You might have seen our recent Nanowerk Spotlight on modern military nanotechnology (Military nanotechnology - how worried should we be?) and read about the hundreds of millions of dollars that the U.S. military pours into nanotech research every year. Well, it turns out that metalsmiths in India perhaps as early as 300 AD, and presumably with a much lower budget, developed a new technique known as wootz steel that produced a high-carbon steel of unusually high purity. Wootz, which are small steel ingots, was widely exported and became particularly famous in the Middle East, where it became known as Damascus steel. This steel had extraordinary mechanical properties and an exceptionally sharp cutting edge. The original Damascus steel swords were made possibly as early as 500 AD to as late as 1750 AD. What's so interesting about this? It turns out that the secret of Damascus steel is carbon nanotubes. Recently discovered in the nanostructure of a 17th century Damascus saber, the nanotubes could have encapsulated iron-carbide (cementite) nanowires that might give clues to the mechanical strength and sharpness of these swords.
The electrical properties of CNTs are extremely sensitive to defects which can be introduced during the growth, by mechanical strain, or by irradiation with energetic particles such as electrons, heavy ions, alpha-particles, and protons. When highly energetic particles collide, a latchup, electrical interference, charging, sputtering, erosion, and puncture of the target device can occur. Therefore the information on the effects of various types of high energetic irradiation on CNTs and other nanomaterials will be important in developing radiation-robust devices and circuits of nanomaterials under aerospace environment. As a result, degradation of the device performance and lifetime or even a system failure of the underlying electronics may happen. Researchers in South Korea conducted a systematic study of the effects of proton irradiation on the electrical properties of CNT network field effect transistor (FET) devices showing metallic or semiconducting behaviors. The most important outcome of this work is that no significant change in the electrical properties of CNT-based FET was observed, even after high-energy proton beam irradiated directly on the device. This result show that CNT-based devices can be a promising substitute for classical silicon-based devices, which are known to be very fragile against proton radiations
Zinc oxide (ZnO) is considered a workhorse of technological development exhibiting excellent electrical, optical, and chemical properties with a broad range of applications as semiconductors, in optical devices, piezoelectric devices, surface acoustic wave devices, sensors, transparent electrodes, solar cells, antibacterial activity etc. Thin films or nanoscale coating of ZnO nanoparticles on suitable substrates are viewed with great interest for their potential applications as substrates for functional coating, printing, UV inks, e-print, optical communication (security-papers), protection, barriers, portable energy, sensors, photocatalytic wallpaper with antibacterial activity etc. Various methods like chemical, thermal, spin coating, spray pyrolysis, pulsed laser deposition have been used for thin film formation but they are limited to solid supports such as metal, metal oxides, glass or other thermally stable substrates. Coating of ZnO nanoparticles on thermolabile surfaces is scarce and coating on paper was yet to be reported. Paper as a substrate is an economic alternative for technological applications having desired portability and flexibility. Researchers from the National Tsing Hua University in Taiwan found a way of coating paper with ZnO nanoparticles using ultrasound.
Synthetic nanopores are promising biosensors, possibly as a robust and versatile replacement for their biological counterparts in characterizing DNA, RNA, and polypeptides. In the past few years since their first introduction, synthetic nanopores have been found in a wide range of biological and nonbiological applications, including characterization of double-stranded DNA length and folding, detection of immune complexes, profiling of optical traps, and basic studies of nanoscale ion transport mechanisms. Given the broad technological importance of synthetic nanopores, it is highly desirable to develop a reliable technique for fabricating these devices using low-cost materials. Researchers at Brown University now report a systematic study of nanopore formation in a plastics system. They also developed a lithography-free technique for fabricating nanopores with biomolecular sensing capabilities.
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.
All major powers are making efforts to research and develop nanotechnology- based materials and systems for military use. Asian and European countries, with the exception of Sweden (Swedish Defence Nanotechnology Programme), do not run dedicated programs for defense nanotechnology research. Rather, they integrate several nanotechnology- related projects within their traditional defense-research structures, e.g., as materials research, electronic devices research, or bio-chemical protection research. Not so the U.S. military. Stressing continued technological superiority as its main strategic advantage, it is determined to exploit nanotechnology for future military use and it certainly wants to be No. 1 in this area. The U.S. Department of Defense (DoD) is a major investor, spending well over 30% of all federal investment dollars in nanotechnology. Of the $352m spent on nanotech by the DoD in 2005, $1m, or roughly 0.25%, went into research dealing with potential health and environmental risks. In 2006, estimated DoD nanotechnology expenditures will be $436m - but the risk-related research stays at $1m.
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.
Building construction and operation is estimated to be a trillion dollar per year industry worldwide. And it is one that is ripe for the innovations offered by nanotechnology and nanomaterials. Already, dozens of building materials incorporate nanotechnology, from self-cleaning windows to flexible solar panels to wi-fi blocking paint. Many more are in development, including self-healing concrete, materials to block ultraviolet and infrared radiation, smog-eating coatings and light-emitting walls and ceilings. Nanotech is also starting to make the smart home a reality. Nanotech-enabled sensors are available today to monitor temperature, humidity, and airborne toxins. The nanosensor market is expected to reach $17.2 billion by 2012. Soon, inexpensive sensors will be available to monitor vibration, decay and other performance concerns in building components from structural members to appliances. Nanotechnology is also rapidly improving the batteries and wireless components used in these sensors. In the not-too-distant future, sensors will be ubiquitous in buildings, gathering data about the environment and building users. Building components will be intelligent and interactive. Nanosensors and nano building materials raise questions for building designers, builders, owners and users. What will the consequences be as buildings become increasingly intelligent and nanomaterials become an everyday part of the buildings that surround us?