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Nantes, France

Vlandas A.,Wolfmahdenstr. 33 | Ewels C.P.,Jean Rouxel Institute | Van Lier G.,Free University of Brussels
Chemical Communications | Year: 2011

A systematic density functional study of chlorine addition to C 70 up to C70Cl12 confirms experimental observations of regioselectivity and stability of C70Cl10. We show that K@C70 follows an alternative addition sequence with different isomers and magic numbers to C70 such as KC 70Cl3. This prediction is important for controlling functionalisation behaviour via encapsulation and endofullerene purification. © 2011 The Royal Society of Chemistry.

Melinon P.,University Claude Bernard Lyon 1 | Begin-Colin S.,IPCMS et OMNT | Duvail J.L.,Jean Rouxel Institute | Gauffre F.,CNRS Chemistry Institute of Rennes | And 6 more authors.
Physics Reports | Year: 2014

It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed. © 2014 Elsevier B.V.

Ciobanu C.S.,National Institute of Materials Physics Bucharest | Massuyeau F.,Jean Rouxel Institute | Constantin L.V.,University of Bucharest | Predoi D.,National Institute of Materials Physics Bucharest
Nanoscale Research Letters | Year: 2011

Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10-xAgx(PO4)6(OH)2 (x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp (x = 0) and Ag:HAp (x = 0.2). The Ag: Hap nanopowder showed higher inhibition. © 2011 Ciobanu et al.

Cadel E.,CNRS Material Physics Group | Barreau N.,Jean Rouxel Institute | Kessler J.,Jean Rouxel Institute | Pareige P.,CNRS Material Physics Group
Acta Materialia | Year: 2010

This article reports the first investigations of CuIn1-xGaxSe2 (CIGSe) polycrystalline thin films by means of atom probe tomography. Attention is focused on the distribution of Na atoms within the films. Both Na-containing and Na-free CIGSe thin films have been investigated. When Na is available during the CIGSe coevaporation, it is observed to be mainly segregated at the grain boundaries of the films; however, it is also detected within the grains of CIGSe at very low concentration. © 2009 Acta Materialia Inc.

Cougnon C.,CNRS Angers Institute of Molecular Science and Technology | Lebegue E.,Jean Rouxel Institute | Pognon G.,Jean Rouxel Institute
Journal of Power Sources | Year: 2015

Modified activated carbon (Norit S-50) electrodes with electrochemical double layer (EDL) capacitance and redox capacitance contributions to the electric charge storage were tested in 1 M H2SO4 to quantify the benefit and the limitation of the surface redox reactions on the electrochemical performances of the resulting pseudo-capacitive materials. The electrochemical performances of an electrochemically anodized carbon electrode and a catechol-modified carbon electrode, which make use both EDL capacitance of the porous structure of the carbon and redox capacitance, were compared to the performances obtained for the pristine carbon. Nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the BET surface area, pore size distribution, pore volume and average pore diameter. The electrochemical behavior of carbon materials was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The EIS data were discussed by using a complex capacitance model that allows defining the characteristic time constant, the global capacitance and the frequency at which the maximum charge stored is reached. The EIS measurements were achieved at different dc potential values where a redox activity occurs and the evolution of the capacitance and the capacitive relaxation time with the electrode potential are presented. Realistic galvanostatic charge/discharge measurements performed at different current rates corroborate the results obtained by impedance. © 2014 Elsevier B.V. All rights reserved.

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