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Scientific activity

1. Astrochemistry

a) Paris meteorite analysis by cluster SIMS imaging and micro-PIXE

M. Noun1,2, M. Pautrat1, B. Nsouli2, M. Roumie2, T. Calligaro3, D. Baklouti4, R. Brunetto4, S. Merouane4, L. d’Hendecourt4 and S. Della Negra1

1 : Institut de Physique Nucléaire d’Orsay, UMR 8608, Université Paris Sud

2 : Lebanese Atomic Energy Commission, National Council for Scientific Research, P.O. Box 11-8281, Beirut, Lebanon

3 : Centre de Recherche et de Restauration des Musées de France (C2RMF), a joint laboratory of the French Ministry of Culture and of the Centre National pour la Recherche Scientifique (CNRS - UMR 171)

4 : Institut d’Astrophysique Spatiale, CNRS, UMR-8617, Université Paris-Sud, Bât. 121, 91405 Orsay Cedex, France

The solar processes study is based on the earliest witnesses of the solar system formation which are the primitive dust and meteorites. In this context we present a new approach of elementary and structural analysis through cluster-ToF-SIMS (mass spectrometry imaging). The study is realized on the “Paris” meteorite (a CM type chondrite). This meteorite is interesting because it belongs to the family of undifferentiated chondrites which keep the memory of their primordial history.

We analyzed a piece of this meteorite, provided by the Muséum National d’Histoire Naturelle in Paris, using bismuth and bismuth cluster beams delivered by the ion source of an ION-TOF V spectrometer at the LAEC in Beirut. Mass spectrometry imaging allows the components identification and their localization. An important part of this study consisted in the pollutions detection followed by their elimination, controlled in order to avoid any information loss. This analysis leads to the establishment of a procedure for all the future analysis. A new cleaning method with argon cluster guns has been proposed and will be tested.

The ionic images obtained show that some abundant elements are equally distributed such as oxygen and sodium, other are localized as calcium, magnesium, sulfur, silicon, iron, chlorine, potassium, aluminum and cyanide. There are also minor components such as fluorine and cyanates and traces, localized or not, of phosphorous oxides, chromium, nickel, manganese, boron, copper, cobalt and organic compounds. A thorough analysis of the ionic images permits to detect several compounds. The calcium ions, their oxides and hydroxides form two families : Ca+, CaOH+, Ca2O+ and a second series (CaO)2+, (CaO)2H+, (CaO)3H+, (CaO)4H+ showing the calcium lithophile character (Fig. 1).

Figure1 : calcium ions, OH- and calcium oxide and hydroxide distributions

On the other hand, the distribution of the sulfur ions and their oxides (S, SO, SO2, SO3, SO4-) overlaps the calcium region which explains the calcium sulfate presence.

Figure 2 : Sulfur, sulfur oxide and calcium sulfite and sulfate distribution

A difference is observed between the positive and negative emissions of silicon ions and their compounds : three main domains are detected, the first one for Si+ and SiOH+, the second one corresponding to Si- and a third one to silicates. This emission difference may be due to the presence of silicon in various compounds and surroundings. We also identified a chondrule (a structure often observed in this meteorite group, resulting from the fast high temperature heating of a solid precursor followed by the cooling) included in a silicate and iron matrix. This chondrule is characterized by an important contribution of magnesium, which agglomerates (Mg+ and Mg2+) around the Silicon (Si). In the areas where the Mg, Si and O elements coexist we find the MgSiO+ compound.

Apart from the minerals two kinds of organic ions, with different locations, have been detected. The first one is of the CxHy type with several compoundsCmHnO2N situated out of the chondrule ; these ions are correlated with iron and anti-correlated with oxygen. The second sort consists of cyanides and cyanates.

Figure 3 : CN- , CNO- and organic ionic molecule distribution

The “Paris” meteorite, studied by ToF-SIMS, has also been investigated through IBA methods with elementary analyses by PIXE (Particle Induced X ray Emission), μ-PIXE and RBS (Rutherford Back Scattering) which showed the complementarities of these approaches to obtain a quantization and a relatively easy determination of the different elementary compounds and of their structure. This will help to find the origin and the conditions in which the organic matter aggregated and/or synthesized to produce prebiotic molecules. This “Paris” meteorite fragment was also analyzed by the usual astrophysical techniques : IR and Raman spectrometry, but with a micrometrical spatial resolution, which provides images of the same sample through several techniques giving complementary structural information.

