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.
Carbon nanotubes (CNTs) are considered the most promising material for field emitters and a practical example are CNTs as electron emitters for field emission displays (FED). CNT emitters are generally fabricated by indirect growth methods such as screen-printing and electrophoresis. These methods show advantages in lowering the coating temperature and scale-up of the substrate size, but the direction of CNTs cannot be well controlled and a post-treatment process is generally necessary to enhance the performance of CNT emitters. In contrast to the indirect method, chemical vapor deposition (CVD) is a common technique for growing nanotubes directly on the substrate with the assistance of metallic catalysts. With the CVD method, CNTs can be grown at desired locations with a specified direction. However,most synthesis technologies such as conventional thermal CVD or plasma enhanced CVD are performed at temperatures over 500 C, which may restrict the application of CNTs on plastic substrates. Therefore, lowering the growth temperature for CNTs is one of the important directions for facilitating CNT applications.
Recent developments in DNA-based nanotechnology have shown the suitability of this novel assembly method for constructing useful nanostructures. DNA molecules can serve as precisely controllable and programmable scaffolds for organizing functional nanomaterials in the design, fabrication, and characterization of nanometer scale electronic devices and sensors. DNA-templated metallic nanowires are such an example and over the past few years DNA scaffolds have been metallized with silver, gold, palladium, platinum and copper. DNA-based fabrication methods could ultimately lead to naturally bio-compatible nanodevices.
Microscale reactor technology has tremendous advantage over conventional macro-scale or batch chemical processes, and offers versatility for a wide range of applications including chemical analyses, drug discovery, radiotracer synthesis, and the fabrication of engineered nanomaterials. Attention is currently focused on developing scaleable process regimes, using an approach engineers call numbering up. Microreactor technology is defined by a series of interconnected, functionally distinct channels formed on a planar surface, utilizing either hydrodynamic or (EOF) for pumping, with channel dimensions typically between 10-300 microns.
Among many nanomaterials with distinct geometric shapes, spheres and cubes are the two simplest forms, yet they possess the highest symmetries. One of the obvious geometric merits of this class of materials is their low resistivity under fluidic conditions, as they can be essentially considered as zero-dimensional entities when their size is trimmed down to the nanoscale regime. So far, most hollow interiors of nanomaterials are created by template-methods. Researchers in Singapore for the first time demonstrated that nanostructured polyhedrons of functional materials with desired interiors can be synthesized template-free through a simple hydrothermal method.
Conventionally, the fabrication of thin film nanostructures is primarily done by using selective etching or templating growth on a prepatterned resist and then performing lift-off. The solvents used in developing resist are typically toxic and add to the cost of lithographic processing. Recently, many environmentally friendly lithographic processes have been designed using either a water-based solution or supercritical carbon dioxide to develop the resist. A novel pure water developable spin-coatable lanthanum strontium manganese oxide (LSMO) resist has been developed by scientists in Taiwan. The use of pure water instead of organic or alkaline solvents would undoubtedly be not only environmentally desirable but also could greatly simplify the imaging process.
Current production methods for carbon nanotubes result in units with different diameter, length, chirality and electronic properties, all packed together in bundles, and often blended with some amount of amorphous carbon. The separation of nanotubes according to desired properties remains a technical challenge. Especially single-walled carbon nanotube (SWCNT) sorting is a challenge because the composition and chemical properties of SWCNTs of different types are very similar, making conventional separation techniques inefficient.
Encapsulating metal nanoparticles inside carbon shells is of considerable significance but fraught with high manufacturing cost due to high energy consumption and intensive use of hardware. This cost issue limits their practical applications. Researchers in China have developed a novel, simple, efficient, and economical synthesis technique for the fabrication of carbon-encapsulated nanostructures where the carbonization is conducted at a relatively low temperature of 160C in water and no toxic reagents are added. This new technique is facile and versatile, and suitable for the coating of other transition metal with carbon.