Showing Spotlights 2273 - 2280 of 2426 in category All (newest first):
With a better understanding of how fullerenes and nanotubes form, scientists and material engineers would be in a better position to provide conditions more favorable for the formation of a particular fullerene or a particular chirality and length nanotube. Researchers have used a number of computational and theoretical tools to explain the experimental observations and develop a picture of the dynamics for fullerene growth, yet no universally agreed model exists for the fullerene growth. To understand the phenomenon of fullerene growth during its synthesis, researchers modeled a minimum energy growth route using a semi-empirical quantum mechanics code. C2 addition leading to C60 was modeled and three main routes, i.e. cyclic ring growth, pentagon and fullerene road, were studied.
Sep 19th, 2006
The ability to generate functional nanoswitches might ultimately allow the integration of nano-components into electronic components. Single molecule switches using scanning tunneling microscope (STM) manipulation have been demonstrated before. Mostly these switches are based on single atoms or small molecules and operate between two distinct states. Researchers now realized the first multi-step switching process by STM manipulation on a single molecule. Instead of small organic molecules they used a large plant molecule which is environmentally friendly and abundant in nature.
Sep 18th, 2006
New research coming out of France opens the route for the processing of numerous multifunctional materials with specific properties. So far, the design of new multifunctional devices based on the combination of different materials has been a real challenge in materials science. One way to develop multifunctional materials is the design of a surface at the nanometer scale. However, modifying the surface of materials by organizing nanoparticles of controlled size, morphology and amount of coverage into a uniform shell has proven to be a considerable hurdle. Numerous approaches are being developed for the synthesis of these materials using organic or inorganic coatings. French researchers used a coating process called supercritical fluid chemical deposition for nanomaterial surface design.
Sep 15th, 2006
The photoconductivity of carbon nanotubes (CNTs) has been studied theoretically in a nanotube p?n junction, a single SWNT transistor, and thin SWNT films. While individual nanotubes generate discrete fine peaks in optical absorption and emission, macroscopic structures consisting of many CNTs gathered together also demonstrate interesting optical behavior. For example, a millimeter-long bundle of aligned multi-walled nanotubes (MWNTs) emits polarized incandescent light by electrical current heating, and recently researchers in China have made multi-walled nanotubes (SWNT) bundles giving higher brightness emission at lower voltage compared with conventional tungsten filaments. Recent achievements in fabricating self-assembled centimeter-long bundles of CNTs have greatly facilitated study on the macroscopic behavior of these bundle structures. Preliminary results such as an optical polarizer and a light bulb based on CNT macrobundles have been reported.
Sep 14th, 2006
For the treatment of eye conditions, conventional eye drops have three major disadvantages: they must be applied frequently; their ocular bioavailability is low (i.e. less than 5% of the administered active is absorbed or becomes available at the site of physiological activity); and, their use is often associated with high systemic exposure to actives. The common alternative option, ophthalmic inserts, achieve sustained drug delivery but suffer from other limitations: they are difficult to insert (especially for the elderly and others with visual impairment) and easy to misapply; they are easily expulsed from the eye; patient compliance is low (discomfort and blurring of vision, difficulty of insertion, need for removal at the end of their useful life); and, they are costly to manufacture. Researchers in the UK believe that biodegradable polymer nanoparticles show great promise as drug delivery devices for the eye. They have developed well-tolerated systems that combine the sustained release characteristics of inserts with the patient acceptability of conventional eye drops.
Sep 13th, 2006
The use of design concepts adapted from nature is a promising new route to the development of advanced materials, with biominerals providing an ample source of examples. For instance, Nature's ability to manipulate poor engineering materials such as calcium carbonate to produce skeletal materials with considerable fracture resistance is an ideal inspiration for this approach. Researchers in the UK now report a simple and general approach to single crystal growth, employing structured films of generic polymers to direct the growth of single crystals. By using straightforward patterning techniques they are able to access a large variety of patterns with a continuous range of length scales from the macroscopic to the nanometer level.
Sep 12th, 2006
Bioactive glass is currently regarded as the most biocompatible material in the bone regeneration field because of its bioactivity, osteoconductivity (ability of a scaffold to support cell attachment and subsequent bone matrix deposition and formation) and even osteoinductivity (a scaffold that encourages osteogenic precursor cells to differentiate into mature bone-forming cells). However, the formulation of bioactive glass has been limited to bulk, crushed powders and micronscale fibers. Now, researchers in South Korea and the UK have for the first time fabricated bioactive glass in nanofibrous form. This material, which shows excellent bioactivity, is likely to open the door to the development of new nano-structured bone regeneration materials for regenerative medicine and tissue engineering.
Sep 11th, 2006
Colloidal crystals constructed by monodispersed microspheres packed in ordered arrays represent a new class of advanced materials that are useful in many areas. For example, due to their novel light diffraction and photonic bandgap properties, colloidal crystals are promising elements in the fabrication of devices such as optical filters and switches, chemical and biochemical sensors, and photonic chips. Various self-assembly techniques have been developed to form colloidal crystals on different substrates, including the flow-cell methods, vertical deposition, micromolding in capillaries and so on. Although existing methods can provide colloidal crystals of different structures and quality, efficient approaches to high stability and large scale colloidal crystals are increasingly attracting attention. Generating ordered microstructures in the colloidal crystal films and colloidal crystals with different structures and configurations are particularly important in the fabrication of optical devices.
Sep 8th, 2006