Tag: Chemistry

Asymmetrical Heteroatom Substitution in the Indenofluorene Framework

Presenter: Nathaniel O’Neal

Mentors: Michael Haley and Jonathan Marshall, Chemistry

Poster: 49

Major: Biochemistry 

Semiconductors are a key component in electronics because they allow for the control of electron flow throughout a device. Research has shown that organic molecules can act as semiconductors and could prove superior to current semiconductors in use. To further this field of study the Haley lab has developed and experimented on the indenofluorene, an n-type organic semiconductor. However, most of the work done on the framework has been on symmetrical heteroatom substitutions. This has left me with the task of using synthetic chemistry techniques in order to produce asymmetrical heteroatom substituted indenofluorene molecules known as benzo-indaceno-thiophenes. Theoretically, this asymmetry will allow for superior stacking of the molecules in a crystal structure and allow for more efficient electron transfer than its symmetrical predecessors. To date, the substitutions have not made a significant of enough change to the overall motif of the structure to produce a notable difference but the knowledge garnered from such experimentation is valuable to the field as a whole.

Silver Tip Preparation for Scanning Tunneling Microscopy

Presenter: William Crowley

Mentors: Ben Taber and George Nazin, Chemistry

Poster: 15

Major: Chemistry

Scanning tunneling microscopy (STM) can be utilized to image, manipulate, and spectroscopically characterize individual atoms and molecules. The scanning probe used in STM is often described as a tip. Tips are conically shaped pieces of metal that are, ideally, atomically defined at one end. Creating well defined tips is essential to obtaining quality STM images. Due to its spectroscopic enhancing plasmonic properties silver is an interesting material for STM. Specifically, enhancements to the factor of 106 to 107 have been reported. The Nazin group has developed a novel method of electroetching sliver to produce well defined STM tips. In our process we utilize a previously unused electrolyte; 1:8 glacial acetic acid to deionized water. Our two-step process first involves an automated primary electrochemical etch in which a 0.5 mm 9.9985% silver wire is etched to form a rough conical shaped. Second, the roughly shaped silver wire is manually etched to produce a well-defined apex. My research has focused on optimizing and parametrizing variables in this two-step process such as voltage bias and rate of etching. Finished tips are then characterized by scanning electron microscopy and energy dispersive x-ray spectroscopy. This process has yielded tips with an apex of approximately 200 nm.

Drug Development with New Catalytic Molecules

Presenter(s): Maribelle Stanley − Pre-chemical Engineering

Faculty Mentor(s): David Tyler

Poster 18

Research Area: Chemistry

Funding: National Science Foundation grant CHE-1503550, UO Summit scholarship

Many drugs are produced by important chemical reactions which form molecules with carbon-carbon or carbon-nitrogen bonds. However, the variety of drugs that can be produced using these reactions is limited by whether a desired molecule is capable of being reacted. To make unreactive molecules react, a catalyst can be used. One common type of catalyst contains a palladium atom, which can interact with other molecules in order to form a catalytic molecule. The catalytic function of these molecules depends on how well the palladium can bring reactants together. The main goal of this research project has been to synthesize a suitable catalyst for these important reactions. Under Dr. David Tyler, and as a continuation of research conducted by Dr. Alex Kendall, novel molecules, called phosphines, have been designed, synthesized, and tested for catalytic behavior. Designing these phosphines required research into previously synthesized molecules published by other groups, and the synthesis of these molecules involved using “air-free” chemistry techniques to protect the sensitive reactants from oxygen. Testing for the presence of these molecules in reaction material was done by analyzing the structure of molecules, with two primary techniques: nuclear magnetic spectroscopy and gas-chromatography mass-spectroscopy. One molecule, called “S-Phos”, was successfully synthesized, and has been found to be catalytic; subsequent molecules are in the process of testing and synthesis. Developing new catalytic molecules can open the door to new varieties of drugs, providing better therapies to help people around the world.

Quantification of Point Defects in Perovskite Solar Cells

Presenter(s): Nicole Wales—Chemistry and Physics

Faculty Mentor(s): Mark Lonergan, Zack Crawford

Session 5: The Bonds that Make Us

In order to improve perovskite solar cell efficiency, it is necessary to minimize defects within the perovskite absorber layer, which may include crystallographic point defects . By understanding how these defects form and contribute to the material’s electronic structure, we will gain insight into routes of Shockley-Read-Hall recombination and associated efficiency loss . Theoretical studies have credited some point defects with the production of energy trap states within the bandgap. As such, we aim to measure and describe the nature and formation of traps in real materials. External quantum efficiency measurements are used to describe a gaussian distribution of traps . Additionally, capacitance techniques are applied with the added advantage of increased sensitivity to the absorber layer . However, capacitance techniques are complicated by the hysteretic perovskite system, which is discussed . The samples used in this study include methylenediammonium dichloride- stabilized alpha-formamidinium lead triiodide, a perovskite with interstitially incorporated chloride . External quantum efficiency measurements showed lower defect densities compared to devices of different compositions, however, one sample did show a small signal with a defect transition energy of 1 .08 ± 0 .01 eV . Findings may point to material suppression of sub-gap defects associated with methylenediammonium dichloride-stabilization compared to alternative compositions . It will be interesting to determine if methylenediammonium dichloride is the source of defect suppression in these samples . To understand how the composition might affect defect states, it will also be necessary to take measurements of other stabilizing agents with different compositions .

