With the dual challenges of meeting global energy demand and mitigating anthropogenic climate change, significant effort is being applied to generating power from renewable sources. The dye-sensitized solar cell (DSC) is a photovoltaic technology capable of generating electricity from sunlight, but suffers losses in efficiency due to deleterious electron transfer...
Halide perovskites, AMX3 (A = monocation, B = Ge, Sn, or Pb, and X = halogen), present a versatile class of solution-processable semiconductors made from earth abundant materials with outstanding electrical and optical properties. Their solar cell efficiencies have dramatically increased from ~9% to ~22% in less than five years...
Ultrafast spectroscopy offers an unprecedented view on the dynamic nature of chemical reactions. From charge transfer in semiconductors to folding and isomerization of proteins, these all important processes can now be monitored and in some instances even controlled on real, physical timescales. One of the biggest challenges of ultrafast science...
Climate change may be one of the most important puzzles the world has attempted to solve and one of the greatest challenges in this area is to improve our understanding of how atmospheric aerosol particles impact climate processes. We seek to overcome this challenge by focusing on the chemistry and...
This dissertation describes the relationship between the surface chemistry of colloidal semiconductor nanocrystals (quantum dots, QDs) and their optoelectronic properties, such as photoluminescence and degree of quantum confinement. We primarily focus our efforts on one particular subset of ligands known to couple strongly to the inorganic core of the QD...
Understanding the nature of quantum effects in dense biological systems is of great interestto many scientists today. It seems that the question is not does quantum mechanics dictatebiological processes, but rather by how much and to what extent. A big challenge though in thisfield is how to properly test and...
In Chapter 1, a series of "constrained geometry" organoactinide complexes, (CGC)An(NMe)2 (CGC = Me2Si(h5-Me4C5)(tBuN); An = Th, 1; U, 2), prepared via efficient in situ, two-step protodeamination routes in good yields and high purity, is presented. Both 1 and 2 are quantitatively converted to the neutrally charged, solvent-free dihalides (1-Cl2,...
Four series of doped CdO thin films have been grown on both amorphous glass and single-crystal MgO(100) substrates by metal-organic chemical vapor deposition (MOCVD), and their phase structure, microstructure, electrical, and optical properties investigated. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited doped CdO thin...
Counteranion effects on the rate and stereochemistry of propylene polymerization mediated by ion-pair complexes derived from dimethylzirconocene precatalysts activated with strongly Lewis-acidic perfluoroarylmetalloid cocatalyst/activators are shown to arise from the strength of the cation-anion interaction. This is quantified using CS-symmetric Me2C(Cp)(Flu)ZrMe2 (Cp = C5H4, η5 cyclopentadienyl; Flu = C13H8, η5...
Local structure determination in amorphous and disordered systems, which are crystallographically intractable, is critical for gaining an understanding of their properties. X-ray absorption spectroscopy (XAS) is an excellent tool for local structure determination in amorphous and disordered environmental materials. Amorphous manganese oxides produced by the freshwater bacterium Leptothrix discophora SP6...
Two new strategies have been developed to accomplish direct nucleophilic acylation reactions. In the first approach, acylsilanes are added to various electrophiles using N-heterocyclic carbenes as catalysts. The second method utilizes O-silyl thiazolium carbinols as stoichiometric acyl anion precursors to afford acylated products under mild reaction conditions.
N-heterocyclic carbenes generated...
High relaxivity contrast agents are of great importance in the advancement of magnetic resonance imaging diagnostics for use in biomaterials. Biomaterials that are implanted into the body, with the goal of repairing or regenerating lost or damaged tissue, need to be tracked noninvasively, over time. I have completed work using...
A catalytic, multi-component coupling reaction for the synthesis of nitrogen-containing heterocycles has been developed, via the reaction of an imine, α-diazoester and unsaturated coupling partner in the presence of a copper(I) or rhodium(II) transition metal catalyst with excellent diastereo-selectivities and high yields. The transition metal-catalyzed decomposition of a diazo compound...
The [(salen)CrCl + LB] catalyst system was found to be a highly active catalyst system for the [aziridine + CO<sub>2</sub>] coupling reaction, and exhibited a marked preference for the formation of 5-substituted oxazolidinone product, especially in the absence of cocatalyst. The activity of this catalyst system is optimized by modifying...
The work described here includes both fundamental and application based studies centered around the use of plasmonic sensors. Fundamental studies focus on probing the optical properties of nanosphere lithography (NSL) fabricated Ag nanoparticles, while surface-enhanced Raman spectroscopy (SERS) sensors are applied to identify and characterize artists' red dye and red...
UV Raman spectroscopy is a powerful tool to investigate hydrocarbons-zeolite systems, including the coke formation mechanism during MTH reactions, the sorbet-framework interactions and the quantitative analysis of catalytic reactions.
First, methanol, dimethyl ether and ethylene reactions were carried out on H-MFI with different Si/Al atomic ratios to study the coke...
This dissertation describes the development and use of novel chemical affinity templates to direct the assembly and preserve the activity of biological molecules in surface- and solution-based biomolecular assays. The majority of work described herein focuses on advancing biological nanoarray technology to enable the study of fundamentally important biological processes...
