+publisher:"University of Colorado" +contributor:("Niels H. Damrauer")

University of Colorado

1. Hopkins, Emily Jane. New Synthetic Approaches to Chromium Dioxide and Synthesis of Group 4 Organometallics Supported by β-Diketonate Ligands.

Degree: MS, 2018, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/296

► CrO₂ is a half-metallic ferromagnet, with calculations suggesting that all spin up electrons are conductive while all spin down electrons have a band gap of… (more)

Subjects/Keywords: chromium dioxide; inorganic chemistry; organometallics; polymerization catalysis; synthetic approaches; Chemistry; Inorganic Chemistry

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APA (6^th Edition):

Hopkins, E. J. (2018). New Synthetic Approaches to Chromium Dioxide and Synthesis of Group 4 Organometallics Supported by β-Diketonate Ligands. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/296

Chicago Manual of Style (16^th Edition):

Hopkins, Emily Jane. “New Synthetic Approaches to Chromium Dioxide and Synthesis of Group 4 Organometallics Supported by β-Diketonate Ligands.” 2018. Masters Thesis, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/296.

MLA Handbook (7^th Edition):

Hopkins, Emily Jane. “New Synthetic Approaches to Chromium Dioxide and Synthesis of Group 4 Organometallics Supported by β-Diketonate Ligands.” 2018. Web. 22 Apr 2021.

Vancouver:

Hopkins EJ. New Synthetic Approaches to Chromium Dioxide and Synthesis of Group 4 Organometallics Supported by β-Diketonate Ligands. [Internet] [Masters thesis]. University of Colorado; 2018. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/296.

Council of Science Editors:

Hopkins EJ. New Synthetic Approaches to Chromium Dioxide and Synthesis of Group 4 Organometallics Supported by β-Diketonate Ligands. [Masters Thesis]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/chem_gradetds/296

University of Colorado

2. Midgett, Aaron G. Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots.

Degree: PhD, Chemistry & Biochemistry, 2011, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/32

► Providing affordable, clean energy is one of the major challenges facing society today, and one of the promising solutions is third generation solar energy… (more)

▼ Providing affordable, clean energy is one of the major challenges facing society today, and one of the promising solutions is third generation solar energy conversion. Present day, first and second-generation solar cells can at most convert each absorbed photon into a single electron hole pair, thereby establishing a theoretical limit to the power conversion efficiency. The process of multiple exciton generation (MEG) in semiconductor quantum dots increases that theoretical efficiency from 33% to 42% by utilizing the excess energy of high energy photons that is otherwise wasted as heat to excite a second electron-hole pair, thereby boosting the potential photocurrent. This thesis explores the benefits of MEG in quantum confined systems and shows that quantum dots are more efficient at generating multiple excitons from a single photon than bulk semiconductors. The variations in optical measurements of MEG have raised skepticism and brought into question the validity of these experiments. The two important questions that this thesis attempts to address are (1) what are the enhanced QYs in isolated PbSe QDs and (2) does quantum confinement enhance MEG over bulk semiconductors. Experimental variations in the enhanced QYs are partially explained by the production of a long-lived photocharged state that increases the apparent photon-to-exciton QYs. A procedure is detailed that decreases the possibility of producing this charged state. By studying the production of these states, conditions are found that minimize their effect and produce less variation in the reported QYs. Variations in the MEG efficiency were studied in films of chemically treated PbSe quantum dots where a different mechanism was responsible for an apparent decrease of the measured QYs. Finally, for the first time, a quantum dot size-dependence in the MEG efficiency was found in colloidal PbSe, PbS, and PbSxSe1-x quantum dot solutions and is attributed to the increased Coulomb interaction in materials with a larger Bohr exciton radius. These results will allow a better understanding of MEG and how this important process may be used to enhance solar energy conversion. Advisors/Committee Members: Arthur J. Nozik, David Jonas, Niels H. Damrauer.

Subjects/Keywords: Carrier Multiplication; Multiple Exciton Generation; Nanocrystal; Quantum Dot; Solar Cell; Nanoscience and Nanotechnology; Physical Chemistry

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APA (6^th Edition):

Midgett, A. G. (2011). Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/32

Chicago Manual of Style (16^th Edition):

Midgett, Aaron G. “Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots.” 2011. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/32.

MLA Handbook (7^th Edition):

Midgett, Aaron G. “Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots.” 2011. Web. 22 Apr 2021.

Vancouver:

Midgett AG. Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/32.

Council of Science Editors:

Midgett AG. Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/chem_gradetds/32

University of Colorado

3. Zhang, Jing. The Mechanism of Thermally-Activated Photoluminescence Quenching and Its Correlation with Transport in Electronically-Coupled PbS Quantum Dot Arrays.

Degree: MS, Chemistry & Biochemistry, 2013, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/145

► We have measured the temperature-dependent photoluminescence (PL) and quantum yield (QY) of a series of alkanedithiol-treated PbS quantum dot (QD) films as a function… (more)

Subjects/Keywords: Band Tail Behavior; Charge Transport; Electronically-Coupled PbS Quantum Dot; PL Quantum Yield; Thermally-Activated Photoluminescence Quenching; Physical Chemistry

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APA (6^th Edition):

Zhang, J. (2013). The Mechanism of Thermally-Activated Photoluminescence Quenching and Its Correlation with Transport in Electronically-Coupled PbS Quantum Dot Arrays. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/145

Chicago Manual of Style (16^th Edition):

Zhang, Jing. “The Mechanism of Thermally-Activated Photoluminescence Quenching and Its Correlation with Transport in Electronically-Coupled PbS Quantum Dot Arrays.” 2013. Masters Thesis, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/145.

MLA Handbook (7^th Edition):

Zhang, Jing. “The Mechanism of Thermally-Activated Photoluminescence Quenching and Its Correlation with Transport in Electronically-Coupled PbS Quantum Dot Arrays.” 2013. Web. 22 Apr 2021.

Vancouver:

Zhang J. The Mechanism of Thermally-Activated Photoluminescence Quenching and Its Correlation with Transport in Electronically-Coupled PbS Quantum Dot Arrays. [Internet] [Masters thesis]. University of Colorado; 2013. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/145.

Council of Science Editors:

Zhang J. The Mechanism of Thermally-Activated Photoluminescence Quenching and Its Correlation with Transport in Electronically-Coupled PbS Quantum Dot Arrays. [Masters Thesis]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chem_gradetds/145

University of Colorado

4. Carey, Thomas James. Development of a Modular Synthesis of Rigid Polyacene Dimers for Mechanistic Exploration of Singlet Fission.

Degree: PhD, 2018, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/263

► Singlet Fission (SF) is a non-radiative, spin-allowed, photophysical process wherein a singlet excited state converts into a pair of spin-coupled triplet states. This process… (more)

▼ Singlet Fission (SF) is a non-radiative, spin-allowed, photophysical process wherein a singlet excited state converts into a pair of spin-coupled triplet states. This process has implications for improving solar cell efficiency, as SF offers a way to process high energy photons by proportionating their energy into pairs of electronic excitations rather than wasting excess energy as heat. Of particular interest has been the study of molecular dimers, as these are the simplest systems capable of SF and offer a platform for understanding mechanistic details for the development of efficient SF systems. This dissertation describes the development of a modular synthesis of rigid polyacene dimers as well as a photophysical exploration of how structural features impact SF. Four polyacene dimers were synthesized; in all final products, the active chromophores are derived from tetracene or pentacene. The chromophores are connected via a norbonyl bridge with two points of attachment to the bridge per chromophore, providing a rigid geometry. The first dimer synthesized, an unsubstituted tetracene dimer (BT1), serves as a comparative baseline for related molecules. BT1 suffered from poor solubility and stability; these issues were addressed in the second dimer synthesized, a triisopropylsilylalkynyl-substituted (TIPS-alkynyl-substituted) tetracene dimer (TIPS-BT1). The route was then extended to the analogous TIPS-alkynyl-substituted pentacene dimer (TIPS-BP1) without success due to unreliable reactivity stemming from difficulties in handling the synthetic intermediates. This route was then modified in order to introduce solubility and stability earlier in the route, leading to the successful synthesis of constitutional isomers of TIPS-BT1 and TIPS-BP1, called TIPS-BT1’ and TIPS-BP1’. The photophysics of this set of four dimers reveal interesting principles regarding the relative importance of energetics and coupling. All four dimers are expected to have poor coupling between the states relevant for SF due to their C_2V symmetry, and all of the tetracene dimers exhibit low SF yields as a result. By contrast, TIPS-BP1’ exhibits appreciable SF yield even in the absence of formal coupling due to its favorable energetics. These findings provide a synthetic as well as a photophysical foundation of mechanistic details for comparison to future dimers based on this molecular platform. Advisors/Committee Members: Niels H. Damrauer, Tarek Sammakia, Oana Luca, David Walba, Justin Johnson.

Subjects/Keywords: dimer; pentacene; polyacene; singlet fission; solar; tetracene; Chemistry; Organic Chemistry

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Carey, T. J. (2018). Development of a Modular Synthesis of Rigid Polyacene Dimers for Mechanistic Exploration of Singlet Fission. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/263

Chicago Manual of Style (16^th Edition):

Carey, Thomas James. “Development of a Modular Synthesis of Rigid Polyacene Dimers for Mechanistic Exploration of Singlet Fission.” 2018. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/263.

MLA Handbook (7^th Edition):

Carey, Thomas James. “Development of a Modular Synthesis of Rigid Polyacene Dimers for Mechanistic Exploration of Singlet Fission.” 2018. Web. 22 Apr 2021.

Vancouver:

Carey TJ. Development of a Modular Synthesis of Rigid Polyacene Dimers for Mechanistic Exploration of Singlet Fission. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/263.

