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N°29 I quarterly I APR IL 2013 Focus | 27 Further reading Hierarchically Structured Porous Materials: From Nanoscience to Catalysis, Separation, Optics, Energy. Bao-Lian Su, Clément Sanchez, Xiao-Yu Yang (Eds.) (Weinheim: Wiley-VCH , 2011). Mean field simulation for Monte Carlo integration. P. Del Moral. (Borsa Roca: Chapman & Hall / CRC Press, 2013). y antenn ae to detect explosiv es neurons. The explosives-detecting microlever (right), covered with TiO2 nanotubes, operates on the same principle. The antennae of a butterfly provided the inspiration for an explosives detector developed by researchers from the NS3E laboratory1 in collaboration with the LMSPC2 in Strasbourg. Consisting of a silicon microlever covered with nearly 500,000 titanium dioxide nanotubes, it can detect concentrations of trinitrotoluene (TNT) as low as 800 ppq (parts per quadrillion), the equivalent of 800 TNT molecules out of 1 quadrillion molecules of air. This represents a tremendous improvement over existing systems, which can only detect one TNT molecule per billion molecules of air. Practically, to determine whether the ambient air contains traces of TNT, the microlever is vibrated: its vibration is modified as it absorbs In the field of new energy technologies, the use of hydrogen is an appealing solution. But its implementation depends on the ability to produce hydrogen in large quantities. The most common process today is electrolysis, in other words the use of electric current to split water molecules. This technique requires platinum as a catalyst. Is it possible to generate hydrogen without this extremely rare and costly metal? “As part of the photosynthesis process, nature uses remarkable catalysts: the enzymes called hydrogenases, which are produced by many organisms,” explains Marc Fontecave.1 To produce hydrogen, hydrogenases only use metals found in abundant quantities, like iron and nickel. A few years ago, a group of chemists from CNRS and the CEA2 took inspiration from this natural phenomenon to develop a synthetic hydrogen catalyst, which they combined with carbon nanotubes to increase efficiency. Today they are keeping up their efforts, improving on the original catalyst, and developing new electrode materials based on the same model but using cobalt. 01. Chimie des processus biologiques (CNRS / Collège de France). 02. Commissariat à l’énergie atomique et aux énergies alternatives. Contact i nformation: Marc Fontecave, mfontecave@cea.fr molecules of explosives. The 500,000 nanotubes are aligned vertically on the microlever, increasing the detection surface a hundred-fold— and thus the likelihood of capturing the target molecules. For this detector, the researchers drew their inspiration from mulberry silk moth antennae, which are able to react to only a few pheromone molecules. The next step will be to adapt the system so that it can detect other explosives and incorporate it into a practical, easy-to-use device. 01. Laboratoire des Nanomatériaux pour les systèmes sous sollicitations extrêmes (CNRS / IS L). 02. Laboratoire des matériaux, surfaces et procédés pour la catalyse (CNRS / Université de Strasbourg). Contact i nformation: Denis Spitzer, denis.spitzer@isl.eu Nature has no equal when it comes to creating boundaries. A good illustration of this principle is the biological cell, with its flexible yet solid wall. In 1965, British researcher Alec Bangham simplified the cell wall model and produced the first liposomes. Ranging in size from 20 nanometers to a few microns, these vesicles are made up of lipids that self-assemble when immersed in water. This principle has now been used to trap useful molecules. By intravenous injection, liposome-encapsulated medicinal substances can be transported in the bloodstream with minimal alteration. Once the liposomes are absorbed by the cells, their membrane is destroyed by enzymes and the active substance is released. One of the challenges facing researchers today is to optimize the targeting of diseased cells. This is the objective pursued by Sylviane Lesieur’s team at the Institut Galien Paris-Sud.1 “The alignment and movement of certain bacteria is influenced by the Earth’s magnetic field,” she explains. “Based on this biological function, we have developed magnetoliposomes. Using a magnet, the anti-cancer drugs they contain can be concentrated within a malignant tumor to treat it more effectively.” At the same laboratory, Angelina Angelova is pioneering yet another innovation in partnership with the Prague Institute of Macromolecular Chemistry (Czech Republic). The nanoparticles she focuses on, known as cubosomes and hexagosomes, act as sponges, soaking up and transporting more than their own volume of biologically-active molecules. 01. CNRS / Université Paris-Sud. Contact i nformation: Sylviane Lesieur, sylviane.lesieur@u-psud.fr Producing hydrogen lik e a plant New deliv ery systems for medic ations q The production of hydrogen under light irradiation, using a bioinspired photocatalyst. q The structural similarity between the CCM V virus (left) and a cubosometype lipid nanoparticle (right). The film Hydrogen at the wheel and an image gallery can be viewed online. An image gallery on liposome structures is available online. © P.Av avian/ACE © G. AANPR LLADN /fotolia © a. angelova, b. angelov, v.m. garamus, p. couvreur, s. lesieur/j. phys. chem. lett. 2012 More images on this subject can be viewed on the online version of the magazine. > www.cnrs.fr/cnrsmagazine


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