Among the various production methods for carbon nanotubes and graphene, currently only chemical vapor deposition techniques demonstrate a significant opportunity for mass production of CNT material. Using the CVD process, which is based on the catalytic action of metals, manufacturers can combine a metal catalyst such as iron with reaction gases such as hydrogen to form carbon nanotubes inside a high-temperature furnace. In order to optimize the synthesis process, a detailed understanding of the interaction between nanotubes or graphene and metal atoms is required - something that has been missing so far. Researchers in France have now shown that it is possible to create atomic-scale defects in carbon nanotubes and in graphene in preselected positions with a focused electron beam and to use these defects as trapping centers for foreign atoms.
Carbon nanotubes' 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, for instance as intercellular molecular delivery vehicles. One of the issues researchers have been exploring is how - once the primary role of CNTs in a therapeutic application is fulfilled - they can promote the rapid removal of CNTs from the body, or the dispersal of aggregated clusters to sub-micron size in order to mitigate the harmful effects. Researchers in India have now demonstrated a novel, optical tweezers based approach to scavenge CNTs from biological fluids such as blood.
Electrically conductive composite materials capable of substantial elastic stretch and bending - conductive rubbers - is an industrially important field. The composites are needed for such applications as smart clothing, flexible displays, stretchable circuits, strain gauges, implantable devices, high-stroke microelectromechanical systems, and actuators. A variety of approaches involving carbon nanotubes and elastic polymers have been suggested for the fabrication of conductive elastic composites. Various studies indicated that high loading of CNTs or other conductive additives into the polymer was necessary to obtain a highly conducting composite. A research team has now demonstrated that a combination of high stretchability and high electrical conductivity can be obtained for composites prepared from three-dimensional CNT structures.
The development of artificial muscles is one of the key areas for bionic enhancements or replacements. The discovery of the electromechanical actuation properties of single-walled carbon nanotubes and the complex behavior of multi-walled carbon nanotubes has led to the development of various carbon nanotube actuators. Besides artificial muscles, potential applications include microelectro-mechanical systems (MEMS), biomimetic micro-and nanorobots, and micro fluidic devices. Recently, a new class of active system, carbon nanotube/polymer composite actuators, has received great attention with regard to macroscopic artificial muscle applications. It has been demonstrated that successful introduction of the highly conductive CNTs could significantly enhance the polymer nanocomposite's electrical, thermal, mechanical, and interface properties, thus providing a suitable material for novel artificial muscle-like actuator investigations.
Graphene is being explored, among many other uses, as a replacement material for silicon in photonic devices to expand the wavelength range of operation and to improve performance. Another area where graphene potentially could replace silicon and could have a huge impact is as light-absorbing material in solar cells. Although it has been well known that graphene has very attractive properties for photovoltaic applications - tunable bandgap and large optical absorptivity - these advantages could not be exploited so far due to the problem of fabricating solution-processable, stable, and large enough, size-controllable graphene structures useful for charge collection in solar cells. Graphene quantum dots might offer a solution to these fabrication problems.
Few technologies on the near-term horizon offer as much potential for game-changing results as do carbon nanotube products. But in an age where the state-of-the-art in global defense, transportation and energy depend on meaningful advancement and delivery of novel materials, it is critical to view scalability to be as important as product performance itself. To date, few nanotechnology manufacturers have solved this scaling problem - choosing instead to focus most of their resources on research and advances in material science. Materials without a meaningful path to volume delivery will remain just that; novel inventions with very little practical value. Instead, addressing the issue of scaled production is the central challenge for today's nanotechnology firms.
It has been known for several years that carbon nanotubes would heat, ignite and luminesce upon exposure to certain types of electromagnetic radiation, including laser light. However, no one expected any form of fullerenes to do the same thing. Until now. A team at the University of Florida has discovered that functionalized fullerenes heat, ignite, glow and transform into other carbon nanostructures such as carbon nanotubes upon exposure to low-intensity laser light. This is the first time these findings have been published. A possible explanation for the optical heating and ignition phenomena that have been observed is a distortion of the symmetrical cage structure of the fullerenes.
Some scientists believe that, with the increased mass production of engineered nanoparticles like carbon nanotubes, there is a realistic chance for these particles to interact with water, soil and air, and subsequently enter the food chain. However, understanding the behavior and impacts of nanomaterials in the environment and in human health is a daunting task. Nevertheless, a general understanding about nanotoxicity is slowly emerging as the body of research on cytotoxicity, genotoxicity, and ecotoxicity of nanomaterials grows. In our Spotlight today we take a look at new biophysical research - a parallel study of carbon-nanoparticle uptake by plant and mammalian cells - that contributes to the general picture of the fundamental behaviors of nanoparticles in both biological and ecological systems.