Atomic structure of nanoparticles: X-ray diffraction and XAFS studies

Yuri L. Slovokhotov 

Nesmeyanov Institute of Organoelement Compounds RAS (INEOS), 28 Vavilov, Moscow 119991, Russian Federation

Abstract

Structural studies of nanocluster materials recently carried out in INEOS, are reviewed. Metal nanoclusters in polymer matrices (Co, Pt, Pt/Pd, etc.), as well as Pd blacks formed by oxidative aggregation of stoichiometric Pd clusters in organic media and binary nanoparticles (MoS2 composites obtained via monolayer dispersions, coated nanocrystallites of TiO2 anatase) were characterized. Laboratory and synchrotron X-ray diffraction data, together with local structural parameters taken from XAFS spectroscopy and the results of XRD simulation using model atomic arrangements, revealed type and distortions of atomic packing. Published single crystal X-ray structural data for big stoichiometric clusters extracted from Cambridge Structure Database (CSD) were represented as new 2D polar histograms and used as references.
Finite size, ligand shell, and electronic effects can modify geometric and electronic structure of nanometric atomic aggregates. Structural monitoring of chemical transformations discussed in the talk include distortion of MoS2x- hexagonal layers in intercalated nanoparticles due to partial retention of a negative charge, as well as air oxidation of small stoichiometric palladium clusters in toluene and large mixed-metal stoichiometric cluster [Ni32Au6(CO)44]6- in acetonitrile. Larger (ca. 13 nm), and chemically stable TiO2 nanocrystallites show local distortions of Ti coordination due to coating by photosensibilizing agents, which may facilitate electron transfer in solar cell prototypes. Structural transformations in chemical processed that produce nanoparticles open a way to nanocluster materials with designed bulk properties.

Presentation: invited oral at E-MRS Fall Meeting 2003, Symposium B, by Yuri L. Slovokhotov
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-13 15:47
Revised:   2009-06-08 12:55
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