Back in March Nanowerk Spotlight reported on work by Sandia researchers who developed a range of novel platinum nanostructures with potential applications in fuel and solar cells (see: Novel platinum nanostructures). Through the use of liposomal templating and a photocatalytic seeding strategy the Sandia team produced a variety of novel dendritic platinum nanostructures such as flat dendritic nanosheets and various foam nanostructures (nanospheres and monoliths). In an intriguing follow-up report on the growth of hollow platinum nanocages, they now show for the first time a one-to-one correspondence between the porphyrin photocatalyst molecules and the seed particles that go on to grow the dendrites. This indicates that the whole process might be used for nanotagging biological molecules and other structures that have been labeled with a photocatalytic porphyrin.
Nanoshells are a novel class of optically tunable nanoparticles that consist of alternating dielectric and metal layers. They have been shown to have tunable absorption frequencies that are dependent on the ratio of their inner and outer radii. Therefore nanoshells can potentially be used as contrast agents for multi-label molecular imaging, provided that the shell thicknesses are tuned to specific ratios. When used as contrast agents, nanoshells of small dimensions offer advantages in terms of delivery to target sites in living tissues, bioconjugation, steric hindrance, and binding kinetics. Besides their improved tissue penetration, smaller nanoshells generate a strong surface plasmon resonance and may exhibit absorption peaks in the visible?near-infrared spectrum. Sub-100 nm nanoshells also provide large surface areas to volume ratios for chemical functionalization that can be used to link multiple diagnostic (e.g. radioisotopic or magnetic) and therapeutic (e.g. anticancer) agents. Researchers at Northwestern University have come up with a relatively easy way to synthesize sub-100 nm nanoparticles that give rise to tunable peaks.
The interest in research on magnetic nanocapsules has increased considerably since it was found that their intermediate states between bulk and atomic materials may present different magnetic behaviors from their correspondent bulk counterparts. This difference offers an opportunity for researchers to develop many important technical applications such as magnetic refrigerators, magnetic recording, or magnetic fluids. As the principal contributor of the novel properties, various magnetic cores of nanocapsules, including rare earths and their carbides, have been researched extensively over the past two decades. In addition, cores of magnetic rare-earth intermetallic compounds are becoming a major research focus. However, there have been considerable difficulties in preventing oxidation of the particles of rare-earth elements and compounds. Researchers in PR China have now succeeded in synthesizing a new type of intermetallic nanocapsule that can be applied in cyrogenic magnetic refrigerator devices.
Various methods have been developed for growing well-aligned CNTs based on variant alignment mechanisms such as 'overcrowding growth', 'template hindrance growth' and 'electric field induced growth'. Compared to other methods, electric field induced growth has been considered to be a more effective and controllable method for producing well-aligned single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Interestingly, while the alignment of CNTs became more controllable and repeatable with the assistance of an electric field, it was also shown that for CNTs grown in an electric field, the diameter uniformity and the crystallinity of graphite sheets of CNTs were clearly improved. This led Chinese researchers to develop an electric-field-induced method to not only improve CNT uniformity but also to create a new approach to control the microstructure of CNTs.
The use of renewable resources (biomass) as an alternate source for fuel and the production of valuable chemicals is becoming a topic of great interest and a driving force behind research into biorefinery concepts. In the early parts of the 20th century, most nonfuel industrial products such as medicines, paints, chemicals, dyes, and fibers were made from vegetables, plant and crops. During the 1970s, petroleum based organic chemicals had largely replaced those derived from plant materials, capturing more than 95% of the markets previously held by products from biological sources. By then, petroleum accounted for more than 70% of our fuel. However, recent developments in biobased materials research show prospects that many petrochemical derived products can be replaced with industrial materials processed from renewable resources. Researchers continue to make progress in research and development of new technologies that bring down the cost of processing plant matter into value-added products. Rising environmental concerns are also suggesting the use of agriculture and forestry resources as alternative feedstock. Being able to develop soft nanomaterials and fuel from biomass will have a direct impact on industrial applications and economically viable alternatives. Researchers already have used plant-derived resources to make a variety of soft nanomaterials, which are useful for a wide range of applications.
As scientific interests and engineering applications delve down to the nanometer scale, there is a strong need to fabricate nanostructures with good regularity and controllability of their pattern, size, and shape. Furthermore, the nanostructures are useful in many applications only if they cover a relatively large sample area and the manufacturing cost is reasonable. Researchers at UCLA have now achieved a breakthrough by developing a simple but efficient fabrication method to produce well-regulated silicon nanostructures over a large sample area with excellent control of their pattern, size, and shape. Affordable surfaces with well-controlled nanostructures over a large area open new applications not only in electronics but also in the physical world through their unique properties originating from their nanoscale geometry.
Adhesives may be broadly divided in two classes: structural and pressure sensitive. To form a permanent bond, structural adhesives harden via processes such as evaporation of solvent or water (white glue), reaction with radiation (dental adhesives), chemical reaction (two part epoxy), or cooling (hot melt). In contrast, pressure sensitive adhesives (PSAs) form a bond simply by the application of light pressure to attach the adhesive to the adherend. PSAs adhere instantly and firmly to nearly any surface under the application of light pressure, without covalent bonding or activation. Waterborne pressure-sensitive adhesives solve the problem of meeting environmental regulations that forbid the emission of volatile organic compounds in manufacturing. However, often waterborne PSAs have poor adhesive performance. Another problem, particularly relevant to display technologies, is how to make an electrically-conducting material that is also flexible and optically transparent. Indium tin oxide is commonly used as a transparent electrode in displays, but it is brittle and prone to mechanical failure or scratching. Adhesives can be made electrically conductive through the addition of metal particles, but then they lose optical transparency, and their adhesiveness is diminished. New research shows that waterborne PSAs containing single-wall carbon nanotubes (SWNTs) meet the requirements of environmental regulations while improving the adhesive performance. The resulting unprecedented combination of adhesion and conductivity properties holds enormous potential for demanding applications in displays and electronics.
Sophisticated biomolecular motors have evolved in nature, where motor proteins actively control the delivery and assembly of materials within cells. In contrast, the development of synthetic nanomotors is in its infancy. Such nanomotors are currently explored for an increasing number of applications in hybrid bionanodevices. Along these lines, gliding motility assays, where reconstituted microtubule filaments are propelled over a substrate by surface-attached motor proteins, have been used to transport micro- and nanosized objects, such as small beads, quantum dots or DNA molecules. However, one prerequisite for controllable nanotransport is the reliable guiding of filament movement along predefined paths, a challenging task that has recently been achieved only via costly and labor-intensive topographical surface modifications. Researchers have now demonstrated a novel approach for the nanostructuring of surfaces with functional motor proteins. In contrast to all other current methods, their approach allows the three-dimensionally oriented deposition of proteins on surfaces, being the result of first binding them to the highly oriented and regulated structures of microtubules and then transferring them to the surface.