The porphyrazines (pzs), a class of porphyrin derivatives, have shown potential as therapeutic and imaging agents due to a combination of their near-IR absorbance/fluorescence and their enhanced chemical flexibility. Cell viability/proliferation assays and fluorescence microscopy were carried out in both tumor and normal cells to characterize the biological activity of...
Part 1. The complex folded structures associated with RNA allow for specific protein-RNA interactions and also create binding sites for small molecules. Developing organic molecules that can bind RNA with high affinity and specificity is a challenge that must be overcome for RNA to be considered a viable drug target....
This thesis consists of the synthesis and photophysical characterization of chlorophyll- and porphyrin- based multichromophore arrays designed for the purpose of studying energy and charge transfer therein. The first series of arrays consists of donor-acceptor dyads in which various arylene diimide electron acceptors are attached through a phenyl group to...
Theoretical studies on electronic structure governing charge transport properties are investigated to understand and improve the prediction of electron charge carrier organic semiconductors used in field-effect transistors. Perfluorinated oligothiophene semiconductors have shown experimental n-type behavior, but placement of fluorinated aryl groups changes charge polarities. Models were developed to investigate how...
The work presented in this dissertation is centered on experimental efforts to maximize the sensitivity of surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) toward their application in ultrasensitive nanoscale chemical analysis. The work focuses on fundamental studies of the plasmonic properties of silver nanostructures, and how those properties...
The work presented here describes investigations into the optical properties of single silver nanoparticles. The contents of this thesis are divided into two parts: (1) single nanoparticle localized surface plasmon resonance (LSPR) spectroscopy and sensing and (2) approaches to combining LSPR spectroscopy with atomic force and transmission electron microscopies. Part...
Nanoplasmonics is an emerging branch of photonics that studies the optical properties of noble metals. Nanostructured noble metal materials, which can strongly interact with light and support various plasmon modes, are exceptional candidates for nanophotonic devices. This work describes the latest advances in the fabrication of ordered silver nanoparticles or...
Alkenylsilanes of varying chain lengths are investigated as simultaneous chain transfer agents + comonomers in organotitanium-mediated olefin polymerization processes. Ethylene + alkenylsilane polymerizations were carried out with activated Me2Si(Me4C5)(NtBu)TiMe2 and (-CH2CH2-3,3'){(5-indenyl )[1-Me2Si(tBuN)]}2Ti2Me4 precatalysts. Alkenylsilane incorporation levels follow the trend C8H15SiH3 < C6H11SiH3 ≈ C4H7SiH3 < C3H5SiH3. Long-chain branching levels versus...
This dissertation covers the synthesis and study of peptide nucleic acids (PNAs), specifically, derivatives of PNA containing amine-bearing sidechains or cyclopentane portions. PNAs are non-natural nucleic acids that have far reaching potential in therapeutics and nucleic acid detection. Despite immense potential and widespread application, improving on the design and applications...
Direct dynamics quasiclassical trajectory (QCT) calculations are performed to study the dynamics of model atom + polyatom reactions. In the first part of this thesis, we examine adiabatic dynamics of H/O reaction with simple alkanes, CD4 and C2H6. Overall good agreement with state-of-the-art experiments shows that the molecular motion is...
Small molecule organic materials based on perylene- and naphthalene- diimide are synthesized and characterized for use as semiconductor thin films in organic field-effect transistors. The orbital energetics of the materials are investigated via electrochemical, spectroscopic, and computational techniques. The thin film solids are characterized by x-ray diffraction techniques and surface...
Metal oxide surfaces are generally recognized as active substrates for many catalytic reactions. Density Functional Theory (DFT) has been found as a useful computational tool to investigate the geometry, energy, electronic structure of reactive oxide surfaces and their interaction with small molecules and fragments. In this thesis, primary efforts have...
Okilactomycin and chrolactomycin are antitumor antibiotics isolated in 1987 and 2001, respectively. These tetracyclic natural products possess a unique 6-5 fused tetrahydropyrone-butyrolactone. The spirocenter is part of a highly functionalized cyclohexene ring, which together with the aforementioned 6-5 system compose the core of these molecules. A six carbon, 1,3-dialkyl-substituted carbon...
Surfaces and interfaces, which are ubiquitous in the environment, control the mobility,speciation, and ultimate fate of groundwater species. The presented work provides insight into the interfacial behavior of three environmental pollutants: hexavalent chromium, oxytetracycline, and morantel. Model surfaces are employed for these studies, including (1-102) α-Al<sub>2</sub>O<sub>3</sub> and a carboxylic acid-terminated...
This dissertation describes the invention and development of a new nanolithographic method: On-Wire Lithography (OWL). OWL is a simple, reproducible, and high-throughput procedure for the synthesis and lithographic processing of metal nanowires (i.e. Au, Ag, Pt, Ni, and Cu) that allows researchers to control the morphology and feature size of...
The overarching theme of this thesis is the development of non-natural oligomers for use in biological applications. Chapter I details the synthesis and studies of modified peptide nucleic acid (PNA) oligomers. PNA is a synthetic oligonucleotide mimic that binds to natural nucleic acids with extremely high affinity and specificity, making...
