High Pressure Studies of Triphenylmethane Dye Molecules (Photosensitization, Adsorption, Isomerism, Semiconductors, Surfaces)
Clark, Frederick Tyson
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https://hdl.handle.net/2142/69758
Description
Title
High Pressure Studies of Triphenylmethane Dye Molecules (Photosensitization, Adsorption, Isomerism, Semiconductors, Surfaces)
Author(s)
Clark, Frederick Tyson
Issue Date
1985
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Abstract
High pressure studies of triphenylmethane (TPM) dye molecules at room temperature in this thesis are conducted in two experiments. In the first case, photocurrent measurements using an electrochemical cell technique have been made to study the effect of pressure to 10 kbar on the adsorption of the methyl derivative of the dye (crystal violet, CV) on oriented ZnO(0001) semiconductor surfaces. Secondly, optical absorption measurements have been made on the hydrogen, methyl and ethyl derivatives both in solution (to 10 kbar) and dissolved in plastic media (to 150 kbar) to study the effect of pressure on the rotational isomerism of these dye molecules dispersed in the various media.
In the photocurrent measurements, similar magnitudes in the red shift with pressure of peaks corresponding to the A and B isomers and the dimer of CV both in the adsorbed and liquid phases are observed, confirming the charge transfer mechanism for the photosensitization process. In addition, the volume change of the system on isomerization and dimerization of the CV monomer in solution and the volume change of the system on adsorption of each species to the ZnO surface are calculated. The results are interpreted to indicate the mode of attachment.
In the optical absorption measurements, three media are used to study the effect of environment on the A and B isomers and on the isomerization process: atactic-PMMA, PC and a buffered aqueous solution. The polymer films are studied in a diamond anvil cell to 150 kbar while the aqueous solution is studied in the liquid state cell to 10 kbar. In these studies, the isomerization process appears to be a sensitive probe of the local structures of these media.
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