Individual carbon nanotubes (CNTs) of different structural and thus electronic characteristics can be joined to build up three-terminal logic devices. However, today this can only be achieved using highly sophisticated nanomanipulation processes. The direct growth of intrinsic functional CNT elements such as Y-shaped CNTS (YCNTs) and helical CNTs (HCNTs) can be considered as an important alternative. YCNTs already have proven to show rapid and nonlinear transistor action without the need for external gating, while HCNTs could be used as inductive elements offering rapid signal processing. Additionally, HCNTs have shown operational functionality as high sensitivity force and mass sensors and are of great interest for nanoelectromechanical systems (NEMS). A research group in Spain now reports that sulfur may be used as a highly efficient additive in chemical vapor deposition (CVD) processes, allowing enhanced selectivity in the synthesis of helical and Y-shaped CNTs.
Imagine to catch one, or a few, molecules dissolved in water, lock them up in a cage with a diameter of a few hundred nanometers, and keep them locked for a given length of time. Then bring these containers with the "captive" molecules to places within the solution where you want to have them, and release the captured molecules from their captivity on chemical command. Or simply keep the molecules in the cage "prison" locked up, add a few more different molecules to water, and watch their chemical reaction following movement across the container wall in "solitary" confinement within the containers with the molecules already captured. Such dreams of nanotechnologists have come much closer to reality as a result of a discovery made by a team of researchers, lead by Professor Julius Vancso of the University of Twente, from the MESA+ Institute for Nanotechnology collaborating with scientists of the Max Planck Institute of Colloids and Interfaces in Golm, Germany.
With a better understanding of how fullerenes and nanotubes form, scientists and material engineers would be in a better position to provide conditions more favorable for the formation of a particular fullerene or a particular chirality and length nanotube. Researchers have used a number of computational and theoretical tools to explain the experimental observations and develop a picture of the dynamics for fullerene growth, yet no universally agreed model exists for the fullerene growth. To understand the phenomenon of fullerene growth during its synthesis, researchers modeled a minimum energy growth route using a semi-empirical quantum mechanics code. C2 addition leading to C60 was modeled and three main routes, i.e. cyclic ring growth, pentagon and fullerene road, were studied.
New research coming out of France opens the route for the processing of numerous multifunctional materials with specific properties. So far, the design of new multifunctional devices based on the combination of different materials has been a real challenge in materials science. One way to develop multifunctional materials is the design of a surface at the nanometer scale. However, modifying the surface of materials by organizing nanoparticles of controlled size, morphology and amount of coverage into a uniform shell has proven to be a considerable hurdle. Numerous approaches are being developed for the synthesis of these materials using organic or inorganic coatings. French researchers used a coating process called supercritical fluid chemical deposition for nanomaterial surface design.
The use of design concepts adapted from nature is a promising new route to the development of advanced materials, with biominerals providing an ample source of examples. For instance, Nature's ability to manipulate poor engineering materials such as calcium carbonate to produce skeletal materials with considerable fracture resistance is an ideal inspiration for this approach. Researchers in the UK now report a simple and general approach to single crystal growth, employing structured films of generic polymers to direct the growth of single crystals. By using straightforward patterning techniques they are able to access a large variety of patterns with a continuous range of length scales from the macroscopic to the nanometer level.
Colloidal crystals constructed by monodispersed microspheres packed in ordered arrays represent a new class of advanced materials that are useful in many areas. For example, due to their novel light diffraction and photonic bandgap properties, colloidal crystals are promising elements in the fabrication of devices such as optical filters and switches, chemical and biochemical sensors, and photonic chips. Various self-assembly techniques have been developed to form colloidal crystals on different substrates, including the flow-cell methods, vertical deposition, micromolding in capillaries and so on. Although existing methods can provide colloidal crystals of different structures and quality, efficient approaches to high stability and large scale colloidal crystals are increasingly attracting attention. Generating ordered microstructures in the colloidal crystal films and colloidal crystals with different structures and configurations are particularly important in the fabrication of optical devices.
While growth processes of nanostructures are well understood, the stability of artificial nanostructures has not been thoroughly investigated. Fully understanding the fluctuations of nanostructures and their interactions with their surroundings is essential in order to achieve complete shape control of nanostructures. In recent work, French scientists address the morphogenesis, instability and catastrophic collapse of nanostructures.
Nanocrystal engineering learned from biominerals holds promises for the development in biology, chemistry, and materials science. Biominerals have inspired novel bottom-up approaches to the development of functional materials for some time now. The morphology, crystallographic orientation, incorporated organic molecules, and emergent properties of carbonate-based biominerals already have been demonstrated. Typical examples of these biominerals are certain layers of seashells, corals, and eggshells. New research now clarifies that biominerals are oriented architectures of calcium carbonate nanocrystals 20?100 nm in size with incorporation of biopolymers.