The ideal drug carrier may be something out of science fiction. In principle, it is injected into the body and transports itself to the correct target, such as a tumor, and delivers the required dose at this target. This idealized concept was first proposed by Paul Ehrlich at the beginning of the 20th century and was nicknamed the "magic bullet" concept. With the advent of nanotechnology and nanomedicine this dream is rapidly becoming a reality. Nanotechnology has already been applied to drug delivery and cosmetics through the use of liposomal technology, and now nanoparticles and nanotubes present an exciting and more promising alternative.
Ethanol is all the rage these days. Although we have been drinking ethanol, an alcohol, for thousands of years (fermented beverages such as beer and wine may contain up to 15-25% ethanol by volume), the recent interest has been sparked by its use as a renewable fuel alternative to gasoline. Indeed, the largest single use of ethanol is as a motor fuel and fuel additive. Ethanol is produced by fermentation when certain species of yeast metabolize sugar. The process works with all biological feedstocks that contain appreciable amounts of sugar or materials that can be converted into sugar such as starch or cellulose. The primary feedstock for ethanol production in the U.S. is corn. In Brazil, the world's leading ethanol producer, it's mostly derived from sugar cane. While there is a heated controversy over the economic and ecological benefits of using biomass for producing ethanol fuel, it seems that nanotechnology's jack-of-all-trades, the carbon nanotube (CNT), might provide a solution here as well. CNTs are increasingly recognized as promising materials for catalysis, either as catalysts themselves, as catalyst additives or as catalyst supports. Researchers in China now have used CNTs loaded with rhodium (Rh) nanoparticles as reactors to convert a gas mixture of carbon monoxide and hydrogen into ethanol. This appears to be the first example where the activity and selectivity of a metal-catalyzed gas-phase reaction benefits significantly from proceeding inside a nanosized CNT reaction vessel.
Scientists involved in cancer research are showing a lot of interest in carbon nanotubes (CNTs) to be used in basically three cancer-fighting areas. CNTs are being developed as targeted delivery vehicles for anticancer drugs right into cancer cells - think of really, really tiny injection needles. They are also used as the therapeutic agent itself; there is research that shows that CNTs can act as nanoscale bombs that literally blow apart a cancer cell. A third area of application is using CNTs as imaging agents. Particularly single-walled CNTs (SWCNTs) are under active development for various biomedical applications. One of the issues in using CNTs for therapeutic applications is the question of how to get them to the desired place within the organism, say a tumor cell. Another significant problem in applying CNTs for biological applications is that the nanotubes do not stay suspended as discrete nanotubes in aqueous solutions. Coupling the CNT with biomolecules, such as proteins, is a good method for targeting specific sites but has the disadvantage of either reducing protein activity or CNT absorption or both. A novel method demonstrates that it is possible to achieve complete retention of enzymatic activity of adsorbed proteins as well as retention of a substantial fraction of the near-infrared (NIR) absorption of SWCNTs.
To achieve the full benefits of the amazing properties of carbon nanotubes (CNTs) researchers are exploring all kinds of CNT composite materials. Material engineers are interested because this will lead to lighter,stronger and tougher materials. Another fascinating area involves CNT/polymer composite structures that will lead to a vast range of improved and novel applications, from antistatic and EMI shielding to more efficient fuel and solar cells, to nanoelectronic devices. One particular area of CNT/polymer composites is dealing with DNA-CNTs hybrids. Although researchers expect a plethora of new applications, the fact that even the formation mechanism of these complexes is not yet clear shows how early in the game this research still is. This might be due to the fact that in spite of the quite large number of experimental investigations on the interaction between DNA and CNTs, the number of theoretical studies is limited. Researchers in Germany now present, for the first time, the results of a systematic quantum mechanical modeling of the stability and the electronic properties of complexes based on single-walled carbon nanotubes, which are helically wrapped by DNA molecules.
Diesel-burning engines are a major contributor to environmental pollution. They emit a mixture of gases and fine particles that contain some 40, mostly toxic chemicals, including benzene, butadiene, dioxin and mercury compounds. Diesel exhaust is listed as a known or probable human carcinogen by several state and federal agencies in the United States. Wouldn't it be nice if we could render diesel soot harmless before it gets released into the environment? Wouldn't it even be nicer if we could use this soot to manufacture something useful? Japanese scientists have come up not only with a unique technique for effectively collecting diesel soot but also a method for using this soot as a precursor for the production of single-walled carbon nanotubes. How is that as a practical example for green nanotechnology?
Over the next few years, semiconductor fabrication will move from the current state-of-the-art generation of 90 nanometer processes to the next 65 nm and 45 nm generations. Intel is even already working on 32 nm processor technology, code-named "Westmere", that is expected to hit the market sometime around 2009. The result of these efforts will be billion-transistor processors where a billion or more transistor-based circuits are integrated into a single chip. One of the increasingly difficult problems that chip designers are facing is that the high density of components packed on a chip makes interconnections increasingly difficult. In order to be able to continue the trend predicted by Moore's law, at least for a few more years, researchers are now turning to alternative materials for transistors and interconnect and one of the prime candidates for this job are single-walled carbon nanotubes (SWCNT). However, one of the biggest limitations of conventional carbon nanotube device fabrication techniques today is the inability to scale up the processes to fabricate a large number of devices on a single chip. Researchers in Germany have now demonstrated the directed and precise assembly of single-nanotube devices with an integration density of several million devices per square centimeter, using a novel aspect of nanotube dielectrophoresis. This development is a big step towards commercial realization of CNT-based electronic devices and their integration into the existing silicon-based processor technologies.
Current production methods for carbon nanotubes (CNT) result in units with different diameter, length, chirality and electronic properties, all packed together in bundles, and often blended with some amount of amorphous carbon. The separation of nanotubes according to desired properties remains a technical challenge. Especially single-walled carbon nanotube (SWCNT) sorting is a challenge because the composition and chemical properties of SWCNTs of different types are very similar, making conventional separation techniques inefficient. In order to find ways to control nanotube diameter and chirality it would be necessary to monitor nanotube growth. Then, if one knew exactly how to grow nanotubes of different characteristics, one could control their electronic properties because, depending on the way the carbon atoms are arrange around the 'waist' of a nanotube, the electronic properties could vary from metallic to semiconducting. An international group of researchers has demonstrated a novel approach to use nanotubes as reaction cells, enabling them to monitor the birth and growth of carbon nanotubes, and taking some spectacular image of this process.
Synthesis of carbon nanotubes (CNTs) is a rapidly advancing field, but there is a lot that researchers don't know about how nanotubes form and grow. Synthesis, while rapidly developing, is currently the weakest link for most nanotube applications, with high yield and high precision diameter and chirality control being important goals. Historically, in situ characterization tools have accelerated progress in synthesis for many advanced materials, and there is widespread recognition that in situ tools have the potential to improve CNT synthesis as well. Ideally one would like to detect individual nanotubes and ensembles as they grow and measure their physical properties while imposing minimal constraints on the synthesis method. In other words, with a good understanding of the synthesis process we would be better able to control the product. It is feasible that by actually observing nanotubes as they grow one will gain a better understanding of the growth process and also better characterize the grown product. Greater control over the physical characteristics of the nanotube product is essential to enable many applications, as well as many fundamental studies. Although chemical vapor deposition (CVD) is now a very standard method to synthesize CNTs, there aren't really standard in situ tools to characterize nanotubes during growth. Researchers in Canada have now shown how global Raman imaging (GRI) can be used to characterize the CVD growth of CNTs in situ and in real time.