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Détourner la spectrométrie de masse pour préserver l’intégrité de molécules sur une surface

par le LRS - 30 janvier 2018

Comprendre comment des molécules sont adsorbées ou réagissent sur une surface nécessite une analyse aux rayons X sous-ultravide. Mais comment déposer dans l’ultra-vide ces molécules souvent grandes et fragiles sans les endommager ? Pour préserver leur intégrité, les chercheurs du Laboratoire de réactivité de surface (CNRS/UPMC), de l’Institut des nanosciences de Paris (CNRS/UPMC) et de l’Institut de recherches de chimie Paris (CNRS/ENSCP), ont ingénieusement détourné un dispositif de spectrométrie de masse. Ce procédé appelé ionisation par électrodéposition consiste à les vaporiser sous forme de microgoutellettes. Il permet aussi de contrôler leur composition chimique originelle pour les étudier sur la surface. Une avancée qui permettrait des analyses plus fiables de phénomènes chimiques aux origines de la vie. Résultats qui font l’objet de deux publications dans Langmuir et le J. Phys. Chem. C. et qui ouvrent de nombreuses perspectives en ingénierie des bio-interfaces

Retrouver l'intégralité sur le site du CNRS

Les matériaux de l’art à l’honneur dans Nature Materials

LAMS - 23 janvier 2018

In the Focus issue of Nature Materials, February 2018 , researchers from Sorbonne Université in Paris and the British Museum in London discuss the contribution of material scientists in understanding the techniques and materials used by painters, sculptors and other artists, and in developing effective strategies to preserve our heritage.

Editorial : Behind the art
Art historians have joined forces with material scientists in order to better understand the objects of interest but also develop better conservation treatments and preservation approaches... link here

ACS Appl. Mat. Interf : Doxorubicin Intracellular Remote Release from Biocompatible OEGMA-based Magnetic Nanogels Triggered by Magnetic Hyperthermia

par Ali Abou-Hassan (PHENIX) - 21 septembre 2017

Esther Cazares-Cortes, Ana Espinosa, Jean-Michel Guigner, Aude Michel, Nébéwia Griffete, Claire Wilhelm, and Christine Ménager

Abstract :

Hybrid nanogels, composed of thermoresponsive polymers and superparamagnetic nanoparticles (MNPs) are attractive nanocarriers for biomedical applications, being able – as polymer matrix – to uptake and release high quantities of chemotherapeutic agents and – as magnetic nanoparticles – to heat when exposed to an alternative magnetic field (AMF), better known as magnetic hyperthermia. Herein, biocompatible, pH-, magnetic- and thermo-responsive nanogels, based on oligo (ethylene glycol) methacrylate monomers (OEGMAs) and methacrylic acid co-monomer (MAA) were prepared by conventional precipitation radical co-polymerization in water, post-assembled by complexation with iron oxide magnetic nanoparticles (MNPs) of maghemite (γ-Fe2O3) and loaded with an anticancer drug (doxorubicin – DOX), for remotely controlled drug release by “hot-spot”, as an athermal magnetic hyperthermia strategy against cancer. These nanogels, noted MagNanoGels, with a hydrodynamic diameter from 328 to 460 nm, as a function of MNPs content, have a swelling-deswelling behavior at their volume phase temperature transition (VPTT) around 47 °C in a physiological medium (pH 7.5), which is above the human body temperature (37 °C). Applying an alternative magnetic field increases twice the release of DOX, while no macroscopic heating was recorded. This enhanced drug release is due to a shrinking of the polymer network by local heating, as illustrated by the MagNanoGels size decrease under AMF. In cancer cells, not only the DOX-MagNanoGels internalize DOX more efficiently than free DOX, but also DOX intracellular release can be remotely triggered under AMF, in athermal conditions, thus enhancing DOX cytotoxicity. ACS Appl. Mater. Interfaces, 2017, DOI : 10.1021/acsami.7b06553

Internal field 59Co NMR study of cobalt-iron nanoparticles

LSIMM – 31 janvier 2018

The catalytic growth of carbon nanotubes by catalytic carbon vapor deposition (CCVD) can be performed on variety of Co, Fe, and Ni catalysts. It is typically a three-step process where an induction period is followed by a steady-state growth and finally an asymptotic approach to the maximal tube length. However, the transition between induction and growth is not yet fully understood.

In the appropriate range of temperature and size, iron and cobalt metal nanoparticles are ferromagnetic opening the unique possibility to perform 59Co or 57Fe NMR in the internal field of the catalysts particles. By mobilizing the potential of the method, we shed new light on what happens during the first tens of seconds in the reactor. During activation, the pure Co metal content dropped and an increase of the ordering of the cobalt-iron alloy in the catalyst was evidenced thus revealing a multistage activation mechanism for the reaction. We propose this ordering process during the induction period to be an intermediate step between the strong ferromagnetic Co rich alloy and the weak ferromagnetic Fe rich one and that it favors the onset of MWCNTs growth. Read more

Andrey S. Andreev, Dmitry V. Krasnikov, Vladimir I. Zaikovskii, Svetlana V. Cherepanova, Mariya A. Kazakova, Olga B. Lapina, Vladimir L. Kuznetsov, Jean-Baptiste d’Espinose de Lacaillerie, Journal of Catalysis 2018, 358, 62.

FS - 30/01/18

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