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Little Clips a Big Deal

The adaptability of building blocks with interlocking clips is well known to any seven-year old with a Lego set. Professors André-Jean Attias1 and Fabrice Charra2 have created a molecular-level version of the children’s toy, resulting in a self-assembling nano-material that could have revolutionary applications in everything from biomedicine to photonics.3
By attaching a “clip” that lets molecules form interlocking links with one another, the researchers can build any number of complex structures, from chains to honeycomb-like matrices. Moreover, this can be done in a controllable, precise way–a valuable advantage at the nanoscale where unpredictability is the rule.
“Our goal was to use a bottom-up approach for nanoscale assembly,” says Charra, who specializes in surface physics research at the CEA. The two French scientists hit upon the idea of using molecular clips during a conference in Cancun. Attias was inspired to get to work immediately: “I designed the molecules on a piece of paper during my return flight. In two or three weeks, we had the first molecules.”


© A. J. Attias. CNRS 2007

Molecules containing one, two, or three clips (red lines) form dimers (left) or 2-D networks (center and right) that spontaneously assemble.

Fabricated in Attias’ lab, the “clips,” (made from alkoxyl and a bistilbene-like material) are best imagined as two arms jutting out from the alkane molecules used in this experiment. These can lock with similar clips on other molecules, like intertwined fingers. Thus the molecules are attached not through chemical covalent bonding, but something similar to the friction a paperclip uses to hold files. The clips are designed to spontaneously assemble from a liquid solution on a graphite surface, a process that Charra was able to observe in real time, using a Scanning Tunneling Microscope. This device is usually used in near-vacuum conditions, rather than the liquid-solid interface where the nanostructures were assembled, molecule by molecule.
“It was very exciting,” remembers Charra. “We were able to see the growth of the domains into hexagonal shapes or chains.” Both Attias and Charra are bullish about the potential for their devices. The clips should be compatible with a wide variety of organic and organometallic materials. Potential applications include designing super-specialized filters, custom made to grab specific materials.
The two labs plan to build on their success–quite literally. Chains and honeycombs are a good start, but Attias says that the clips need to reach out in a new direction. “We are now trying to develop these into three-dimensional structures. This is what we are currently working on,” he says.
The precise micro-scale design and construction allowed by these clips has Charra excited by their potential for building nano-engineered photonics devices. “We expect to be able to create single-molecule light sources,” he says, explaining that such nano-bulbs could be used to transmit information at the speed of light. The impact on computer speed and processing power would be astonishing. The same structures could also be used in biomedical devices, helping doctors identify and possibly treat illness at the molecular level. Attias credits the breakthrough to the breadth of experience that was brought to the problem. “It was a multidisciplinary project–made possible by the conjugated efforts of physicists and chemists working together.”
Mark Reynolds

Notes :

1. Laboratoire Chimie des polymères
(CNRS / Université Pierre et Marie Curie).
2. Service de Physique et Chimie des Surfaces et Interfaces (Commissariat à l'énergie atomique).
3. D. Bléger et al., “Surface Noncovalent Bonding for Rational Design of Hierarchical Molecular Self-Assemblies,” Angewandte Chemie. 46: 7404-07. 2007.

Contacts :

André-Jean Attias, Chimie des polymères, Paris,

Fabrice Charra, CEA, Saclay,


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