Research articles

Zeolite nanocrystals with three-dimensionally ordered mesoporous structures are important for designing molecularly accessible and selective catalysts. With a single zeolite synthesis procedure, uniform nanocrystals and crystal zeolites with ordered imprinted mesoporosity can now be obtained.

How do entangled polymer rings relax? Linear polymers can ease their stress because their chains have ends, but cyclic polymers do not. Even trace amounts of linear chains dominate the mechanical properties if present as impurities. Investigation of carefully purified ring polymers reveals they exhibit self-similar dynamics and a power-law stress relaxation.

To enable the development of devices based on the electrical manipulation of magnetic molecules, their magnetic state needs to be conserved when electrical contacts are applied. N@C₆₀ molecules have now been integrated as part of single-molecule transistors, and their spin states retained. This achievement may lead towards their use in high-density information storage and quantum-state control.

Defects can significantly alter the physical properties of materials. A detailed experimental analysis of defects in carbon nanotubes enables the relationship between the atomic response and the broadly available macrosopic behaviour to be captured.

Flexible electronics require that all parts can be printed on plastic substrates, but finding materials that can act as high-capacitance dielectrics is a priority. An emerging class of polymer electrolytes, ion gels, can do the job—with high capacitance and at low voltage.

Nanocrystalline materials usually exhibit high strength and their deformation caused by stress is limited. Nanocrystalline CdS with spherical and hierarchical shell geometry is shown not only to withstand extreme stresses, but also to deform considerably before failure.

A new polymer is investigated as a drug-delivery vehicle for the treatment of inflammatory diseases, such as cardiac dysfunction. The biocompatibility, neutral degradation products and controlled-release properties of the polyketal microparticles indicate the material’s promising future in inflammation inhibition.

Conversion electrodes for lithium-ion batteries are capable of high capacity but low energy efficiency and low voltages are problematic. The electrochemical reactivity of MgH₂ with Li shows promise in using metal-hydride electrodes for both lithium-ion-battery and hydrogen storage applications.

Increasing the carrier density of a material to the limit at which superconductivity can be induced has been a long-standing challenge. This is now realized in an insulator by using an electric-double-layer gate in an organic electrolyte.

The trapping of electrons by grain boundaries in semiconducting and insulating materials is important for a wide range of devices such as sensors, and solar and fuel cells. First-principles calculations on MgO, LiF and NaCl reveal a novel type of electron trapping at grain boundaries associated with the negative electron affinity of these materials.

Characterizing medium-range order in disordered solids and liquids is crucial for elucidating their structure and transport properties, but it has so far proved difficult. Using a combination of X-ray diffraction and Raman scattering, the pressure-dependent and atomic-void structure of amorphous red phosphorous is determined.

A universal feature of disordered glasses is the appearance of the so-called boson peak in neutron-scattering experiments. A universal link between this boson peak and transverse phonons has now been discovered, and linked to locally favoured structures in the glass.

In a device design that brings mechanical flexibility to silicon photovoltaics, Jongseung Yoon, Alfred J. Baca and colleagues demonstrate how transfer-printing of ultrathin silicon films onto flexible substrates leads to semitransparent and large-scale arrays of integrated solar microcells with high solar-energy conversion efficiencies of 6–8%.

A new, asymmetric glassy state is identified in soft colloidal mixtures composed of large and small star polymers. The results will enable the design, control and tuning of the rheological properties of other soft composite materials.

The structure of C₆₀ is well-known: a perfectly symmetrical sphere of 12 isolated pentagons. But this is only one of 1,812 possible isomers, and the only one to obey the isolated-pentagon rule. So far it has been the only form observed. But now two isomers without isolated pentagons have been made.

Pores in thin films tend to lie in the plane of the substrate, which makes it impractical for applications where diffusion into the pores is necessary. Nanometre-scale epitaxy on a patterned substrate is now used to form vertically oriented pores in honeycomb-structured films.

We are used to thinking that a macroscopic phenomenon can be described in terms of either classical physics or quantum mechanics. But sometimes it can be both. For example, it is shown that the linear magnetoresistance in InSb can be achieved by a classical or quantum route.

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.