Council of Science Editors:

Carey TJ. Development of a Modular Synthesis of Rigid Polyacene Dimers for Mechanistic Exploration of Singlet Fission. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/chem_gradetds/263

University of Colorado

5. Abdelhaq, Mirvat. Design, Synthesis a nd Characterization of Ruthenium Polypyridyl Complexes Towards Structural and Conformational Control of Intramolecular Electron Transfer.

Degree: PhD, Chemistry & Biochemistry, 2012, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/62

► The demand for carbon neutral sources of energy has led researchers to turn toward strategies involving conversion of solar photons to produce electricity and… (more)

▼ The demand for carbon neutral sources of energy has led researchers to turn toward strategies involving conversion of solar photons to produce electricity and fuels. Solar conversion is initiated by photoinduced electron transfer (ET) processes. Donor-Bridge-Acceptor (DBA) complexes are a common platform for investigating photoinduced intramolecular electron transfer processes. In this work, two series of DBA complexes have been synthesized and characterized to investigate the role of structural elements on rates of photoinduced intramolecular electron transfer. The DBA complexes are comprised of a ruthenium polypyridyl donor covalently linked to a 4,4'-bipyridinium acceptor by a bridging aryl subunit. We hypothesize that the addition of steric bulk on the donor chromophore and the bridging subunit will alter the lifetimes for forward and back electron transfer processes. New electroactive asymmetric ligands were synthesized in high yields and complexed to produce seven new DBA complexes which were characterized by absorption and emission spectroscopies, cyclic voltammetry and spectroelectrochemistry, electronic structure calculations and picosecond transient absorption techniques. The first series of DBA complexes was prepared to investigate how lifetimes of intramolecular ET are affected by increased methylation on ancillary ligands which is expected to alter driving forces for ET. The electron lifetimes were measured for three complexes that share an electroactive ligand but differ in ancillary ligand. It was determined that the lifetime for forward ET was not significantly altered but the lifetimes for back ET differed by a factor of two. For the second DBA series, methyl groups were systematically introduced onto various positions of the bridging subunit to determine if steric bulk is effective at disrupting electron communication within the complex thereby altering ET lifetimes. Reductive spectroelectrochemistry and transient absorption spectra revealed that steric bulk was effective at localizing electron density onto the acceptor moiety. The measured ET lifetimes showed that the number of methyl substituents on the bridging subunit was more of a determining factor of ET lifetimes than the methyl substituent position. Advisors/Committee Members: Niels H. Damrauer, Gordana Dukovic, Tarek Sammakia, Veronica Bierbaum, Jerry Peterson.

Subjects/Keywords: Chemistry; Physical Chemistry

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APA (6^th Edition):

Abdelhaq, M. (2012). Design, Synthesis a nd Characterization of Ruthenium Polypyridyl Complexes Towards Structural and Conformational Control of Intramolecular Electron Transfer. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/62

Chicago Manual of Style (16^th Edition):

Abdelhaq, Mirvat. “Design, Synthesis a nd Characterization of Ruthenium Polypyridyl Complexes Towards Structural and Conformational Control of Intramolecular Electron Transfer.” 2012. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/62.

MLA Handbook (7^th Edition):

Abdelhaq, Mirvat. “Design, Synthesis a nd Characterization of Ruthenium Polypyridyl Complexes Towards Structural and Conformational Control of Intramolecular Electron Transfer.” 2012. Web. 22 Apr 2021.

Vancouver:

Abdelhaq M. Design, Synthesis a nd Characterization of Ruthenium Polypyridyl Complexes Towards Structural and Conformational Control of Intramolecular Electron Transfer. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/62.

Council of Science Editors:

Abdelhaq M. Design, Synthesis a nd Characterization of Ruthenium Polypyridyl Complexes Towards Structural and Conformational Control of Intramolecular Electron Transfer. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/chem_gradetds/62

University of Colorado

6. Hewitt, Joshua Thomas. Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes.

Degree: PhD, Chemistry & Biochemistry, 2013, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/77

► A novel ruthenium(II) polypyridyl complex [Ru(bpy-An)(tpy-φ-MV)]4+ (where tpy-An = 4’-(9-anthrcenyl)-2,2’:6’,2’’-terpyridine and tpy-&phi-MV,2+ = 4’-(1-(1’-methyl-4,4-bipyridinium-1-yl)-phenyl)-2,2’:6’,2’’-terpyridine) capable of undergoing energy transfer (EnT) or electron transfer (ET)… (more)

▼ A novel ruthenium(II) polypyridyl complex [Ru(bpy-An)(tpy-φ-MV)]4+ (where tpy-An = 4’-(9-anthrcenyl)-2,2’:6’,2’’-terpyridine and tpy-&phi-MV,2+ = 4’-(1-(1’-methyl-4,4-bipyridinium-1-yl)-phenyl)-2,2’:6’,2’’-terpyridine) capable of undergoing energy transfer (EnT) or electron transfer (ET) following photoexcitation to the metal-to-ligand charge transfer (MLCT) state is investigated. Adaptive feedback control (AFC) pulse shaping, which has proven to be a versatile experimental tool for probing photoinduced dynamics in a variety of chemical systems, is used try and control the EnT and ET reactivity in this complex with the goal of informing the underlying EnT and ET dynamics. To allow for interpretation of the aforementioned AFC experiments the photophysics of [Ru(bpy-An)(tpy-φ-MV)]4+ and a family of six closely related bis-terpyridine Ru(II) complexes are characterized using static absorption, electochemical, and ultrafast pump-probe techniques. These experiments reveal previously unreported dynamics such as equilibration between the 3MLCT and 3MC (where MC = metal centered excited state) and interligand electron transfer. Furthermore, the EnT and ET reactions in [Ru(bpy-An)(tpy-φ-MV)]4+ (and the associated model complexes) are found to occur on a sub-picosecond and picosecond timescale, respectively. These are the fastest EnT and ET timescales reported for any Ru(II) bis-terpyridine based complexes. As an addendum, photophysics of the mononuclear water oxidation catalysts [Ru(bpy)(tpy)(OH₂)]2+ and [Ru(bpy)(tpy)(OD₂)]2+ in neat H₂O and D₂O solvent, respectively, are reported. Ultrafast pump-probe experiments reveal an inverse kinetic isotope effect with the excited state lifetime being shorter for the D₂O complex than the H₂O complex. This is attributed to interactions between the coordinated aqua (or D₂O) and solvent in the MLCT excited state and suggests design principles applicable to synthesis of photo-driven water oxidation assemblies. Advisors/Committee Members: Niels H. Damrauer, Garry Rumbles, Gordana Dukovic, David Jonas, Charles Musgrave.

Subjects/Keywords: Physical Chemistry

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APA (6^th Edition):

Hewitt, J. T. (2013). Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/77

Chicago Manual of Style (16^th Edition):

Hewitt, Joshua Thomas. “Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes.” 2013. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/77.

MLA Handbook (7^th Edition):

Hewitt, Joshua Thomas. “Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes.” 2013. Web. 22 Apr 2021.

Vancouver:

Hewitt JT. Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/77.

Council of Science Editors:

Hewitt JT. Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chem_gradetds/77

University of Colorado

7. Snyder, Jamie Lynn. A Symmetry Exploration into Covalent Tetracene Dimers with Tunable Electronic Coupling for Singlet Fission.

Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/177

► One process that has the potential of efficiently harvesting solar energy is singlet fission (SF), a process by which one photon of light can… (more)

▼ One process that has the potential of efficiently harvesting solar energy is singlet fission (SF), a process by which one photon of light can produce two excited states. Investigations of three different series of bistetracene (BT) were used to explore the effect of symmetry on the rate and driving force of SF, as well as the electronic coupling. A dimer and the corresponding monomer were used to build a synthetic infrastructure and explore preliminary photophysics. All of the dimers were connected by one to three norbornyl bridges and exhibit various amounts of electronic coupling. The first section of this dissertation will discuss a series of cofacial BT dimers with C_2v symmetry that have one (BT1) to three (BT3) norbornyl bridges linking the two tetracene chromophores. Density functional theory calculations of BT1-BT3 were used to explore the SF driving force and the change in through-space versus through-bond contributions to the electronic coupling. The C_2v symmetry was found to be unprofitable to SF, but vibrations accessible to the ground state would break the C_2v symmetry. The thorough synthetic investigation of the monomeric tetracene-norbornyl bridge was developed to build a synthetic library that aided the synthesis of BT1, the first rigid SF dimer. Preliminary photophysics of BT1 and its monomer will also be described. In the second portion of this work, the SF driving force, electronic coupling will be calculated for the second and third series of BT dimers, which are symmetry adaptations of BT1-BT3. In the second series, the orbital overlap of the norbornyl bridge and tetracene arms will be exploited by changing how the bridge and arms are connected to make dimers of C₂ and C_s symmetry. In the final series, a heteroatom substitution of BT1 creates a series of C₂ and C_s dimers that can be built using the synthetic infrastructure developed above. Both symmetry adapted series of BT dimers were found to lead to an increase in electronic coupling, which is expected to be productive for SF. Advisors/Committee Members: Niels H. Damrauer, Tarek Sammakia, Robert Parson, Veronica Bierbaum, Charles Musgrave.

Subjects/Keywords: Density Functional Theory; Dimer; Singlet Fission; Tetracene; Organic Chemistry; Physical Chemistry

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APA (6^th Edition):

Snyder, J. L. (2015). A Symmetry Exploration into Covalent Tetracene Dimers with Tunable Electronic Coupling for Singlet Fission. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/177

Chicago Manual of Style (16^th Edition):

Snyder, Jamie Lynn. “A Symmetry Exploration into Covalent Tetracene Dimers with Tunable Electronic Coupling for Singlet Fission.” 2015. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/177.

MLA Handbook (7^th Edition):

Snyder, Jamie Lynn. “A Symmetry Exploration into Covalent Tetracene Dimers with Tunable Electronic Coupling for Singlet Fission.” 2015. Web. 22 Apr 2021.

