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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
Subject(s):Chemistry, Analytical
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.
Issue Date:1986
Description:179 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.
Other Identifier(s):(UMI)AAI8610951
Date Available in IDEALS:2014-12-15
Date Deposited:1986

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