Platinum nanoparticles are widely used as the cathode material in hydrogen/oxygen fuel cells due to their efficiency in catalyzing the oxygen reduction reaction (ORR), the process that breaks the bonds of the oxygen molecules. Although platinum is still considered the state-of-the-art ORR catalyst, it does not exhibit good stability. Typically, catalyst performance degradation begins as soon as the catalyst is introduced into a fuel cell and continues until it is no longer active. Platinum can lose its effectiveness either by clumping together or by becoming 'poisoned' by carbon monoxide, requiring high hydrogen purity or higher catalyst densities for the fuel cell to stay effective. This, together with the high cost of platinum is seen as one of the major showstoppers to producing mass market fuel cells for commercial applications. Researchers now found that vertically-aligned nitrogen-containing carbon nanotubes could be used as effective ORR electrocatalysts.
While the concept of a 'machine' can be extended to the nano-world, these nanomachines can not be built by just further miniaturizing machine blueprints from the macro-world. On the nanoscale, the nanomachine components would be atomic or molecular structures each designed to perform a specific task which, all taken together, would result in a complex function. The problem is that functional nanomachinery will need to take into account the quantum effects that dominate the behavior of matter at the nanoscale, affecting the optical, electrical and magnetic behavior of materials. An alternative approach to miniaturizing machines down to the nanoscale is to borrow from the highly successful design shop of Mother Nature. Until a few years ago, catalytic micro- and nanomotors have been more or less unknown outside biology. With the explosive growth in nanotechnology, however, catalyzed nanoscale motion has become a heavily researched phenomenon. Scientists find that there is much to be learned from nature's motor systems for the development of artificial nanoscale machinery. Joseph Wang, who runs the Laboratory for Nanobioelectronics at the Department of NanoEngineering at UC San Diego, has just published a review where he addresses the question: Can Man-Made Nanomachines Compete with Nature Biomotors?
The properties of a quantum dot are not only determined by its size but also by its shape, composition, and structure, for instance if it's solid or hollow. A reliable manufacturing technology that makes use of nanocrystals' properties - for a wide-ranging number of applications in such areas as catalysis, electronics, photonics, information storage, imaging, medicine, or sensing - needs to be capable of churning out large quantities of nanocrystals where each batch is produced according to the exactly same parameters. In a recent review article, Sara Skrabalak from Indiana University and Younan Xia from Washington University in St. Louis, describe recent advances in seeded growth as the ultimate approach to producing metal nanocrystals with precisely controlled sizes, shapes, and compositions - the necessary first step toward their use and assembly for large-scale applications.
DNA, the fundamental building block of life, has become an intense nanotechnology research field. DNA molecules can serve as precisely controllable and programmable scaffolds for organizing functional nanomaterials in the design, fabrication, and characterization of nanoscale devices such as sensors and electronics. Most DNA research on controlled self-assembly deals with two-dimensional, i.e. flat, patterns and an expansion of these arrays into the third dimension has been challenging. New research coming out of UC Santa Barbara describes the self-assembly of multilayer hexagonal DNA arrays through highly regular interlayer packing. The researchers found that DNA arrays assembled into a two dimensional hexagonal pattern, or a sheet, assemble further into multilayer stacks.
In a previous Nanotechnology Spotlight, we describe how, in order to develop tomorrow's supermaterials, scientists need to unlock nature's structural design rules, in particular for nanoscopic hierarchical molecular structures, and make them available to engineers. This is only possible through a deep understanding of the structure-property relations in biological materials. There is also a surprising relationship between these material design issues and the understanding (or rather lack thereof) of genetic diseases, where structural changes are due to mutations on the molecular level that lead to changed chemical and mechanical properties, which in turn lead to a malfunction of the protein network under mechanical load. Hierarchical nanostructures - ranging through atomistic, molecular and macroscopic scales - represent universal features of biological protein materials. New work by MIT professor Markus Buehler discusses the role of these structural hierarchies in determining properties of biological materials.
Among the many challenges that researchers have to overcome in developing bottom-up nanotechnology fabrication techniques and processes, the requirement for extremely precise, nanometer-scale control of positioning and shaping of objects is one of the most vexing. New work by a team of scientists in Korea demonstrates the position- and shape-controlled growth of nanoarchitectures using the selective growth of nanowalls with conventional lithography and catalyst-free metal organic vapor-phase epitaxy (MOVPE). This presents a significant advance towards the fabrication of artificial 1D and 2D nanomaterials as functional components in many integrated electronic and photonic devices.
Colloidal materials have been playing a major role in many research fields such as chemistry, materials science, condensed matter physics, applied optics, fluid dynamics, and biology. Most of these studies require the use of monodisperse colloidal particles with uniformity in shape, size, composition, structure and surface properties. Both our current understanding of various physical phenomena and our capability to fabricate new functional materials have been considerably enriched by the development of synthetic strategies that are capable of generating copious quantities of colloidal entities of good size uniformity. Nevertheless, most of the available monodisperse colloidal materials are spherical because this represents a thermodynamically favorable state in terms of surface energy. This strongly limits the number of new structures which can be engineered by using these colloids as building blocks. A novel synthetic route can now produce a full set of new non-spherical, binary colloids with regular morphology in a high yield.
One of the major concerns regarding the potential risks of nanotechnology applications are possible toxic effects of nanoparticles. The concern is that these materials have the capacity to penetrate cells and potentially translocate to other cells, tissues and organs remote from the portal of entry to the body. This is considered to be a necessary step in the movement of particles deposited in the lung, entering the blood, acting upon cells in other tissues, manifesting ultimately in a physiological response. The importance of translocation in nanoparticle toxicology has been the subject of a recently completed nanotoxicology research project called 'Cell Pen', conducted by the Institute of Occupational Medicine in the UK together with a team of multi-disciplinary experts. As with so many previous nanotechnology risk review reports, it appears that this documents highlight more the uncertainties and the unknown than what is actually known about the interaction of nanoparticles with cells.