Chemistry Commons^™

Carbon Quantum Dots: Bridging The Gap Between Chemical Structure And Material Properties, Timothy J. Pillar-Little Jr.

Theses and Dissertations--Chemistry

Carbon quantum dots (CQDs) are the latest generation of carbon nanomaterials in applications where fullerenes, carbon nanotubes, and graphene are abundantly used. With several attractive properties such as tunable optical property, edge-functionalization, and defect-rich chemical structure, CQDs have the potential to revolutionize optoelectronics, electro- and photocatalysis, and biomedical applications. Chemical modifications through the addition of heteroatoms, chemical reduction, and surface passivation are found to alter the band gap, spectral position, and emission pathways of CQDs. Despite extensive studies, fundamental understanding of structure-property relationship remains unclear due to the inhomogeneity in chemical structure and a complex emission mechanism for CQDs.

This …

Study Of The Effect Of Steric Bulk Of Side Chains On The Properties Of Conjugated Polymers, Bei Zhang

Theses and Dissertations--Chemistry

Donor-acceptor conjugated polymers opened a new era for conjugated polymer research due to the abundant selection and combination of different conjugated units. This class of polymers function as semiconductor materials with potential application in plastic consumer electronics. The frontier molecular orbital energies of the polymers are generally determined by the selection of donor and acceptor units in the backbone structure, and their substituents. The side chains attached to the backbone not only affect the solubility of the materials, but also their self-assembly and morphological characteristics, which indirectly govern optoelectronic properties. It is important therefore to consider backbone architectures and the …

Catalytic Conversion Of Monosaccharides Into 5-(Hydroxymethyl)Furfural In Ionic Liquids Using Aluminum Complexes Bearing Bidentate (Aminomethyl)Phenolate Ligands, Daudi Sayialel Saang'onyo

Theses and Dissertations--Chemistry

Currently, the major sources of fuel, energy, and chemicals are nonrenewable fossil resources such as petroleum, natural gas, and coal. Additionally, petroleum is used for the production of most transportation fuels and for the production of about 95% of organic chemicals. However, the production and use of non-renewable fossil fuels are unsustainable. For economic and environmental sustainability, there is a need to search for new and/or renewable resources and technologies for energy, fuels, and chemicals production that have the potential of effectively substituting fossil resources. In this context, lignocellulosic biomass is one of the candidates that meet these requirements due …

Heterogeneous Catalytic Deoxygenation Of Lipids To Fuel-Like Hydrocarbons Over Improved Bimetallic Nickel Catalysts, Ryan Andrew Loe

Theses and Dissertations--Chemistry

Diminishing petroleum reserves and environmental considerations have strengthened the demand for developing renewable fuel technologies. One alternative is deoxygenating plant oils, animal fats, and waste lipid streams to fuel-like hydrocarbons. These fuels offer a drop-in replacement to petroleum products while potentially becoming carbon neutral, satisfying both fuel and environmental concerns. This fuel is obtained through catalytic deoxygenation via either hydrodeoxygenation (HDO) or decarboxylation/ decarbonylation (deCO_x). HDO requires problematic sulfided catalysts and extreme hydrogen pressures to convert lipids to fuel-like hydrocarbons. Therefore, this work focuses on the deCO_x pathway, where hydrogen is not required for deoxygenation to take …

Design And Synthesis Of Functional Organic Materials, Anthony Joseph Petty Ii

Theses and Dissertations--Chemistry

Control of solid state ordering in conjugated small molecules is paramount to the continued development and implementation of organic materials in electronic devices. However, there exists no reliable method on which to predicatively determine how a change to the molecular structure will impact the solid-state packing. As such, the molecule must be synthesized before its solid-state packing can be definitively evaluated. However, once the packing structure of a material is known there exist both qualitative structure- function relationships derived from the literature, as well as quantitative computational methods that can be employed to suggest if a material will perform well …

Aqueous Photochemistry Of 2-Oxocarboxylic Acids, Alexis Eugene

Theses and Dissertations--Chemistry

Atmospheric aerosols affect climate change by altering the energy balance of the atmosphere, and public health due to their variable chemical composition, size, and shape. While the formation of secondary organic aerosol (SOA) from gas phase precursors is relatively well understood, it does not account for the abundance of SOA observed during field measurements. Recently it has become apparent that in-aerosol aqueous chemical reactions likely provide some of the missing sources of SOA production, and many studies of aqueous phase processes are underway.

