Research articles

Stretching experiments on single molecules offer a unique way to study the fundamental theories of statistical mechanics. Researchers have now shown that entangled calix[4]arene dimers can be used in such experiments as a tuneable model system for investigating the strength of hydrogen bonds on a single-molecule level.

Indium tin oxide (ITO) is widely used as a transparent conducting coating, but it has been difficult to combine electrical conductivity with good optical properties in the visible region. Researchers have now created layers of ITO nanowires that show optimum electronic and optical properties, and have demonstrated their use as fully transparent top contacts for light-emitting devices.

Current-induced forces in atomic wires are shown to be non-conservative, which means that they are able to do net work and to drive atomic-scale motors. Numerical simulations are presented of a motor that turns like a waterwheel when current runs through it

The ability to assemble weakly-interacting subsystems is a prerequisite for implementing quantum-information processing. In recent years, molecular nanomagnets have been proposed as suitable candidates for qubit encoding and manipulation, with antiferromagnetic Cr₇Ni rings of particular interest. It has now been shown that such rings can be chemically linked to each other and the coupling between their spins tuned through the choice of chemical linker.

Atomic force microscopy can be used to detect the early onset of osteoarthritis in cartilage samples obtained from mice and patients, well before conventional diagnosis methods. This work could lead to a minimally invasive tool for the early detection of osteoarthritis and the development of more effective therapies for treating this disease.

Information has been encoded into the quantum wavefunctions of a two-dimensional electron gas using electronic holograms constructed from single molecules. The information is stored in two spatial dimensions and one energy dimension and is read with a scanning tunnelling microscope, to enable information densities exceeding 20 bits nm⁻².

There is a requirement for site-specific and on-demand cooling in a wide array of electronic, optoelectronic and bioanalytical applications. Thermoelectric coolers, fabricated from nanostructured superlattices based on bismuth and tellurium, have now been integrated into state-of-the-art electronic packages in the first demonstration of a viable chip-scale refrigeration technology.

The interplay between atomic and electronic structure, in association with applied mechanical stress, can lead to surprising differences between the atomic arrangements found in nanoscale and macroscopic structures. The spontaneous formation of the smallest possible metal nanotube with a square cross-section has now been observed during the elongation of silver nanocontacts.

Nanocrystals - such as quantum dots and magnetic nanoparticles - embedded in lipoproteins can be used to image and quantify the kinetics of lipid metabolism in vivo in a non-invasive manner using fluorescence and dynamic magnetic resonance imaging.

A ‘smart dust’ biosensor — composed of tiny particles that can move, sense and process signals — can capture, tag and transport analytes to a detection region. Built from antibody-functionalized microtubules and kinesin motors powered by caged ATP molecules, this small and autonomous sensor could have many applications in biomedicine and biodefence.

A voltage-induced symmetry change in a ferromagnetic material can change its magnetization or magnetic anisotropy, but these effects are too weak to be used in memory devices. Researchers have now shown that a relatively small electric field can cause a large change in the magnetic anisotropy of a few atomic layers of iron. The results could lead to low-power logic devices and non-volatile memory cells.

Membrane proteins are central to many biological processes, but it is difficult to measure their interactions with other objects. Sensors based on arrays of resonating microcantilevers have now performed label-free and time-resolved measurements of the interactions between a protein receptor and a bacterial virus under physiological conditions.

Electronic devices based on semiconductor nanowires will rely on the location and number of dopant atoms in the host semiconductor being controlled during the fabrication process. It has now been shown that the properties of dopant atoms — in particular, their ionization energies — change with nanowire radius more markedly than previously predicted.

Knowledge about strain at the nanoscale is essential for tailoring the mechanical and electronic properties of materials. It has now been shown that infrared near-field microscopy can provide direct, non-invasive mapping of residual strain fields, with nanoscale resolution. In addition, plasmon-assisted near-field imaging of free-carrier properties in nanoscale strain fields has been demonstrated.