Showing Spotlights 1945 - 1952 of 2140 in category (newest first):
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.
Dec 21st, 2006
Gears, bearings, and liquid lubricants can reduce friction in the macroscopic world, but the origins of friction for small devices such as micro- or nanoelectromechanical systems (NEMS) require other solutions. Despite the unprecedented accuracy by which these devices are nowadays designed and fabricated, their enormous surface-volume ratio leads to severe friction and wear issues, which dramatically reduce their applicability and lifetime. Traditional liquid lubricants become too viscous when confined in layers of molecular thickness. This situation has led to a number of proposals for ways to reduce friction on the nanoscale, such as superlubricity and thermolubricity. Researchers in Switzerland now describe a resonance-induced superlubricity, which also occurs in many natural phenomena from biological systems to the motion of tectonic plates. This new method provides an efficient way to switch friction on and off at the atomic scale and, as a simple way of preventing mechanical damage without chemical contamination, could be of enormous importance for the development of NEMS.
Dec 20th, 2006
In recent years, the manipulation of single atoms and molecules has been a major advance in the application of the scanning tunneling microscope (STM). The main appeal of STM manipulation is the ability to access, control and modify the interactions between the tip and the adsorbate, a few angstroms apart. So far, however, atom manipulation using a STM or an AFM -tip has been restricted to flat surfaces. Manipulation of atoms on a rough terrain requires much more precise control at the atomic scale. Researchers now report extraction and manipulation of individual silver atoms on three dimensional silver nanoclusters. This is the first demonstration that individual atoms can be repeatedly pulled out from a silver cluster on a silver surface using STM tip. It is also the first atom manipulation work done on a 3-D surface. There are still very few research groups that have demonstrated single atom manipulation with atomic scale precision on flat surfaces. This remarkable achievement has an impact on the fundamental understanding of interactions between the matters. While it certainly is not a commercial production technique, it does further the fundamental understanding of the interaction between atoms, and it is an atom production technique that can be used to extract the atoms for atomistic construction.
Dec 19th, 2006
Drug intoxication, developed as a result of accidental overdosing, is a serious health problem. Drug overdoses are sometimes also caused intentionally to commit suicide, but many drug overdoses are usually the result of either irresponsible behavior, or the misreading of product labels. Other causes of overdose (especially heroin) include multiple drug use with counter indications (cocaine/amphetamines/alcohol) or use after a period of abstinence. According to the National Center for Health Statistics, in the U.S. alone almost 20,000 people a year die due to drug overdoses and accidental poisoning. While there has been a tremendous effort to develop drug delivery methods using nanotechnology, a new report shows that this could work the other way around as well, and that porous nanoparticles can soak up drug molecules in the body like a sponge. This could help to reduce fatalities from overdoses, according to tests showing that tiny spheres of poly(acrylic acid) can absorb substantial amounts of an antidepressant and an anesthetic in just a few minutes. In short, nanoparticles can act as potent antidotes!
Dec 18th, 2006
A novel discipline is emerging in medicine: nanoscopic medicine. Based on the premises that diseases manifest themselves as defects of cellular proteins, these proteins have been recently shown to form specific complexes exerting their functions as if they were nanoscopic machines. Nanoscopic medicine refers to the direct visualization, analysis (diagnosis) and modification (therapy) of nanoscopic protein machines in life cells and tissues with the aim to improve human health. The term nanoscopic medicine was coined by a group of researchers in Germany whose mission is to extend live cell nanoscopy into a comprehensive diagnostic and therapeutic scheme. This includes both the creation of a set of novel instruments and the analysis of nanoscopic protein machine networks in health and disease. In addition, they seek to construct artificial devices mimicking cellular nanomachines.
Dec 15th, 2006
Along the way to all-optical devices in communication and information technology, photonic crystals play a significant role. They form a basis material for the future realization of optical components and circuits, and maybe even complex optical circuits or optical computers. Examples include complex waveguides, integrated microcavities, channel drop filters, optical switches and low-threshold lasers. All such devices depend on the inclusion of defect structures, non-linear materials and/or light-emitters into photonic bandgap material. The combination of several devices into one photonic crystal would allow to realize the optical equivalent of an electronic circuit. So far, the intentional inclusion of such combined structures was very difficult to realize in practice, however. A group of German and Italian researchers now present a powerful technique that allows to create such photonic circuits inside photonic crystals by controlled micro-infiltration of liquid substances with sub-micron resolution. This approach forms an enabling technology for the realization of all optical devices and circuits.
Dec 14th, 2006
Due to the the increased use of modern bombs in terrorist attacks worldwide, where the amount of metal used is becoming very small, the development of a new approach capable of rapidly and cost-efficiently detecting volatile chemical emission from explosives is highly desirable and urgently necessary nowadays. The trained dogs and physical methods such as gas chromatography coupled to a mass spectrometer, nuclear quadrupole resonance, electron capture detection as well as electrochemical approaches are highly sensitive and selective, but some of these techniques are expensive and others are not easily fielded in a small, low-power package. As a complementary method, however, chemical sensors provide new approaches to the rapid detection of ultra-trace analytes from explosives, and can be easily incorporated into inexpensive and portable microelectronic devices. Researchers in PR China have developed a nanocomposite film that shows very fast fluorescence response to trace vapors of explosives such as TNT, DNT or NB.
Dec 13th, 2006
There is much discussion of molecules as components for future electronic devices and in recent years it has been possible to position single molecules in electrical junctions. Molecular and nanoscale structures have been shown to be capable of basic electronic functions such as rectification, negative differential resistance and single-electron transistor behavior. These observations show that molecular-electronic functions can be controlled through chemical manipulation. However, the contacts, the local environment and the temperature can all affect molecules' electrical properties. This sensitivity, particularly at the single-molecule level, may limit the use of molecules as active electrical components, and therefore it is important to design and evaluate molecular junctions with a robust and stable electrical response over a wide range of junction configurations and temperatures. A step in this direction, researchers in the UK now report an approach to monitor the electrical properties of single-molecule junctions, which involves precise control of the contact spacing and tilt angle of the molecule.
Dec 12th, 2006