Nanospheres made of aromatic amino acids: The most rigid organic nanostructures to date

Sep 30, 2010

(PhysOrg.com) -- 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 often exhibit unique mechanical properties; for example 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 , 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 , the 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.

Explore further: Existence of two-dimensional nanomaterial silicene questioned

More information: Ehud Gazit, Self-Assembled Organic Nanostructures with Metallic-Like Stiffness, Angewandte Chemie International Edition, dx.doi.org/10.1002/anie.201002037

Related Stories

A new process for making much-sought iron nanospheres

Feb 19, 2007

Using a process that creates bubbles as hot as the surface of the sun, chemists are reporting development of a new method for making hollow hematite (iron oxide) nanospheres. The University of Illinois at Urbana-Champaign's ...

Soft Materials Buckle Up for Measurement

Jun 22, 2006

Buckling under pressure can be a good thing, say materials scientists at the National Institute of Standards and Technology. Writing in the June 13 issue of Macromolecules, they report a new method to evalua ...

NIST imaging system maps nanomechanical properties

Dec 12, 2007

The National Institute of Standards and Technology has developed an imaging system that quickly maps the mechanical properties of materials—how stiff or stretchy they are, for example—at scales on the ...

Proteins as Parents

Jul 31, 2006

So that we can move, and so that our heart beats, we need proteins with special mechanical properties, "molecular springs", which give our tissues the necessary strength and take care of elasticity and tensibility.

Recommended for you

Simulating the invisible

2 minutes ago

Panagiotis Grammatikopoulos in the OIST Nanoparticles by Design Unit simulates the interactions of particles that are too small to see, and too complicated to visualize. In order to study the particles' behavior, he uses ...

Building 'invisible' materials with light

50 minutes ago

A new method of building materials using light, developed by researchers at the University of Cambridge, could one day enable technologies that are often considered the realm of science fiction, such as invisibility ...

User comments : 0