In situ optical observation of oxygen-adsorption-induced reversible change in the shape of small supported silver particles

We studied, in situ and in real time, the optical absorption spectrum of small silver particles supported on silica. A reversible change induced by a change of ambient gas between 5%H 2/He and 1%O 2/He was observed at temperatures between 373 and 573 K. Calculations of the optical spectrum of small...

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Bibliographic Details
Published in:Surface science 1992-03, Vol.264 (1), p.147-156
Main Authors: Akihisa, Yanase, Hiroshi, Komiyama
Format: Article
Language:English
Subjects:
Chemistry
Exact sciences and technology
General and physical chemistry
Solid-gas interface
Surface physical chemistry
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Summary:We studied, in situ and in real time, the optical absorption spectrum of small silver particles supported on silica. A reversible change induced by a change of ambient gas between 5%H 2/He and 1%O 2/He was observed at temperatures between 373 and 573 K. Calculations of the optical spectrum of small silver particles were made using the Maxwell-Garnett theory with respect to the effects of a change in particle shape and the formation of a surface oxide layer. Comparison of experimental with calculated spectra indicates a reversible change in the shape of silver particles between spherical in 5%H 2/He and oblate-spheroidal in 1%O 2/He. The change was rapid and enhanced with increasing temperature. The mechanism of this phenomenon is discussed, using a model in which the small supported silver particle is treated as a liquid droplet on a solid surface: The adsorption and desorption of oxygen causes a large change in the surface stress of the droplet.
ISSN:0039-6028
1879-2758
DOI:10.1016/0039-6028(92)90173-4