This work explores the fates of the simplest 2-oxocarboxylic acids, glyoxylic acid (GA) and pyruvic acid (PA), …

The Role Of Catalytic Residue PKA On The Hydrolysis/Transglycosylation Partition In Family 3 Β-Glucosidases, Inacrist Geronimo, Christina M. Payne, Mats Sandgren

Chemical and Materials Engineering Faculty Publications

β-Glucosidases (βgls) primarily catalyze the hydrolysis of the terminal glycosidic bond at the non-reducing end of β-glucosides, although glycosidic bond synthesis (called transglycosylation) can also occur in the presence of another acceptor. In the final reaction step, the glucose product or another substrate competes with water for transfer to the glycosyl-enzyme intermediate. The factors governing the balance between the two pathways are not fully known; however, the involvement of ionizable residues in binding and catalysis suggests that their pK_a may play a role. Through constant pH molecular dynamics simulations of a glycoside hydrolase Family 3 (GH3) βgl, we …

Fluoroethoxy-1,4-Diphenethylpiperidine And Piperazine Derivatives: Potent And Selective Inhibitors Of [3H]Dopamine Uptake At The Vesicular Monoamine Transporter-2, Emily R. Hankosky, Shyam R. Joolakanti, Justin R. Nickell, Venumadhav Janganati, Linda P. Dwoskin, Peter A. Crooks

Pharmaceutical Sciences Faculty Publications

A small library of fluoroethoxy-1,4-diphenethyl piperidine and fluoroethoxy-1,4-diphenethyl piperazine derivatives were designed, synthesized and evaluated for their ability to inhibit [³H]dopamine (DA) uptake at the vesicular monoamine transporter-2 (VMAT2) and dopamine transporter (DAT), [³H]serotonin (5-HT) uptake at the serotonin transporter (SERT), and [³H]dofetilide binding at the human-ether-a-go-go-related gene (hERG) channel. The majority of the compounds exhibited potent inhibition of [³H]DA uptake at VMAT2, with Ki values in the nanomolar range (K_i = 0.014–0.073 μM). Compound 15d exhibited the highest affinity (K_i = 0.014 μM) at VMAT2, and had 160-, 5-, …

Layer-By-Layer Assembled Membranes With Immobilized Porins, Sebastián Hernández, Cassandra Porter, Xinyi Zhang, Yinan Wei, Dibakar Bhattacharyya

Chemical and Materials Engineering Faculty Publications

New and advanced opportunities are arising for the synthesis and functionalization of membranes with selective separation, reactivity, and stimuli-responsive behavior. One such advancement is the integration of bio-based channels in membrane technologies. By a layer-by-layer (LbL) assembly of polyelectrolytes, outer membrane protein F trimers (OmpF) or “porins” from Escherichia coli with central pores ∼2 nm in diameter at their opening and ∼0.7 × 1.1 nm at their constricted region are immobilized within the pores of poly(vinylidene fluoride) microfiltration membranes, in contrast to traditional ruptured lipid bilayer or vesicle processes. These OmpF-membranes demonstrate selective rejection of non-charged organics over ionic solutes, …

Synthesis And Characterization Of Thermoresponsive Hydrogels Based On N-Isopropylacrylamide Crosslinked With 4,4′-Dihydroxybiphenyl Diacrylate, Shuo Tang, Martha Floy, Rohit Bhandari, Manjula Sunkara, Andrew J. Morris, Thomas D. Dziubla, J. Zach Hilt

Chemical and Materials Engineering Faculty Publications

A novel crosslinker [4,4′-dihydroxybiphenyl diacrylate (44BDA)] was developed, and a series of temperature-responsive hydrogels were synthesized through free radical polymerization of N-isopropylacrylamide (NIPAAm) with 44BDA. The temperature-responsive behavior of the resulting gels was characterized by swelling studies, and the lower critical solution temperature (LCST) of the hydrogels was characterized through differential scanning calorimetry. Increased content of 44BDA led to a decreased swelling ratio and shifted the LCST to lower temperatures. These novel hydrogels also displayed resiliency through multiple swelling–deswelling cycles, and their temperature responsiveness was reversible. The successful synthesis of NIPAAm-based hydrogels crosslinked with 44BDA has led to a …

Process For Detection Of Alzheimer's Disease From A Serum Sample, Mark A. Lovell, Bert C. Lynn

