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|Title:||Light-Induced Electron Transfer and Energy Transfer in Thin Polymer Films and Zeolites|
|Author(s):||Renschler, Clifford Lyle|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Light-induced electron transfer and energy transfer reactions are essential to the collection and storage of light in photosynthesis. The purpose of this work is to better understand both types of reactions, to develop the means to better control them, and to make them more efficient. Electron transfer reactions between neutral species produce ion pairs. If these ions could be separated from each other to prevent immediate recombination, they might be used to drive other useful reactions. Two media, thin polymer films and zeolites, which showed promise in maintaining charge separation, were used in this study.
Since thin films tend to be weak absorbers, it would be useful to develop an efficient method of collecting photons and transporting their energy (i.e., an energy "antenna") to a reaction center. Successive Forster transfer between sites in the film, in a "hopping" mechanism, was used for this purpose.
The thin film studies involved three stages. In the first, fluoranthene (FA) singlets were quenched by tetrabromo-o-benzoquinone (TBBQ), both homogenously dispersed in a polystyrene matrix. A method was developed to distinguish quantitatively between contact quenching and Forster quenching. It was shown that the FA system is ineffective as an antenna.
A limited antenna, with a diffusion length for excitons of ca. 32 (ANGSTROM), was developed using 9,10-diphenylanthracene (DFA) and TBBQ in polystyrene. Diffusion lengths of excitons were determined as a function of DPA concentration.
A more effective antenna was developed using rhodamine B quenched by Acid Black 24 in poly(vinylalcohol). Diffusion lengths were about eight times as large as those found for similar concentrations of DPA.
For the zeolite studies, the tris(2,2'-bipyridyl)ruthenium(II) ion (Ru(bpy)(,3)('2+)) was exchanged into both zeolites 13X and 4A. It was shown that while Ru(bpy)(,3)('2+) exchanged into both interior and exterior sites of 13X particles, only exterior exchange sites were available on 4A. In addition, a light-induced electron transfer from N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) to Ru(bpy)(,3)('2+) exchanged in 13X was accomplished with stabilization of the products.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
|Date Available in IDEALS:||2014-12-15|