Elaboration of metallic anisotropic nanocrystals for energy and magnetic applications

International audienceThe elaboration of new materials with specific properties (catalytic, magnetic,…) needs to control the synthesis of the nanocrystals that constitute it. In particular their size, nanomorphology and cristallinity have to be carefully defined. To design NCs with desired properties, it is necessary to first understand the mechanisms involved in the nucleation and growth processes. Soft chemical synthesis offer a versatile way to produce a large variety of NCs however the understanding is very complex due to the presence of reactants and products that can modify the nucleation and crystal growth. This presentation will show some example of anisotropic platinum and palladium NCs obtained from a thermodynamic or a kinetic controlled growth 1,2. As the modification of the kinetic of the reaction has an influence on the nucleation and growth of the nanoparticles, we have recently developed a new synthesis giving the opportunity to produce nanoalloy nanocrystals 1,3 and hcp cobalt nanocrystals ferromagnetic at room temperature 4 by controlling their nucleation and growth.(1) Salzemann, C.; Kameche, F.; Ngo, A.-T.; Andreazza, P.; Calatayud, M.; Petit, C. Faraday Discuss 2015, 181, 19(2) Petit, C.; Salzemann, C.; Demortiere, A. In Complex-Shaped Metal Nanoparticles; Sau, T. K., Rogach, A. L., Eds.; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2012; pp 305–337.(3) Kameche, F.; Ngo, A.-T.; Salzemann, C.; Cordeiro, M.; Sutter, E.; Petit, C. Phys Chem Chem Phys 2015, 28162(4) Meziane, L.; Salzemann, C.; Aubert, C.; Gérard, H.; Petit, C.; Petit, M. Nanoscale 2016, 8 (44), 18640

Élaboration raisonnée de nanomatériaux mono- et bimétalliques

L'élaboration raisonnée de nanomatériaux consiste, en amont de l'application, à comprendre les différents processus intervenant dans la synthèse. Cette approche permet de définir les conditions de synthèse qui conduiront au contrôle de leur cristallinité, composition et morphologie.Ce manuscrit d'habilitation à diriger des recherches présente mes travaux et projet de recherche sur "Élaboration raisonnée de nanomatériaux mono- et bimétalliques". Il s'articule autour de quatre chapitres qui apportent des éléments de compréhension quant au contrôle des différents paramètres requis pour l'élaboration de systèmes valorisables en catalyse et/ ou dans le stockage d'information. Cela concerne d'une part la synthèse contrôlée (cristallinité, morphologie, composition) de nanoobjets mono- et/ou bimétalliques et d'autre part le contrôle de leur organisation en des réseaux au sein desquels il est possible de moduler les interactions

Elaboration of metallic anisotropic nanocrystals for energy and magnetic applications

International audienceThe elaboration of new materials with specific properties (catalytic, magnetic,…) needs to control the synthesis of the nanocrystals that constitute it. In particular their size, nanomorphology and cristallinity have to be carefully defined. To design NCs with desired properties, it is necessary to first understand the mechanisms involved in the nucleation and growth processes. Soft chemical synthesis offer a versatile way to produce a large variety of NCs however the understanding is very complex due to the presence of reactants and products that can modify the nucleation and crystal growth. This presentation will show some example of anisotropic platinum and palladium NCs obtained from a thermodynamic or a kinetic controlled growth 1,2. As the modification of the kinetic of the reaction has an influence on the nucleation and growth of the nanoparticles, we have recently developed a new synthesis giving the opportunity to produce nanoalloy nanocrystals 1,3 and hcp cobalt nanocrystals ferromagnetic at room temperature 4 by controlling their nucleation and growth.(1) Salzemann, C.; Kameche, F.; Ngo, A.-T.; Andreazza, P.; Calatayud, M.; Petit, C. Faraday Discuss 2015, 181, 19(2) Petit, C.; Salzemann, C.; Demortiere, A. In Complex-Shaped Metal Nanoparticles; Sau, T. K., Rogach, A. L., Eds.; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2012; pp 305–337.(3) Kameche, F.; Ngo, A.-T.; Salzemann, C.; Cordeiro, M.; Sutter, E.; Petit, C. Phys Chem Chem Phys 2015, 28162(4) Meziane, L.; Salzemann, C.; Aubert, C.; Gérard, H.; Petit, C.; Petit, M. Nanoscale 2016, 8 (44), 18640