Chemistry Faculty Patents

Disclosed is a method of detecting a concentration of a biomarker in a human subject having or being at risk of developing Alzheimer's disease or Mild Cognitive Impairment (MCI). Also disclosed is a process for detecting a concentration of a biomarker in a human subject having or being at risk of developing Alzheimer's disease or Mild Cognitive Impairment (MCI) comprising (a) detecting a first concentration of lipocalin-PDS/TTR complex in a blood sample or urine sample from the subject, (b) determining a second concentration of PDS/TTR complex in a blood sample or urine sample from an unaffected individual, and ( c) …

Vibronically Coherent Ultrafast Triplet-Pair Formation And Subsequent Thermally Activated Dissociation Control Efficient Endothermic Singlet Fission, Hannah L. Stern, Alexandre Cheminal, Shane R. Yost, Katharina Broch, Sam L. Bayliss, Kai Chen, Maxim Tabachnyk, Karl J. Thorley, Neil Greenham, Justin Hodgkiss, John E. Anthony, Martin Head-Gordon, Andrew J. Musser, Akshay Rao, Richard H. Friend

Chemistry Faculty Publications

Singlet exciton fission (SF), the conversion of one spin-singlet exciton (S₁) into two spin-triplet excitons (T₁), could provide a means to overcome the Shockley–Queisser limit in photovoltaics. SF as measured by the decay of S₁ has been shown to occur efficiently and independently of temperature, even when the energy of S₁ is as much as 200 meV less than that of 2T₁. Here we study films of triisopropylsilyltetracene using transient optical spectroscopy and show that the triplet pair state (TT), which has been proposed to mediate singlet fission, forms on ultrafast timescales …

Organelle-Specific Single-Molecule Imaging Of Α4Β2 Nicotinic Receptors Reveals The Effect Of Nicotine On Receptor Assembly And Cell-Surface Trafficking, Ashley M. Fox-Lee, Faruk H. Moonschi, Christopher I. Richards

Chemistry Faculty Publications

Nicotinic acetylcholine receptors (nAChRs) assemble in the endoplasmic reticulum (ER) and traffic to the cell surface as pentamers composed of α and β subunits. Many nAChR subtypes can assemble with varying subunit ratios, giving rise to multiple stoichiometries exhibiting different subcellular localization and functional properties. In addition to the endogenous neurotransmitter acetylcholine, nicotine also binds and activates nAChRs and influences their trafficking and expression on the cell surface. Currently, no available technique can specifically elucidate the stoichiometry of nAChRs in the ER versus those in the plasma membrane. Here, we report a method involving single-molecule fluorescence measurements to determine the …

High-Statistics Β+/Ec-Decay Study Of 122Xe, B. Jigmeddorj, P. E. Garrett, C. A. Andreoiu, G. C. Ball, T. Bruhn, D. S. Cross, A. B. Garnsworthy, B. Hadinia, M. Moukaddam, J. Park, J. L. Pore, A. J. Radich, M. M. Rajabali, E. T. Rand, U. Rizwan, C. E. Svensson, P. Voss, Z. Wang, J. L. Wood, Steven W. Yates

Chemistry Faculty Publications

Low-lying excited states of ¹²²Xe have been studied via the β⁺/EC decay of ¹²²Cs with the 8π γ-ray spectrometer at the TRIUMF Isotope Separator and Accelerator facility. The data collected have enabled the observation of new in-band transitions in the excited 0⁺ state bands. In addition, the 2⁺ members of the second 0⁺ and third 0⁺ state bands have been firmly confirmed by angular correlation analysis.

Unmanned Aerial Systems For Monitoring Trace Tropospheric Gases, Travis J. Schuyler, Marcelo I. Guzman

Chemistry Faculty Publications

The emission of greenhouse gases (GHGs) has changed the composition of the atmosphere during the Anthropocene. Accurately documenting the sources and magnitude of GHGs emission is an important undertaking for discriminating the contributions of different processes to radiative forcing. Currently there is no mobile platform that is able to quantify trace gases at altitudes(UASs) can be deployed on-site in minutes and can support the payloads necessary to quantify trace gases. Therefore, current efforts combine the use of UASs available on the civilian market with inexpensively designed analytical systems for monitoring atmospheric trace gases. In this context, this perspective introduces the …

Spectroscopic And Computational Characterization Of Lanthanum-Mediated C-H And N-H Bond Activation Of Amines, Silver Nyambo, Yuchen Zhang, Dong-Sheng Yang

Commonwealth Computational Summit

Metal-mediated bond activation of small organic and inorganic molecules plays critical roles in chemical transformation of small molecules into value-added products.

This is because few of such chemical reactions would occur under mild conditions without the metal activation.

