thermal conductivity in filled skutterudites has been ascribed to rattling atoms inducing a phonon glass. Experimental evidence now shows that the phonon glass description is incorrect, and provides essential insight for the development of microscopic models aimed at describing the thermoelectric properties of these materials.

Ammonia is an important compound for producing pharmaceuticals, fertilisers and explosives. It is known to form hydrogen-bonded solids at high pressure, but ionic solids of ammonium amide are now predicted at even higher pressure.

Cell–matrix interactions have critical roles in regeneration, development and disease. Encapsulated human mesenchymal stem cells can now be induced to differentiate down osteogenic and adipogenic pathways by controlling their three-dimensional environment using tethered small-molecule functional groups.

Nanowire lasers have so far consisted of homogeneous semiconductor structures. The achievement of lasing from a multi-quantum-well heterostructure deposited on a nanowire demonstrates a new complexity in nanophotonic devices.

Developing novel strategies to drive or manipulate the migration of particles in solutions is important for lab-on-a-chip technologies, especially in the context of biological and chemical analysis. A strongly amplified and tunable migration of large particles using a passive transport phenomenon is now reported.

Magneto-chiral dichroism is an effect in which unpolarized light is absorbed differently for parallel and antiparallel propagation with respect to an applied magnetic field. Previous observations have only seen a rather weak demonstration of this effect. Following a challenging synthesis, strong magneto-dichroism has now been observed in enantiopure chiral ferromagnets.

The observation of Rabi-oscillations between single and triplet states in an organic light-emitting diode demonstrates the possibility of manipulating the spin states in organic electronic devices. The data also provide direct evidence of very slow spin-dephasing, which should prove crucial for the development of organic spintronics.

Geometric information on lithium diffusion is crucial to understanding electrode reactions for lithium ion battery applications. Combining high-temperature powder neutron diffraction and the maximum entropy method, experimental evidence for a curved one-dimensional chain for lithium motion in Li_xFePO₄ is now provided.

Stimuli-responsive hydrogels show potential as smart materials for drug delivery, however, the triggers used must be applicable in vivo. Now, a hydrogel has been synthesized that contains protein–protein interactions that respond to a specific pharmaceutical drug and enable the hydrogel to controllably release its load of a human growth factor, which increases cell proliferation.

Do you think there are too many scientific papers coming out of China? Think again. As our special focus on China highlights, improvements in quality over quantity are inevitable.

As economic competition in the region increases, Hong Kong has to reinvent itself as a knowledge-based society.

Nature Materials spoke to Lu Yongxiang, President of the Chinese Academy of Sciences, on the roles that the academy and its more than 100 research-related institutions have in advancing science and technology in China.

Fluorine-containing species can cause titania to crystallize with an unusually large fraction of reactive {001} facets.

Colloidal nanocrystals randomly turn their photoluminescence off and on under continuous light illumination. Growing thick shells around the crystals can reduce the blinking effect dramatically, with great potential advantage for applications.

Controlling simultaneously the electric and thermal properties of materials can lead to very efficient thermoelectric devices. Advances following different routes were highlighted at a recent conference.