Showing Spotlights 2033 - 2040 of 2240 in category All (newest first):
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
Artificial opals are gemstones that are of considerable scientific and technological interest as photonic crystals, as components of light sources, solar cells, and chemical sensors. They are conveniently made from periodic stackings of nanospheres. It would be exciting if one could fabricate optical cavities in these photonic crystals by removing, or adding high dielectric material to a single unit cell in the structure. These optical cavities would localize light that potentially enables the fabrication of high-resolution miniature on-chip sensors, or even qubits for quantum computers. Previously, such controlled modification of the nanostructure of a single colloid in an opal has not been achieved. Now, researchers in The Netherlands developed a method for realizing both single and arrays of material cavities, or defects, in individual colloids on the surface of silicon dioxide artificial opals by a focused ion beam milling technique. This research could ultimately lead to the fabrication of a photon-on-demand light source.
Nov 30th, 2006
While the first reported fullerenes and nanotube structures were composed of carbon, it was soon recognized that a plethora of comparable inorganic candidates should also exist. A rich assortment of IF (inorganic fullerene-like structures, or IF for short) nanostructures have been synthesized, and are finding practical uses in tribology, photonics, batteries, and catalysis. On such inorganic molecule that can achieve fullerene-like nanostructures, cesium oxide, is particularly useful for a multitude of applications in photoemissive systems. Unfortunately, it is extremely reactive in the ambient atmosphere, so its production and handling require high vacuum and very pure inert conditions; which translates into problematic and expensive manufacturing and handling, which in turn limits its technological scope and device lifetime. In their quest for a relatively uncomplicated high-yield synthesis method for chemically stable cesium oxide IFs, scientists succeeded in exploiting highly concentrated solar radiation (ultrabright incoherent light) toward that end. This resulted in a simple, inexpensive, and reproducible photothermal procedure for synthesizing IF nanoparticles.
Nov 29th, 2006
Wound healing is a complex process and has been the subject of intense research for a long time. Wound healing proceeds through an overlapping pattern of events including coagulation, inflammation, proliferation, and matrix and tissue remodeling. The holy grail for wound healing is accelerated healing without scars. Silver has been used for centuries to prevent and treat a variety of diseases. Its antibacterial effect may be due to blockage of the respiratory enzyme pathways and alteration of microbial DNA and the cell wall. In addition to its recognized antibacterial properties, some authors have reported on the possible pro-healing properties of silver. The use of silver in the past has been restrained by the need to produce silver as a compound, thereby increasing the potential side effects. Nanotechnology has provided a way of producing pure silver nanoparticles and this has provided a new therapeutic modality for use in burn wounds. Nonetheless, the beneficial effects of silver nanoparticles on wound healing remain unknown. A new study reports that silver nanoparticles can promote wound healing and reduce scar appearance.
Nov 28th, 2006