In this work, lanthanum atom reactions with alkylamines are carried out in a laser-ablation supersonic molecular beam source; C-H and N-H bond activation in these species is investigated.

The reaction products are observed with photoionization time-of-flight mass spectrometry and characterized by mass-analyzed threshold ionization (MATI) spectroscopy and theoretical calculations.

Adiabatic ionization energy and metal-ligand and ligand-based vibrational frequencies of several short-lived lanthanum …

Differentiating The Impact Of Nitrogen Chemical States On Optical Properties Of Nitrogen-Doped Graphene Quantum Dots, Timothy Pillar-Little, Doo Young Kim

Chemistry Faculty Publications

The optical properties of top-down synthesized oxidized graphene quantum dots (ox-GQDs) and nitrogen-incorporating graphene quantum dots (N-GQDs) along a range of hydrothermal treatment temperatures were observed. By controlling the hydrothermal treatment temperature, different chemical states of nitrogen atoms were incorporated into GQDs. Below 150 °C, edge-terminating amines and amides dominated the nitrogen content of N-GQDs. Above 150 °C, nitrogen was primarily present in the forms of pyridinic, pyrrolic and quaternary N. In addition to the absorbance and emission profiles of ox-GQDs and N-GQDs, pH-dependent emission spectra were collected to probe chemical states of nitrogen atoms and investigate the relationship between …

A Stimulated Emission Study Of The Ground State Bending Levels Of Bh2 Through The Barrier To Linearity And Ab Initio Calculations Of Near-Spectroscopic Accuracy, Bing Jin, Dennis J. Clouthier, Riccardo Tarroni

Chemistry Faculty Publications

The ground state bending levels of ¹¹BH₂ have been studied experimentally using a combination of low-resolution emission spectroscopy and high-resolution stimulated emission pumping (SEP) measurements. The data encompass the energy range below, through, and above the calculated position of the barrier to linearity. For the bending levels (0,3,0) and above, the data show substantial K-reordering, with the K"_a = 1 levels falling well below those with K"_a = 0. A comparison of the high-resolution rotationally resolved SEP data to our own very high level ab initio calculations of the rovibronic energy levels shows agreement approaching …

Design, Synthesis, And Biological Activity Of 5'-Phenyl-1,2,5,6-Tetrahydro-3,3'-Bipyridine Analogues As Potential Antagonists Of Nicotinic Acetylcholine Receptors, Yafei Jin, Xiaoqin Huang, Roger L. Papke, Emily M. Jutkiewicz, Hollis D Showalter, Chang-Guo Zhan

Pharmaceutical Sciences Faculty Publications

Starting from a known non-specific agonist (1) of nicotinic acetylcholine receptors (nAChRs), rationally guided structural-based design resulted in the discovery of a small series of 5′-phenyl-1,2,5,6-tetrahydro-3,3′-bipyridines (3a – 3e) incorporating a phenyl ring off the pyridine core of 1. The compounds were synthesized via successive Suzuki couplings on a suitably functionalized pyridine starting monomer 4 to append phenyl and pyridyl substituents off the 3- and 5-positions, respectively, and then make subsequent modifications on the flanking pyridyl ring to provide target compounds. Compound 3a is a novel antagonist which is highly selective for α3β4 nAChR (K_i = 123 nM) …

Selective Inhibitors Of Human Mpges-1 From Structure-Based Computational Screening, Ziyuan Zhou, Yaxia Yuan, Shuo Zhou, Kai Ding, Fang Zheng, Chang-Guo Zhan

Molecular Modeling and Biopharmaceutical Center Faculty Publications

Human mPGES-1 is recognized as a promising target for next generation of anti-inflammatory drugs. Although various mPGES-1 inhibitors have been reported in literature, few have entered clinical trials and none has been proven clinically useful so far. It is highly desired for developing the next generation of therapeutics for inflammation-related diseases to design and discover novel inhibitors of mPGES-1 with new scaffolds. Here, we report the identification of a series of new, potent and selective inhibitors of human mPGES-1 with diverse scaffolds through combined computational and experimental studies. The computationally modeled binding structures of these new inhibitors with mPGES-1 provide …

Lanthanum-Mediated Dehydrogenation Of 1- And 2-Butynes: Spectroscopy And Formation Of La(C4H4) Isomers, Wenjin Cao, Dilrukshi C. Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-butyne and 2-butyne are carried out in a laser-vaporization molecular beam source. Both reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butynes. The dehydrogenated species La(C₄H₄) is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of La(C₄H₄) produced from the two reactions exhibit two identical transitions, each consisting of a strong origin band and several vibrational intervals. The two transitions are assigned to the ionization of two isomers: La(η⁴–CH₂CCCH …

