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.
Lavenus S.,University of Nantes |
Lavenus S.,Jean Rouxel Institute |
Ricquier J.-C.,Jean Rouxel Institute |
Louarn G.,Jean Rouxel Institute |
Layrolle P.,University of Nantes
Nanomedicine | Year: 2010
Metals such as titanium and alloys are commonly used for manufacturing orthopedic and dental implants because their surface properties provide a biocompatible interface with peri-implant tissues. Strategies for modifying the nature of this interface frequently involve changes to the surface at the nanometer level, thereby affecting protein adsorption, cell-substrate interactions and tissue development. Recent methods to control these biological interactions at the nanometer scale on the surface of implants are reviewed. Future strategies to control peri-implant tissue healing are also discussed. © 2010 Future Medicine Ltd.
Dupre N.,Jean Rouxel Institute |
Cuisinier M.,Jean Rouxel Institute |
Electrochemical Society Interface | Year: 2011
Li NMR is a powerful tool to study the surface layer on Li-ion battery electrode materials, especially coupled with techniques giving chemical information such as XPS or FTIR. Concerning the organic part of the interphase, the use of 13C NMR has proved also to be of great interest to understand the decomposition or reaction pathway of organic solvents even though the need of isotopic enrichment and the sensitivity of 13C NMR to the presence of paramagnetic centers complicate the detection. In the case of materials containing transition metals with unpaired electrons, in addition to the chemical composition and quantification, it is possible to extract physical or topological information from electron-nucleus dipolar interaction. The detection and observation of electrode/electrolyte interphase using NMR technique is now applied to a wide range of cathode and anode materials for lithium-ion batteries and is becoming an efficient characterization tool in this research area.
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.
Dupre N.,Jean Rouxel Institute |
Cuisinier M.,Jean Rouxel Institute |
Martin J.-F.,Jean Rouxel Institute |
Guyomard D.,Jean Rouxel Institute
ChemPhysChem | Year: 2014
The present review reports the characterization and control of interfacial processes occurring on olivine LiFePO4 and layered LiNi 1/2Mn1/2O2, standing here as model compounds, during storage and electrochemical cycling. The formation and evolution of the interphase created by decomposition of the electrolyte is investigated by using spectroscopic tools such as magic-angle-spinning nuclear magnetic resonance (7Li, 19F and 31P) and electron energy loss spectroscopy, in parallel to X-ray photoelectron spectroscopy, to quantitatively describe the interphase and unravel its architecture. The influence of the pristine surface chemistry of the active material is carefully examined. The importance of the chemical history of the surface of the electrode material before any electrochemical cycling and the strong correlation between interface phenomena, the formation/evolution of an interphase, and the electrochemical behavior appear clearly from the use of these combined characterization probes. This approach allows identifying interface aging and failure mechanisms. Different types of surface modifications are then investigated, such as intrinsic modifications upon aging in air or methods based on the use of additives in the electrolyte or carbon coatings on the surface of the active materials. In each case, the species detected on the surface of the materials during storage and cycling are correlated with the electrochemical performance of the modified positive electrodes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Tanguy F.,Jean Rouxel Institute |
Gaubicher J.,Jean Rouxel Institute |
Guyomard D.,Jean Rouxel Institute
Electrochimica Acta | Year: 2010
The electrochemical characterization related to the capacity fading of Li1.1V3O8 nano grains has been investigated. It reveals that capacity loss is associated to the use of liquid electrolyte and that it mainly stems from the active material irrespective of the nature of the liquid electrolyte, the water content, synthesis routes and the positive electrode chemistry. SEM and in operando XRD experiments allow elucidating undergoing physical processes. A film forms from electrolyte decomposition on the surface of the electrode and progressively propagates on cycling through the electrode thickness. Embedded grains become either less or none electrochemically reactive. In the former case, embedded grains give rise to strongly polarized and energetically less favored processes. In the latter case the capacity is not accessible anymore within the potential range resulting in capacity fading. © 2009 Elsevier Ltd. All rights reserved.
Zykwinska A.,Jean Rouxel Institute |
Radji-Taleb S.,Jean Rouxel Institute |
Cuenot S.,Jean Rouxel Institute
Langmuir | Year: 2010
The surface of carbon nanotubes was noncovalently modified by layer-by-layer deposition of synthetic polyelectrolytes. The efficiency of an easy functionalization process based on alternatively dipping of carbon nanotubes into solutions containing oppositely charged polyelectrolytes was demonstrated. From transmission electron microscopy (TEM) analysis, it was shown that the thickness of the adsorbed polyelectrolyte layers increases linearly with the bilayers number up to reach 6 nm. This easy functionalization covered homogeneously the whole surface of nanotubes as revealed by atomic force microscopy (AFM) images. Then, the adsorbed polyelectrolyte layers were used as anchoring ones to subsequently graft a natural biopolymer. Such postfunctionalization opens the way to design new (nano)biodevices based on carbon nanotubes. © 2009 American Chemical Society.