Vancouver:

Snyder JL. A Symmetry Exploration into Covalent Tetracene Dimers with Tunable Electronic Coupling for Singlet Fission. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/177.

Council of Science Editors:

Snyder JL. A Symmetry Exploration into Covalent Tetracene Dimers with Tunable Electronic Coupling for Singlet Fission. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/177

University of Colorado

8. Utterback, James Keller. Excited-State Dynamics of Semiconductor Nanocrystals: Trapped-Hole Diffusion and Electron-Transfer Kinetics in CdS and CdSe Nanorods.

Degree: PhD, 2018, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/249

► Colloidal semiconductor nanocrystals have many remarkable properties—such as exceptionally tunable excited states and surface chemistry—that have led to an enthusiastic interest in using them for… (more)

▼ Colloidal semiconductor nanocrystals have many remarkable properties—such as exceptionally tunable excited states and surface chemistry—that have led to an enthusiastic interest in using them for optoelectronic applications such as solar-energy conversion. Such technologies require control over the generation, separation, and extraction of photoexcited electrons and holes. However, the interpretation of experimentally measured excited-state decay curves is challenging because they typically exhibit complicated shapes that are elusive to simple kinetic models. To understand the principles that govern electron and hole relaxation dynamics in these complex systems, models rooted in fundamental physical phenomena are needed. This dissertation describes efforts to understand the dynamics of recombination, charge carrier trapping, trapped holes, and charge transfer in photoexcited Cd-chalcogenide nanocrystals using a combination of ultrafast spectroscopy and kinetic modeling. The first part of this dissertation focuses on studying the spatial dynamics of trapped holes. In CdS and CdSe nanocrystals, photoexcited holes rapidly and efficiently trap to localized states on the surface. We demonstrate evidence that trapped holes are mobile in CdS nanorods, CdSe nanorods, and CdSe/CdS and ZnSe/CdS dot-in-rod heterostructures, and that they likely undergo a diffusive random walk between trap sites on the nanocrystal surface. The second part of the dissertation focuses on modeling charge-transfer kinetics in heterogeneous ensembles of donor–acceptor complexes. In complexes of CdS nanorods and [FeFe] hydrogenase, electron transfer is the key step for photochemical H₂ production. By accounting for the distributions in the numbers of electron traps and enzymes adsorbed, we determine the rate constants and quantum efficiencies for electron transfer. The relatively simple analytical models developed here establish a detailed conceptual and quantitative picture of the rich carrier dynamics in these systems, providing important insights for the design of semiconductor nanocrystals for light-driven applications. Advisors/Committee Members: Gordana Dukovic, Joel D. Eaves, Niels H. Damrauer, David M. Jonas, Garry Rumbles.

Subjects/Keywords: nanocrystals; photochemistry; photophysics; solar energy; ultrafast spectroscopy; Chemistry; Nanoscience and Nanotechnology; Physical Chemistry

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APA (6^th Edition):

Utterback, J. K. (2018). Excited-State Dynamics of Semiconductor Nanocrystals: Trapped-Hole Diffusion and Electron-Transfer Kinetics in CdS and CdSe Nanorods. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/249

Chicago Manual of Style (16^th Edition):

Utterback, James Keller. “Excited-State Dynamics of Semiconductor Nanocrystals: Trapped-Hole Diffusion and Electron-Transfer Kinetics in CdS and CdSe Nanorods.” 2018. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/249.

MLA Handbook (7^th Edition):

Utterback, James Keller. “Excited-State Dynamics of Semiconductor Nanocrystals: Trapped-Hole Diffusion and Electron-Transfer Kinetics in CdS and CdSe Nanorods.” 2018. Web. 22 Apr 2021.

Vancouver:

Utterback JK. Excited-State Dynamics of Semiconductor Nanocrystals: Trapped-Hole Diffusion and Electron-Transfer Kinetics in CdS and CdSe Nanorods. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/249.

Council of Science Editors:

Utterback JK. Excited-State Dynamics of Semiconductor Nanocrystals: Trapped-Hole Diffusion and Electron-Transfer Kinetics in CdS and CdSe Nanorods. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/chem_gradetds/249

University of Colorado

9. Thompson, Michael. Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy.

Degree: PhD, 2018, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/260

► The interactions of anionic species with other molecules opens up new avenues to study the process of bond formation or charge transfer. Gas phase… (more)

Subjects/Keywords: species; anion; electron; molecular; infrared photodissociation spectroscopy; Chemistry; Physical Chemistry

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APA (6^th Edition):

Thompson, M. (2018). Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/260

Chicago Manual of Style (16^th Edition):

Thompson, Michael. “Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy.” 2018. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/260.

MLA Handbook (7^th Edition):

Thompson, Michael. “Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy.” 2018. Web. 22 Apr 2021.

Vancouver:

Thompson M. Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/260.

Council of Science Editors:

Thompson M. Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/chem_gradetds/260

University of Colorado

10. Fatur, Steven M. Tuning Iron(II) Excited States with Bulky Ligands and Investigating Chromium(III) Photocatalytic Mechanisms for Earth-Abundant Photocatalysis.

Degree: PhD, 2018, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/266

► Photocatalysis opens up new synthetic pathways and is a potential method for storing solar energy in chemical bonds. Many transition metal photocatalysts utilize long-lived… (more)

▼ Photocatalysis opens up new synthetic pathways and is a potential method for storing solar energy in chemical bonds. Many transition metal photocatalysts utilize long-lived metal-to-ligand charge transfer (MLCT) states as the catalytically active state. However, earth-abundant Fe(II) analogues of successful Ru(II) photocatalysts are plagued by ultrafast relaxation. Decreased ligand-field splitting in these first-row metal complexes opens new relaxation pathways via low-lying metal-centered states. To design potential photocatalysts with Fe(II) centers we chose to exploit the decreased ligand-field splitting by destabilizing the singlet state until the lowest energy quintet state became the ground state, opening up a distinct dynamical picture and lengthening the MLCT excited-state lifetime. In general, this class of complexes displays a > 100-fold improvement relative to the ~100 fs MLCT lifetime of the low-spin parent, Fe(II) bis-terpyridine. This is accomplished using a sterically demanding bis-terpyridyl ligand framework in which interligand repulsion destabilizes lower spin states to force the quintet ground state. Furthermore, this framework is easily altered synthetically by employing substituents with either steric or electronic effects, allowing for substantial tunability. We have systematically synthesized a range of these compounds and investigated them using x-ray crystallography, electrochemistry, magnetic measurements, and transient absorption spectroscopy. Through this effort, we highlight a novel approach to controlling excited-state dynamics and ground-state absorption in Fe(II) polypyridines with potential photocatalysis applications. A secondary project explores the mechanisms of Cr(III) photocatalyzed [4+2] cycloadditions. Cr(III) polypyridyl complexes have been found to serve as replacements for more expensive Ru(II) photocatalysts in these reactions. However, their application to a wider scope of reactions is limited by a lack of mechanistic understanding. With static and time-resolved photoluminescence spectroscopy and Stern-Volmer quenching studies, we show that [Cr(Ph₂phen)₃]³+ (Ph₂phen = 4,7-diphenyl-phenanthroline) is a potent photooxidant for promoting radical cation Diels-Alder reactions. Further experiments show that atmospheric oxygen is critical for turning over the catalyst. Finally, the mechanistic study of a related reaction with the same catalyst suggests that an energy transfer mechanism is also feasible in certain cases. This broader understanding of mechanistic pathways uncovers a rich vein for further mechanistic studies and Cr(III) catalyst development. Advisors/Committee Members: Niels H. Damrauer, Oana R. Luca, Michael P. Marshak, Gordana Dukovic, Matthew P. Shores.

Subjects/Keywords: chromium(iii); excited-state lifetimes; high-spin iron(ii); iron(ii) terpyridyl; photocatalyst; quintet mlct; Chemistry; Inorganic Chemistry

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APA (6^th Edition):

Fatur, S. M. (2018). Tuning Iron(II) Excited States with Bulky Ligands and Investigating Chromium(III) Photocatalytic Mechanisms for Earth-Abundant Photocatalysis. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/266

Chicago Manual of Style (16^th Edition):

Fatur, Steven M. “Tuning Iron(II) Excited States with Bulky Ligands and Investigating Chromium(III) Photocatalytic Mechanisms for Earth-Abundant Photocatalysis.” 2018. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/266.

MLA Handbook (7^th Edition):

Fatur, Steven M. “Tuning Iron(II) Excited States with Bulky Ligands and Investigating Chromium(III) Photocatalytic Mechanisms for Earth-Abundant Photocatalysis.” 2018. Web. 22 Apr 2021.

Vancouver:

Fatur SM. Tuning Iron(II) Excited States with Bulky Ligands and Investigating Chromium(III) Photocatalytic Mechanisms for Earth-Abundant Photocatalysis. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/266.

