04 October 2010
Organic nanostructures are key elements of nanotechnology because these building blocks can be made with tailored chemical properties. Their disadvantage has been that their mechanical properties have so far been significantly inferior to those of metallic nanostructures. Ehud Gazit, Itay Rousso, and a team from the Tel Aviv University, the Weizmann Institute of Science and the Ben-Gurion University of the Negev (Israel) have now introduced organic nanospheres that are as rigid as metal. As the scientists report in the journal Angewandte Chemie, they are interesting components for ultrarigid biocomposite materials.
Nanoscale biological structures often exhibit unique mechanical properties; for example spider silk is 25 times as strong as steel by weight. The most rigid synthetic organic materials known to date are aramids, such as Kevlar. Their secret is a special spatial arrangement of their aromatic ring systems and the network of interactions between their planar amide bonds. The new nanospheres are based on a similar construction principle. However, unlike the large polymeric chains, they are formed in a self-organization process from very simple molecules based on aromatic dipeptides of the amino acid phenylalanine.
Using an atomic force microscope, the scientists examined the mechanical properties of their nanospheres. This device uses a nanotip (cantilever), a tiny flexible lever arm with a very fine tip at the end. When this tip is pressed against a sample, the deflection of the lever indicates whether the tip of the needle can press into the sample object and how far in it can go. A metal needle was not able to make any impression on the nanospheres; only a needle made of diamond was able to do it. The researchers used these measurements to calculate the elasticity modulus (Young’s modulus) for the nanospheres. This value is a measure of the stiffness of a material. The larger the value, the more resistance a material has to its deformation. By using a high-resolution scanning electron microscope equipped with a nanomanipulator, it was possible to directly observe the deformation of the spheres.
For the nanospheres, the team measured a remarkably high elasticity modulus (275 GPa), which is higher than many metals and similar to the values found for steel. This makes these nanostructures the stiffest organic molecules to date; they may even eclipse aramids. In addition to having outstanding mechanical properties, the nanospheres are also transparent. This makes them ideal elements for the reinforcement of ultrarigid biocomposite materials, such as reinforced plastics for implants or materials for tooth replacement, aerospace, and other applications that require inexpensive, lightweight materials with high stiffness and unusual stability.
E. Gazit et al., Angew. Chem. Int. Ed. ; DOI: 10.1002/anie.201002037
Tel Aviv University Press Release
Nanotechnology team reports the strongest organic nano-material ever developed
A revolutionary new spherical nanostructure, fully derived from very simple organic elements, yet strong as steel, has been developed and characterized at the laboratories of Ehud Gazit of Tel Aviv University and Itay Rousso of the Weizmann Institute of Science. Lightweight and exceptionally strong, easy and inexpensive to produce, friendly to the environment and biologically compatible, these promising bio-inspired nano-spheres have innumerable potential uses – from durable composite materials to medical implants. The groundbreaking work was recently published in the leading journal Angewandte Chemie.
The researchers, Prof. Gazit, Dr. Lihi Adler-Abramovich and Inbal Yanai from TAU’s Department of Molecular Biology and Biotechnology, working in collaboration with Dr. Itay Rousso and Nitzan Kol from the Weizmann Institute and David Barlam and Roni Shneck of Ben-Gurion University, used a simple dipeptide, consisting of only two amino acids, to form spherical nanostructures. Self-assembling under ambient conditions - without any heating or manipulation – this remarkable new material is the first bio-inspired nano-material known to date that is mechanically equal and even superior to many metallic substances. While demonstrating chemical properties similar to those of the ultra-rigid Kevlar® polymer, already used for bullet-proof vests, the new substance is built from much simpler building blocks, enabling some important advantages: manipulation and deposition at the nano-scale, the fabrication of nano-materials of tubular, spherical and other geometries, and spontaneous formation by self-assembly. Here, indeed is a perfect building block for numerous applications:
Hard and strong as steel, this new nanostructure is an ideal element for the reinforcement of composite materials used in the space, aviation and transportation industries; biologically compatible yet extremely rigid and durable, it is an excellent candidate for replacing metallic implants; tough, light and impenetrable, it is an exceptional option for manufacturing bullet-proof vests; - to name just a few high-potential uses.
The new nanotechnology development now emerging from Tel Aviv University is based on extensive research which began in Prof. Gazit’s laboratory in 2003. In an earlier achievement, the team was able to fabricate tubular nanostructures that assemble themselves into vast “forests” featuring exceptional mechanical and physical properties. This earlier work, based on the doctoral thesis of Dr. Lihi Adler-Abramovich, and published in 2009 in the prestigious Nature Nanotechnology scientific journal, may eventually generate self-cleaning windows and solar panels, as well as supreme energy storage devices with exceptionally high energy density.
The link to the original paper:
Prof. Ehud Gazit
Author: Adrian Miller