Showing Spotlights 1609 - 1616 of 2276 in category All (newest first):
Nanostructured boron and boron-related compounds have attracted considerable scientific attention to exploit their potential use in high temperature electronics, thermoelectrics, and photovoltaics due to their unique chemical and physical properties, such as chemical inertness, hardness, and adjustable energy bandgap. Boron's theoretical tubular structures may even have higher electrical conductivity than carbon nanotubes (CNTs). So far, carbon nanotubes have been considered the most promising material for field emitters, for instance as electron emitters for field emission displays. Field emission results from the tunneling of electrons from a metal tip into vacuum, under application of a strong electric field. The small diameter and high aspect ratio of CNTs is very favorable for field emission. Due to the still existing difficulties of synthesizing CNTs with uniform chirality, a number of technical questions - such as stability, low melting point and uniformity of field emission - remain to be overcome. So scientists still looking to find other ideal candidates. New experiments conducted by scientists in China suggest that boron nanowires might fit the bill.
Oct 29th, 2008
Antireflection coatings have become one of the key issues for mass production of silicon solar cells. Silicon solar cells are the most common solar cells on the market today. They are constructed with layers of n-type silicon having many electrons and p-type silicon having many electron holes. When hit by sunlight, an equal number of electrons and electron holes are generated at the interface between the two silicon layers and, as the electrons migrate from the n-type silicon to the p-type silicon, an electric flow is generated. One of the problems with silicon solar cells is the high refractive index of silicon, which causes more than 30% of incident light to be reflected back from the surface of the silicon crystals. Solar cell manufacturers have therefore developed various kinds of antireflection coatings (ARCs) to reduce the unwanted reflective losses. Currently, quarter-wavelength silicon nitride thin films deposited by plasma-enhanced chemical vapor deposition (PECVD) are the industrial standard for ARCs on crystalline silicon substrates. Unfortunately, current top-down lithographic techniques for creating subwavelength silicon gratings, such as electron-beam lithography, nanoimprint lithography, and interference lithography, require sophisticated equipment and are expensive to implement, thus contributing to the still high costs of this type of solar cells. Borrowing from Mother Nature's millions of years old design book, researchers have now come up with a nanotechnology antireflection coating inspired by the eyes of moths.
Oct 28th, 2008
A major issue for using self-contained nanodevices, for instance as implantable nanosensors or environmental monitoring devices, is the question of how to power these tiny machines with an independent power source. Options include nanobatteries and nanogenerators that harvest energy from their environment. By converting mechanical energy from body movement, engine vibrations, or water or air flow into electricity, these nanoscale power plants could make possible a new class of self-powered medical devices, sensors and portable electronics. Probably the leading team that is driving forward the work on nanogenerators for converting mechanical energy into electricity is Zhong Lin Wang's group at Georgia Tech. Wang's team has now designed and demonstrated an innovative approach to fabricating a nanogenerator by integrating nanowires and pyramid-shaped nanobrushes into a multilayer power generator. By demonstrating an effective way for raising the output current, voltage and power, this work provides the technological platform for scaling up the performance of nanogenerators to a level that some day might be able to independently power devices like pacemakers or iPods.
Oct 27th, 2008
The method that has been traditionally used in binary information storage is by making a distinction between storage (designated as 1) and non-storage (designated as 0). In reality, each imprint (or non-imprint) can store either 1 or 0. Thus the sequence and the numbers of 1 and 0 define everything with respect to the amount of information that can be stored and retrieved at the hardware level, no matter how sophisticated the overlaying software routines are. Ever since computers were developed, information storage has adhered to the eight-bit system. No matter how sophisticated information storage technologies have become - exploiting magnetoresistance, developing optical storage media such as CDs, DVDs and blue-ray discs, or the development of holographic storage media - a bit is always represented by manipulating a single feature, i.e., a transition or non-transition. Now, in contrast, consider the following: There are four colors, each of which could at least represent two or more bits; whereas in conventional methods only a single bit is available. In terms of color, this is somewhat similar to a black and white system that can support at most two kinds of transitions - 0 to 1 and 1 to 0. On the other hand, in four-color coded systems there can be 16 such unique transitions.
Oct 23rd, 2008
There is a general perception that nanotechnologies will have a significant impact on developing 'green' and 'clean' technologies with considerable environmental benefits - be it in areas ranging from water treatment to energy breakthroughs and hydrogen applications. As a matter of fact, renewable energy applications probably are the areas where nanotechnology will make its first large-scale commercial breakthroughs. Conflicting with this positive message is the growing body of research that raises questions about the potentially negative effects of engineered nanoparticles on human health and the environment. However, there is one area of nanotechnology that so far hasn't received the necessary attention: the actual processes of manufacturing nanomaterials and the environmental footprint they create, in absolute terms and in comparison with existing industrial manufacturing processes. Analogous to other industrial manufacturing processes, nanoproducts must proceed through various manufacturing stages to produce a material or device with nanoscale dimensions.
Oct 22nd, 2008
Nanoscale membranes are of great interest to researchers not only for nanofiltration applications but also in areas such as flexible electronics, extremely sensitive sensors, nanomedical applications and biomolecular research. Many of these applications would require the nanomembranes to be arranged in three-dimensional structures such as tubes, helices, rings, or wrinkles. So far, the roll-up of ultra-thin layers was heavily limited in materials choice, in most cases involving epitaxial semiconductor layers. The fabrication often requires a selective underetching procedure to release the nanomembranes from their substrate, a process which not only removes the underlying sacrificial layer but also in many cases dissolves the nanomembrane material itself. A new approach developed by scientists in Germany and Hong Kong now allows controlled fabrication of pure metal and oxide tubes as well as many other material combinations. They describe a general method to produce well-defined micro- and nanotubes from thin solid films deposited by mass production tools.
Oct 21st, 2008
The European Commission's current assessment of nanotechnology applications to the food chain range from the almost certain (e.g., membranes, antibacterials, flavors, filters, food supplements, stabilizers) through to the probable (e.g., pathogen and contaminant sensors, environmental monitors, coupled sensing and warning devices, and remote sensing and tracking devices) to the improbable (e.g., 'creating unlimited amounts of food by synthesis at the atomic level'). The European Commission has now decided that it would like to address the possible safety issues arising from nanoscience and nanotechnologies in a stepwise fashion, thereby facilitating the establishment of a roadmap for future actions in the area of food and feed safety and the environment. As a first step in this exercise, the Commission has asked the European Food Safety Authority (EFSA) to prepare a scientific opinion in order to identify the needs for risk assessment, to assess the appropriateness of methods for risk assessment, and to perform an assessment of the potential risks posed by nanoscience and nanotechnologies in the food and feed area, and assess the appropriateness of current risk assessment methods.
Oct 20th, 2008
Poll after poll shows that most people today, assuming they have even heard the term, don't understand what nanotechnology is. Those who have heard about it are often misinformed by science fiction books and movies or tend to either focus on hype or fear surrounding available information about nanotechnologies. A team of scientists have described the key issues quite nicely: There is a general recognition that few people understand the implications of the technology, the technology itself or even the definition of the word. This lack of understanding stems from a lack of knowledge about science in general but more specifically difficulty in grasping the size scale and symbolism of nanotechnology. A potential key to informing the general public is establishing the ability to comprehend the scale of nanotechnology. Transitioning from the macro to the nanoscale seems to require an ability to comprehend scales of one-billion. Scaling is a skill not common in most individuals and tests of their ability to extrapolate size based upon scaling a common object demonstrates that most individuals cannot scale to the extent needed to make the transition to nanoscale.
Oct 17th, 2008