Council of Science Editors:

Fatur SM. Tuning Iron(II) Excited States with Bulky Ligands and Investigating Chromium(III) Photocatalytic Mechanisms for Earth-Abundant Photocatalysis. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/chem_gradetds/266

University of Colorado

11. Grennell, Amanda N. Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals.

Degree: PhD, 2017, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/269

► Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between… (more)

▼ Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between the electron and hole. Thus, type-II heterostructures are promising materials for solar-to-fuel conversion, as extended excited-state lifetimes make transfer of charges to a catalyst more competitive with intrinsic nanocrystal decay processes. However, due to fast and efficient hole trapping and non-uniform morphologies, the photophysics of dot-in-rod heterostructures are more rich and complex than this simple picture. Using transient absorption spectroscopy, we observe that the behavior of electrons in the CdS “rod” or “bulb” regions of non-uniform ZnSe/CdS and CdSe/CdS dot-in-rods is similar regardless of the “dot” material, which supports previous work demonstrating that hole trapping and particle morphology drive electron dynamics. Furthermore, we show that the longest lived state in these dot-in-rods is not generated by the type-II or quasi type-II band alignment between the dot and the rod, but rather by electron-hole dissociation that occurs due to fast hole trapping in the CdS rod and electron localization to the bulb. We propose that specific variations in particle morphology and surface chemistry determine the mechanism and efficiency of charge separation and recombination in these nanostructures, and therefore impact their excited-state dynamics to a greater extent than the heterostructure energy level alignment alone. When coupled to a [Fe-Fe] hydrogenase, which catalyzes reduction of protons to H₂, we observe faster rates of electron transfer and higher quantum efficiency of electron transfer with CdSe/CdS and ZnSe/CdS dot-in-rods, but only from the bulb and interface states. Furthermore, the total efficiency of electron transfer of the ensemble is highest when the bulb/interface state is directly populated. This indicates that the bulb morphology is essential to efficient electron transfer in a dot-in-rod hydrogenase system. Advisors/Committee Members: Gordana Dukovic, Joel D. Eaves, Mathias M. Weber, Niels H. Damrauer, Margaret M. Murnane.

Subjects/Keywords: electron transfer; heterostructures; nanocrystals; nanorods; photophysics; ultrafast spectroscopy; Nanoscience and Nanotechnology; Physical Chemistry

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APA (6^th Edition):

Grennell, A. N. (2017). Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/269

Chicago Manual of Style (16^th Edition):

Grennell, Amanda N. “Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals.” 2017. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/269.

MLA Handbook (7^th Edition):

Grennell, Amanda N. “Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals.” 2017. Web. 22 Apr 2021.

Vancouver:

Grennell AN. Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/269.

Council of Science Editors:

Grennell AN. Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/chem_gradetds/269

University of Colorado

12. Pearce, Orion Magruder. Photoinduced Hole Transfer and Recombination Dynamics of a Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst.

Degree: PhD, 2019, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/297

► Artificial photosynthesis represents a promising strategy to capture and store solar energy through the production of carbon neutral fuels. This process begins with absorption of… (more)

▼ Artificial photosynthesis represents a promising strategy to capture and store solar energy through the production of carbon neutral fuels. This process begins with absorption of a photon by a semiconductor creating an electron-hole pair which are then separated and used to drive reduction and oxidation reactions. CdS nanostructures are model light absorbers for studying these charge transfer reactions and have already demonstrated photoinduced electron transfer to drive a variety of reactions. However, there has been comparatively little progress in understanding how CdS nanostructures may be used to sensitize oxidation reactions such as water oxidation. To this end, we undertook a thorough study of the excited state charge transfer behavior of a model system consisting of a mononuclear Ru water oxidation catalyst attached to the surface of a CdS quantum dot. Through careful analysis of the electron and hole sensitive measurements, we were able to determine parameters relevant for successful water oxidation. The first part of this dissertation consists of a study on the rate and efficiency of hole transfer to the catalyst. By modelling time resolved and steady state emission data it was discovered that the catalyst strongly binds to the quantum dot and engages in rapid photoinduced-hole transfer. The efficiency of hole transfer is limited only by competition with the tendency of holes to localize to quantum dot surface trap states. The second part of this dissertation determines the fate of the electron and hole following hole trapping or transfer. The population of quantum dots that transferred holes was found to decay to the ground state over the course of nanoseconds, while hole trapping appears to facilitate electron transfer to the catalyst. The final part of this dissertation explores the binding between quantum dot and catalyst using NMR spectroscopy. The two bind in a specific orientation which appears to facilitate hole transfer by provide a charge transfer pathway between the electronic states of the catalyst and quantum dot. This work establishes data analysis methods and design principles which may be leveraged in the development of future catalyst/quantum dot systems. Advisors/Committee Members: Gordana Dukovic, Niels H. Damrauer, Jennifer N. Cha, Michael P. Marshak, Garry Rumbles.

Subjects/Keywords: artificial photosynthesis; cadmium sulfide; hole transfer; quantum dot; ruthenium complex; water oxidation; Chemistry; Nanoscience and Nanotechnology; Physical Chemistry

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APA (6^th Edition):

Pearce, O. M. (2019). Photoinduced Hole Transfer and Recombination Dynamics of a Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/297

Chicago Manual of Style (16^th Edition):

Pearce, Orion Magruder. “Photoinduced Hole Transfer and Recombination Dynamics of a Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst.” 2019. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/297.

MLA Handbook (7^th Edition):

Pearce, Orion Magruder. “Photoinduced Hole Transfer and Recombination Dynamics of a Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst.” 2019. Web. 22 Apr 2021.

Vancouver:

Pearce OM. Photoinduced Hole Transfer and Recombination Dynamics of a Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/297.

Council of Science Editors:

Pearce OM. Photoinduced Hole Transfer and Recombination Dynamics of a Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/chem_gradetds/297

University of Colorado

13. Wallas, Jasmine Melissa. Atomic and Molecular Layer Deposition for Efficient Capacitive Deionization, Plasma Corrosion Protection and Stable High-Energy Lithium Ion Batteries.

Degree: PhD, 2019, University of Colorado

URL: https://scholar.colorado.edu/chemistry_gradetds/4

► Atomic layer deposition (ALD) is a technique to deposit thin films with great precision. Molecular layer deposition (MLD), developed as an analog of ALD, is… (more)

Subjects/Keywords: atomic layer deposition; energy storage; moleculary layer deposition; thin films; Chemistry; Materials Chemistry

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APA (6^th Edition):

Wallas, J. M. (2019). Atomic and Molecular Layer Deposition for Efficient Capacitive Deionization, Plasma Corrosion Protection and Stable High-Energy Lithium Ion Batteries. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chemistry_gradetds/4

Chicago Manual of Style (16^th Edition):

Wallas, Jasmine Melissa. “Atomic and Molecular Layer Deposition for Efficient Capacitive Deionization, Plasma Corrosion Protection and Stable High-Energy Lithium Ion Batteries.” 2019. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chemistry_gradetds/4.

MLA Handbook (7^th Edition):

Wallas, Jasmine Melissa. “Atomic and Molecular Layer Deposition for Efficient Capacitive Deionization, Plasma Corrosion Protection and Stable High-Energy Lithium Ion Batteries.” 2019. Web. 22 Apr 2021.

Vancouver:

Wallas JM. Atomic and Molecular Layer Deposition for Efficient Capacitive Deionization, Plasma Corrosion Protection and Stable High-Energy Lithium Ion Batteries. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chemistry_gradetds/4.

Council of Science Editors:

Wallas JM. Atomic and Molecular Layer Deposition for Efficient Capacitive Deionization, Plasma Corrosion Protection and Stable High-Energy Lithium Ion Batteries. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/chemistry_gradetds/4

University of Colorado

14. Carlson, Eric. Molecular Alignment and Morphology Control Techniques for Liquid Crystal Organic Semiconductors.

Degree: PhD, 2019, University of Colorado

URL: https://scholar.colorado.edu/chemistry_gradetds/6

► Since the dawn of the digital age that began with the discovery of semiconductors in 1947, digital electronics have changed the way humanity operates.… (more)

▼ Since the dawn of the digital age that began with the discovery of semiconductors in 1947, digital electronics have changed the way humanity operates. As technology continues to mature, the need for new, multifunctional, and affordable electronics grows stronger. Organic semiconductors (OSCs) fill this need as low cost, highly-flexible, easily-processible, and biocompatible materials for a new wave of flexible, wearable, and biosensing electronics. One major barrier to commercialization of organic electronics, however, is the relatively poor electrical performance of current versions of these devices. Because device performance primarily depends on the electronic structure of the material it is important to develop and understand techniques to improve the molecular order and alignment, and thus, electronic structure in OSC materials. In this work we explore the use of soft lithography and solvent processing of thin films to control the molecular alignment and morphology in two liquid crystal (LC) OSC systems. First, we use the soft lithography techniques of capillary force molding and template-assisted self-assembly with an elastomeric polydimethylsiloxane (PDMS) microchannel mold to align the exotic helical nanofilament (HNF) LC phase. We find that the use of PDMS preferentially aligns the highly crystalline HNF “nanowires”, and after removal of the mold, leaves exposed well-aligned, freestanding microchannels of HNFs. We also studied the relationship between thin film morphology and solvent composition in spin coated thin films of the monoalkyl-[1]benzothieno[3,2-b][1]benzothiophene (BTBT) LC OSC derivatives Th-BTBT-C8 and Th-BTBT-C10. In thin films of both Th-BTBT-C8 and Th-BTBT-C10 spin coated from chlorobenzene (CB), terraced mounds are observed, to the best of our knowledge, for the first time in an OSC material. We also find that mixing CB and chloroform (CF) at a ratio of 20% to 80% produces the highest quality thin films of Th-BTBT-C10. Thin films made from the same solvent mixtures are shown to have improved charge transport over CB, CF and other solvent mixture ratios in organic field-effect transistors (OFETs). The use of solvent mixture engineering to improve electronic properties of OSC thin films extends to another monoalkyl-BTBT derivative, Ph-BTBT-C8, where the 20% CB to 80% CF solvent mixture produces films with superior charge transport over films made from either CB or CF solutions alone. This trend is not observed in two other dialkyl-BTBT derivatives. Overall, we find that the novel use of PDMS microchannels to align HNFs, and solvent engineering to improve thin film morphology and electrical properties of LC OSCs, can be used to help move the field of organic electronics towards commercialization. Advisors/Committee Members: David M. Walba, Sean E. Shaheen, Matthew Glaser, Douglas L. Gin, Niels H. Damrauer.

Subjects/Keywords: alignment; liquid crystals; organic electronics; organic field-effect transistors; organic semiconductors; soft lithography; Chemistry

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APA (6^th Edition):

Carlson, E. (2019). Molecular Alignment and Morphology Control Techniques for Liquid Crystal Organic Semiconductors. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chemistry_gradetds/6

Chicago Manual of Style (16^th Edition):

Carlson, Eric. “Molecular Alignment and Morphology Control Techniques for Liquid Crystal Organic Semiconductors.” 2019. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chemistry_gradetds/6.

