Showing Spotlights 2065 - 2072 of 2275 in category All (newest first):
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
A large portion of nanoscience and nanomaterial engineering is about trying to copy what has evolved in Nature. Take diatoms; a major group of hard-shelled algae and one of the most common types of phytoplankton. A characteristic feature of diatom cells is that they are encased within a unique cell wall made of silica. Silicate materials are very important in nature and they are closely related to the evolution of living organisms. Diatom walls show a wide diversity in form, some quite beautiful and ornate, but usually consist of two symmetrical sides with a split between them, hence the group name. Diatomaceous earth consists of fossilized remains of diatoms and, as an environmentally friendly material, finds wide use especially in filter applications. It is also used as a mild abrasive, as a mechanical insecticide, as an absorbent for liquids, as an activator in blood clotting studies, and as a component of dynamite. As it is also heat-resistant, it can be used as a thermal insulator. Artificial synthesis of hollow cell walls of diatoms, as generally re-creating the silicate chemistry of Nature by chemical methods, is a key target of nanomaterial science. Researchers in Japan have now reported a method to produce artificial diatomaceous earth-like materials.
Dec 11th, 2006
There has been a great deal of interest in the toxicity of nanoparticles in the context of respiratory health. The responses of cells exposed to nanoparticles have been studied with regard to toxicity, but very little attention has been paid to the possibility that some types of particles can protect cells from various forms of lethal stress. Research has shown that nanoparticles composed of cerium oxide or yttrium oxide protect nerve cells from oxidative stress and that the neuroprotection is independent of particle size. This has led researchers to the conclusion that there is a potential for engineering this group of nanoparticles for therapeutic purposes.
Dec 8th, 2006
A large number of DNA-based nanomechanical devices have been described, controlled by a variety of methods: These include pH changes and the addition of other molecular components, such as small molecule effectors, proteins and DNA strands. The most versatile of these devices are those that are controlled by DNA strands: This versatility results because they can be addressed specifically by strands with particular sequences; these strands can be added to the solution directly, or perhaps they can result from another process ongoing within the local environment. Researchers have now shown that the state of a DNA-based nanomechanical device can be controlled by RNA strands, which means that nanomechanical devices could potentially be run from transcriptionally derived RNA molecules.
Dec 7th, 2006
The controlled synthesis of single-walled carbon nanotubes (SWCNTs), which generally requires a nanoscale catalyst metal, is crucial for their application to nanotechnology. In the chemical vapor deposition (CVD) of SWCNTs, the known effective catalyst species are the iron-family elements iron, cobalt, and nickel, with which a high SWCNT yield can be obtained. However, gold, silver, and copper have never been reported to produce SWCNTs. It is well known that iron, cobalt, and nickel have the catalytic function of graphite formation but that gold does not. The difference between the iron-family metals and gold is that the binding energy of carbon is much larger for the iron-family metals. Carbon atoms cannot stay on gold long enough to form a graphitic network. Thus, it is rather natural for iron, cobalt, and nickel to generate SWCNTs, but it is totally unexpected that gold would produce them too. The same picture is applicable to silver and copper. Nevertheless, researchers in Japan succeeded in developing a nanoparticle activation method that shows that even gold, silver, and copper act as efficient catalysts for SWCNT synthesis. These non-magnetic catalysts could provide new routes for controlling the growth of SWCNTs.
Dec 6th, 2006
Artificial photosynthesis, using solar energy to split water generating hydrogen and oxygen, is often considered a 'Holy Grail' of chemistry which can offer a clean and portable source of energy supply as durable as the sunlight. It takes about 2.5 volts to break a single water molecule down into oxygen along with negatively charged electrons and positively charged protons. It is the extraction and separation of these oppositely charged electrons and protons from water molecules that provides the electric power. The photocatalytic splitting of water into hydrogen and oxygen using solar light is a potentially clean and renewable source for hydrogen fuel. Although massive efforts have been made in this area, many researchers have faced different types of challenges reaching from fundamental sciences to engineering. Titanium dioxide has been considered one of the most promising photocatalytic materials due to its relatively low cost, chemical stability, and photostability. However, the catalytic property of titanium dioxide is limited with ultraviolet (UV) regions which accounts for only approx. 4% of the incoming solar energy and thus renders the overall process impractical. Tungsten trioxide has been recently focused on as a new photoanode material, or as a mixture material with titanium dioxide, for water splitting because the tungsten trioxide can offer relatively small band gap (approx. 2.5 eV) and corrosion stability in aqueous solution. Although tungsten trioxide has shown great potential such as photooxidation of water with visible light and high photocurrent with nanocrystals, the quantum yield is still low. In new research, titanium oxide nanotubes coated with tungsten oxide were prepared to harvest more solar light for the first time. The tungsten trioxide coatings significantly enhanced the visible spectrum absorption of the titanium dioxide nanotube array, as well as their solar-spectrum induced photocurrents.
Dec 5th, 2006
Imagine a toothpaste that not only seeks out but actually repairs damage to tooth enamel. For those who dread their annual visit to the dentist, this may sound like science fiction. For people in Japan, it is a reality. Using nanoparticles, Japan's Sangi Company, Ltd., has sold more than 50 million tubes - and continues to expand its line of products containing nanoparticles. Scientists have learned to synthesize hydroxyapatite, a key component of tooth enamel, as nanosized crystals. When nano-hydroxyapatite is used in toothpaste, it forms a protective film on tooth enamel, and even restores the surface in damaged areas. Availability of similar products that claim to actually repair cavities is just around the corner. Unlikely as it seems at first blush, the $200 billion global cosmetics industry is one of the major players in the emerging field of nanotechnology. According to the Centre for the Study of Environmental Change at Lancaster University in Britain, the cosmetics industry already holds the largest number of patents for nanoparticles - and be it toothpaste, sunscreen, shampoo, hair conditioner, lipstick, eye shadow, after shave, moisturizer or deodorant, the industry is leading the way.
Dec 4th, 2006
The last few years saw tremendous progress in the use of nanoparticles to enhance the in vivo efficiency of many drugs. Currently used pharmaceutical nanocarriers, such as liposomes, micelles, nanoemulsions, polymeric nanoparticles and many others demonstrate a broad variety of useful properties, such as for instance increased longevity in the blood, specific targeting to certain disease sites, or enhanced intracellular penetration. Some of these pharmaceutical carriers have already made their way into clinics, while others are still under preclinical development. In the next phase of developing nanocarriers, researchers are intrigued by the possibility to synthesize pharmaceutical nanocarriers that possess not only one but several properties. Such particles can significantly enhance the efficacy of many therapeutic and diagnostic protocols. A brandnew review paper considers current status and possible future directions in the emerging area of multifunctional nanocarriers with primary attention on the combination of such properties as longevity, targetability, intracellular penetration and contrast loading.
Dec 1st, 2006