Search

 

PressCNRS international magazine

Table of contents

Nanotechnology

Giant Leaps in a Small World

CNRS is actively involved in nanotechnology research, with applications in a variety of fields. This pluridisciplinary approach facilitates active communication between the different fields, since findings in one discipline can benefit research in very different scientific areas, linking for instance life sciences with material chemistry. Here are some of the latest published results.

Building Dots

Researchers from two CNRS laboratories, LCC1 and LAAS,2 have developed “dots”–nano-size particles arranged in grids used in nanoelectronics to store information–from a material capable of reacting to the slightest change in heat, pressure, magnetic field, or chemical composition, at ambient temperatures.3

The material's reactivity ensues from its spin crossover properties. Spin crossover is a phenomenon by which a material can switch between two electronic states, called spin states, which contain alternate representations of binary information.

“Years ago, scientists tried to elaborate dot grids out of these materials but they weren't able to maintain the spin crossover properties unless they worked at very low temperatures,” says group leader Azzedine Bousseksou. “So this is a first.”

The principal application will be to develop high-density computer memory. The team reports that they managed to create dots 30 nm in diameter–at least twice as small as those currently manufactured. “You can place a lot more dots by surface unit. Since each dot contains one bit of information, the storage of information can be gigantic,” says Bousseksou. “In practice, this means we will have hard drives with extremely high storage densities.”

The authors also envision more complex applications. Since the material reacts to tiny changes in pressure, temperature, and light, it could be used to create sophisticated measurement tools, or optical filters capable of modifying the information contained in light beams, in telecommunication applications, for example. 

 

1. Laboratoire de chimie de coordination (CNRS).

2. Laboratoire d'analyse et d'architecture des systèmes (CNRS).

3. G. Molnár et al., “A Combined Top-Down/Bottom-Up Approach for the Nanoscale Patterning of Spin Crossover Coordination Polymers,” Adv. Mater. 19: 2163-7. 2007.

Contact:

Azzedine Bousseksou, LCC, Toulouse.

boussek@lcc-toulouse.fr

 

 

 

Emulating

Sea Sponges

By mixing the therapeutic peptide lanreotide with a precursor of silica in water, researchers have elaborated glass nanotubes 10 times narrower than those currently available.1

Frank Artzner's CNRS team in Rennes2 first observed that the tiny molecules of lanreotide, when placed in water, assemble in series of tubes 24 nanometers in diameter. They discovered that this molecule could serve as a matrix for glass carbon nanotubes simply by mixing lanreotide with silica in water. Silica, a basic compound of glass, coats lanreotide molecules as they assemble, which ensures the formation of perfectly uniform and calibrated tubes, like those observed in nature. “This is similar to shell, spine, and spicule formation by underwater organisms, that also use silica in this process,” comments CNRS researcher Erik Dujardin.3 “Until now, no one had managed to reproduce what occurred in nature,” he adds.

The team is now testing other materials, hoping this process could be used in the future to create fibers of even smaller diameters to use in optical imaging or computer information storage devices, for instance. Their work, also useful to marine biologists, paves the way to new technological applications.

 

1. E. Pouget et al., “Hierarchical architectures by synergy between dynamical template self-assembly and biomineralization,” Nat Mater. 6: 434-9. 2007.

2. Groupe Matériaux et Matière Condensée (CNRS / Université Rennes I).

3. Centre d'Elaboration de Matériaux et d'Etudes Structurales (CNRS).

Contacts :

> Franck Artzner, GMCM, Rennes.

Franck.artzner@univ-rennes1.fr

> Erik Dujardin, CEMES, Toulouse.

Erik.dujardin@cemes.fr

 

 

 

Bending Transistors

 

nanotubes

 

Will we soon be able to carry an e-paperback rolled in our pocket? Well, researchers at IEMN1 and from the CEA2 are working on it. For the first time, they have succeeded in making transistors from carbon nanotubes, using a simple and cheap method called dielectrophoresis to obtain uniform deposition of a large number of aligned nanotubes on a silicon substrate.3 The transistors reached maximum operation frequencies of 30 Gigahertz, a world-record for nanotube-based transistors. “Theoretical studies suggest we could reach 1000 GHz,” says CNRS / IEMN researcher Arnaud Le Louarn. “Because of the great advances made in recent years, this doesn't appear to be out of reach.”