Nanocristaux de Cuivre de taille et forme variables (étude structurale et propriétés optiques)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Understanding How in Situ Generated Hydrogen Controls the Morphology of Platinum Nanoparticles

International audienceSmall adsorbed molecules play a key role in the morphology of inorganic nanoparticles. The presence of in situ 11 generated hydrogen during the synthesis of platinum nanoparticles is found to drive the growth of cubic nanocrystals, but little is 12 known about the processes occurring at the molecular level. In this paper, we use standard ab initio calculations to show that 13 hydrogen preferentially adsorbs on (100) Pt facets compared to (111) stabilizing the cubic morphology. Moreover, we provide 14 experimental and theoretical evidence that moderate partial pressure of hydrogen is needed to obtain nanocubes. In the absence 15 of hydrogen, or for low partial pressures, small nanoparticles with undefined shape are formed; however, longer exposure to 16 hydrogen pressure around 1 atm leads to the formation of cubes. Finally, this theoretical result allows presenting an experimental 17 protocol to be used to obtain platinum nanocubes with different degree of truncation. 18 ■ INTRODUCTION 19 Many physical and chemical properties depend on the shape of 20 the particles forming the material, 1 hence the challenge of 21 controlling the crystal morphology in a wide range of scientific 22 and technological applications. The chemical route is largely used 23 to control the shape of inorganic nanocrystals, although there is 24 still no theoretical drawback of the main forces driving it. Despite 25 many studies found in the literature, the theoretical and 26 computer simulation of nanoparticles' synthesis and growth are 27 still in the initial stage of development, and most of these works 28 do not take into account the complexity of the chemical 29 synthesis. It is still paramount to explain the mechanisms at the 30 origin of the uniformity of shape. Indeed, the field is still wide 31 open to future research aiming at identifying the conditions to 32 control the nanomorphology. 33 In the chemical synthesis of the nanocrystals, the chemical 34 bath possesses a complex composition containing various 35 reactants, solvents, surfactants, (counter)ions, and impurities. 36 Moreover, during the reaction, byproducts can be formed, which 37 could play a role in the nuclei formation and the following 38 nanoparticles' growth. 2 For instance, the role of dissolved gas H 2 39 on the shape control of platinum nanocrystals has recently been 40 demonstrated experimentally. 3 Some authors also report the role 41 of halide, ligands, or adsorbed CO on the nanomorphology. 4−6 42 Besides, the role of the initial shape of the nanocrystals and the 43 growth kinetics have been emphasized. 7,8 Beyond the exper-44 imental recipe, a theoretical approach is needed to rationalize and 45 predict the stability of the nano-objects. In the present paper, the 46 goal is to emphasize the role of a byproduct generated during the 47 chemical synthesis in the final nanoparticle morphology. We 48 focus here on the specific case of platinum. We use ab initio 49 calculations to explain how the presence of in situ generated H 2 50 drives the formation of cubic nanoparticles. We also explain the 51 impact of the experimental conditions, namely, the partia

Role of the nanocrystallinity on the chemical ordering of Co x Pt 100-x nanocrystals synthesized by wet chemistry

International audienceCo x Pt 100-x nanoalloys have been synthesized by two different chemical processes either at high or at low temperature. Their physical properties and the order/disorder phase transition induced by annealing have been investigated depending on the route of synthesis. It is demonstrated that the chemical synthesis at high temperature allows stabilization of the fcc structure of the native nanoalloys while the soft chemical approach yields mainly poly or non crystalline structure. As a result the approach of the order/disorder phase transition is strongly modified as observed by high-resolution transmission electron microscopy (HR-TEM) studies performed during in-situ annealing of the different nanoalloys. The control of the nanocrystallinity leads to significant decrease in the chemical ordering temperature as the ordered structure is observed at temperatures as low as 420 ºC. This in turn preserves the individual nanocrystals and prevents their coalescence usually observed during the annealing necessary for the transition to an ordered phase