MLA Handbook (7^th Edition):

Carlson, Eric. “Molecular Alignment and Morphology Control Techniques for Liquid Crystal Organic Semiconductors.” 2019. Web. 22 Apr 2021.

Vancouver:

Carlson E. Molecular Alignment and Morphology Control Techniques for Liquid Crystal Organic Semiconductors. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chemistry_gradetds/6.

Council of Science Editors:

Carlson E. Molecular Alignment and Morphology Control Techniques for Liquid Crystal Organic Semiconductors. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/chemistry_gradetds/6

University of Colorado

15. Courtney, Trevor Laurence. Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy into the Short-Wave Infrared.

Degree: PhD, Chemistry & Biochemistry, 2012, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/69

► Two-dimensional Fourier Transform (2D FT) spectroscopy in the short-wave infrared (1-2 &mu) enables high frequency and time resolution experiments of molecular dyes, third-generation photovoltaic… (more)

▼ Two-dimensional Fourier Transform (2D FT) spectroscopy in the short-wave infrared (1-2 &mu) enables high frequency and time resolution experiments of molecular dyes, third-generation photovoltaic systems, and carotenoids - all rich in electronic transitions in this spectral region. Such experiments require short pulses with broad spectra to probe fast dephasing or solvation dynamics as well as couplings between widely spaced electronic transitions. Stable, low-dispersion interferometers at Brewster's angle are introduced for multioctave-spanning nonlinear spectroscopies. We adapt a compact, phase-characterized Mach-Zehnder interferometer to the short-wave infrared; active stabilization produces accurate and evenly spaced time delays between the two excitation pulses in 2D FT spectroscopy. An intrinsically phase-stable Sagnac interferometer is introduced to enhance the interferometric signal detection with respect to the copropagating local oscillator in partially collinear 2D FT spectroscopy. These interferometers exploit the air-glass interface Brewster's angle of thin-film metallic beam splitters to preserve expected output phase shifts and to minimize secondary reflections over multiple octaves. A homebuilt short-wave IR noncollinear optical parametric amplifier with a periodically poled crystal provides broadband excitation and detection. The output pulses are compressed with a deformable mirror using second-harmonic generation feedback in a genetic algorithm to pulse durations as low as 10 fs. Together this light source and the interferometric 2D spectrometer have enabled the first 2D FT electronic spectroscopy in this wavelength range; we analyze the early time solvation dynamics of IR-26 dye. Agreement between experimental and simulated purely absorptive 2D spectra of this dye proves the feasibility of the spectrometer design. Accurate evolution time delays in the partially collinear geometry reduce ambiguities in the phasing of these 2D spectra. Finally, initial 2D spectra of lead chalcogenide quantum dots exhibit first exciton transition (bleach) peaks; weak negative peaks potentially reflect biexciton shifts. These spectra lay the groundwork for broadband 2D FT spectroscopy to find exciton couplings and dephasing rates to help establish the mechanism of carrier multiplication for high-efficiency photovoltaics. Advisors/Committee Members: David M. Jonas, Steven T. Cundiff, Niels H. Damrauer, Gordana Dukovic, Robert P. Parson.

Subjects/Keywords: Interferometry; Short-Wave Infrared; Two-Dimensional Spectroscopy; Optics; Physical Chemistry

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APA (6^th Edition):

Courtney, T. L. (2012). Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy into the Short-Wave Infrared. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/69

Chicago Manual of Style (16^th Edition):

Courtney, Trevor Laurence. “Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy into the Short-Wave Infrared.” 2012. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/69.

MLA Handbook (7^th Edition):

Courtney, Trevor Laurence. “Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy into the Short-Wave Infrared.” 2012. Web. 22 Apr 2021.

Vancouver:

Courtney TL. Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy into the Short-Wave Infrared. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/69.

Council of Science Editors:

Courtney TL. Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy into the Short-Wave Infrared. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/chem_gradetds/69

University of Colorado

16. Peters, Willliam Kenneth. Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules.

Degree: PhD, Chemistry & Biochemistry, 2012, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/73

► Degenerate femtosecond pump-probe transient absorption measurements are presented of hot carrier dynamics following above band-edge absorption in colloidal lead sulfide quantum dots. A transient… (more)

Subjects/Keywords: Chemistry; Physical Chemistry

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APA (6^th Edition):

Peters, W. K. (2012). Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/73

Chicago Manual of Style (16^th Edition):

Peters, Willliam Kenneth. “Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules.” 2012. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/73.

MLA Handbook (7^th Edition):

Peters, Willliam Kenneth. “Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules.” 2012. Web. 22 Apr 2021.

Vancouver:

Peters WK. Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/73.

Council of Science Editors:

Peters WK. Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/chem_gradetds/73

University of Colorado

17. Tseng, Huan-Wei. Photophysical Studies of Chromium Sensitizers Designed for Excited State Hole Transfer to Semiconductors and Sequential Hole/Electron Transfers from Photoexcited Cadmium Sulfide Nanorods to Mononuclear Ruthenium Water-Oxidation Catalysts.

Degree: PhD, Chemical & Biochemical Engineering, 2013, University of Colorado

URL: https://scholar.colorado.edu/chbe_gradetds/38

► This dissertation describes three research projects related to solar cells and solar water splitting with a goal of utilizing solar energy, a renewable energy… (more)

▼ This dissertation describes three research projects related to solar cells and solar water splitting with a goal of utilizing solar energy, a renewable energy source. The first project is focused on photophysical studies of four newly-synthesized Cr(III) tris-bipyridyl complexes featuring the 4-dmcbpy (dimethyl 2,2'-bipyridine-4,4'-dicarboxylate) ligand. Static and time-resolved emission results suggest that the complexes store ~1.7 eV of energy for multiple microseconds. Using cyclic voltammetry, it is found that the inclusion of 4-dmcbpy shifts the E_1/2 of CrIII/II by +0.2 V from the homoleptic parent complexes without 4-dmcbpy. All four complexes have excited state potentials of CrIII*/II between +1.8 and +2.0 V vs. NHE, placing them among the most powerful photooxidants reported and making them candidates for hole-injection sensitizers. The second project continues with Cr(III) complexes, but using iminopyridine Schiff base ligands. Two complexes feature hexadentate ligands and the other two are their tris-bidentate analogues. One of each pair contains methyl ester groups for attachment to semiconductors. Cyclic voltammograms show that the hexadentate and tris-bidentate analogues have almost identical reduction potentials, but the addition of ester substituents shifts the reduction potentials by +0.2 V. The absorption spectra of the hexadentate complexes show improved absorption of visible light compared to the tris-bidentate analogues. For freshly prepared sample solutions in CH₃CN, time-resolved emission and transient absorption measurements for the Cr(III) tris-bidentate ester complex show a doublet excited state with a 17-19 microsecond lifetime at room temperature, while no emission or transient absorption signals from the doublet states are observed for the hexadentate analogue under the same conditions. The dramatic difference is due to the presence of a nonligated bridgehead nitrogen atom. The third project features charge transfer interactions between a photoexcited cadmium sulfide nanorod and [Ru(diethyl 2,2'-bipyridine-4,4'-dicarboxylate)(2,2':6',2"-terpyridine)Cl]+, a mononuclear water-oxidation catalyst. Upon photoexcitation, hole transfer from the cadmium sulfide nanorod oxidizes the catalyst (Ru2+ to Ru3+) on a 100 ps to 1 ns timescale. This is followed by electron transfer (10-100 ns) from the nanorod to reduce the Ru3+ center. The relatively slow electron transfer dynamics may provide opportunities for the accumulation of multiple holes at the catalyst, which is required for water oxidation. Advisors/Committee Members: Professor Niels H. Damrauer, Cortlandt G. Pierpont, Gordana Dukovic, Charles B. Musgrave, Wei Zhang.

Subjects/Keywords: Cadmium Sulfide; Chromium; Electron Transfer; Hole Transfer; Ruthenium

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APA (6^th Edition):

Tseng, H. (2013). Photophysical Studies of Chromium Sensitizers Designed for Excited State Hole Transfer to Semiconductors and Sequential Hole/Electron Transfers from Photoexcited Cadmium Sulfide Nanorods to Mononuclear Ruthenium Water-Oxidation Catalysts. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chbe_gradetds/38

Chicago Manual of Style (16^th Edition):

Tseng, Huan-Wei. “Photophysical Studies of Chromium Sensitizers Designed for Excited State Hole Transfer to Semiconductors and Sequential Hole/Electron Transfers from Photoexcited Cadmium Sulfide Nanorods to Mononuclear Ruthenium Water-Oxidation Catalysts.” 2013. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chbe_gradetds/38.

MLA Handbook (7^th Edition):

Tseng, Huan-Wei. “Photophysical Studies of Chromium Sensitizers Designed for Excited State Hole Transfer to Semiconductors and Sequential Hole/Electron Transfers from Photoexcited Cadmium Sulfide Nanorods to Mononuclear Ruthenium Water-Oxidation Catalysts.” 2013. Web. 22 Apr 2021.

Vancouver:

Tseng H. Photophysical Studies of Chromium Sensitizers Designed for Excited State Hole Transfer to Semiconductors and Sequential Hole/Electron Transfers from Photoexcited Cadmium Sulfide Nanorods to Mononuclear Ruthenium Water-Oxidation Catalysts. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chbe_gradetds/38.

Council of Science Editors:

Tseng H. Photophysical Studies of Chromium Sensitizers Designed for Excited State Hole Transfer to Semiconductors and Sequential Hole/Electron Transfers from Photoexcited Cadmium Sulfide Nanorods to Mononuclear Ruthenium Water-Oxidation Catalysts. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chbe_gradetds/38

University of Colorado

18. Abdulagatov, Aziz Ilmutdinovich. Growth, Characterization and Post-processing of Inorganic and Hybrid Organic-inorganic Thin Films Deposited using Atomic and Molecular Layer Deposition Techniques.