Preventing the build-up of indoor pollutants represents an emerging goal in environmental chemistry. Heterogeneous catalysis provides an attractive method of remediating indoor air pollution, but optimization through rational catalyst design requires a detailed understanding of the catalytic surface and surface-pollutant interactions. In this work, a chemical ionization mass spectrometry (CIMS)...
Interfaces and surfaces are ubiquitous in the environment. Heterogeneous binding events and reactions control the transport and speciation of dissolved pollutants in groundwater. Many heterogeneous processes occur at mineral oxide/water interfaces, and can be controlled either by the mineral oxide, or organic molecules bound to the surface. The prevalent natural...
The first section of this thesis focuses on applications of DNA-modified gold nanoparticles (AuNPs) while the second part addresses the fundamental properties that arise from conjugating DNA to inorganic AuNPs. Two types of applications are discussed. The first application utilizes the colorimetric properties of AuNPs to screen duplex and triplex...
This dissertation focuses on the utilization of two coordination chemistry-based synthetic approaches, which provide the ability to rapidly and quantitatively assemble sophisticated supramolecular cofacial porphyrin complexes. Significantly, by adopting a coordination chemistry-based approach, the porphyrin-porphyrin interactions can be regulated in situ via the addition or removal of chemical effector molecules....
Two new methods have been developed employing silicon-containing molecules in novel organic transformations. The first strategy utilizes Lewis base-activation of triethoxysilylalkynes to deliver mild acetylide nucleophile equivalents. The second approach involves the use of enolate additions to acylsilanes to generate β-silyloxy homoenolate intermediates.
Lewis base-catalyzed activation of triethoxysilylalkynes promotes the...
The work presented in this thesis describes investigations into linear and nonlinear optical properties of two-dimensional silver nanoparticle arrays. The linear optical measurements - extinction measurements were performed on two-dimensional square arrays of L-shaped silver nanoparticles fabricated by electron beam lithography in order to study the effect of dipole coupling...
This dissertation describes the use of alkanethiols and polymers for the development of lithographic affinity and resist array templates that can be utilized for directing the assembly of biological molecules, for building up multilayered polyelectrolyte thin films, and for fabricating metal solid-state nanostructures. The first two chapters of the work...
Theoretical analysis of DNA bridge-mediated electron transfer (ET) led to the proposal that photoinduced ET might occur via either superexchange or hopping mechanisms. Electron transfer has been proposed to occur via a superexchange mechanism at short distances and via a hopping mechanism at longer distances. However, a crossover in mechanism...
The contents of this dissertation are divided into two sections: (1) the preparation and characterization of quaternary rare-earth chalcogenides and oxychalcogenides and (2) the localized surface plasmon resonance (LSPR) spectroscopy of metallic nanoparticles fabricated by nanosphere lithography (NSL).
Single crystals of CsTmCoS3, CsYbCoS3, CsHoCoSe3, CsYbCoSe3, and CsYbZnSe3 have been prepared...
The work described in this dissertation focuses on the optical characterization of micron-sized structures with mesoscale (100-1000 nm) features to investigate of the optical analog to the quantum corral. Lithographically patterned arrays of metallic rings and ellipses were used to study how light can be manipulated and confined within these...
This thesis attempts a combined theoretical/experimental investigation of two fundamental scaling laws in charge transfer reactions: how the rate of those reactions varies as a function of distance between an electron donor and an electron acceptor and how the rate varies as a function of the number of distinct pathways...
This thesis investigates singlet exciton fission, a physical process that converts one singlet exciton to a pair of triplet excitons. Singlet fission was discovered nearly forty years ago, but the mechanism for this process is still not well understood. Recent work has suggested that singlet fission may be capable of...
Metallic nanostructures are able to confine and manipulate electromagnetic fields because light can couple to free electron oscillations called surface plasmons (SPs). These plasmons exist on metal surfaces as localized (short-range) or as propagating (long-range) modes depending upon the size and geometry of the nanostructure. This dichotomy is primarily an...
This thesis summarizes our research efforts on the application of the nano-structured anodic aluminum oxide (AAO) membrane in heterogeneous catalysis. Procedures for growing the AAO membrane in the center of an aluminum disc have been developed by appropriately masking the disk's perimeter during the anodization and etching steps. The remaining...
Chemical vapor deposition (CVD) is a well-developed technique for growing thin films of a wide variety of materials, which relies on the development of new and better performing metal-organic precursors. To this end, three studies have been conducted into the compatibility of sulfur and phosphine containing ligands with low- and...
Conjugated organic molecules and polymers hold significant promise for use as active materials in electronic devices. Employing such "soft" materials can decrease cost of device fabrication, while enabling unique properties such as mechanical flexibility, large-area coverage, and highly tunable materials properties. A primary roadblock to the realization of this dream...
Metal nanoprisms are a novel class of anisotropic nanomaterials with unique optical properties dependent on their size, shape, and composition. Silver nanoprisms are of particular interest because their surface plasmon resonance bands are readily tunable in the visible and near-IR region. The objectives of this thesis research focus on photochemical...