Having come a long way from pottery and tableware, modern advanced ceramics are high-performance materials that find use in things such as bio-medical implants, jet engine turbine blades, superconductors, missile nose cones, scratch-proof watches, or the heat protection tiles used on the Space Shuttle. Super-tough and ultra-high temperature resistant materials are in critical need for applications under extreme conditions such as jet engines, power turbines, catalytic heat exchangers, military armors, aircrafts, and spacecrafts. Structural ceramics have largely failed to fulfill their promise of revolutionizing engines with strong materials that withstand very high temperature. The major problem with the use of ceramics as structural materials is their brittleness. Although many attempts have been made to increase their toughness, including incorporation of fibers and particles, currently available ceramics and their composites are still not as tough as metals and polymers. The brittleness of ceramic materials has not yet been overcome and it has proven difficult to solve this problem by conventional material engineering approaches. The extraordinary mechanical properties of carbon nanotubes (CNTs) have generated strong research interest in their possible use in reinforced composite materials because incorporating CNTs into a ceramic matrix might be expected to produce tough as well as highly stiff and thermostable ceramic composites.
The use of spontaneous self-assembly as a lithography- and external field-free means to construct well-ordered, often intriguing structures has received much attention for its ease of organizing materials on the nanoscale into ordered structures and producing complex, large-scale structures with small feature sizes. These self-organized structures promise new opportunities for developing miniaturized optical, electronic, optoelectronic, and magnetic devices. An extremely simple route to intriguing structures is the evaporation-induced self-assembly of polymers and nanoparticles from a droplet on a solid substrate. However, flow instabilities within the evaporating droplet often result in non-equilibrium and irregular dissipative structures, e.g., randomly organized convection patterns, stochastically distributed multi-rings, etc. Therefore, fully utilizing evaporation as a simple tool for creating well-ordered structures with numerous technological applications requires precise control over several factors, including evaporative flux, solution concentration, and the interfacial interaction between solute and substrate.
The electrical properties of graphene have been the topic of recent interest from various disciplines because this novel carbon material offers exciting opportunities to develop nanocomposites with unusual electronic catalytic properties. Most of these studies involve mechanical peeling of individual graphene sheets - one at a time - from a block of graphite. The requirement to obtain graphene as individual sheets and to maintain it in the reduced form introduces a certain level of complexity into the process of designing composite systems where, for instance, semiconductor or metal nanoparticle are anchored on graphene sheets. Without some form of intervention, the strong van der Waals interactions between reduced graphene sheets would cause them to collapse and aggregate. Researchers have now developed a simple photocatalytic method to anchor semiconductor nanoparticles on a single sheet of graphene using a solution-based process.
Electrometers are instruments that measure electric charge or electrical potential difference by means of electrostatic force. While early electrometers such as developed by Lord Kelvin in the 19th century were crude instruments, modern electrometers based on solid state technology are high-precision electronic devices that, in extreme cases, are so sensitive they can count individual electrons as they pass through a circuit. As the dimensions of electronic devices shrink further, the probes required to measure the voltage inside a miniature conductor have to be miniaturized, too. An alligator clip cannot be scaled down indefinitely to perform such tasks. Furthermore, as devices reach the nanoscale, the perturbation of the measurement on the device itself cannot be neglected and must be assessed. A few techniques, many of which are based on scanning a small object such as an atomic force microscope (AFM) tip, have been developed in the past to address this challenge. Each technique has its pros and cons.
Various techniques are being developed to enhance the already impressive properties of carbon nanotubes (CNTs) further by combining them with other materials. We have covered plenty of examples in our Spotlights. For instance, encapsulating carbon nanofibers with CNTs transforms cheap commercial carbon nanotubes into highly efficient carbon for electrochemical energy storage applications. Another study demonstrated that the redox properties of iron and iron oxide particles are tunable via encapsulation within CNTs, suggesting that a host-guest interaction between the confined metal particles and CNTs, which is different from that on the outside of the nanotubes. Researchers are still busy trying to understand some of the CNT basics, for instance something as fundamental as 'how do nanotubes grow'? How can their various properties - electronic, transport, or mechanical - be modified? Or how can you make use of CNT's structure and properties to build novel nanotools. A new model demonstrates that sufficiently small liquid metal droplets can be drawn inside a CNT via capillary action.
Scientists consider the exploration of carbon nanotubes (CNTs) for biomedical applications as a field with significant potential, leading to applications where CNTs could act as magnetic nano-heaters, drug-carrier systems and sensors which allow a diagnostic and therapeutic usage on a cellular level. The EU, for instance, has funded a four-year nanotechnology research program that studies the chemical and physical properties of CNTs in order to find mechanisms which can be applied for a biomedical purpose in appropriate medical devices. Studies of their interaction with biological environments (immune response, toxicity, interaction with the single cell) will provide the basis for applying the CNT for imaging (nanoparticles-based contrast agents), sensoring (nanoparticles-based diagnostics) and cancer treatment (hyperthermia, nanotechnology-based targeted drug delivery). A new study that exploits the unique properties of single-walled CNTs (SWCNT) for biomedical purposes shows the use of SWCNTs as an efficient platform for immunotherapeutic applications. Scientists demonstrate the surface area tunability of SWCNT bundles by chemical treatment and its effect on antibody adsorption and subsequent T cell activation. T cells are central players in initiating and maintaining immune responses. An important goal of successful immunotherapy is the stimulation of T cell immune responses against targets of interest such as tumors.
Nanoparticles with at least one dimension of 100 nanometers or less fall in the transitional zone between individual atoms or molecules and the corresponding bulk material, which can drastically modify the physicochemical properties of the material and may generate adverse biological effects in organisms. As the discussion about potentially undesired side effects of engineered nanoparticles heats up, research on toxicological effects of nanomaterials gets increasing attention. Nanotoxicology is quickly being established as a new field, with its major focus on human and animal studies. However, very few studies have been conducted to assess the toxicity of nanomaterials to ecological terrestrial species, particularly plants. So far, the mechanisms of nanoparticle phytotoxicity ? the ability to cause injury to plants ? remain largely unknown and little information on the potential uptake of nanoparticles by plants and their subsequent fate within the food chain is available.
Cells are the basic building blocks of life. The ability to sense and modify intracellular processes is important for, among other things, bettering our understanding of biological processes, developing drugs and evaluating their effectiveness, and modifying cell function. Due to the cell's small size and fragility, probing the cell's interior with high precision is not a simple task. To address this challenge, researchers have developed nanoscale, carbon-based cellular probes ('carbon nanopipettes' or CNP). The CNP consists of a glass capillary lined with a carbon film along its inner surface and terminating with an exposed carbon nanopipe. The probes are fabricated through a process that does not require any assembly and that facilitates quantity fabrication. Depending on controllable process conditions, the carbon tip's diameter may vary from tens to hundreds of nanometers and its length can range from zero to a few micrometers.