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The Reactions of C2H2 and CH3C2H on Ag Powder

Published online by Cambridge University Press:  28 February 2011

Paul B. Dorain  and
Joseph E. Boggio
Paul B. Dorain
Affiliation:
Amherst College, Amherst, MA 01002
Joseph E. Boggio
Affiliation:
Fairfield University, Fairfield, CT 06430
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Abstract

Ag powder is activated by pulsing it with NO2 gas which forms fresh Ag microclusters. This powder is then exposed to subsequent pulses of C2H2 or CH3C2H (3.7% in N2 ). The surface enhanced Raman scattering (SERS) spectra show dramatic intensity variations due to rapid changes in adatom concentration. Normalization of these time-dependent SERS spectra to the background scattering intensity, which is proportional to the adatom concentration, provides spectra which represent adsorbate coverage if major surface reconstruction does not occur. The temporal development of the SERS spectra of C2H2 shows rapid degradation with no evidence for adsorbed species. In contrast, propyne reacts more slowly, as evidenced by the behavior of the intensity at 1980cm−1 due to adsorbed -C2-. The reactions observed are in accord with the models developed by Barteau and Madix[1] and Vohs, Carney, and Barteau[2]. Exposure to both alkynes results in the appearance of SERS active NO, an adsorbant not previously observed at room temperature. Ellipsometric measurements are consistent with the presence of a carbon overlayer, which may stabilize the NO and render the system inert to further chemical reaction.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 111: Symposium O – Microstructure and Properties of Catalysts , 1987 , 207
Copyright
Copyright © Materials Research Society 1988

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