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22 Octobre 2013 - Alina BRUMA

Atomic scale microscopy and Density Functional Theory study of Gold-Palladium nanoclusters

par LABGPM - publié le

Atomic scale microscopy and Density Functional Theory study of Gold-Palladium nanoclusters
Mardi 22 Octobre 2013 à 10h en Salle de Conférences du GPM

Alina BRUMA - CRISMAT Caen.

The research presented in this talk is focused on the investigation of the structural properties of small, medium and large bimetallic AuPd nanoparticles by means of experimental and theoretical analysis. The first studied system is the Au24Pd1 nanoparticles supported on Multiwall Carbon Nanotubes. Using the High Angle Annular Dark Filed Scanning Transmission Electron Microscope (HAADF-STEM) we propose a quantitative analysis of the total number of atoms based on the information from single Au atoms found in the immediate vicinity of nanoparticles [1]. The morphological analysis is direc tly correlated with the theoretical one based on the use of Basin Hopping Monte Carlo Density Functional Theory (BHMC-DFT), whose aim has been to identify the putative global minimum. Furthermore, a Löwdin population analysis is performed in order to identify the charge transfer in the nanoparticles and to gain an insight in the enhanced catalytic activity of the nanoparticles towards the aerobic oxidation of benzyl alcohol [2]. For the second system, the 98-atom nanoparticles, a theoretical approach based on the use of Genetic Algorithms coupled with Gupta empirical potentials and DFT calculations aimed to get an insight on the putative global minimum morphology for this size range. This theoretical study stands as base for an understanding of the equilibrium structures of the third system, large evaporated AuPd nanoparticles [3]. For the latter system, a further analysis of the effect of thermal treatment at a temperature of 500 K of the evaporated AuPd nanoparticles has been employed. Using HAADF-STEM and electron diffraction, we have observed the formation of L12 superlattices. The global aim of this study has been to understand better the morphology and energetics of AuPd nanoparticles with potential applications in nanocatalysis.

References :
[1]. “Direct atomic imaging and density functional theory study of the Au24Pd1 cluster catalyst”,
A. Bruma, F.R. Negreiros, S. Xie, T. Tsukuda, R.L. Johnston, A. Fortunelli and Z.Y. Li, Nanoscale, (2013).

[2]. “Enhancement in the aerobic alcohol oxidation catalysis of Au25 clusters by single Pd atom doping”,
S. Xie, H. Tsunoyama, W. Kurashige, Y. Negishi, T. Tsukuda, ACS Catal., 2, 1519, (2012).

[3]. “DFT study of the structures and energetics of 98-atom AuPd clusters”,
A.Bruma , R. Ismail , L. Paz-Borbón , H. Arslan , G. Barcaro , A. Fortunelli , Z. Y. Li and R. L. Johnston, Nanoscale, 5, 646, (2013).