Degree: PhD, Chemistry & Biochemistry, 2012, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/83

► Atomic layer deposition (ALD) and molecular layer deposition (MLD) are advanced thin film coating techniques developed for deposition of inorganic and hybrid organic-inorganic films… (more)

▼ Atomic layer deposition (ALD) and molecular layer deposition (MLD) are advanced thin film coating techniques developed for deposition of inorganic and hybrid organic-inorganic films respectively. Decreasing device dimensions and increasing aspect ratios in semiconductor processing has motivated developments in ALD. The beginning of this thesis will cover study of new ALD chemistry for high dielectric constant Y₂O₃. In addition, the feasibility of conducting low temperature ALD of TiN and TiAlN is explored using highly reactive hydrazine as a new nitrogen source. Developments of these ALD processes are important for the electronics industry. As the search for new materials with more advanced properties continues, attention has shifted toward exploring the synthesis of hierarchically nanostructured thin films. Such complex architectures can provide novel functions important to the development of state of the art devices for the electronics industry, catalysis, energy conversion and memory storage as a few examples. Therefore, the main focus of this thesis is on the growth, characterization, and post-processing of ALD and MLD films for fabrication of novel composite (nanostructured) thin films. Novel composite materials are created by annealing amorphous ALD oxide alloys in air and by heat treatment of hybrid organic-inorganic MLD films in inert atmosphere (pyrolysis). The synthesis of porous TiO₂ or Al₂O₃ supported V₂O₅ for enhanced surface area catalysis was achieved by the annealing of inorganic TiV_xO_y and AlV_xO_y ALD films in air. The interplay between phase separation, surface energy difference, crystallization, and melting temperature of individual oxides were studied for their control of film morphology. In other work, a class of novel metal oxide-graphitic carbon composite thin films was produced by pyrolysis of MLD hybrid organic-inorganic films. For example, annealing in argon of titania based hybrid films enabled fabrication of thin films of intimately mixed TiO₂ and nanographitized carbon. The graphitized carbon in the film was formed as a result of the removal of hydrogen by pyrolysis of the organic constituency of the MLD film. The presence of graphitic carbon allowed a 14 orders of magnitude increase in the electrical conductivity of the composite material compared fully oxidized rutile TiO₂. Advisors/Committee Members: Steven M. George, Cortlandt G. Pierpont, Niels H. Damrauer, Gordana Dukovic, Rishi, Raj.

Subjects/Keywords: annealing; atomic layer deposition; hybrid organic-inorganic films; molecular layer deposition; post-processing; pyrolysis; Chemistry; Materials Chemistry; Physical Chemistry

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APA (6^th Edition):

Abdulagatov, A. I. (2012). Growth, Characterization and Post-processing of Inorganic and Hybrid Organic-inorganic Thin Films Deposited using Atomic and Molecular Layer Deposition Techniques. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/83

Chicago Manual of Style (16^th Edition):

Abdulagatov, Aziz Ilmutdinovich. “Growth, Characterization and Post-processing of Inorganic and Hybrid Organic-inorganic Thin Films Deposited using Atomic and Molecular Layer Deposition Techniques.” 2012. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/83.

MLA Handbook (7^th Edition):

Abdulagatov, Aziz Ilmutdinovich. “Growth, Characterization and Post-processing of Inorganic and Hybrid Organic-inorganic Thin Films Deposited using Atomic and Molecular Layer Deposition Techniques.” 2012. Web. 22 Apr 2021.

Vancouver:

Abdulagatov AI. Growth, Characterization and Post-processing of Inorganic and Hybrid Organic-inorganic Thin Films Deposited using Atomic and Molecular Layer Deposition Techniques. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/83.

Council of Science Editors:

Abdulagatov AI. Growth, Characterization and Post-processing of Inorganic and Hybrid Organic-inorganic Thin Films Deposited using Atomic and Molecular Layer Deposition Techniques. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/chem_gradetds/83

University of Colorado

19. Donohoo-Vallett, Paul John. Control of Photophysical Processes Through Nuclear Motions — Design and Characterization.

Degree: PhD, Chemistry & Biochemistry, 2013, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/94

► In order to achieve third-generation solar devices, the basic photophysics of light-absorbing materials must be thoroughly understood. Herein, vibrational motions are explored as potential… (more)

▼ In order to achieve third-generation solar devices, the basic photophysics of light-absorbing materials must be thoroughly understood. Herein, vibrational motions are explored as potential methods by which excited-state dynamics can be controlled. In an effort to prevent charge-recombination, vibrationally activated photoinduced dissociative electron transfer (ET) of the type [Ru^II(A)_n(L–X)] ²⁺ + hν⟶ [Ru^III(A)_n(L–X)•^–]²+*⟶ [Ru^III (A)_n(L•)]³⁺ + X^– (L = polypyridine ligand; X = halogen; A = ancillary ligand) is explored computationally and experimentally. Density functional theory (DFT) calculations employed a thermochemical cycle to determine structural and electronic factors influencing ΔE_rxn. Intramolecular strain is shown to decrease ΔE_rxn and the formation of a contact ion pair (CIP) state is determined to be a favored product. Thus, parent complex [Ru(tpy)₂]²⁺ (1) (tpy = 2,2':6',2''-terpyridine) is compared with two compounds [Ru(6,6''-Br₂-tpy)(tpy)]²⁺ (2) and [Ru(6,6''-Br₂-tpy)₂]²⁺ (3), that incorporate interligand strain. The crystal structure of 3 is distorted due to strain as compared to 1. While electronic absorption in 2 and 3 is weakened relative to transitions in 1, a strong interligand charge transfer (CT) transition is observed. Ultrafast transient absorption spectroscopy revealed coherent vibrational dynamics in 3 and 2 that were assigned to Br motion. In spite of additional strain, the excited-state lifetime of 3 is ~6x longer than 2. Constrained-DFT calculations shows the strain-induced geometric distortions in 3 causes a nesting of excited state surfaces, extending excited-state lifetime. Kinetic evidence is presented for C–Br bond scission in 3 and formation of the predicted CIP. A secondary project explores singlet fission (SF) — a process where one photon produces two excited-states. DFT calculations are used to explore a series of bistetracene (BT) molecular dimers connected by norbonyl bridges that exhibit through-space and through-bond electronic coupling. Dimer orientation and separation is shown to significantly affect SF driving force, Davydov splitting, and the magnitude of matrix elements important to CT-mediated SF. It is determined that BT1-cis, a norbonyl bridged dimer connected at the 1,2 tetracene positions with both tetracenes extending in the same direction, is most favorable for SF due to an exoergic SF driving force (–119 meV) and increased magnitudes of Davydov splitting and ET matrix elements. Advisors/Committee Members: Niels H. Damrauer, David M. Jonas, Cortland G. Pierpont, Joel Eaves, Henry Kapteyn.

Subjects/Keywords: density functional theory; electron transfer; photophysics; singlet fission; Chemistry; Physical Chemistry

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APA (6^th Edition):

Donohoo-Vallett, P. J. (2013). Control of Photophysical Processes Through Nuclear Motions — Design and Characterization. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/94

Chicago Manual of Style (16^th Edition):

Donohoo-Vallett, Paul John. “Control of Photophysical Processes Through Nuclear Motions — Design and Characterization.” 2013. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/94.

MLA Handbook (7^th Edition):

Donohoo-Vallett, Paul John. “Control of Photophysical Processes Through Nuclear Motions — Design and Characterization.” 2013. Web. 22 Apr 2021.

Vancouver:

Donohoo-Vallett PJ. Control of Photophysical Processes Through Nuclear Motions — Design and Characterization. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/94.

Council of Science Editors:

Donohoo-Vallett PJ. Control of Photophysical Processes Through Nuclear Motions — Design and Characterization. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chem_gradetds/94

University of Colorado

20. Anderson, Virginia Rose. Atomic Layer Deposition of Platinum Particles, Titanium Oxide Film, and Alkoxysilane Surface Layers.

Degree: PhD, Chemistry & Biochemistry, 2014, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/116

► Atomic Layer Deposition (ALD) is a an excellent technique for depositing conformal thin films on complex geometries in layer by layer fashion. The mechanisms… (more)

▼ Atomic Layer Deposition (ALD) is a an excellent technique for depositing conformal thin films on complex geometries in layer by layer fashion. The mechanisms of depositing TiO₂, platinum, and ethoxysilane molecules were probed with in situ Fourier transform infrared (FTIR) in order to better understand and improve the process. Each of these studies involves TiO₂. There are many uses for thin films of titanium dioxide, a semiconductor and high dielectric material. Current Atomic Layer Deposition (ALD) of TiO₂ generally involves water or ozone, which can oxidize and corrode some substrates of interest. Ritala et al. successfully deposited an assortment of metal oxides using no water, but instead, metal alkoxides and metal halides as precursors. Presented is a study of ALD of titanium dioxide using titanium tetrachloride (TiCl₄) and titanium tetraisopropoxide (TTIP). In situ Fourier transform infrared (FTIR) studies revealed that the mechanism for TiO₂ ALD using titanium tetrachloride and titanium tetraisopropoxide changed with temperature. At temperatures between 250 and 300°, the isopropoxide species after TTIP exposures quickly underwent β-hydride elimination to produce TiOH species on the surface. The observation of propene by quadrupole mass spectrometry supported the β-hydride elimination reaction pathway. Deposition was investigated between 150 and 300° on substrates including zirconia, alumina, and silica. Quartz crystal microbalance results and X-ray reflectivity showed that the system grew 0.5-0.6 Å/cycle at 250° X-Ray photoelectron studies also confirmed TiO₂ film growth. In another aspect of ALD use, self-limiting chemistry assisted with terminating a surface with alkoxysilanes. Tire rubber contains additives such as carbon black or silica particles to provide strength. Although in theory Kevlar fibers would provide strength while lowering the density and increasing car fuel efficiency, in practice Kevlar fibers disperse only very poorly in the rubber, leading to inhomogeneity. In order the increase the mixing likelihood between rubber and Kevlar, the reactions of some sulfurous siloxanes were examined on both aluminum oxide and titanium oxide. The titanium oxide adhesion layer allowed the deposition of molecules on the surface that looked promising for improving mixing with rubber and decreasing the weight of tires. Atomic layer deposition offers the possibility of more precision in platinum deposition. In a platinum deposition study, the nucleation and growth of non-conformal platinum on TiO₂ and WO_x powder using Pt(hfac)₂ and formalin was examined with in-situ FTIR and transmission electron microscopy (TEM). Interest in substitution of Pt/C as the oxidation reduction reaction catalyst in polymer electrolyte membrane fuel cells (PEMFCs) led to the ALD synthesis of Pt/WO_x and Pt/TiO₂. A nucleation period on the order of 100 cycles was observed, after… Advisors/Committee Members: Steven M. George, Will J. Medlin, Cortland G. Pierpont, Niels H. Damrauer, David M. Jonas.

