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|Title:||Fluorescent Probes and Optical Standing Waves for Spatial Characterization of Polymer Modified Electrodes|
|Author(s):||Laley, Steven Lawrence|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||This project has addressed the considerations necessary and the work involved in using fluorescent probes with optical standing waves for observation of dimensional changes of polymer modified electrodes. A fundamental goal of this study has been to evaluate the efficiency of fluorescent probe layers to determine in situ film thickness variations of thin polymer films on electrodes.
A suitable assembly was constructed consisting of a thin (100-350 nm) poly(styrene sulfonate) film spin-coated onto a nickel film electrode. A fluorescein isothiocyanate-labelled poly(vinyl alcohol) probe layer was synthesized and spin-coated over the poly(styrene sulfonate) layer to complete the assembly.
Interference patterns were established in the polymer layer due to reflected light at the metal surface--causing optical standing waves in the electric field of an incident excitation beam. Dimensional changes in the polymer layer were monitored by observing anti-nodal positions in the excitation or emission spectrum of the probe layer. These patterns are due to the presence of a high electric field in the vicinity of the probe layer, and affect the fluorescent intensity observed. The wavelength at which the anti-nodal position occurs is directly proportional to the distance between the electrode (mirror) and the fluorescent probe layer.
Swelling studies with neat, 6 million molecular weight PSS films in contact with a H(,2)O/CH(,3)CN solution indicate that the polymer layer's geometric thickness increases linearly with H(,2)O concentration after a threshold concentration of approximately 6 percent H(,2)O has been added to the acetonitrile.
In situ film thickness measurements of PSS films containing electrostatically bound Ru(bpy)(,3)('2+) and Os(bpy)(,3)('2+) centers indicate small thickness variations (less than 5 percent). The thickness variations exhibited during oxidation and reduction of the centers were consistent with previous electrochemical studies of the two systems and were self-consistent with a model developed to describe the assembly.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.
|Date Available in IDEALS:||2014-12-15|