Showing Spotlights 1497 - 1504 of 2284 in category All (newest first):
One of the ultimate goals of nanotechnology is to fabricate functional devices at the nanoscale. A nanodevice is expected to integrate components of different material compositions and geometries. The integration is likely to be carried out on silicon if information processing is required. Thus far, the basic building blocks for nanodevices are nanoparticles, for which there are many material candidates; and nanotubes, for which the candidates are fewer (they are mostly carbon, although non-carbon based tubes have been fabricated as well). One-dimensional (1-D) nanomaterials such as nanotubes are useful for component connection and for the transport of charge, heat and vibration. In addition to the limited material selection, common 1-D nanomaterials are usually straight. Composite 1-D nanomaterials are rarer. Often they are also produced as discrete and unorganized units. Scientists in Singapore have now successfully fabricated a family of aligned one-dimensional C-curved nanoarches of different compositions by a simple and scalable method for the first time.
Jul 1st, 2009
Graphene has two distinct types of edges produced when it is cut - armchair type or zigzag type - which correspond to the two crystal axis of graphene. These edge types are predicted theoretically to have distinct electronic, magnetic, and chemical properties, but current fabrication methods have no way of controlling which type of edge is produced and are dominated by disorder. For example, a common method is to use plasma etching which is an isotropic etching process and is not selective in which crystallographic direction it etches. This is a problem in especially nanoelectronics applications and devices where the potential performance of the device depends strongly on the edge structure as well. A solution to this problem has now been found. Researchers have demonstrated anisotropic etching in single-layer graphene which produces connected graphene nanostructures with crystallographically oriented edges. This opens many future avenues to study graphene nanostructures such as nanoribbons, nanoconstrictions, and quantum dots with crystallographic edges.
Jun 30th, 2009
You can find them in all kinds of products, from socks to food containers to coatings for medical devices - we are talking about silver nanoparticles. Valued for its infection-fighting, antimicrobial properties, silver in its modern incarnation as silver nanoparticles, has become the promising antimicrobial material in a variety of applications because the nanoparticles can damage bacterial cells by destroying the enzymes that transport cell nutrient and weakening the cell membrane or cell wall and cytoplasm. Despite their wide use, the issue of possible adverse effects and toxicity of nanoparticles for the human body is progressively, albeit slowly, recognized as central by an increasing number of studies. A widely accepted consensus on the detailed molecular mechanism of silver nanoparticles toxicity is still missing and very often the drive toward new formulations overwhelms the interest for a better assessment of the cytotoxicity of the nanoparticles. Scientists at the University of Trieste in Italy have now developed a novel non-cytotoxic nanocomposite hydrogel material based on natural polysaccharides and silver nanoparticles for antimicrobial applications.
Jun 29th, 2009
A few days ago we ran a Nanowerk Spotlight on a nanostructuring technique that uses an extremely narrow electron beam to knock individual carbon atoms from carbon nanotubes with atomic precision, a technique that could potentially be used to change the properties of the nanotubes. In contrast to this deliberately created defect, researchers are concerned about unintentional defects created by electron beams during examination of carbon nanomaterials with transmission electron microscopes like a high-resolution transmission electron microscope (HRTEM). For a long time it has been thought that if the accelerating voltage of electrons could be reduced to 80 kV in an electron microscope, then the electrons would not possess sufficient energy to cause knock-on damage in carbon nanomaterials. Knock-on damage occurs when electrons are scattered by the nucleus of the atom they are probing. Upon scattering, energy is transferred. In some circumstances this energy can be large enough to dislodge the atom from its position. A British-German team has examined how electrons accelerated at 80 kV interact with singe-walled carbon nanotubes and shown that in some circumstances SWCNTs were unstable.
Jun 25th, 2009
Gas sensing applications are numerous in our modern society and include process monitoring, environmental compliance, health applications, homeland security, agriculture, etc. Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. Thus, the more surface available, the more sensitive the sensor will be. Nanoscale materials are intriguing materials for next-generation nanotechnology gas sensors since their relative surface areas are so large. A problem with existing gas nanosensors is the cross-interference of other gas analytes. For instance, carbon nanotube based gas sensors for the prominent air pollutant nitrogen dioxide have shown strong interference of ethanol and ammonia gases to the NO2 response. Another cross-interference often is caused by humidity, i.e. the water vapor in the air. New research now demonstrates how the manufacturing of a nanosensor for ammonia gas can be tuned to eliminate the interference of water vapor. The trick lies in accurately controlling the synthesis of the sensing nanomaterial.
Jun 23rd, 2009
A broad spectrum of therapeutics or effector molecules that address several areas of medicine, from inflammation, to cancer, and regenerative medicine, are insoluble in water (they are soluble primarily in solvents generally regarded as unsuitable for injection). The water insolubility of these therapeutics limits the means by which those compounds can be administered to the body. Rapid strategies to package and disperse these drugs in biocompatible vehicles while also maintaining their potent activity can have major implications in advancing fundamental, translational, and commercial/scale-up aspects of accelerating their clinical impact. A new study now shows a way in which nanodiamonds can be applied towards enhancing water dispersion of otherwise poorly watersoluble therapeutics. It realizes a high throughout strategy to solubilize a broad range of water-insoluble drugs, which coupled with the innate biocompatibility of nanodiamonds, provides an important foundation towards a nanotechnology platform approach for advanced drug delivery.
Jun 22nd, 2009
One of the outstanding challenges in nanotechnology generally, and in the exploitation of so-called 'bottom-up' assembly of basic nanoscale building blocks such as nanowires, is the development of techniques for assembling large numbers of such nanostructures into more complex systems and precisely specified patterns in an accurate, deterministic manner. For instance, it is possible to build transistors, optical devices, and sensors with very specific properties using nanowires. Thus many useful applications of nanowires will depend on the ability to take these building blocks and organize them in some deterministic way in order to ultimately construct and interface with a nanowire-based system. New work demonstrates the basic capability for, and elucidates some of the guiding principles in, the use of dielectrophoretic behavior to direct the placement of large numbers of nanowires on complex, pre-patterned structures as might be required for integration of nanowires with, for example, silicon-based microelectronic circuitry. It shows that a high level of placement precision can be achieved by paying careful attention to the signal frequency as well as the macroscopic electrode architecture that is employed.
Jun 19th, 2009
The manifold properties of carbon nanotubes (as well as other carbon nanomaterials such as fullerenes and graphene) are related to the various ways the carbon atoms can be arranged to form the tube lattice. Studies have shown that atomic-scale defects in these lattices can strongly influence the electronic and mechanical properties of the nanotubes. The simplest defect type is a vacancy where an atom is missing from the lattice site. Such defects can also be seen as chemically active sites for tube side wall functionalization. Due to the difficulty of observing vacancies directly, it remained unclear under what conditions vacancies in nanotubes are stable or exist at all. Researchers have now demonstrated a technique that allows them to remove carbon atoms from carbon nanotubes with atomic precision and in a controlled way with an extremely focused electron beam.
Jun 18th, 2009