Subjects/Keywords: deposition; platinum; Pt; sulfur; Ti; Titanium; Chemistry

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APA (6^th Edition):

Anderson, V. R. (2014). Atomic Layer Deposition of Platinum Particles, Titanium Oxide Film, and Alkoxysilane Surface Layers. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/116

Chicago Manual of Style (16^th Edition):

Anderson, Virginia Rose. “Atomic Layer Deposition of Platinum Particles, Titanium Oxide Film, and Alkoxysilane Surface Layers.” 2014. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/116.

MLA Handbook (7^th Edition):

Anderson, Virginia Rose. “Atomic Layer Deposition of Platinum Particles, Titanium Oxide Film, and Alkoxysilane Surface Layers.” 2014. Web. 22 Apr 2021.

Vancouver:

Anderson VR. Atomic Layer Deposition of Platinum Particles, Titanium Oxide Film, and Alkoxysilane Surface Layers. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/116.

Council of Science Editors:

Anderson VR. Atomic Layer Deposition of Platinum Particles, Titanium Oxide Film, and Alkoxysilane Surface Layers. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/chem_gradetds/116

University of Colorado

21. Grumstrup, Erik Martin. Elucidation of Ultrafast Photophysics with Optical Pulse Shaping.

Degree: PhD, Physics, 2011, University of Colorado

URL: https://scholar.colorado.edu/phys_gradetds/182

► Optical pulse shaping is an incisive tool of laser spectroscopy that allows the experimentalist extensive flexibility to manipulate the electric field of an excitation… (more)

▼ Optical pulse shaping is an incisive tool of laser spectroscopy that allows the experimentalist extensive flexibility to manipulate the electric field of an excitation laser pulse. In this thesis, four applications of optical pulse shaping are examined. In Chapter 2, a partially non-collinear implementation of two-dimensional electronic spectroscopy is demonstrated for the first time on rubidium vapor. The use of a pulse shaper in this context is advantageous as it significantly reduces the complexity of the experimental apparatus. Unfortunately, non-ideal pulse shaping due to pixelation effects in some pulse-shaping devices leads to spurious pulse generation when the spatial masks become highly modulated. To model the effects on recovered 2D spectra, the optical Bloch model is numerically propagated with an explicit inclusion of the electric field modified by pixelation effects. Finally, steps necessary to minimize distortions are outlined. Chapter 3 describes a series of experiments designed to study the mechanism of multiple exciton generation in semiconductor quantum dots through open and closed loop coherent control schemes. The data collected with open loop control methods indicate that the initially formed exciton relaxes on an ultrafast time scale (<20 fs) revealing the reason for a lack of controllability in adaptive, closed-loop optimizations. Chapter 4 of this thesis examines the process of singlet fission in tetracene thin films employing coherent control and ultrafast pulse shaping. Singlet fission is a promising avenue to achieving highly efficient third generation photovoltaic devices, and in this work, closed-loop control suggests that low-frequency nuclear motions play a mechanistic role in tetracene singlet fission. Finally, Chapter 5 examines a specific class of pulse shaping, sinusoidal spectral phase modulation, which is widely employed in the coherent control community as a route toward an intuitive probe into molecular dynamics. This work seeks to build a bridge between the fields of nonlinear spectroscopy and coherent control by describing the light-matter interactions characteristic of this type of pulse shaping using the tools of time-dependent perturbation theory. This description allows experimentalists to predict and test theories of coherent control simply and with little ambiguity, furthering the usefulness of coherent control as a spectroscopic tool. Advisors/Committee Members: Niels H. Damrauer, David M. Jonas, Margaret Murnane, Gordana Dukovic, Joel Eaves.

Subjects/Keywords: 2DE spectroscopy; coherent control; pulse shaping; Optics; Physical Chemistry

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APA (6^th Edition):

Grumstrup, E. M. (2011). Elucidation of Ultrafast Photophysics with Optical Pulse Shaping. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/182

Chicago Manual of Style (16^th Edition):

Grumstrup, Erik Martin. “Elucidation of Ultrafast Photophysics with Optical Pulse Shaping.” 2011. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/phys_gradetds/182.

MLA Handbook (7^th Edition):

Grumstrup, Erik Martin. “Elucidation of Ultrafast Photophysics with Optical Pulse Shaping.” 2011. Web. 22 Apr 2021.

Vancouver:

Grumstrup EM. Elucidation of Ultrafast Photophysics with Optical Pulse Shaping. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/phys_gradetds/182.

Council of Science Editors:

Grumstrup EM. Elucidation of Ultrafast Photophysics with Optical Pulse Shaping. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/182

University of Colorado

22. Cook, Jasper Donald. Informing Singlet Fission Chromophore Design via Photophysical Exploration of Tetracene and Tetracene-Inspired Covalent Dimers.

Degree: PhD, 2017, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/206

► Singlet fission (SF) is a spin-allowed process wherein a singlet excited state on one molecule shares its energy with a neighbor to create a pair… (more)

Subjects/Keywords: covalent dimers; electronic coupling; photophysics; polyacenes; singlet fission; tetracene; Chemistry; Energy Systems; Physical Chemistry

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APA (6^th Edition):

Cook, J. D. (2017). Informing Singlet Fission Chromophore Design via Photophysical Exploration of Tetracene and Tetracene-Inspired Covalent Dimers. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/206

Chicago Manual of Style (16^th Edition):

Cook, Jasper Donald. “Informing Singlet Fission Chromophore Design via Photophysical Exploration of Tetracene and Tetracene-Inspired Covalent Dimers.” 2017. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/206.

MLA Handbook (7^th Edition):

Cook, Jasper Donald. “Informing Singlet Fission Chromophore Design via Photophysical Exploration of Tetracene and Tetracene-Inspired Covalent Dimers.” 2017. Web. 22 Apr 2021.

Vancouver:

Cook JD. Informing Singlet Fission Chromophore Design via Photophysical Exploration of Tetracene and Tetracene-Inspired Covalent Dimers. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/206.

Council of Science Editors:

Cook JD. Informing Singlet Fission Chromophore Design via Photophysical Exploration of Tetracene and Tetracene-Inspired Covalent Dimers. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/chem_gradetds/206

University of Colorado

23. Grennell, Amanda Norell. Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals.

Degree: PhD, Chemistry & Biochemistry, 2017, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/222

► Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between… (more)

▼ Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between the electron and hole. Thus, type-II heterostructures are promising materials for solar-to-fuel conversion, as extended excited-state lifetimes make transfer of charges to a catalyst more competitive with intrinsic nanocrystal decay processes. However, due to fast and efficient hole trapping and non-uniform morphologies, the photophysics of dot-in-rod heterostructures are more rich and complex than this simple picture. Using transient absorption spectroscopy, we observe that the behavior of electrons in the CdS “rod” or “bulb” regions of non-uniform ZnSe/CdS and CdSe/CdS dot-in-rods is similar regardless of the “dot” material, which supports previous work demonstrating that hole trapping and particle morphology drive electron dynamics. Furthermore, we show that the longest lived state in these dot-in-rods is not generated by the type-II or quasi type-II band alignment between the dot and the rod, but rather by electron-hole dissociation that occurs due to fast hole trapping in the CdS rod and electron localization to the bulb. We propose that specific variations in particle morphology and surface chemistry determine the mechanism and efficiency of charge separation and recombination in these nanostructures, and therefore impact their excited-state dynamics to a greater extent than the heterostructure energy level alignment alone. When coupled to a [Fe-Fe] hydrogenase, which catalyzes reduction of protons to H2, we observe faster rates of electron transfer and higher quantum efficiency of electron transfer with CdSe/CdS and ZnSe/CdS dot-in-rods, but only from the bulb and interface states. Furthermore, the total efficiency of electron transfer of the ensemble is highest when the bulb/interface state is directly populated. This indicates that the bulb morphology is essential to efficient electron transfer in a dot-in-rod hydrogenase system. Advisors/Committee Members: Gordana Dukovic, Joel D. Eaves, Mathias M. Weber, Niels H. Damrauer, Margaret M. Murnane.

Subjects/Keywords: Electron transfer; Heterostructures; Nanocrystals; Nanorods; Photophysics; Ultrafast spectroscopy; Nanoscience and Nanotechnology; Physical Chemistry

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APA (6^th Edition):

Grennell, A. N. (2017). Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/222

Chicago Manual of Style (16^th Edition):

Grennell, Amanda Norell. “Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals.” 2017. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/222.

MLA Handbook (7^th Edition):

Grennell, Amanda Norell. “Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals.” 2017. Web. 22 Apr 2021.

