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- Title
- POLARIZATION DEPENDENT TWO-PHOTON ABSORPTION PROPERTIES OF CHIRAL MOLECULES.
- Creator
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Toro, Carlos, Hernandez, Florencio, University of Central Florida
- Abstract / Description
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Molecules that are non-superimposable on their mirror image are named chiral or optically active compound. Over the years, molecular chirality has played an essential role in the understanding of fundamental aspects associated the origin of life, drug and food technologies and, asymmetric catalysis, among others. Moreover, most of the groundbreaking discoveries and advances made in this field have happened due to the development of spectroscopic techniques based on the natural asymmetry of...
Show moreMolecules that are non-superimposable on their mirror image are named chiral or optically active compound. Over the years, molecular chirality has played an essential role in the understanding of fundamental aspects associated the origin of life, drug and food technologies and, asymmetric catalysis, among others. Moreover, most of the groundbreaking discoveries and advances made in this field have happened due to the development of spectroscopic techniques based on the natural asymmetry of the enantiomers and their ability to preferentially absorb right or left polarized light. For instance, circular dichroism (CD), which measures the difference in absorption between these two states of polarized light, has emerged as one of the most useful spectroscopic methods to identify and characterize chiral compounds. Unfortunately, CD is based on linear absorption which, in most common organic molecules, takes place in the UV region of the spectrum where the majority of organic solvents absorb as well. This certainly imposes limitations in the indiscriminated applicability of this technique to the study of chiral chromophores of biological interest in non-aqueous solutions. Consequently, a systematic and comprehensive characterization of the electronic and optical properties of such molecular entities still remains a major issue to be addressed. On this regard, nonlinear optics offers new alternatives to overcome some of the shortcomings of the standard linear CD-based spectroscopy. In order to surmount the existent limitations in this field and deepen in the fundamental understanding of chiral systems, we have mainly directed the attention of our research to the experimental and theoretical study of the polarization dependent two-photon absorption (2PA) of several chiral azo-compounds and binaphthol derivatives in solution. The first part of this dissertation (Chapters I-IV) covers a full characterization of the linear and nonlinear optical properties of a series of non-chiral and chiral azo derivatives. The combination of experimental techniques such as absorption, fluorescence, excitation anisotropy, circular dichroism, two-photon absorption and two-photon absorption circular-linear dichroism in combination with density functional theory calculations allowed us to unambiguously distinguish and assign the spectral position of the main electronic transitions (n-* and -*) in azobenzene derivatives. Our results represent a major contribution to the understanding of the electronic structure of these organic chromophores which have been reported of potential interest in the design of optoelectronic devices. Then, Chapter V describes the development of a novel experimental technique called the synchronized double L-scan for the study of polarization dependent multiphoton absorption in chiral samples. The high sensitivity of this technique resides in the use of ÃÂ"twinÃÂ" pulses to account for energy and mode fluctuations of the excitation pulse when determining absorption nonlinearities as a function of the light polarization. The robustness of this method was validated by measuring the first ever reported two-photon absorption circular dichroism (2PA-CD) spectrum on a chiral binaphthol derivative in solution. Finally, Chapters VI and VII compile an ample experimental and theoretical investigation of the chirality-dependent 2PA of axial enantiomers in solution. We combined the use of the synchronized double L-scan technique with state-of-the-art density functional theory calculations to provide a precise and reliable description of the contribution of the different electronic excited states to the 2PA-CD and 2PA-CLD spectra. Our findings are foreseen to have a tremendous impact in the comprehension of some of the most fundamental aspects of chiral phenomena.
Show less - Date Issued
- 2010
- Identifier
- CFE0003284, ucf:48529
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003284
- Title
- DECOLORIZATION OF AN AZO AND ANTHRAQUINONE TEXTILE DYE BY A MIXTURE OF LIVING AND NON-LIVING TRAMETES VERSICOLOR FUNGUS.
- Creator
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Dykstra, Christine, Randall, Andrew, University of Central Florida
- Abstract / Description
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Wastewater from the textile industry is difficult to treat effectively due to the prevalent use and wide variety of synthetic dyes that are resistant to conventional treatment methods. White-rot fungi, such as Trametes versicolor, have been found to be effective in decolorizing many of these synthetic dyes and current research is focusing on their application to wastewater treatment. Although numerous studies have been conducted on the ability of both living and nonliving Trametes versicolor...
Show moreWastewater from the textile industry is difficult to treat effectively due to the prevalent use and wide variety of synthetic dyes that are resistant to conventional treatment methods. White-rot fungi, such as Trametes versicolor, have been found to be effective in decolorizing many of these synthetic dyes and current research is focusing on their application to wastewater treatment. Although numerous studies have been conducted on the ability of both living and nonliving Trametes versicolor to separately decolorize textile dyes, no studies were found to have investigated the use of a mixture of live and dead fungus for decolorization. This study explored potential interactions between live and dead, autoclaved Trametes versicolor biomass in a mixed system by utilizing a series of batch tests with two structurally different synthetic textile dyes. Samples were analyzed by spectrophotometer and compared with controls to determine the effect of any interactions on decolorization. The results of this study indicate that an interaction between living and nonliving biomass occurred that affected the specific dye removal for both Reactive Blue 19, an anthraquinone textile dye, and Reactive Orange 16, an azo textile dye. This interaction was seen to improve the specific dye removal during the first 10-46 hours of experimentation but then diminish the specific dye removal after this period. This effect could be due to hydrophobins, which are surface-active proteins excreted by live fungi that may alter hydrophobicity. Additionally, the presence of adsorptive dead biomass could affect dye contact with degrading enzymes released from the live fungus. By expanding current knowledge of the interactions that take place in a fungal bioreactor and their effect on textile dye decolorization, this research aims to inspire more effective and less costly bioreactor designs for the treatment of textile wastewater.
Show less - Date Issued
- 2011
- Identifier
- CFH0003823, ucf:44720
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0003823