Platinum and platinum based nanoalloys synthesized by wet chemistry

International audiencePlatinum nanocrystals and their derivatives with palladium and cobalt are of fundamental interest due to their wide field of application in chemistry and physics. Their properties are strongly dependent on their shape and composition. However the chemical route is far from allowing control of both shape and composition. In this paper, we show both experimentally and theoretically the important role of the interaction of small adsorbed molecules on the shape but also on the composition. This has been studied by comparing the case of pure palladium and platinum nanocrystals and the case of PtPd and PtCo nanoalloys synthesized by the liquid–liquid phase transfer method

Structural characterization of Cu-Nanoparticles

Structural characterization of Cu-Nanoparticles Salzemann, Caroline 1,2; Lisiecki, Isabelle 2; Urban, Jochen 1; Schloegl, Robert 1 ; Pileni, Marie-Paule 2 1 Fritz-Haber-Institut der Max-Planck-Gesellschaft Abt AC, Faradayweg 4-6, D-14195 Berlin. 2 Université P. et M. Curie, laboratoire LM2N, BP52, Bât 74 4 place Jussieu, 75005 Paris Fax : …………… E-mail :[email protected] Syntheses of Copper nanoparticles have been carried out in reverse micelles [1] which are used as templates to control the size and the shape of nanoparticles [2] . It has been also observed that the reducing agent plays an important role in the control of particle size and in final oxidation state of the surface [3]. The particles have been prepared by using reverse micelles made of a mixture of Sodium and Copper di(2-ethylhexyl) sulfosuccinate. Hydrazine (N2H4) is the reducing agent. By using this procedure Copper metal nanocrystals and the oxide derivature are obtained. This is demonstrated by High Resolution Electron Microscopy. The calculation of the power spectra of the images is used for the symmetry interpretation and the measuring of structural data. Typical structures of pure metallic Copper as cubic structure and multiply twinned particles [4] and also cuprite structure Cu2O for the oxidized particles were observed. [1] Lisiecki I, Pileni MP, J.Am.Chem.Soc. 1993, 115, 3887. [2] Tanori J, Pileni MP, Adv.Mater. 1995, 7, 862. [3] Lisiecki I, Pileni MP, J.Phys.Chem. 1995, 99, 5077. [4] Lisiecki I, Filankembo A, Sack-Kongehl H, Weiss K, Pileni MP, Urban J, Phys.Rev.B61, 2000, 4968

Elaboration of mesostructures based on magnetic nanocrystals: modulation of dipolar interactions from super-ferromagnetism to magnetic decorellation

International audienceIn an assembly of highly concentrated magnetic nanoparticles (NPs), the materials’ magnetic properties can be greatly influenced by their mutual dipolar interactions. In particular, the existence of a long-range ordered state where their individual magnetic moments are aligned ferromagnetically (dipolar superferromagnetic state, SFM) is predicted [1]. However, a clear-cut experimental evidence of it in real 3D NP assemblies has so far remained elusive. This is most likely due to the stringent geometrical/physical conditions required for inducing a dipolar SFM state. In this context, we intend to produce a dipolar SFM state in columnar supercrystals of dodecanoic acid coated Co NPs. This presentation focuses on the synthesis and characterizations of Co nanoparticles [2] and in the elaboration of mesostructures (labyrinths, voids and columns) obtained by the evaporation of a colloidal solution under an external magnetic field [3,4].(1) Majetich, S. A.; Sachan, M. J. Phys. Appl. Phys. 2006, 39 (21), R407.(2) Lisiecki, I.; Pileni, M. P. Langmuir 2003, 19 (22), 9486.(3) Salzemann, C.; Richardi, J.; Lisiecki, I.; Weis, J.-J.; Pileni, M. P. Phys. Rev. Lett. 2009, 102 (14).(4) Germain, V.; Richardi, J.; Ingert, D.; Pileni, M. P. J. Phys. Chem. B 2005, 109 (12), 5541

Chemical Evolution of Pt–Zn Nanoalloys Dressed in Oleylamine

International audienc