Ultrathin Iridium Oxide Catalyst on a Conductive Support for the Oxygen Evolution Reaction in Acid

Presenter(s): Nathan Stovall—Chemistry

Faculty Mentor(s): Shannon Boettcher, Raina Krivina S

ession 5: The Bonds that Make Us

Anthropogenic climate change has driven interest in the research and development of clean
energy alternatives . Great advancements in renewable energy production have been made, but its intermittent nature requires the development of a large-scale storage technology . Water electrolysis is a promising solution to the storage dilemma, via the state-of-the-art proton exchange membrane (PEM) electrolyzers that can convert renewable energy into hydrogen fuel . However, the acidic operating conditions of PEM cells results in slow kinetics of the oxygen evolution reaction (OER) . Iridium oxide is the only catalyst capable of withstanding these harsh conditions, but its low abundance and high costs limit large-scale implementation . My research focuses on designing a novel sub-monolayer-thick iridium oxide catalyst on an inexpensive conductive support that would allow to decrease iridium loading while maximizing activity . We have developed a novel synthetic method for adhering a cheap commercially available iridium precursor (IrCODCl dimer) to the surfaces of inexpensive acid-stable metal oxide nanoparticles . The mechanism of the assembly was investigated with UV-vis spectroscopy, X-ray photoelectron spectroscopy, and NMR . We discovered that the dimer attaches in a surface-limited manor allowing for precise control over the catalyst’s thickness . The determination of the mass loadings was accomplished via x-ray fluorescence and ex-situ inductively coupled plasma induced mass spectroscopy . Electrochemical measurements conducted in pH 1 have shown exceptionally high intrinsic activity at significantly reduced mass loadings . We are currently working on improving the catalyst’s stability which might in the future allow for industrial-scale implementation of water electrolysis as renewable energy storage .

Quantifying the spatial morphology of organic films through polarization- dependent imaging

Presenter(s): Madelyn Scott—Chemistry, Physics

Faculty Mentor(s): Kelly Wilson, Cathy Wong

Session 2: Cells R Us

Organic semiconducting materials are appealing, green alternatives to conventional semiconductors because they can be solution-processed into flexible films . However, solution-processing fabrication methods can be prone to morphological disorder, meaning that crystalline structures in the
film exhibit a variety of sizes and shapes . A large degree of morphological disorder inhibits the electronic functionality of a film for use in technological devices . Examining how film morphology varies with different deposition conditions allows us to connect the physical properties of organic semiconducting films to macroscopic perturbations in their formation environments . In this work, we used a homebuilt microscope to image the polarization-dependent absorption of organic films, and developed an image analysis software package to characterize their spatial morphology . A series of pictures are collected of the sample, rotating the polarizer between each image . For every pixel in the image, the absorption signal as a function of polarization angle is fit to a sinusoidal curve . These fits are employed to assign pixels in the image to discrete aggregate domains within the film . Quantitative domain metrics are computed to describe the morphology of the film . Several organic films are produced under different deposition conditions and their resulting morphologies are compared . By better understanding the relationship between deposition conditions and film formation, existing solution-processing techniques can be further controlled and refined to achieve target physical properties in organic semiconducting materials .

The Atomistic Reconstruction of Coarse-Grained Polymeric Systems via Machine Learning Techniques

Presenter(s): Jake Olsen—Chemistry and Mathematics

Faculty Mentor(s): Marina Guenza, Jake Searcy

Session 1: It’s a Science Thing

Polymeric systems, things like proteins, DNA, and synthetic plastics, are of great interest for their applications in material design and the biomedical industry . Therefore, having time-efficient and inexpensive approaches to investigate these systems on multiple scales, from the microscopic to the macroscopic level, is of great importance and necessity . Molecular dynamics (MD) simulations are one such tool for investigating these systems; however, MD simulations that simulate polymer systems in their atomistic (AT) representation are unable to reach the time scale necessary so that the system exhibits the correct chain characteristics . Thus, coarse-graining (CG) methods, a process by which the local degrees of freedom are averaged out, are applied to improve upon computational time . Unfortunately, the computational gain is coupled with the loss of statistical information from the CG process . Therefore, to regain the lost AT information the CG trajectories need to be transformed back to an AT representation . This process is known as backmapping . Utilizing state- of-the-art machine learning techniques coupled with AT data, we have developed a backmapping procedure for CG polymeric systems . The model, centered around a recurrent neural network (RNN), shows strong agreement with the AT data across many statistical quantities prompting further investigation and development of the model .

