A few days ago we ran a Nanowerk Spotlight on a nanostructuring technique that uses an extremely narrow electron beam to knock individual carbon atoms from carbon nanotubes with atomic precision, a technique that could potentially be used to change the properties of the nanotubes. In contrast to this deliberately created defect, researchers are concerned about unintentional defects created by electron beams during examination of carbon nanomaterials with transmission electron microscopes like a high-resolution transmission electron microscope (HRTEM). For a long time it has been thought that if the accelerating voltage of electrons could be reduced to 80 kV in an electron microscope, then the electrons would not possess sufficient energy to cause knock-on damage in carbon nanomaterials. Knock-on damage occurs when electrons are scattered by the nucleus of the atom they are probing. Upon scattering, energy is transferred. In some circumstances this energy can be large enough to dislodge the atom from its position. A British-German team has examined how electrons accelerated at 80 kV interact with singe-walled carbon nanotubes and shown that in some circumstances SWCNTs were unstable.
Gas sensing applications are numerous in our modern society and include process monitoring, environmental compliance, health applications, homeland security, agriculture, etc. Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. Thus, the more surface available, the more sensitive the sensor will be. Nanoscale materials are intriguing materials for next-generation nanotechnology gas sensors since their relative surface areas are so large. A problem with existing gas nanosensors is the cross-interference of other gas analytes. For instance, carbon nanotube based gas sensors for the prominent air pollutant nitrogen dioxide have shown strong interference of ethanol and ammonia gases to the NO2 response. Another cross-interference often is caused by humidity, i.e. the water vapor in the air. New research now demonstrates how the manufacturing of a nanosensor for ammonia gas can be tuned to eliminate the interference of water vapor. The trick lies in accurately controlling the synthesis of the sensing nanomaterial.
A broad spectrum of therapeutics or effector molecules that address several areas of medicine, from inflammation, to cancer, and regenerative medicine, are insoluble in water (they are soluble primarily in solvents generally regarded as unsuitable for injection). The water insolubility of these therapeutics limits the means by which those compounds can be administered to the body. Rapid strategies to package and disperse these drugs in biocompatible vehicles while also maintaining their potent activity can have major implications in advancing fundamental, translational, and commercial/scale-up aspects of accelerating their clinical impact. A new study now shows a way in which nanodiamonds can be applied towards enhancing water dispersion of otherwise poorly watersoluble therapeutics. It realizes a high throughout strategy to solubilize a broad range of water-insoluble drugs, which coupled with the innate biocompatibility of nanodiamonds, provides an important foundation towards a nanotechnology platform approach for advanced drug delivery.
The manifold properties of carbon nanotubes (as well as other carbon nanomaterials such as fullerenes and graphene) are related to the various ways the carbon atoms can be arranged to form the tube lattice. Studies have shown that atomic-scale defects in these lattices can strongly influence the electronic and mechanical properties of the nanotubes. The simplest defect type is a vacancy where an atom is missing from the lattice site. Such defects can also be seen as chemically active sites for tube side wall functionalization. Due to the difficulty of observing vacancies directly, it remained unclear under what conditions vacancies in nanotubes are stable or exist at all. Researchers have now demonstrated a technique that allows them to remove carbon atoms from carbon nanotubes with atomic precision and in a controlled way with an extremely focused electron beam.
The importance of novel markers for microcopy cannot be underestimated. Such markers can provide novel information about functioning of protein in cell. Owing to their unlimited photostability diamond nanoparticles can be used for long-term monitoring of intracellular processes. Diamond nanoparticles also appear to be ideal candidates for ultra microscopy techniques like STED. Furthermore, nitrogen-vacancy color centers in diamond have non-zero spin in the ground state. This allows their use as markers for magnetic resonance imaging with very high sensitivity. To date, few methods exist to produce diamond nanoparticles containing color centers (c-diamond), but they are only laboratory-scale. The most common, large-scale nanodiamond production method, detonation, produces diamond nanoparticles which do not contain any color centers but impurities such as surface-or lattice-aggregated nitrogen and metals in significant amounts. A German-French research team has now developed a high yield method for the large-scale production of fluorescent nanodiamonds.
In a previous Spotlight we wrote about the fact that the environmental footprint created by today's nanomanufacturing technologies are conflicting with the general perception that nanotechnology is 'green' and clean. Adding to these concerns, a new study looks at the waste solids generated by the production of metallofullerenes and fullerenes and addresses the question whether feedstock-associated metals pose potential risks to aquatic receptors. The intent of this new study was to communicate that the purity of nanomaterials should be heavily characterized to ensure that the toxicological ramifications of the actual finished nanoproduct is accurately represented. Additionally, the authors suggest that carbon nanomanufacturing byproducts should be characterized so as to facilitate more informed decision-making on management of their associated waste streams.
Increasing the efficiencies of polymer-based solar cells while at the same time keeping production complexity and cost low will require the preparation of new classes of polymers that can be prepared with a minimum of synthetic steps. Combining strong electron acceptors such as fullerenes (C60) with commodity polymers to make electronically active polymers promises to be one possible route. So far, though, the photovoltaic efficiencies of polymer/C60 blends are generally not as good as those for photovoltaic devices made from the currently used main classes of polymers, P3HT and PCBM. Researchers in France came up with a way to very simply prepare polymers from fullerenes without having to strongly change the aromaticity of the C60 sphere. This means that many of the original properties of C60 may be found to be retained even when combined with the beneficial properties of polymers.
Theoretical studies have long predicted that the exceptional physical and chemical properties of a rigid monatomic linear chain of carbon atoms could function as the component of molecular devices, for instance in nanoelectronics. The problem has been that there was no reliable and effective way to produce these carbon chains and therefore scientists couldn't study them experimentally. While linear carbon chains have been already prepared either in solution or by vaporizing graphite, researchers in Japan have for the first time succeeded to derive the carbon atomic chains from graphene in a well controlled manner. This approach to realize freestanding carbon atomic chains employs energetic electron irradiation inside a transmission electron microscope.