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Investigation of chiral porphyrin aggregates with heterodyne-detected vibrational sum frequency generation spectroscopy

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dc.contributor.authorLindberg, Kathryn A., author
dc.contributor.authorKrummel, Amber, advisor
dc.contributor.authorLevinger, Nancy, committee member
dc.contributor.authorSambur, Justin, committee member
dc.contributor.authorGelfand, Martin, committee member
dc.date.accessioned2019-01-07T17:19:57Z
dc.date.available2021-01-03T17:19:53Z
dc.date.issued2018
dc.description.abstractIn nature, photosynthetic organisms harvest and transport solar energy through the finely-tuned interplay between vibrational, electronic, and excitonic characteristics within photosynthetic reaction centers. These characteristics depend intimately on the precise arrangement of the reaction centers' molecular building blocks. Further knowledge of the relationship between structure and function in these natural systems is key to advancing synthetic solar technologies like dye-sensitized solar cells and artificial photosynthesis. Photosynthetic pigments, such as chlorophyll and bacteriochlorophyll, are of particular interest since their absorptive role is the first step in the solar harvesting process. Porphyrins, a group of macrocyclic organic compounds closely related to these pigments, have gained attention as simpler models for their more complicated natural counterparts. Tetra(4-sulfonatophenyl) porphyrin (TSPP), which closely resembles bacteriochlorophyll, is particularly valuable because it forms molecular aggregates analogous to the highly quantum-efficient light-harvesting "antennae" present in green sulfur bacteria chlorosomes. Imaging and spectroscopic studies indicate that the helical nanotubular TSPP aggregates are chiral and have distinct exciton contributions along different axes. However, the precise arrangement of TSPP monomers within the aggregate walls is still debated, prompting further, more detailed studies. Heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy is a phase-sensitive, second-order nonlinear technique which probes the vibrational characteristics of noncentrosymmetric molecular environments. HD-VSFG experiments can also probe excitonic and vibronic characteristics via experimental double resonance. By use of polarization conditions, theoretical modeling, and computational fitting, detailed information on the orientation of vibrational, vibronic, and excitonic transition dipoles can be extracted from HD-VSFG spectra. This work presents doubly-resonant HD-VSFG spectra of TSPP thin films drop-cast on gold, which demonstrates the technique's sensitivity to the relationship between complex phase and excitonic versus monomeric characteristics. HD-VSFG is then used to compare spectra of TSPP thin films prepared from racemic and chiral aqueous solutions. This comparison includes a polarization condition sensitive to only chiral environments, further demonstrating HD-VSFG as a valuable tool in the structural investigation of TSPP aggregates.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierLindberg_colostate_0053N_15276.pdf
dc.identifier.urihttps://hdl.handle.net/10217/193230
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.subjectHD-VSFG
dc.subjectporphyrin
dc.subjectTSPP
dc.subjectnonlinear spectroscopy
dc.subjectaggregates
dc.subjectsum frequency generation
dc.titleInvestigation of chiral porphyrin aggregates with heterodyne-detected vibrational sum frequency generation spectroscopy
dc.typeText
dcterms.embargo.expires2021-01-03
dcterms.embargo.terms2021-01-03
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineChemistry
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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