Rational Design and Synthesis for Nickel Catalyzed Hydrosilylation

Presenter(s): Parker Morris—Chemistry

Faculty Mentor(s): Amanda Cook, Kiana Kawamura

Session: Prerecorded Poster Presentation

The chemical industry, which accounts for ~7% of the US’s energy consumption, is the source of synthetic products used every day, from plastics to pharmaceuticals . Catalysts are used abundantly in industry because they make reactions faster and more selective, thus generating less waste . One important class of reactions is alkene hydrosilylation, which combines two molecules (an alkene with a carbon-carbon double bond and a silane) into one molecule that is then used to make products like rubbers and cosmetics . Hydrosilylation is limited because purifying the starting alkene is energy intensive . Current industrial catalysts use rare platinum metal and produce waste . In our research, we utilize catalysts based on nickel, an Earth-abundant metal, for hydrosilylation of alkenes . In this project, 15 nickel catalysts were tested to determine their reactivity with styrene and diphenyl silane . Two of the 15 catalysts were designed and synthesized in multi-step organic synthesis . A primary objective of the work was designing and synthesizing a library of proposed catalytic compounds . It was found that of the 15, the two synthesized in lab were the most effect catalysts in terms of both selectivity and yield . Based on the work, we were able to hypothesize a catalytic reaction mechanism . Using this rational approach to catalyst design, we aim to develop a novel catalyst that can influence the chemical industry .

The Reactions Between Iron and Selenium

Presenter(s): Dylan Bardgett—Chemistry

Faculty Mentor(s): Dave Johnson, Danielle Hamann

Session 6: Interact & React

In the wake of the recent discovery of high-temperature superconductivity in iron selenide, FeSe, chemists, physicists, and materials scientists from around the globe have tried to develop new FeSe- based materials with higher and higher superconducting critical temperatures . However, none have yet explored the fundamental chemistry of how Fe and Se react . We investigated the interactions between solid Fe and Se in the absence of the diffusion limitations often confronted in solid state chemistry by preparing layered precursors of elemental Fe and Se with layer thicknesses on the order of a few angstroms with a variety of Fe/Se compositions . The initial structures and subsequent reactions were monitored via x-ray diffraction and x-ray fluorescence as the precursors were gently annealed . Structural and compositional analysis of the samples indicates that, unlike other transition metal selenides, the reactions between Fe and Se are not kinetically limited by diffusion processes . Even at temperatures well below standard reaction temperatures, thermodynamic products between Fe and Se appear to dominate the macro-architecture of the precursors . These findings may hold significant consequences for the development of future FeSe-based materials, as the low reaction barriers to form the thermodynamic products may impede efforts to kinetically trap metastable FeSe materials .

Metal-Ligand Bond Dynamics in Metal-Organic Frameworks Confirmed by Variable Temperature Vibrational Spectroscopy

Presenter(s): Stacey Andreeva—Chemistry

Faculty Mentor(s): Carl Brozek

Session 5: The Bonds that Make Us

Dynamic chemical bonds reversibly break and reform with minimal heat, light, or pressure . This type of bonding is responsible for the basic mechanism of crystallization for many material systems because erroneous bond formation can be corrected through facile reversal until the material settles into the most favorable crystalline phase . A particularly important class of crystalline materials that emerge from this dynamic process are metal-organic frameworks (MOFs) . MOF architecture is dependent on two building blocks: the metal ions or metal clusters and the organic ligands that bridge the metals . For the past two decades, MOFs have been viewed as rigid structures, but we propose that even after formation, MOFs contain metal-ligand bonds that remain dynamic such that the crystalline structure contains mixtures of partially bound and unbound arrangements . We hypothesize that metal-carboxylate bonds— which constitute the majority of MOFs—are especially dynamic, with large fraction of these bonds existing in unbound states . To understand this metal- ligand interaction, our research focuses on monitoring the changes in the vibrational frequencies as a function of temperature . Variable temperature vibrational spectroscopy shows a lowering in energy of the stretches associated with these dynamic bonds at increased temperatures, indicative of bond weakening . By understanding this relationship, more general insights can be made regarding important material behavior such as crystallization and self-healing responsiveness. Insight into their labile nature would provide a predictive model their growth mechanism and inspire important applications such as the use of MOF for self-healing membranes .