Research articles

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.

In solid-state lighting, phosphors are typically used to complement the blue light of the original emitter to achieve white-light emission. The capability to deposit certain phosphors at much lower temperatures than previously enables their use on organic substrates and opens the door to fabricate large-area white-light emitters.

The scales of a fish are its first level of defence. Now, the multilayered structure of fish scales has been analysed according to its mechanical properties and penetration resistance. This study of the four different layers provides a mechanistic understanding of evolutionary design as well as inspiring new materials for armour protection.

Electrodes exhibiting single-phase lithium insertion processes can be advantageous for storage applications such as lithium-ion batteries. By modifying the particle size and ion ordering of LiFeFO₄ electrodes an unprecedented single-phase room-temperature process is observed.

Precise control over the geometry of nanoscale one-dimensional structures is challenging. Cylindrical polymer brushes have now been used to synthesize organo-silica hybrid nanowires that are not only soluble in water but also in many organic solvents.

Although lithium iron phosphate is a promising electrode material for lithium-ion batteries, its intercalation mechanism remains unclear. Characterization by X-ray diffraction and electron microscopy demonstrates that the lithium deintercalation process occurs as a wave moving through the crystal, and can be described by a domino-cascade model

Typically, metal alloys are protected from corrosion through the formation of an oxide layer. Nevertheless, alloy degradation does occur. It is now shown that metallic nanoparticles in the oxide layer are instrumental to this process. On the basis of this understanding, improvements in alloy degradation by careful choice of composition are demonstrated.

Although phase-change materials are of significant importance for optical and electronic information storage applications, the search for new materials so far has been based on empirical methods. Now, the discovery that their crystalline phase shows resonant bonding opens the way to a deterministic search for new phase-change materials.

Elucidation of the framework structure of zeolites can sometimes prove difficult. The combination of powder diffraction and electron microscopy using a charge-flipping algorithm enables ordered silicon vacancies in a zeolite catalyst to be revealed.

Recent work has provided evidence for the existence of a liquid–liquid transition (LLT) in some single-component fluids. It is now shown that the LLT can be used to control the fluidity and miscibility of triphenyl phosphite with another molecular liquid, demonstrating the possibility of the first definite application for exploiting this phenomenon.

The presence of organic solvents in solar cells has hindered the application of devices, especially in flexible cells. Now, by mixing three solid salts, a solvent-free liquid electrolyte for dye-sensitized solar cells has been discovered that shows both excellent efficiency and stability.

The interfaces between some perovskite oxide insulators show spectacular electronic properties, originating from the formation of an electron gas. The spatial extent of the electron gas is still under debate. Conducting tip atomic force microscopy is now used to show that, depending on the growth conditions, the high-mobility electron gas can extend to hundreds of micrometres or to just a few nanometres from the interface.

The toughness of human bone is difficult to measure, as it is more difficult to break than to split. It is now shown that in the transverse orientation, relevant for breaking, bone is much tougher than previously thought owing to a surprising increase in toughness during the growth of small cracks.