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CINaM - Centre Interdisciplinaire de Nanoscience de Marseille

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Accueil du site > Séminaires > A venir ...

A venir ...

 
Jeudi 28 Mai 2015
Stéphane Viel
Aix-Marseille Université, CNRS, Institut de Chimie Radicalaire (UMR 7273), 13397 Marseille, France
Structural investigation of materials by solid-state dynamic nuclear polarisation (DNP) nuclear magnetic resonance (NMR) spectroscopy
Solid-state nuclear magnetic resonance (SSNMR) is a versatile and purely non-destructive technique that can provide high-resolution molecular structural information on a large variety of materials, either directly by acquiring the NMR experiments at high magnetic fields or indirectly by taking advantage of multidimensional correlation schemes (or both). Contrary to scattering techniques, SSNMR is perfectly suited for the analysis of powdered samples (i.e. single crystals are not required), and it can access supramolecular structural information without the need of long-range translational order. The Achilles’ heel of NMR, however, remains its low sensitivity that usually precludes analysis of structural details, which are intrinsically associated with NMR signals of low intensity. One of the most promising methods for boosting the SSNMR sensitivity is dynamic nuclear polarisation (DNP), which enhances nuclear magnetisation through the microwave-driven transfer (usually at cryogenic temperatures) of electron spin polarisation to nuclei via exogenous paramagnetic centres. DNP is nowadays attracting renewed attention owing to recent spectacular technological and theoretical developments. This communication will describe recent advances in the field of DNP SSNMR for the characterisation of materials in the solid-state by focusing both on inorganic and organic materials (including organic polymers).

Jeudi 04 Juin 2015
Dr. Olivier DOUHERET
Chimie des Matériaux Nouveaux (CMN), Materia-Nova, Université de Mons, Mons, Belgique
Electrical characterisation of organic semiconducting nanostructures
With the tremendous developments of information and communication technologies, the latest decades witnessed continuous research and breakthroughs in new materials likely to be incorporated in electronic devices. Among them, organic semiconductors rose particular interest as they can actually replicate standard components such as transistors, (light-emitting) diodes or photovoltaic cells, with attractive advantages such as fabrication cost, low operating power, large scale display and flexibility. Though significant performances are today’s reached, much remains to be understood as for the chemical and physical mechanisms at stake within and between the different materials composing the investigated devices. Far from the monocrystalline structures of standard Si and III-V nanotechnologies, the degree of organization of organic semiconductors is shown to play a key role on the resulting performances of the devices. In organic photovoltaic cells (OPV), for instance, this organization is to be controlled at the nanoscale to satisfy both the ultimate intermix between traditional donor and acceptor semiconducting materials, but also to exhibit sufficiently degree of crystallinity to ensure efficient carrier transport across the device. The local analysis of these nanostructures was possible provided versatile scanning probe microscopy characterization methods. In particular, conducting atomic force microscopy (C-AFM) has shown to be of prime interest to investigate local electrical properties. Scanning softly semiconducting organic nanostructures with a metallic probe dc biased regarding to the sample, allowed both for the electrical delineation of nanostructured materials or blends, and for the characterization of conductive properties by means of local I-V profiles. Quadratic variations of the current with the voltage are often reported as an evidence for C-AFM current originating from space charge limited current. More recently, original experimental protocols have been proposed to demonstrate the local aspect of the current measured. Provided an appropriate and non-numerical model, the spatial resolution of the measurements could be estimated within 10 nm whilst characterization of electrical properties allow for quantitative determination of local carrier density and mobility.
References:
1 D. Moerman, R. Lazzaroni and O. Douhéret, Applied Physics Letters, 2011, 99, 093303
2 D. Moerman, N. Sebaihi, S. E. Kaviyil, P. Lclère, R. Lazzaroni and O. Douhéret, Nanoscale, 2014, 6, 10596-10603

