INIFTA 05425
INSTITUTO DE INVESTIGACIONES FISICO-QUIMICAS TEORICAS Y APLICADAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Change of the shape of Pt nanoparticles when embedded in porous SBA. A TEM, SAXS and EXAFS study.
Autor/es:
L.J. GIOVANETTI; S.J. FIGUEROA; J.M. RAMALLO-LÓPEZ; F.G. REQUEJO; A.F. CRAIEVICH; M.M. KOEBEL; M. FOXE; L. JONES; G.A. SOMORJAI; M. SALMERON
Lugar:
Casa Grande Spa and Resort Hotel, Ensenada's Beach, Guarujá, São Paulo
Reunión:
Congreso; VII Annual Meeting of the Brazilian Materials Society (SBPMat); 2008
Institución organizadora:
SBPMat
Resumen:
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The size and shape of the PVP-capped Pt
nanoparticles (NPs) in ethanol suspension and embedded in a nanoporous SBA
substrate were studied by transmission electron microscopy (TEM), small-angle
X-ray scattering (SAXS) and extended X-ray absorption fine structure (EXAFS).
The EXAFS technique was also applied to characterize the local structure around
Pt atoms. We found an increase of about 15% in the values of the average radius
of gyration determined by SAXS for NPs embedded in SBA compared to NPs in liquid
suspension. A decrease of the Pt-Pt first shell average coordination number for
NPs in SBA was also found by EXAFS. These results indicate a significant change
in the NPs shape, from spherical to non-spherical shape. This change of the NPs
shape after impregnation suggests the existence of a strong interaction between
Pt NPs and the surface atoms of mesoporous SBA. The shapes of Pt NPs embedded
in SBA may be long rods or flattened pancakes.
Diapositiva 1
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The size and shape of the PVP-capped Pt
nanoparticles (NPs) in ethanol suspension and embedded in a nanoporous SBA
substrate were studied by transmission electron microscopy (TEM), small-angle
X-ray scattering (SAXS) and extended X-ray absorption fine structure (EXAFS).
The EXAFS technique was also applied to characterize the local structure around
Pt atoms. We found an increase of about 15% in the values of the average radius
of gyration determined by SAXS for NPs embedded in SBA compared to NPs in liquid
suspension. A decrease of the Pt-Pt first shell average coordination number for
NPs in SBA was also found by EXAFS. These results indicate a significant change
in the NPs shape, from spherical to non-spherical shape. This change of the NPs
shape after impregnation suggests the existence of a strong interaction between
Pt NPs and the surface atoms of mesoporous SBA. The shapes of Pt NPs embedded
in SBA may be long rods or flattened pancakes.
