The toxicity issues surrounding carbon nanotubes (CNTs) are highly relevant for two reasons: Firstly, as more and more products containing CNTs come to market, there is a chance that free CNTs get released during their life cycles, most likely during production or disposal, and find their way through the environment into the body. Secondly, and much more pertinent with regard to potential health risks, is the use of CNTs in biological and medical settings. CNTs interesting structural, chemical, electrical, and optical properties are explored by numerous nanomedicine research groups around the world with the goal of drastically improving performance and efficacy of biological detection, imaging, and therapy applications. In many of these envisaged applications, CNTs would be deliberately injected or implanted in the body. While it has been shown that carbon nanotubes can indeed act as a means for drug delivery, negative effects such as unusual and robust inflammatory response, oxidative stress and formation of free radicals, and the accumulation of peroxidative products have also been found as a result of carbon nanotubes and their accumulated aggregates. As a possible solution, scientists have provided compelling evidence of the biodegradation of carbon nanotubes by horseradish peroxidase and hydrogen peroxide over the period of several weeks. This marks a promising possibility for nanotubes to be degraded by horseradish peroxidase in environmentally relevant settings.
There is a general perception that nanotechnologies will have a significant impact on developing 'green' and 'clean' technologies with considerable environmental benefits - be it in areas ranging from water treatment to energy breakthroughs and hydrogen applications. As a matter of fact, renewable energy applications probably are the areas where nanotechnology will make its first large-scale commercial breakthroughs. Conflicting with this positive message is the growing body of research that raises questions about the potentially negative effects of engineered nanoparticles on human health and the environment. However, there is one area of nanotechnology that so far hasn't received the necessary attention: the actual processes of manufacturing nanomaterials and the environmental footprint they create, in absolute terms and in comparison with existing industrial manufacturing processes. Analogous to other industrial manufacturing processes, nanoproducts must proceed through various manufacturing stages to produce a material or device with nanoscale dimensions.
Safe, efficient and compact hydrogen storage is a major challenge in order to realize hydrogen powered transport. According to the U.S. Department of Energy Freedom CAR program roadmap, the on-board hydrogen storage system should provide 6 weight % of hydrogen capacity at room temperature to be considered for technological implementation. We have written several Nanowerk Spotlights where we introdduced and described novel, nanotechnology-based concepts for economically viable hydrogen storage methods. Scientists consider the storage of hydrogen in the absorbed form as the most appropriate way to solve the storage problem and one particular group of materials they have focused on are carbon nanomaterials like nanotubes or fullerenes. Offering a novel material approach, a theoretical investigation by researchers in Greece has shown that CNTs and graphene sheets could be combined to form novel 3-D nanostructures capable of enhancing hydrogen storage.
Nanotechnology applications could provide decisive technological breakthroughs in the energy sector and have a considerable impact on creating the sustainable energy supply that is required to make the transition from fossil fuels. Possibilities range from gradual short- and medium-term improvements for a more efficient use of conventional and renewable energy sources all the way to completely new long-term approaches for energy recovery and utilization. With enough political will - and funding - nanotechnology could make essential contributions to sustainable energy supply and global climate protection policies. The technological foundation is there, all it takes is political leadership to create the right research and investment conditions to make it happen.
You might have seen the news article that made the rounds a few days ago about how the stained glass windows in medieval churches actually were a nanotechnology application capable of purifying air. While this is a pretty cool headline to capture readers' interest, the underlying finding is much more profound and could open up a new direction in catalysis and herald significant changes in the economy and environmental impact of chemical production. One of the great challenges for catalysis is to find catalysts which can work well under visible light. If scientists manage to crack this problem it would mean that we could use sunlight - the ultimate free, abundant and 'green' energy source - to drive chemical reactions. This is in contrast to today's conventional chemical reactions that often require high temperatures and therefore waste a lot of energy.
While everybody talks about oil prices, water scarcity and water pollution are two increasingly pressing problems that could easily and quickly surpass the oil issue. Renewable energy sources can substitute for fossil fuels - but freshwater can't be replaced. This makes the ability to remove toxic contaminants from aquatic environments rapidly, efficiently, and within reasonable costs an important technological challenge. Nanotechnology could play an important role in this regard. An active emerging area of research is the development of novel nanomaterials with increased affinity, capacity, and selectivity for heavy metals and other contaminants. The benefits from use of nanomaterials may derive from their enhanced reactivity, surface area and sequestration characteristics. Numerous nanomaterials are in various stages of research and development, each possessing unique functionalities that are potentially applicable to the remediation of industrial wastewater, groundwater, surface water and drinking water. The main goal for most of this research is to develop low-cost and environmentally friendly materials for removal of heavy metals from water. A recent example is a novel low-cost magnetic sorbent material for the removal of heavy metal ions from water, developed by scientists in China.
Radioactive material is toxic because it creates ions when it reacts with biological molecules. These ions can form free radicals, which damage proteins, membranes, and nucleic acids. Free radicals damage components of the cells' membranes, proteins or genetic material by "oxidizing" them - the same chemical reaction that causes iron to rust. This is called 'oxidative stress'. Many forms of cancer are thought to be the result of reactions between free radicals and DNA, resulting in mutations that can adversely affect the cell cycle and potentially lead to malignancy. Nanotechnology has provided numerous constructs that reduce oxidative damage in engineering applications with great efficiency. As a new research report shows, nanotechnology applications could also help to remediate radioactive contamination at the source, by removing radioactive ions from the environment. Environmental contamination with radioactive ions that originate from the processing of uranium or the leakage of nuclear reactors is a potential serious health threat because it can leach into groundwater and contaminate drinking water supplies for large population areas. The key issue in developing technologies for the removal of radioactive ions from the environment and their subsequent safe disposal is to devise materials which are able to absorb radioactive ions irreversibly, selectively, efficiently, and in large quantities from contaminated water.
Remember the movie blockbuster Erin Brockovich? The film is based on a real world legal case that revolves around hexavalent chromium, also known as chromium (VI), used by the Pacific Gas and Electric Company to control corrosion in cooling towers in its Hinkley, CA compressor station. Chromium (VI), a natural metal, is known to be toxic and is recognized as a human carcinogen via inhalation. It also is widely used by industry in the manufacture of stainless steel, welding, painting and pigment application, electroplating, and other surface coating processes. Researchers in Germany now have developed a novel method of multilayer anticorrosion protection including the surface pre-treatment by sonication and deposition of polyelectrolytes and inhibitors. This method results in the formation of a smart polymer nanonetwork for environmentally friendly organic inhibitors.