Real-Time Sensing Of Single-Ligand Delivery With Nanoaperture-Integrated Microfluidic Devices, W. Elliott Martin, Ning Ge, Bernadeta R. Srijanto, Emily Furnish, C. Patrick Collier, Christine A. Trinkle, Christopher I. Richards

Chemistry Faculty Publications

The measurement of biological events on the surface of live cells at the single-molecule level is complicated by several factors including high protein densities that are incompatible with single-molecule imaging, cellular autofluorescence, and protein mobility on the cell surface. Here, we fabricated a device composed of an array of nanoscale apertures coupled with a microfluidic delivery system to quantify single-ligand interactions with proteins on the cell surface. We cultured live cells directly on the device and isolated individual epidermal growth factor receptors (EGFRs) in the apertures while delivering fluorescently labeled epidermal growth factor. We observed single ligands binding to EGFRs, …

Level Lifetimes And The Structure Of 134Xe From Inelastic Neutron Scattering, Erin E. Peters, Anagha Chakraborty, Benjamin P. Crider, S. F. Ashley, E. Elhami, S. F. Hicks, A. Kumar, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, J. N. Orce, Francisco M. Prados-Estévez, Steven W. Yates

Chemistry Faculty Publications

The level structure of ¹³⁴Xe was studied with the inelastic neutron scattering reaction followed by γ-ray detection. A number of level lifetimes were determined for the first time with the Doppler-shift attenuation method and the low-lying excited states were characterized. From this new spectroscopic information, the third excited state, a 0⁺ level which had only been observed in a previous inelastic neutron scattering study, was verified. Reduced transition probabilities were calculated; comparisons were drawn with a vibrational description of the nucleus and found lacking. The 3⁻ octupole phonon has been confirmed, and the complete negative-parity multiplet …

The Entangled Triplet Pair State In Acene And Heteroacene Materials, Chaw Keong Yong, Andrew J. Musser, Sam L. Bayliss, Steven Lukman, Hiroyuki Tamura, Olga Bubnova, Rawad Hallani, Aurélie Meneau, Roland Resel, Munetaka Maruyama, Shu Hotta, Laura M. Herz, David Beljonne, John E. Anthony, Jenny Clark, Henning Sirringhaus

Chemistry Faculty Publications

Entanglement of states is one of the most surprising and counter-intuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which mediates the spin-conserving fission of one spin-0 singlet exciton into two spin-1 triplet excitons. Despite long theoretical and experimental exploration, the nature of the triplet-pair state and inter-triplet interactions have proved elusive. Here we use a range of organic semiconductors that undergo singlet exciton fission to reveal the photophysical properties of entangled triplet-pair states. We find that the triplet pair is bound with respect to …

Mechanism-Informed Refinement Reveals Altered Substrate-Binding Mode For Catalytically Competent Nitroreductase, Warintra Pitsawong, Chad A. Haynes, Ronald L. Koder, David W. Rodgers, Anne-Frances Miller

Chemistry Faculty Publications

Nitroreductase from Enterobacter cloacae (NR) reduces diverse nitroaromatics including herbicides, explosives and prodrugs, and holds promise for bioremediation, prodrug activation and enzyme-assisted synthesis. We solved crystal structures of NR complexes with bound substrate or analog for each of its two half-reactions. We complemented these with kinetic isotope effect (KIE) measurements elucidating H-transfer steps essential to each half-reaction. KIEs indicate hydride transfer from NADH to the flavin consistent with our structure of NR with the NADH analog nicotinic acid adenine dinucleotide (NAAD). The KIE on reduction of p-nitrobenzoic acid (p-NBA) also indicates hydride transfer, and requires revision of …

Ionic Thermoelectric Paper, Fei Jiao, Ali Naderi, Dan Zhao, Joshua Schlueter, Maryam Shahi, Jonas Sundström, Hjalmar Granberg, Jesper Edberg, Ujwala Ail, Joseph W. Brill, Tom Lindström, Magnus Berggren, Xavier Crispin

Physics and Astronomy Faculty Publications

Ionic thermoelectric materials, for example, polyelectrolytes such as polystyrene sulfonate sodium (PSSNa), constitute a new class of materials which are attracting interest because of their large Seebeck coefficient and the possibility that they could be used in ionic thermoelectric SCs (ITESCs) and field effect transistors. However, pure polyelectrolyte membranes are not robust or flexible. In this paper, the preparation of ionic thermoelectric paper using a simple, scalable and cost-effective method is described. After a composite was fabricated with nanofibrillated cellulose (NFC), the resulting NFC–PSSNa paper is flexible and mechanically robust, which is desirable if it is to be used in …