Vancouver:

Grennell AN. Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/222.

Council of Science Editors:

Grennell AN. Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/chem_gradetds/222

University of Colorado

24. Tiwari, Vivek. Non-Adiabatic Mechanism for Photosynthetic Energy Transfer and All-Optical Determination of Concentration using Femtosecond Lasers.

Degree: PhD, Chemistry & Biochemistry, 2014, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/122

► Development of efficient light-harvesting technologies hinges on our understanding of the fundamental physics of light-harvesting in both natural and artificial systems. This work addresses… (more)

▼ Development of efficient light-harvesting technologies hinges on our understanding of the fundamental physics of light-harvesting in both natural and artificial systems. This work addresses the following topics, i.) the mechanism underlying the remarkably efficient electronic energy transfer in natural light harvesting antennas, ii.) a femtosecond time-resolved photonumeric technique to quantitatively characterize transient chemical species. A non-adiabatic model for photosynthetic energy transfer in light harvesting antennas is proposed. Light harvesting antennas use a set of closely spaced pigment molecules held in a controlled relative geometry by a protein. It is shown that in the Fenna-Matthews-Olson (FMO) antenna protein, the antenna found in green sulfur bacteria, the excited state electronic energy gaps are resonant with a quantum of vibrational energy on its pigment, bacteriochlorophyll a. Through a dimer model loosely based on FMO, it is shown that such a resonance leads to an unavoidable nested non-adiabatic energy funnel on the excited states of photosynthetic antennas. The non-adiabatic model presented here leads to enhanced vibrational oscillations on the ground electronic state of these antennas, the 2D spectroscopic signatures and oscillation frequencies of which are consistent with all the reported 2D signatures of long-lived oscillations, including the ones that are not explained by prior models of excited state electronic energy transfer. Extensions that account for both resonant and near-resonant pigment vibrations suggest that photosynthetic energy transfer presents a novel design in which electronic energy transfer proceeds non-adiabatically through clusters of vibrations with frequencies distributed around electronic energy gaps. The latter part of the thesis presents absolute measurements of femtosecond pump-probe signal strength. The experiments demonstrate quantitative time-resolved measurement of absolute number of excited state molecules. Based on these measurements, an all-optical technique that simultaneously determines concentration and extinction coefficient of an unknown sample is presented. Unlike prior such analytical techniques, the present photonumeric method does not require any sample isolation, physical handling or in situ calibrant. In principle, the experimental and theoretical framework developed allows extensions towards characterization of transient chemical species. Advisors/Committee Members: David M. Jonas, Joel D. Eaves, Robert P. Parson, Steven T. Cundiff, Niels H. Damrauer.

Subjects/Keywords: 2D Spectroscopy; Absolute Pump-Probe; Exciton; Forster Resonance Energy Transfer; Photonumeric; Transient Chemical Species; Analytical Chemistry; Physical Chemistry

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APA (6^th Edition):

Tiwari, V. (2014). Non-Adiabatic Mechanism for Photosynthetic Energy Transfer and All-Optical Determination of Concentration using Femtosecond Lasers. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/122

Chicago Manual of Style (16^th Edition):

Tiwari, Vivek. “Non-Adiabatic Mechanism for Photosynthetic Energy Transfer and All-Optical Determination of Concentration using Femtosecond Lasers.” 2014. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/122.

MLA Handbook (7^th Edition):

Tiwari, Vivek. “Non-Adiabatic Mechanism for Photosynthetic Energy Transfer and All-Optical Determination of Concentration using Femtosecond Lasers.” 2014. Web. 22 Apr 2021.

Vancouver:

Tiwari V. Non-Adiabatic Mechanism for Photosynthetic Energy Transfer and All-Optical Determination of Concentration using Femtosecond Lasers. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/122.

Council of Science Editors:

Tiwari V. Non-Adiabatic Mechanism for Photosynthetic Energy Transfer and All-Optical Determination of Concentration using Femtosecond Lasers. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/chem_gradetds/122

University of Colorado

25. Spettel, Karen Elizabeth. Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells.

Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/164

► To explore the impact of structure on photoinduced electron transfer processes, systematically tuned 4′-aryl-substituted terpyridyl ruthenium(II) complexes are synthesized and then studied in solution,… (more)

▼ To explore the impact of structure on photoinduced electron transfer processes, systematically tuned 4′-aryl-substituted terpyridyl ruthenium(II) complexes are synthesized and then studied in solution, film, and device settings. These complexes are introduced in the framework of dye-sensitized solar cells (DSSCs)—a low cost alternative to conventional silicon-based devices. A monolayer of ruthenium chromophores attached to a mesoporous TiO₂ semiconductor is designed to efficiently absorb photons and initiate the separation of charge across a dye/semiconductor interface. Acting as a working electrode in a complete cell, this construction of sensitized TiO₂ particles allows for the conversion of photons to current. In our work, structural tuning is performed within the aryl-terpyridine ligands, by systematically introducing methyl substituents at the ortho positions of the aryl moiety in order to explore dynamical electron transfer coupling at ruthenium/TiO₂ interfaces. First, syntheses, electrochemical potentials, static emission, and temperature-dependent excited-state lifetimes of several 4′-aryl-substituted terpyridyl complexes of ruthenium(II) are presented. In these solution phase studies, the power of structural tuning manifests primarily with a 14-fold decrease in the excited-state lifetime of dimethylated species relative to unsubstituted aryl-terpyridine species. Next, an overview of the materials and procedures utilized to make complete DSSCs is presented. In an effort to determine the implications of structural tuning of these complexes within the DSSCs, total solar power conversion efficiency measurements are performed. These are then deconstructed to better understand the fundamental processes and how they impact light-to-current conversion. Injection yields are identified as the primary factor limiting the efficiencies of these ruthenium terpyridyl DSSCs. The final chapter presents an investigation of the kinetics of charge recombination—an energy-wasting back electron transfer process at play in photoinduced charge-separated processes. Transient absorption spectroscopy is applied to sensitized TiO₂ films in an electrochemical setup simulating device conditions. The addition of methyl steric bulk is found to inhibit charge recombination, with measured recombination lifetimes increasing by over 12-fold across the series of structurally-tuned complexes. If injection yields can be improved, the structural tuning of recombination rate constants may be an important design rule for improving solar conversion efficiency in solar cells and water splitting devices. Advisors/Committee Members: Niels H. Damrauer, Cortlandt G. Pierpont, Gordana Dukovic, Steven M. George, Charles Rogers.

Subjects/Keywords: Conformational Control; Dye Sensitized Solar Cells; Electron Transfer; Ruthenium Polypyridyl; Steric Hindrance; Physical Chemistry

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APA (6^th Edition):

Spettel, K. E. (2015). Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/164

Chicago Manual of Style (16^th Edition):

Spettel, Karen Elizabeth. “Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells.” 2015. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/164.

MLA Handbook (7^th Edition):

Spettel, Karen Elizabeth. “Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells.” 2015. Web. 22 Apr 2021.

Vancouver:

Spettel KE. Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/164.

Council of Science Editors:

Spettel KE. Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/164

University of Colorado

26. Park, Samuel D. Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots.

Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado

URL: https://scholar.colorado.edu/chem_gradetds/175

► Quantum dots have applications in lighting displays and in biomedical imaging, and potential applications in next generation photovoltaics. The fine structure, optical inhomogeneity, coupling… (more)

▼ Quantum dots have applications in lighting displays and in biomedical imaging, and potential applications in next generation photovoltaics. The fine structure, optical inhomogeneity, coupling between excitons, and exciton dephasing rates are important to quantify because they affect the optical properties of quantum dots. These observables are encrypted in linear absorption lineshapes but can be measured with nonlinear spectroscopy. The first two-dimensional (2D) Fourier transform spectra of lead chalcogenide quantum dots in the short-wave infrared are presented. With the additional dimension afforded by 2D spectra, linewidths from homogeneous and inhomogeneous broadening can be separated. Simulations to model the experimental 2D spectra are performed at long relaxation times to extract the optical inhomogeneity of a PbSe quantum dot ensemble. Additional information can be determined more accurately from 2D spectra than from transient absorption measurements. Specifically, the simulation of experimental 2D spectra shows that the excited state absorption redshift, which has been attributed to the bi-exciton binding energy, is larger than previously reported results, suggesting new interpretations. Pump-probe polarization anisotropy measurements with 15 fs pulse durations are employed to investigate the electronic structure of chlorine-passivated PbS quantum dots at the bandgap. The measurement of the initial anisotropy required the removal of unwanted signal contribution from cross-phase modulation. The presence of cross-phase modulation motivated the calculation, simulation, and measurement of this signal for spectrally resolved pump-probe transients and two-dimensional Fourier transform spectroscopy. The initial anisotropy contains information about both bi-exciton states and some hot single exciton states, and the time dependence quantifies the timescale of intervalley scattering. Our results for PbS quantum dots indicate a lower initial anisotropy than expected from the effective mass approximations for PbS quantum dots with a rapid loss of any anisotropy in less than 20 fs. Advisors/Committee Members: David M. Jonas, Robert P. Parson, Veronica Vaida, Charles Rogers, Niels H. Damrauer.

Subjects/Keywords: quantum dots; photovoltaics; fourier transform spectra; chalcogenide quantum dots; cross-phase modulation; Physical Chemistry

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APA (6^th Edition):

Park, S. D. (2015). Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/175

Chicago Manual of Style (16^th Edition):

Park, Samuel D. “Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots.” 2015. Doctoral Dissertation, University of Colorado. Accessed April 22, 2021. https://scholar.colorado.edu/chem_gradetds/175.

MLA Handbook (7^th Edition):

Park, Samuel D. “Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots.” 2015. Web. 22 Apr 2021.

Vancouver:

Park SD. Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Apr 22]. Available from: https://scholar.colorado.edu/chem_gradetds/175.

Council of Science Editors:

Park SD. Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/175

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