Research articles

For high-power white-light-emitting diodes (LEDs) to become a technological reality there is a need to find more efficient red-emitting phosphor materials. Eu²⁺-doped Sr[LiAl₃N₄], a member of the nitridoaluminates compound class, is now proved to be a high-performance narrow-band red-emitting phosphor material that can be easily coupled with existing GaN-based blue-LED technology for use in white LEDs.

Peptide-based nanofibres with bioactive proteins attached can now be made such that the protein ligands are introduced in a controlled manner. This tailoring of the nanofibre’s composition enables the ratio of multiple different proteins to be highly tuned within the assemblies. By changing the protein content of the nanofibres, it is possible to adjust the antibody responses in mice to the different nanofibres.

Malignant phenotypes in the mammary epithelium have been correlated to increases in extracellular matrix stiffness. It is now shown that the effect of matrix stiffness in normal mammary epithelial cells can be offset by an increase in basement-membrane ligands and that both the stiffness and composition of the matrix are sensed by the β4 integrin. The results suggest that the relationship between matrix stiffness and composition is a more relevant predictor of breast-cancer progression.

Block copolymers can self-assemble into nanostructures that simultaneously facilitate ion transport and provide mechanical stability. Highly asymmetric charge cohesion effects are now shown to induce the formation of nanostructures with percolated phases desired for ion transport. This strategy could lead to the design of enhanced battery electrolyte materials.

The fracture behaviour of micro- and macroscale bone is shown to be different. In situ micropillar compression experiments on ovine bone demonstrate that microscale lamellar bone is strong and ductile, and shows no damage, whereas on the macroscale, bone shows little ductility and fails in a quasi-brittle manner.

Although several techniques have been reported to obtain electron-rich colloidal quantum dots, these materials usually suffer from poor stability under air exposure. It is now shown that the use of strongly bound ligands and a careful ligands-exchange strategy lead to air-stable n-type quantum dots that can be used in solar cells and chemical sensors.

Nanoparticle-based fluorescence imaging does not usually allow cell membrane-bound particles and intracellular particles to be distinguished from each other. Now, using functionalized silver nanoparticles as plasmonic probes, this distinction can be made following a rapid, non-toxic etching process that selectively removes the extracellular nanoparticles but leaves the intracellular nanoparticles unharmed.

Carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) have similar surface crystallography and mechanical properties. It is now shown that the interlayer sliding friction in multilayer CNTs and BNNTs is, however, different: whereas the telescopic sliding of semi-metallic multiwalled CNTs is known to be vanishingly small, multiwalled insulating BNNTs exhibit ultrahigh interlayer friction that is proportional to the contact area—a result ascribed to the ionic character of boron nitride.

Liquid-crystalline elastomers combine rubber-like elasticity with the optical properties of liquid crystals, yet some of their properties depend on the particular liquid-crystal phase. Now, stretchable gels of the liquid-crystalline blue-phase I are reported. The blue-phase gels are electro-optically switchable under a moderate applied voltage, and their optical properties can be manipulated by an applied strain.

Acoustic impedance-matched surfaces do not reflect incident waves. Traditional means of acoustic absorption have so far resulted in imperfect impedance matching and bulky structures, or require costly and sophisticated electrical design. Inspired by electromagnetic metamaterials, a subwavelength acoustically reflecting surface with hybrid resonances and impedance-matched to airborne sound at tunable frequencies is now demonstrated.

Perovskite oxides have attracted significant attention as energy conversion materials owing to their unique physical and electronic properties. Anion-based intercalation pseudocapacitance as well as oxygen intercalation in a nanostructured lanthanum-based perovskite (LaMnO₃) have now been exploited for fast energy storage.

Variations in the internal conformational dynamics of supramolecular nanostructures may be important for their function, yet such dynamics have been difficult to probe experimentally. Now, the molecular motion through a nanofibre cross-section at subnanometre resolution has been quantified using site-directed spin labelling and electron paramagnetic resonance spectroscopy.

Transitions between stable quantum phases of matter typically involve going through an unstable quantum critical point, the unique properties of which have become a focus of research in the past decade or so. Extensive bulk measurements on the nickel oxypnictide system CeNiAsO uncover heavy-fermion behaviour, suggesting the family of oxipnictides may be ideal materials for examining quantum criticality more broadly.

Fabricating low-temperature solution-processed solar cells with good power-conversion efficiency and stability in ambient conditions has proved challenging. The use of ligands that protect colloidal quantum dots from degradation in air and tune their energy levels is now shown to be a viable approach for the realization of spin-coated solar cells with very high efficiency.

A state of matter known as a three-dimensional Dirac semimetal has latterly garnered significant theoretical and experimental attention. Using angle-resolved photoelectron spectroscopy, it is shown that Cd₃As₂ is an experimental realization of a three-dimensional Dirac semimetal that is stable at ambient conditions.

The surface electronic states associated with topological insulators have attracted considerable attention due to their robust nature. Using low-field susceptibility measurements, a paramagnetic singularity that is common to the (Bi,Sn)₂(Se,Te)₃ family of topological insulators is observed, and explained in terms of the topological surface states.

The Jahn–Teller distortion is an electronic effect that is known to couple charge, orbital and magnetic ordering phenomena in many complex solids. Using a combination of scattering and microscopy approaches, it is now shown that cooperative Jahn–Teller distortions in Na_5/8MnO₂ are coupled to an unusual ordering of Na vacancies.

Disordered photonic materials have the ability to control the flow of light through random multiple scattering. This has the drawback of randomizing both the direction and phase of the propagating light. Now, confined and interacting light modes are demonstrated for a two-dimensional disordered photonic structure.

At sufficiently low temperature, liquid water crystallizes into ices with cubic or hexagonal symmetry. A simulation study now shows that the nucleation of water into atomic stackings of cubic and hexagonal ices occurs through a metastable precursor phase with tetragonal symmetry, and that this scenario provides an explanation for the unusual pressure dependence of water’s homogeneous crystal-nucleation temperature.

Mode-selective vibrational excitations can be used to transiently induce a range of phenomena in strongly correlated states of matter. It is now shown that by exciting apical oxygen distortions in the cuprate system YBa₂Cu₃O_6.5, an unusual photoconductive effect is induced both at low and at high temperatures.