A control over spin-electron interactions is vital for development of spintronic devices and for quantum computation. When a magnetic impurity is surrounded by free electrons, a realignment of the electron spins occurs below a critical temperature due to spin-electron interactions; this causes an increase in resistivity of the material - a phenomenon known as the "Kondo" effect. The Kondo effect has been observed in a wide range of systems including single atoms/molecules, quantum-dots, and carbon nanotubes, however two-dimensional molecular Kondo systems have yet to be explored. Molecules with magnetic properties recently have great appeal as they offer an ideal platform to advance the fundamental understanding of spin related mechanisms, and can act as templates for molecular spintronic device fabrication due to their propensity for spontaneous self assembly. By manipulating nearest-neighbor molecules with a scanning tunneling microscope tip researchers now were able to tune the spin-electron coupling of the center molecule inside a small hexagonal molecular assembly in a controlled step-by-step manner. This variation of Kondo effect might be useful for instance for storing or manipulating data in spintronic memory devices.
Finely divided carbon particles, including charcoal, lampblack, and diamond particles, have been used for ornamental and official tattoos since ancient times. The importance of carbon nanomaterials in biological applications has been recently recognized. Owing to their low chemical reactivity and unique physical properties, nanodiamonds could be useful in a variety of biological applications such as carriers for drugs, genes, or proteins; novel imaging techniques; coatings for implantable materials; and biosensors and biomedical nanorobots. Therefore, it is essential to ascertain the possible hazards of nanodiamonds to humans and other biological systems. Researchers now have, for the first time, assessed the cytotoxicity of nanodiamonds ranging in size from 2 to 10 nm. Assays of cell viability such as mitochondrial function (MTT) and luminescent ATP production showed that nanodiamonds were not toxic to a variety of cell types. Furthermore, nanodiamonds did not produce significant reactive oxygen species. Cells can grow on nanodiamond-coated substrates without morphological changes compared to controls. These results suggest that nanodiamonds could be ideal for many biological applications in a diverse range of cell types.
Nanoparticles exhibit unique properties that make them ideal for a wide-variety of applications. Also unique, and largely unknown, are the interactions that occur between the biological environment and nanoparticles. On the upside, the ability of quantum dots and fullerenes to penetrate intact skin provides potential benefits for the development of nanomaterial applications involving drug delivery. On the downside, this ability poses potential risks associated with manufacturing and handling such nanoparticles. A new study now confirms that fullerene-based peptides can penetrate intact skin and that mechanical stressors, such as those associated with a repetitive flexing motion, increase the rate at which these particles traverse into the dermis. These results are important for identifying external factors that increase the risks associated with nanoparticle exposure during manufacturing or consumer processes. Future assessments of nanoparticle safety should recognize and take into account the effect that repetitive motion and mechanical stressors have on nanoparticle interactions with the biological environment. Additionally, these results could have profound implications for the development of nanoparticle use in drug delivery, specifically in understanding mechanisms by which nanoparticles penetrate intact skin.
Novel and robust networks, tailored from nanostructures as building blocks, are the foundations for constructing nano- and microdevices. However, assembling nanostructures into ordered micronetworks remains a significant challenge in nanotechnology. The most suitable building blocks for assembling such networks are nanoparticle clusters, nanotubes and nanowires. Unfortunately, little is known regarding the different ways networks can be created and their physicochemical properties as a function of their architecture. It is expected that, when 1D nanostructures are connected covalently, the resulting assemblies possess mechanical, electronic, and porosity properties that are strikingly different from those of the isolated 1D blocks. In extensive theoretical studies, researchers now have shown that the properties of 2D and 3D networks built from 1D units are dictated by the specific architecture of these arrays. Specifically, they demonstrate that one could join nanotubes and make supernetworks that exhibit different properties when compared to the individual building blocks (i.e. the nanotubes). Besides the unique and unusual mechanical and electronic properties, the porosity of these systems makes them good candidates for exploring novel catalysts, sensors, filters, or molecular storage properties. The crystalline 2D and 3D networks are also expected to present unusual optical properties, in particular when the pore periodicity approaches the wavelength of different light sources, such as optical photonic crystals.
Bacteria are ubiquitous in the earth's surface, subsurface, fresh water, and oceanic environment. Bacteria are remarkable in that they are capable of respiring aerobically and anaerobically using a variety of compounds, including metals, as terminal electron acceptors. Metal reducing bacteria can significantly affect the geochemistry of aquatic sediments, submerged soils, and the terrestrial subsurface. Microbial dissimilatory reduction of metals is a globally important biogeochemical process driving the cycling of iron and manganese, associated trace metals, and organic matte. Microbial metal reduction is of significant interest among scientists who are researching remediation of environmental contaminants. However, little is known about the biochemical or molecular mechanisms underlying bacterial metal reduction. Conducting research with toxic metal reducing bacteria, researchers discovered that bacteria produce electrically conductive nanowires in response to electron-acceptor limitation. These findings could be used to bioengineer electrical devices such as microbial fuel cells.
With its historic development tracing back to the Bronze Age, welding serves modern industry in broad areas such as construction, manufacturing, and engineering. Spot welding,a type of resistance welding used to weld various sheet metals, was originally developed in the early 1900s. The process uses two shaped copper alloy electrodes to concentrate welding current and force between the materials to be welded. The result is a small "spot" that is quickly heated to the melting point, forming a nugget of welded metal after the current is removed. Perhaps the most common application of spot welding is in the automobile industry, where it is used almost universally to weld the sheet metal forming a car. Spot welders can also be completely automated, and many of the industrial robots found on assembly lines are spot welders. With the continuing development of bottom-up nanotechnology fabrication processes, with self-assembly at its core, spot welding may likewise play an important role in interconnecting carbon nanotubes (CNTs), nanowires, nanobelts, nanohelixes, and other nanomaterials and structures for the assembly of nanoelectronics and nanoelectromechanical systems (NEMS).
Animals that cling to walls and walk on ceilings owe this ability to micro- and nanoscale attachment elements. The highest adhesion forces are encountered in geckos. A gecko is the heaviest animal that can 'stand' on a ceiling, with its feet over its head. This is why scientists are intensely researching the adhesive system of the tiny hairs on its feet. On the sole of a gecko's toes there are some one billion tiny adhesive hairs, about 200 nanometers in both width and length. These hairs put the gecko in direct physical contact with its environment. The shape of the fibers is also significant; for example, spatula-shaped ends on the hairs provide particularly strong adhesion. Researching how insect and gecko feet have evolved to optimize adhesion strength is leading to bio-inspired development of artificial dry adhesive systems. Potential applications range from protective foil for delicate glasses to reusable adhesive fixtures - say goodbye to fridge magnets, here comes the hairy stuff, which will also stick to your mirror, your cupboard and your windows.
The controllable fabrication of highly ordered homogeneous nanostructures on surfaces remains a difficult challenge. Nevertheless, motivated by potential applications in micro- and optoelectronic devices, the problem of organic nanoscale structures on surfaces with long-range order and uniform size has attracted considerable attention in recent years. Researchers in Switzerland have now grown ordered arrays of fullerene nanochains on a gold surface. This demonstration constitutes a successful proof-of-principle for the concept of site-selective molecular anchoring on nanostructured template surfaces, and provides the perspective of fabricating complex supramolecular nanostructures being of potential technological relevance by site-selective anchoring and selfassembly methods using properly designed functional molecular building blocks.