Showing Spotlights 2041 - 2048 of 2284 in category All (newest first):
The combination of sp3, sp2, and sp hybridized atoms can give rise to a large number of carbon allotropic forms and phases, starting from carbon crystals based on all sp3 (diamond) and sp2 (graphite, fullerene) are well known and characterized. In addition there are innumerable transitional forms of carbon where sp2 and sp3 hybridization bonds coexist in the same solid such as in amorphous carbon, carbon black, soot, cokes, glassy carbon, etc. Solids based on sp hybridization, although subject of intense experimental efforts, seem to be the most elusive of the different carbon families. Such one-dimensional (1D) structures - "real" carbon nanowires - are linear chains of carbon atoms linked by alternating single and triple bonds (polyynes) or only double bonds (polycumulene). They are considered the building blocks for the elusive "carbyne": an ideal crystal constituted by carbon atoms with sp hybridization only. In solid and stable form this would represent a new carbon allotrope whose existence was a matter of great debate in the 1980s. With the immense interest in carbon nanomaterials, sp carbon nanostructures have become objects of renewed interest in recent years since they are considered precursors in the formation of fullerenes and carbon nanotubes; moreover they are interesting in astrophysics since they are considered constituents of interstellar dust. 1D carbon nanowires are expected to show interesting optical, electrical and mechanical properties. Some techniques already permit the synthesis of linear carbon chains in solution. However, their extremely high reactivity against oxygen - they can literally explode - and a strong tendency to interchain crosslinking makes synthesis of pure carbyne solids a major challenge. Researchers in Italy have now presented a simple method to obtain a solid system where polyynes in a silver nanoparticle assembly display long-term stability at ambient conditions.
Feb 5th, 2007
The study of adverse health effects of nanosized particles is nothing new. Particle toxicology is a mature science, dealing with the exposure to airborne nanosized (or ultrafine) particles that either occur naturally or have increasingly been introduced through human activities or industrial products such as materials that include asbestos fibers and coal dust. Research on ultrafine particles has laid the foundation for the emerging field of nanotoxicology, with the goal of studying the biokinetics of engineered nanomaterials and their potential for causing adverse effects. Most, if not all, toxicological studies on nanoparticles rely on current methods, practices and terminology as gained and applied in the analysis of micro- and ultrafine particles and mineral fibers. Together with recent studies on nanoparticles, this provides an initial basis for evaluating the primary issues in a risk assessment framework for nanomaterials. Given the many parameters involved, nanotoxicology requires an interdisciplinary team approach, even more so than classical toxicology, in order to arrive at an appropriate risk assessment. As a still-maturing science, nanotoxicology will expand the boundaries of traditional toxicology from a testing and auxiliary science to a new discipline where toxicological knowledge of nanomaterials can be put to constructive use in therapeutics as well as the development of new and better biocompatible materials.
Feb 2nd, 2007
Nanotechnology-enabled tissue engineering is receiving increasing attention. The ultimate goal of tissue engineering as a medical treatment concept is to replace or restore the anatomic structure and function of damaged, injured, or missing tissue. At the core of tissue engineering is the construction of three-dimensional scaffolds out of biomaterials to provide mechanical support and guide cell growth into new tissues or organs. Biomaterials can be variously permanent or biodegradable, naturally occurring or synthetic, but inevitably need to be biocompatible. Using nanotechnology, biomaterial scaffolds can be manipulated at atomic, molecular, and macromolecular levels. Creating tissue engineering scaffolds in nanoscale also may bring unpredictable new properties to the material, such as mechanical (stronger), physical (lighter and more porous) or chemical reactivity (more active or less corrosive), which are unavailable at micro- or macroscales. For bone tissue engineering, a special subset of osteoinductive, osteoconductive, integrative and mechanically compatible materials are required. Such materials need to provide cell anchorage sites, mechanical stability, structural guidance and an in vivo milieu. Moreover, they need to provide an interface able to respond to local physiological and biological changes and to remodel the extracellular matrix (ECM) in order to integrate with the surrounding native tissue. Scientists in Singapore have developed a new nanoscale biocomposite that brings researchers one step closer to mimicking the architecture of the ECM.
Feb 1st, 2007
Carbon nanotubes (CNTs) belong to the most exciting nanomaterials discovered so far and the buzz associated with them has to do with their amazing properties. Depending on their structure, they can be metals or semiconductors. They exhibit extraordinary mechanical properties, which make them extremely strong materials with good thermal conductivity. Their tensile strength is several times that of steel. These characteristics have generated strong interest in their possible use in reinforced composites, nanoelectronics, nanomechanical devices, circuits and computers. Single-wall nanotubes (SWNTs) are an intriguing variant of carbon nanotubes because they exhibit important electrical properties that are not shared by the multi-walled carbon nanotubes (MWNT). SWNTs are the most likely candidate for miniaturizing electronics toward the nanoscale. Because of their enormous commercial potential, universities, start-ups, and corporations have aggressively sought patent protection on nanotube-based products. A recent legal paper identifies key patents claiming compositions of matter, methods of production, and products incorporating nanotubes. The authors summarize potential patent invalidity arguments that may be raised against certain patents in the field and explain how the patent landscape impacts the commercialization of nanotube-based products. A proposed "Nanotube Patent Forum" could be a means for industry to facilitate cost-effective licensing transactions between patent holders and manufacturers.
