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TWO-PHOTON CROSS SECTION ENHANCEMENT OF PHOTOCHROMIC COMPOUNDS FOR USE IN 3D OPTICAL DATA STORAGE

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Date Issued:
2011
Abstract/Description:
Rewritable photochrome-based 3D optical data storage requires photochromic molecules with high two-photon absorption (2PA) cross sections. Currently, the low value of two-photon absorption cross sections of existing photochromes makes them unsuitable for practical application in 3D data storage. Worldwide attempts to increase the cross section of photochromic molecules by altering the chemical structure have yielded poor results. In this work, two ways to increase the two-photon absorption cross sections of photochromes were investigated. In the first method, partial success demonstrated by extending the conjugation of a photochromic molecule, a high two-photon absorption cross section of the closed form isomer and high photoconversion to the closed form were realized. At the same time, a decrease in photoswitching quantum yield and low photoconversion to open form was observed. A discussion is provided to explain the results, suggesting that the proposed method of extending the conjugation may not solve the problem. For this reason a new method for effective two-photon absorption cross section enhancement of photochromes was proposed. As a proof of principle, a new two-photon absorbing dye with a hydrogen bonding moiety was synthesized and used for the formation of supramolecular structures with a photochromic compound. Theoretical reasoning and experimental demonstration of energy transfer from the dye to the photochrome under one and two-photon excitation confirmed the practical value of the method. The effects of a 2PA dye on the photochromic properties of a diarylethene were investigated using a model compound to simplify data analysis. Formation of supramolecular structures was revealed using 1H NMR spectroscopic methods. The model compound, having the same hydrogen bonding moiety as 2PA dye, has been demonstrated to bind with photochrome molecules at very low concentrations. Photochromic properties of 2,3-bis(2,4,5-trimethyl-3-thienyl)maleimide, including conversions at the photostationary state, extinction coefficients, photoisomerization reaction rates and quantum yields, were shown to be affected by hydrogen bonding with the model compound - 2,6-bis-(acetamido)pyridine. The extent of this change was determined and discussed, demonstrating a balanced supramolecular strategy to modulate photochemical and photophysical properties of this important class of photochromic material.
Title: TWO-PHOTON CROSS SECTION ENHANCEMENT OF PHOTOCHROMIC COMPOUNDS FOR USE IN 3D OPTICAL DATA STORAGE.
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Name(s): Luchita, Gheorghe, Author
Belfield, Kevin, Committee Chair
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2011
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Rewritable photochrome-based 3D optical data storage requires photochromic molecules with high two-photon absorption (2PA) cross sections. Currently, the low value of two-photon absorption cross sections of existing photochromes makes them unsuitable for practical application in 3D data storage. Worldwide attempts to increase the cross section of photochromic molecules by altering the chemical structure have yielded poor results. In this work, two ways to increase the two-photon absorption cross sections of photochromes were investigated. In the first method, partial success demonstrated by extending the conjugation of a photochromic molecule, a high two-photon absorption cross section of the closed form isomer and high photoconversion to the closed form were realized. At the same time, a decrease in photoswitching quantum yield and low photoconversion to open form was observed. A discussion is provided to explain the results, suggesting that the proposed method of extending the conjugation may not solve the problem. For this reason a new method for effective two-photon absorption cross section enhancement of photochromes was proposed. As a proof of principle, a new two-photon absorbing dye with a hydrogen bonding moiety was synthesized and used for the formation of supramolecular structures with a photochromic compound. Theoretical reasoning and experimental demonstration of energy transfer from the dye to the photochrome under one and two-photon excitation confirmed the practical value of the method. The effects of a 2PA dye on the photochromic properties of a diarylethene were investigated using a model compound to simplify data analysis. Formation of supramolecular structures was revealed using 1H NMR spectroscopic methods. The model compound, having the same hydrogen bonding moiety as 2PA dye, has been demonstrated to bind with photochrome molecules at very low concentrations. Photochromic properties of 2,3-bis(2,4,5-trimethyl-3-thienyl)maleimide, including conversions at the photostationary state, extinction coefficients, photoisomerization reaction rates and quantum yields, were shown to be affected by hydrogen bonding with the model compound - 2,6-bis-(acetamido)pyridine. The extent of this change was determined and discussed, demonstrating a balanced supramolecular strategy to modulate photochemical and photophysical properties of this important class of photochromic material.
Identifier: CFE0003928 (IID), ucf:48695 (fedora)
Note(s): 2011-08-01
Ph.D.
Sciences, Department of Chemistry
Doctorate
This record was generated from author submitted information.
Subject(s): Two-photon
FRET
supramolecular assembly
photochrome
hydrogen bonding
3D
data storage
cross section
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0003928
Restrictions on Access: campus 2012-07-01
Host Institution: UCF

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