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Photophysics and oxygen quenching of transition-metal complexes on fumed silica

Carraway, E. R. and Demas, J. N. and DeGraff, B. A. (1991) Photophysics and oxygen quenching of transition-metal complexes on fumed silica. Langmuir, 7 (12). pp. 2991-2998. ISSN 0743-7463. doi:10.1021/la00060a015.

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Pressed fumed silica has unique mechanical, chemical, and optical properties. It forms dense (1 g/mL), optically transparent disks, yet has a surface area of 200 m^2/g, which is the same as the unpressed material. The disks are highly porous and respond quickly to changes in gas composition. Before pressing, the silica can be impregnated by adsorption with a variety of materials. As a means of probing this surface and determining its potential utility, we have adsorbed luminescent RuL_3^(2+) ~(L = α-diimine) complexes and examined their luminescence and oxygen quenching. The adsorption sites are highly heterogeneous as shown by nonexponential decays in the presence or absence of an O_2 quencher. By use of a newly developed method, quenching is shown to be predominantly or exclusively by dynamic rather than static processes. Modeling of the quenching indicates that the results are best fit by surface quenching by adsorbed O_2 that obeys a Freundlich adsorption isotherm, although a two-site model with different quenching constants yields reasonable fits. The high density, transparency, porosity, and ease of preparation of homogeneously dispersed high levels of adsorbed species suggest that pressed fumed silica has potential as a support for luminescence sensors and photocatalysts.

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Additional Information:© 1991 American Chemical Society. Received March 6, 1991. In Final Form: May 6, 1991. We gratefully acknowledge support by the National Science Foundation (Grants CHE 86-00012 and 88-17809). We thank Coleman Jones and Professor F. E. Wawner, Jr., for assistance with the surface area measurements and Robert Paine for pointing out the unique ability of Cab-O-Si1 to glass on pressing. We thank Hewlett-Packard for the gift of the 8452A spectrophotometer and Henry Wilson for his kind assistance.
Funding AgencyGrant Number
NSFCHE 86-00012
NSFCHE 88-17809
Issue or Number:12
Record Number:CaltechAUTHORS:20180720-111444673
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Official Citation:Photophysics and oxygen quenching of transition-metal complexes on fumed silica E. R. Carraway, J. N. Demas, and B. A. DeGraff Langmuir 1991 7 (12), 2991-2998 DOI: 10.1021/la00060a015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88059
Deposited By: George Porter
Deposited On:23 Jul 2018 21:54
Last Modified:16 Nov 2021 00:23

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