Neutron Scattering Cross Section Measurements For 56Fe, Anthony Paul D. Ramirez, J. Vanhoy, S. F. Hicks, Marcus T. Mcellistrem, Erin E. Peters, Sharmistha Mukhopadhyay, T. D. Harrison, T. J. Howard, D. T. Jackson, P. D. Lenzen, T. D. Nguyen, R. L. Pecha, B. G. Rice, B. K. Thompson, Steven W. Yates

Chemistry Faculty Publications

Elastic and inelastic differential cross sections for neutron scattering from ⁵⁶Fe have been measured for several incident energies from 1.30 to 7.96 MeV at the University of Kentucky Accelerator Laboratory. Scattered neutrons were detected using a C₆D₆ liquid scintillation detector using pulse-shape discrimination and time-of-flight techniques. The deduced cross sections have been compared with previously reported data, predictions from evaluation databases ENDF, JENDL, and JEFF, and theoretical calculations performed using different optical model potentials using the TALYS and EMPIRE nuclear reaction codes. The coupled-channel calculations based on the vibrational and soft-rotor models are found to describe …

Crystal Structure Of 4,4′-Bis­­[3-(Piperidin-1-Yl)Prop-1-Yn-1-Yl]-1,1′-Biphen­Yl, Anqi Walbaum, E. Kim Fifer, Sean R. Parkin, Peter A. Crooks

Chemistry Faculty Publications

The title compound, C₂₈H₃₂N₂, (I), is one of a second generation of compounds designed and synthesized based on a very potent and selective α9α10 nicotinic acetyl­choline receptor antagonist ZZ161C {1,1′-[[1,1′-biphen­yl]-4,4′-diylbis(prop-2-yne-3,1-di­yl)]bis­(3,4-di­methyl­pyridin-1-ium) bromide}, which has shown analgesic effects in a chemotherapy-induced neuropathy animal model. Compound (I) was synthesized by the reaction of 4,4′-bis­(3-bromo­prop-1-yn-1-yl)-1,1′-biphenyl with piperidine at room temperature in aceto­nitrile. The single-crystal used for X-ray analysis was obtained by dissolving (I) in a mixture of di­chloro­methane and methanol, followed by slow evaporation of the solvent. In the crystal of (I), the biphenyl moiety has a twisted …

Regioselective Baeyer–Villiger Oxidation Of Lignin Model Compounds With Tin Beta Zeolite Catalyst And Hydrogen Peroxide, John Adam Jennings, Sean R. Parkin, Eric Munson, Sean Delaney, Julie L. Calahan, Mark Isaacs, Kunlun Hong, Mark Crocker

Chemistry Faculty Publications

Lignin depolymerization represents a promising approach to the sustainable production of aromatic molecules. One potential approach to the stepwise depolymerization of lignin involves oxidation of the benzylic alcohol group in β-O-4 and β-1 linkages, followed by Baeyer–Villiger oxidation (BVO) of the resulting ketones and subsequent ester hydrolysis. Towards this goal, BVO reactions were performed on 2-adamantanone, a series of acetophenone derivatives, and lignin model compounds using a tin beta zeolite/hydrogen peroxide biphasic system. XRD, ¹¹⁹Sn MAS NMR spectroscopy, DRUVS and XPS were used to determine tin speciation in the catalyst, the presence of both framework Sn and extra framework …

Real-Time Atomistic Observation Of Structural Phase Transformations In Individual Hafnia Nanorods, Bethany M. Hudak, Sean W. Depner, Gregory R. Waetzig, Anjana Talapatra, Raymundo Arroyave, Sarbajit Banerjee, Beth S. Guiton

Chemistry Faculty Publications

High-temperature phases of hafnium dioxide have exceptionally high dielectric constants and large bandgaps, but quenching them to room temperature remains a challenge. Scaling the bulk form to nanocrystals, while successful in stabilizing the tetragonal phase of isomorphous ZrO₂, has produced nanorods with a twinned version of the room temperature monoclinic phase in HfO₂. Here we use in situ heating in a scanning transmission electron microscope to observe the transformation of an HfO₂ nanorod from monoclinic to tetragonal, with a transformation temperature suppressed by over 1000°C from bulk. When the nanorod is annealed, we observe with …