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.
Bioactive glass is currently regarded as the most biocompatible material in the bone regeneration field because of its bioactivity, osteoconductivity (ability of a scaffold to support cell attachment and subsequent bone matrix deposition and formation) and even osteoinductivity (a scaffold that encourages osteogenic precursor cells to differentiate into mature bone-forming cells). However, the formulation of bioactive glass has been limited to bulk, crushed powders and micronscale fibers. Now, researchers in South Korea and the UK have for the first time fabricated bioactive glass in nanofibrous form. This material, which shows excellent bioactivity, is likely to open the door to the development of new nano-structured bone regeneration materials for regenerative medicine and tissue engineering.
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.
These days we are debating if nanoparticles in sunblock and toothpaste are safe. The ancient Greeks and Romans didn't know about such things - but they already used nanotechnology in their cosmetics. A group of researchers in France showed that lead-based chemistry, which was initiated in Egypt more than 4000 years ago, could result in the synthesis of lead sulfide (PbS, galena) nanocrystals. With a diameter of about 5 nm, the appearance of these crystals is quite similar to PbS quantum dots synthesized by modern materials science techniques.
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.