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Essential characteristics of self-assembled quantum dots

Semiconductor photonics, electronics and optoelectronics infrastructure is at the core of the information society. As the length scales of electronic devices continue to shrink, the cost of traditional approaches to device fabrication involving lithography is becoming excessive. It is regarded that self-assembled growth methods are a solution to the problem of fabricating smaller devices at a lower cost. Self-assembled quantum dots (QDs) are providing the possibility of new devices for this infrastructure in the short, medium and long term. QDs are ideal for the study of the fundamental properties of nanostructures, which is applicable across the nanotechnology and nanoscience sector. Research in self-assembled semiconductor QDs is therefore characterized by a remarkably well-matched combination of the two main motivations for scientific research, namely academic interest and the potential for industrial applications. As a consequence, there is an intense scientific activity in materials growth, structural characterization, optical and transport spectroscopy, device engineering and computational modeling. The field of self-assembled semiconductor nanostructures started in 1985 in Europe by a French group at the Centre National d'Etudes des Telecommunications - CNET.

Oct 12th, 2006

Molecular automaton plays tic-tac-toe

DNA computing is a form of computing which uses DNA and molecular biology instead of the traditional silicon-based computer technologies. Molecular computation is currently focused on building molecular networks analogous to electrical engineering designs. These networks consist of logic gates, which perform Boolean logical operations such as AND, NOT, and OR on one or more inputs to produce an output. While individual molecular gates and small networks have previously been constructed, these gates are yet to be integrated at higher levels of complexity. Such integration in electrical engineering arises from massive parallelism and interconnections, rather than fundamental component complexity. The ability to truly integrate molecular components remains crucial for the construction of next-generation molecular devices. Researchers have now succeeded in building a medium- scale integrated molecular circuit, integrating 128 deoxyribozyme-based logic gates, 32 input DNA molecules, and 8 two-channel fluorescent outputs across 8 wells.

Oct 11th, 2006

Anti-bioterrorism applications with carbon nanotubes

Anthrax is an acute infectious disease caused by the bacteria Bacillus anthracis and is highly lethal in some forms. Anthrax spores can and have been used in biological warfare. "Weaponizing" the spores requires a process to make an aerosol form of anthrax so that they easily can enter the lungs. Inhalation is the most lethal form of anthrax infection. Consequently there has been significant interest in the surface structure and characteristics of anthrax spores as related to their binding by molecular species. The investigation of such binding is obviously important to the development of countermeasure technologies for the detection and decontamination of anthrax spores. A group of researchers at Clemson University have come up with an agent that clings to the anthrax spores to make their inhalation into the lungs difficult.

Oct 10th, 2006

A new promising class of non-precious metal catalysts for fuel cells

Fuel cells are electrochemical energy conversion devices for the direct conversion of the chemical energy of a fuel into electricity. They are among the key enabling technologies for the transition to a hydrogen-based economy. Of several different types of fuel cells under development today, polymer electrolyte fuel cells (PEFCs) have been recognized as a potential future power source for zero emission vehicles. However, to become commercially viable, PEFCs have to overcome the barrier of high catalyst cost caused by the exclusive use of platinum and platinum-based catalysts in the fuel-cell electrodes. Researchers at Los Alamos National Laboratory now demonstrate a new class of low cost (non-precious metal)/(heteroatomic polymer) nanocomposite catalysts for the PEFC cathode, capable of combining high oxygen-reduction activity with good performance durability. The results of their study show that heteroatomic polymers can be used not only to stabilize the nonprecious metal in the acidic environment of the PEFC cathode but also to generate active sites for oxygen reduction reaction.

Oct 6th, 2006

A new spin on an older technology

electrospinningBecause of the huge effective surface area, the ability to blend different types of polymers, and the fact that the process is conducted at room temperature so that biological compounds can be loaded into the fibers, electrospinning has enormous potential to create new families of higher performance products across a wide array of industry sectors. For a technique invented in 1934, we are just now beginning to see its true potential.

Oct 5th, 2006

A tabletop technique to probe the spin dependent transport in single nanosized objects

Researchers have developed an original process to investigate the spin transport properties of a single nanoparticle and provided evidence for its successful realization. This new approach paves the way for a more in-depth study of magneto-Coulomb phenomena in nanosized clusters. While only two results are available up to now on connecting a 0D nano-object to ferromagnetic electrodes enabling spin polarized injection and detection, extensive theoretical studies have been undertaken, leaving the field wide open for experiments.

Oct 4th, 2006

Highly efficient antibacterial nanocomposite coatings with gold and silver nanoparticles

The potential use of antimicrobial surface coatings ranges from medicine, where medical device infection is associated with significant healthcare costs, to the construction industry and the food packaging industry. Thin films which contain silver have been seen as promising candidate coatings. Silver is known as one of the oldest antimicrobial agents. Silver ions are thought to inhibit bacterial enzymes and bind to DNA. Silver has been used effectively against different bacteria, fungi and viruses. Researchers in Germany developed a new method for producing antibacterial metal/polymer nanocomposite coatings, where silver and gold nanoparticles are only incorporated in a thin surface layer. The new material shows a greatly enhanced antibacterial efficiency of the thin films.

Oct 3rd, 2006

Nature's bottom-up nanofabrication of armor

Seashells are natural armor materials. The need for toughness arises because aquatic organisms are subject to fluctuating forces and impacts during motion or through interaction with a moving environment. Nacre (mother-of-pearl), the pearly internal layer of many mollusc shells, is the best example of a natural armor material that exhibits structural robustness, despite the brittle nature of their ceramic constituents. This material is composed of about 95% inorganic aragonite with only a few percent of organic biopolymer by volume. New research at the university of South Carolina reveals the toughening secrets in nacre: rotation and deformation of aragonite nanograins absorb energy in the deformation of nacre. The aragonite nanograins in nacre are not brittle but deformable. The new findings may lead to the development of ultra-tough nanocomposites, for instance for armor material, by realizing the rotation mechanism.

Oct 2nd, 2006