Electrochemistry of Adsorbed Organic Dye Molecules

Citation

Askew, Deidre Ann (1984) Electrochemistry of Adsorbed Organic Dye Molecules. Master's thesis, California Institute of Technology. doi:10.7907/3yjq-7a97. https://resolver.caltech.edu/CaltechTHESIS:03292010-082538471

Abstract

Molecular luminescence has been used to study the mechanism of charge transfer in electrode-bound films and coatings. This sensitive, fast technique enables one to observe occurrences on the electrode surface which could not be observed with conventional electrochemical or spectroelectrochemical methods. In general, electrodes should be excellent quenchers of fluorescence due to energy transfer or electron transfer. We want to examine the mechanism of the surface quenching of the fluorescence. By reproducibly adsorbing a known amount of an organic dye of high quantum yield to the electrode surface, one should be able to determine if electron transfer is a pathway in the quenching mechanism by varying the potential of the electrode. This report describes the electrochemistry of several organic dyes adsorbed on graphite electrodes which could be used for the luminescence studies. Methylene blue adsorption and electrochemistry are studied in detail. The methylene blue system is excellent in terms of adsorption characteristics. Adsorption isotherms are presented which show the range of surface coverage, Γ, that one can achieve. Methylene blue also has clean reversible electrochemistry to facilitate spectroelectrochemical experiments. However, methylene blue has a small fluorescence quantum yield and short fluorescence lifetime. This may make it a poor choice for luminescence experiments. Several other organic dyes were studied. While their electrochemistry is not as clean as that of methylene blue, their fluorescence quantum yields are much higher.

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