The flexibility of carbon nanotubes, combined with their high electron mobility, make them an ideal material for devices like electronic paper. Besides, the process used can be carried out at room temperature, which makes it compatible with low-cost substrates such as glass or plastic, and opens up new prospects for mainstream applications that require high operating frequencies.

 

1. Institut d'électronique, de microélectronique et de nanotechnologie (CNRS / Universités Lille 1 et Valenciennes /  Institut supérieur de l'électronique et du numérique).

2. Commissariat à l'Energie Atomique.

3.  A. Le Louarn et al., “Intrinsic current gain cutoff frequency of 30 GHz with carbon nanotube transistors,” Applied Physics Letters. 90: 233108. 2007.

Contact:

Arnaud Le Louarn, IEMN, Lille.

Arnaud.le-louarn@iemn.univ-lille1.fr

 

 

Glowing from Inside

glowing from insideUsing luminescent nanoparticles that can glow for hours after excitation, scientists from UPCG1 have created an optical imaging technique they hope could be ultimately used on humans. Indeed, the technique avoids the inherent problems encountered in classical optical imaging based on fluorescence–problems that so far have limited its use on animals and humans.

Currently, optical imaging techniques use nanoparticles that are injected inside the bloodstream and excited by an external source of light as they travel through the body. The particles' signal–or fluorescence–is then detected by an external camera. But the method has its limitations, mainly due to the tissue's autofluorescence in response to the external excitation light, adding unwanted noise to the nanoparticles' signal.

The new technique, described in a study published in PNAS,2 uses nanoparticles made up of a material that can be excited prior to injection. The distribution of the particles inside the body can then be followed in real-time for more than an hour without the need of an external light source. “This way, we avoid artifacts due to tissue autofluorescence,” says UPCG director Daniel Scherman.

Working on mice, the team was able to guide its probes to different destinations by chemically modifying the surface of these nanoparticles. When covered with polyethylene glycol, for instance, the particles concentrated in tumors.

After successful usage in mice, the team envisions to use this technique to visualize tumors in humans. “For the moment, there is no optical technique capable of detecting tumors in human beings,” says Scherman. “And optical probes are cheap compared to classical imaging techniques such as MRI.”

 

1. Unité de pharmacologie chimique et génétique (CNRS / INSERM / Ecole Nationale Supérieure de Paris / Université René Descartes).

2. Q. Le Masne de Chermont et al., “Nanoprobes with near-infrared persistent luminescence for in vivo imaging,” PNAS. 104: 9266-71. 2007.

Contact:

Daniel Scherman, UPCG, Paris.

daniel.scherman@univ-paris5.fr

 

 

 

 

Storing Hydrogen

storing hydrogenHydrogen is a non-polluting energy source that could replace fossil fuels if cheap and efficient storage conditions existed. Storing it in metals is both expensive and inefficient. Trapping the gas in porous materials like carbon nanotubes is cheaper, yet the weak interaction between carbon and hydrogen in these tubes makes storage possible only at very low temperatures.

Currently, researchers from CNRS,1 together with colleagues from Spain and the UK suggest that carbon nanohorns could be a practical middle ground.2 Nanohorns are horn-like shaped carbon nanotubes 2 to 3 nm in length that assemble in secondary particles of about 100 nanometers. Scientists have investigated the interaction between carbon nanohorns and hydrogen using high-resolution neutron spectroscopy. Their results show that their interaction with hydrogen is much stronger than that of carbon nanotubes. “We have to further investigate their binding mechanisms, but it seems that storage in porous materials could now be possible at ambient temperatures,” says group leader Marie-Louise Saboungi.

 

1. Centre de recherche sur la matière divisée (CNRS / Université d'Orléans).

2. F. Fernandez-Alonso et al., “Nature of the bound states of molecular hydrogen in carbon nanohorns,” Phys Rev Lett. 98: 215503. 2007.

Contact:

Marie-Louise Saboungi, CRMD, Orléans.

mls@cnrs-orleans.fr


Top

Back to homepageContactcredits