Jan 31st, 2007
The potential benefits of Nanofoods - foods produced using nanotechnology - are astonishing. Advocates of the technology promise improved food processing, packaging and safety; enhanced flavor and nutrition; 'functional foods' where everyday foods carry medicines and supplements, and increased production and cost-effectiveness. In a world where thousands of people starve each day, increased production alone is enough to warrant worldwide support. For the past few years, the food industry has been investing millions of dollars in nanotechnology research and development. Some of the world's largest food manufacturers, including Nestle, Altria, H.J. Heinz and Unilever, are blazing the trail, while hundreds of smaller companies follow their lead. Yet, despite the potential benefits, compared with other nanotechnology arenas, nanofoods don't get a lot of publicity. The ongoing debate over nanofood safety and regulations has slowed the introduction of nanofood products, but research and development continue to thrive - though, interestingly, most of the larger companies are keeping their activities quiet (when you search for the term 'nano' or nanotechnology' on the websites of Kraft, Nestle, Heinz and Altria you get exactly zero results). Although the risks associated with nanotechnology in other areas, such as cosmetics and medicine, are equally blurry, it seems the difference is that the public is far less apt to jump on the nanotechnology bandwagon when it comes to their food supply.
Dec 28th, 2006
As their name suggests, nerve agents attack the nervous system of the human body. All such agents function the same way: by interrupting the breakdown of the neurotransmitters that signal muscles to contract, preventing them from relaxing. Nerve agents, depending on their purity, are clear and colorless or slightly colored liquids and may have no odor or a faint, sweetish smell. They evaporate at various rates and are denser than air, so they accumulate in low areas. Nerve agents include tabun(GA), sarin(GB), soman(GD), and VX. The military has a number of devices to detect nerve agent vapor and liquid. Current methods to detect nerve agents include surface acoustic wave (SAW) sensors, conducting polymer arrays, vector machines, and the most simple, color change paper sensors. Most of these systems have have certain limitations including low sensitivity and slow response times. By using readily synthesized network films of single-walled carbon nanotube bundles researchers have built a sensor capable of detecting G-series nerve agents such as Soman and Sarin (Sarin was used in the Tokyo subway terrorist attack in 1995). This research opens new opportunities in the design of real-time chemical warfare agent (CWA) sensors with independent response signatures.
Jan 29th, 2007
Micro-and/or nano-electromechanical systems (MEMS/NEMS) are the basis of future nanotechnology, because they combine miniature sensors and actuators with electronics. The selection of appropriate materials for MEMS/NEMS fabrication is based on the careful consideration of a material's properties with regard to its intended application. For example, many MEMS devices, such as pressure, chemical and bio sensors, rely on actuation of a membrane structure and require a high fracture toughness material for the enhanced durability and shock resistance. On the other hand, for fabrication of controlled nanostructures, the material should be machinable up to atomic level. Currently, the materials used for MEMS/NEMS fabrication are based on silicon or oxides, which are brittle and have size effects such as lattice defects, anisotropy, grains and grain boundaries. These effects are the limiting factors in the reduction of pattern size, especially when a dimension of the pattern approaches a few tenths of a nanometer. Researchers in Japan now have introduced zirconium-based glass thin films for the fabrication of 3D micro- and nanostructures. These materials exhibit excellent micro/nano-formability under very low stresses, and are expected to become one of the most useful materials for fabricating NEMS/MEMS devices.
Jan 26th, 2007
There seem to be an increasing number of websites, articles and investment reports that push, some might say hype, nanotechnology stocks as the next stock market super growth area. On the other hand, some investors are wary of a nanotechnology boom, where too much money chases too few listed companies, turning into a dot.com-like bust. Hype usually involves a bit of underlying truth about a trend but says nothing about whether something is going to be a good investment. As the International Herald Tribune put it: "While nanotechnology is spurring a revolution in electronics and medicine, investors seeking to benefit may need a lot of luck, as they did during the Internet bubble of the 1990s." The current interest in nanotech stocks is driven by the many advances that nanoscience and nanotechnology promise. The commercial realization of most of these promises lies in the (some say near, some say distant) future; things like quantum computing, molecular electronics, or lab-on-a chip medicine. In its current state, nanotechnology to a large degree takes place in labs and there is only a trickle of products coming to the market. All of these products are incremental improvements of existing products - scratch-resistant paint, better engine oil, antimicrobial household products, smaller chips, improved cosmetics, etc. What we are seeing right now is the beginning of a large technological trend and a stock buyer has to understand the difference between the many promises of nano- technologies, the research taking place today, and the actual contribution of nanotechnologies to commercial products. Let's look at a few facts that might give some perspective on what investing in nanotechnology stocks today is about - how has the market performed so far? what exactly is a "nanotechnology stock"? and the issue with these trillion dollar market size forecasts.
Jan 25th, 2007