Jeudi 11 Juin 2015
Dr. Chantal Abergel & Jean-Michel Claverie
Structural and Genomic Information laboratory, CNRS-AMU UMR 7256, IMM, Parc Scientifique de Luminy, Marseille, France
The rapidly expanding universe of giant viruses
"Giant virus" is a typical oxymoron if we refer to the origin of the virus concept: an infectious agent capable of passing through the filter designed by Chamberland to stop all microbes known at the time of Pasteur (in the mid nineteen century). We identified the first giant virus called "Mimivirus" (for microbe mimicking virus) in 2003. With a particle of 0.7 micrometer in diameter packing a 1.2 Mb genome encoding 979 proteins, Mimivirus was the first virus overlapping the world of bacteria both in terms of particle size and genome complexity. These giant viruses are not rare and many Mimivirus relatives (the Megaviridae) were then quickly isolated, culminating with Megavirus chilensis, encoding 1,120 proteins among which 7 aminoacyl-tRNA synthetases, until then considered hallmarks of cellular microorganisms. As we thought we were finally reaching the limit of viral complexity and started to build a new paradigm about the evolution of DNA viruses, the discovery of the Pandoraviruses came ruining this newly built theoretical edifice. With 1.2 micron-long particles packing a genome of 2.5 Mb encoding more than 2,500 proteins, Pandoravirus salinus is now surpassing the complexity of the smallest eukaryotic cells, such as parasitic microsporidia species. However, with less than 10% of their predicted proteins resembling anything, as well as their unique mode of replication, the Pandoraviruses clearly represent a class of giant viruses totally unrelated to the Megaviridae. Finally, I will present the discovery of Pithovirus sibericum, isolated from a >30,000-y-old radiocarbon-dated sample of Siberian permafrost. This third type of giant virus combine an even larger pandoravirus-like particle 1.5 μm in length with a surprisingly smaller 600 kbAT-rich genome, a gene content more similar to Iridoviruses and Marseillevirus, and a fully cytoplasmic replication reminiscent of the Megaviridae. Pandoravirus-like particles may thus be associated with a variety of virus families more diverse than previously envisioned. To conclude, I will briefly present the hypotheses that have been proposed about the origin and evolution of DNA viruses and their possible link with the emergence of eukaryotes.

Jeudi 18 Juin 2015
Prof. Graca VICENTE & Prof. Kevin M. S
Department of Chemistry, Louisiana State University (USA)
15h : Reactivity and Photophysical properties of halogenated BODIPYs
16h : Photosensitizers from Chlorophyll

Jeudi 25 Juin 2015
Marco Abbarchi
Aix-Marseille Université, CNRS, Centrale Marseille, IM2NP, UMR 7334, Campus de St. Jérôme, 13397 Marseille, France
Fabrication and optical properties of ultra-large arrays of silicon-based Mie resonators
Based on Mie-modes of electric and magnetic multipoles nature, sub-micrometric resonant cavities made of high refractive index materials have been recently reported by several groups [1-6]. In this class of novel resonators, polarization currents are formed by the incoming light inducing strong magnetic and electric multi-polar modes ruling the optical properties of the far field scattering pattern [1,2,5,6]. Common approaches for the implementation of dielectric Mie resonators (MR) include laser sputtering [1,2], e-beam lithography [5], CVD [4] and two-step nano-imprint [6]. Here [8] we propose the use of solid state dewetting of a thin crystalline silicon on insulator substrate [7], a one-step dry process, for the production of high density MR over large areas. This method is shown to allow the production of monocrystaline MRs that feature two resonant modes in the visible spectrum, as observed in confocal scattering spectroscopy. Homogeneous scattering responses and improved spatial ordering of the Si-based resonators are observed when dewetting is assisted by electron-beam litography. Finally, exploiting different agglomeration regimes, we highlight the versatility of this technique, which, when assisted by focussed ion beam nanopatterning, produces monocrystalline nanocrystals with ad hoc size, position and organization in complex oligomers. Our findings [8] open new ways of playing with ordered and disordered metamaterials for thin-film anti-reflection coating and broad band and wide angle light-coupling. Furthermore, when dewetting SOI substrates patterned by E-Beam or by FIB we obtain ad-hoc arrangements of complex oligomers. References:
[1] Miroshnichenko et al., Sci. Rep. 2, 492 (2012)
[2] Fu et al, Nat. Comm. 4, 1527 (2013)
[3] Coenen et al, ACS Nano 7, 1689 (2013)
[4] Shi et al, Adv. Mat. 24, 5934 (2012)
[5] Staude et al, ACS Nano 7 7824 (2013)
[6] Spinelli et al, Nat. Comm 3, 692 (2012)
[7] Aouassa et al, Appl. Phys. Lett. 101, 013117 (2012)
[8] Abbarchi et al, ACS Nano 8, 11181 (2014)