These experiments are developed to prepare the laboratory analysis of future samples collected in space and particularly of carbon rich asteroids. The emphasis is also laid on the advantages of coupling techniques used in remote sensing (IR spectroscopy) and laboratory techniques with a high spatial resolution (μ-Raman and IR, Cluster-ToF-SIMS and μ-RBS and PIXE).

b) Organic residues from UV photochemistry of ices : a key to cosmic organic complexity for prebiotic chemistry

Paola Modica1 ; P de Marcellus1 ; D Baklouti1 ; R Brunetto1 ; M Noun2 ; S Della Negra2 ; L Le Sergeant d’Hendecourt1 ; M De Person1 ; F Moussa1

1 : Institut d’Astrophysique Spatiale, CNRS, UMR-8617, Université Paris-Sud, Bât. 121, 91405 Orsay Cedex, France

2 : Institut de Physique Nucléaire d’Orsay, UMR 8608, Université Paris Sud

A second part of these studies is related to the simulation of interstellar and pre-comet environments. L. d’ Hendecourt’s team has got a great experience in this matter and developed convenient methods. Basically, admixtures of simple gas molecules (H2O, CH3OH, and NH3) are prepared at room temperature and condensed under vacuum on an 80 K cold substratum to simulate the aggregation of these molecules on dust grains in space. These samples are then irradiated with UV light in place of the spatial radiation field. The sample so obtained is heated up to room temperature to follow an ice thermal evolution. The remaining organic residue is analyzed at the cycle end. The IR spectroscopy is used to keep an eye on the samples during their preparation. The analysis was performed through IR spectroscopy and CG MS (gaseous chromatography and mass spectrometry). Our contribution, in the collaboration, consists in the use of other techniques : HPLC, MALDI and Cluster-SIMS spectrometry. The first results of these residues analysis showed that they are made of a complex organic admixture with a wide mass distribution, where macro-molecular entities of masses between 1000 and 3000 u are detected for the first time in a laboratory residue. These macro-molecular components are interesting because of their properties, such as their high chemical functionality and solubility in water, which make them possible candidates for pre-biotic chemistry. Concurrently, an ionic impact analysis is performed on these samples ; the main job is to settle protocols allowing to detect the pollutions, due to the sample preparation procedure, and to eliminate them.

2. Nanoparticles

S. Della-Negra1, M. Noon1, V. Huc2, B. Rasser3

1 : Institut de Physique Nucléaire d’Orsay, UMR 8608, Université Paris Sud, F91406 Orsay Cedex

2 : Institut de Chimie Moléculaire et des Matériaux d’Orsay, UMR 8182, Uni. Paris-Sud 11, F91405 Orsay

3 : OrsayPhysics, ZA Saint Charles, F13710 FUVEAU

The first part of these studies was realized in collaboration with Orsay-Physics : metallic nano-droplet beams were produced by an ion source and a FIB (Focused Ion Beam) column COBRAX developed by Orsay-Physics. The ion beam characteristics obtained are similar to those of the columns and ion sources I developed at the IPNO.

The second component was performed in collaboration with V. Huc from the Institut de Chimie Moléculaire et des Matériaux d’Orsay. We used the mass spectrometry to control the nano-particle synthesis processes implemented by V. Huc. The latter makes use of a new ligand : the calixarene, functionalized by a thioester, for the synthesis of metallic nanoparticles like gold and platinum. In these cases he observes small nano-crystals of a nanometric size with a narrow distribution indicating that a size selection process occurs during the synthesis. This process could be related to the calyx[8]arene structure and to the number of thiolate type ligands per molecule. The modifications of this kind of molecules size and the number of available bindings on the metallic surface allows to choose the nano-objects size. With this work we started to characterize nano-structured surfaces, which is one of ANDDROMEDE application domains. The cluster-SIMS mass spectrometry is among the best analysis tool for it is the only experimental technique which permits the direct observation of molecular objects grafted on a surface. It is particularly important as the most promising candidates for the molecular information stocking are made up of an oxide nucleus surrounded by organic ligands. This magnetic surface structure, based on oxides, is as often as not used for molecular grafts, which makes the separation between the substrate and the molecular graft difficult with the “usual” tools (XPS, AFM, IRRAS …)

3. Biology (in progress)

Martine Caroff, Luis Augusto (IGM), Alexey Novikoff, Asmaa Jobic (Lpsbiosciences)

4. Interaction between nanoparticles and matter (in progress)

Collaboration TAMU / IPNO


 

IPN

Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

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