Jeudi 02 Juillet 2015
Prof. Jacky Even
Laboratoire FOTON, CNRS-UMR6082, INSA Rennes, Université Rennes-1, 20 avenue des Buttes de Coësmes, 35708 Rennes, France
Introduction aux pérovskites hybrides : aspects théoriques, applications photovoltaïques et optoélectroniques
Les pérovskites hybrides en couches ont longtemps occupé le devant de la scène en partie pour leurs propriétés optiques exceptionnelles, mais aussi pour la grande flexibilité offerte en termes d'élaboration, d'auto-assemblage et de synthèse chimique. L'histoire des pérovskites hybrides 3D pour le photovoltaïque s'accélère brutalement, après quelques résultats initiaux Japonais et Coréens, au milieu de l'année 2012 sous l'impulsion conjointe de deux équipes: l'équipe de l'EPFL et l'équipe d'Oxford. Les rendements photovoltaïques record obtenus atteignent très rapidement 10% (2012), 15% (2013) puis 20% (2014). Ces progrès reposent à la fois sur de nouveaux procédés d'élaboration et de dépôt des pérovskites hybrides, une meilleure compréhension des phénomènes fondamentaux, une meilleure maîtrise de la physico-chimie des matériaux, mais aussi sur de nouvelles architectures de cellules solaires ou de composants optoélectroniques. Très récemment, une première démonstration de luminescence blanche des pérovskites 3D semble indiquer que l'histoire de ces matériaux pourra également s'inscrire dans le domaine de l'émission de lumière. Le séminaire introduira le sujet des pérovskites hybrides et donnera quelques éléments sur les travaux théoriques développés par le groupe de physico-chimistes Rennais (FOTON,UMR6082/ISCR,UMR6226) qui travaille sur le sujet depuis 2010. Refs: J. Even, et al. Phys. Rev. B. 2012, 86, 205301 ; J. Phys. Chem. Lett. 2013, 4, 2999-3005.

Jeudi 09 Juillet 2015
Caroline Tardivat
Directrice, Ceramic Synthesis and Functionalization Laboratory, Laboratoire commun CNRS / Saint-Gobain CREE, Cavaillon, France
Non-SOFC applications of ion-conductive ceramics

Jeudi 8 Octobre 2015
Pr. Paul KNOCHEL
Département de Chimie, Ludwig-Maximilians University, Münich, Allemagne
Chimie organométallique polyfonctionnelle en synthèse hétérocyclique

Jeudi 29 Octobre 2015
Jean-Marie DUBOIS
Institut Jean Lamour (UMR 7198 CNRS – Université de Lorraine), Parc de Saurupt, CS50840, F-54011 Nancy
Push-Pull Alloys and the Legacy of Dan Shechtman
With his famous discovery of quasicrystalline order in 1982-84, Dan Shechtman, the 2011 Nobel Laureate for Chemistry, has granted us with a fascinating field in materials science that has nowadays spread out to a variety of domains in metallurgy, geology, polymer science, artificial nanostructured materials, low temperature physics, and art. Push-pull alloys stand at the heart of the heritage and teach us a lot about the roots of order in Nature, its influence on properties, and by the way open new niches for applications. A short review of the most salient features of this domain will be given. We will begin with a simplified view at the way atomic order may be described in complex intermetallics and quasicrystals. The talk will continue with electron transport properties, which provide a signature of the breakdown of periodic order in those systems made of metals. We will then examine surface properties, with a view at the potential application niches and one, yet commercially available, application will be addressed. The talk will merely draw attention to A-B-C ternary alloys, in which the elemental constituents A, B and C are chosen in such a way that B-C interactions are repulsive, but A-B and A-C are attractive in the respective binary systems. I call such alloys “push-pull alloys” in reminiscence of push-pull amplifiers that are designed to amplify an electric signal. Push-pull alloys amplify complexity, forming complex intermetallics with tens to thousands atoms per unit cell. Few of them lead to the ultimate degree of complexity, when quasiperiodic order substitutes for crystal periodicity, which opens the way to discovering unprecedented properties such as heat insulation in Al62Cu25Fe13 (at. %). Many more compounds are known today, which share the same elemental characteristics (the picture may be extended to specific binary alloys). The results will be interpreted in terms of self-organized criticality [1]. In order to promote discussion about the essence of the quasicrystalline state (“why are the atoms where they are?”), a preliminary model will be suggested. It is based on the assumption that d-like electrons, facing the energy gaps opened at the boundaries of the Jones zone via Mizutani’s interference rule [2], impose a second wavelength to the scattering mechanism that is different from the one characteristic of the (orthogonal) s-p wave functions. Appropriate tuning of the two interference systems may cancel periodicity as predicted by the Lifshitz-Petrich model [3]. 1. P. Bak, How Nature works: the science of self-organized criticality (Copernicus Press, New York, 1996). 2. U. Mizutani et al., Chem. Soc. Rev. 41 (2012) 6799-6820. DOI: 10.1039/c2cs35161g. 3. R. Lifshitz and D.M. Petrich, Phys. Rev. Lett. 79-7 (1997) 1261-1264.

Jeudi 19 Novembre 2015
Khalifa AGUIR
Institut Matériaux Microélectronique Nanosciences de Provence, IM2NP, UMR CNRS 7334, Universités d'Aix-Marseille et de Toulon, Campus de St. Jérôme, 13397 Marseille, France
De l'intérêt de la miniaturisation des capteurs pour le suivi de la qualité de l'air