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198 results on '"O'Keefe, Christopher A."'

1. Displacive Jahn--Teller transition in NaNiO$_2$

Author

Nagle-Cocco, Liam Agostino Vincenzo, Genreith-Schriever, Annalena R., Steele, James M. A., Tacconis, Camilla, Bocarsly, Joshua D., Mathon, Olivier, Neuefeind, Joerg C., Liu, Jue, O'Keefe, Christopher A., Goodwin, Andrew L., Grey, Clare P., Evans, John S. O., and Dutton, Siân E.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

Below its Jahn--Teller transition temperature, $T_\mathrm{JT}$, NaNiO$_2$ has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO$_6$ and Jahn-Teller-distorted NiO$_6$ octahedra. Above $T_\mathrm{JT}$ where NaNiO$_2$ is rhombohedral, diffraction measurements show the absence of a cooperative Jahn-Teller distortion, accompanied by an increase in the unit cell volume. Using neutron total scattering, solid-state Nuclear Magnetic Resonance (NMR), and extended X-ray absorption fine structure (EXAFS) experiments as local probes of the structure we find direct evidence for a displacive, as opposed to order-disorder Jahn-Teller transition at $T_\mathrm{JT}$. This is supported by \textit{ab initio} molecular dynamics (AIMD) simulations. To our knowledge this study is the first to show a displacive Jahn-Teller transition in any material using direct observations with local probe techniques., Comment: Under review. For SI, email the authors

Published
2024

2. Publisher Correction: Unlocking Li superionic conductivity in face-centred cubic oxides via face-sharing configurations

Author

Chen, Yu, Lun, Zhengyan, Zhao, Xinye, Koirala, Krishna Prasad, Li, Linze, Sun, Yingzhi, O’Keefe, Christopher A, Yang, Xiaochen, Cai, Zijian, Wang, Chongmin, Ji, Huiwen, Grey, Clare P, Ouyang, Bin, and Ceder, Gerbrand

Subjects
Inorganic Chemistry, Chemical Sciences, Physical Sciences, Good Health and Well Being, Nanoscience & Nanotechnology
Abstract

Correction to: Nature Materialshttps://doi.org/10.1038/s41563-024-01800-8, published online 2 February 2024. In the version of the article initially published, the x axes in Figs. 2b,d and 5a,b originally read “T−1 (K−1)” and have now been amended to “1000 T−1 (K−1)” in the HTML and PDF versions of the article.

Published
2024

3. Unlocking Li superionic conductivity in face-centred cubic oxides via face-sharing configurations

Author

Chen, Yu, Lun, Zhengyan, Zhao, Xinye, Koirala, Krishna Prasad, Li, Linze, Sun, Yingzhi, O’Keefe, Christopher A, Yang, Xiaochen, Cai, Zijian, Wang, Chongmin, Ji, Huiwen, Grey, Clare P, Ouyang, Bin, and Ceder, Gerbrand

Subjects
Chemical Sciences, Physical Chemistry, Engineering, Physical Sciences, Materials Engineering, Nanoscience & Nanotechnology
Abstract

Oxides with a face-centred cubic (fcc) anion sublattice are generally not considered as solid-state electrolytes as the structural framework is thought to be unfavourable for lithium (Li) superionic conduction. Here we demonstrate Li superionic conductivity in fcc-type oxides in which face-sharing Li configurations have been created through cation over-stoichiometry in rocksalt-type lattices via excess Li. We find that the face-sharing Li configurations create a novel spinel with unconventional stoichiometry and raise the energy of Li, thereby promoting fast Li-ion conduction. The over-stoichiometric Li-In-Sn-O compound exhibits a total Li superionic conductivity of 3.38 × 10-4 S cm-1 at room temperature with a low migration barrier of 255 meV. Our work unlocks the potential of designing Li superionic conductors in a prototypical structural framework with vast chemical flexibility, providing fertile ground for discovering new solid-state electrolytes.

Published
2024

5. Structural and Dynamic Disorder, Not Ionic Trapping, Controls Charge Transport in Highly Doped Conducting Polymers

Author

Jacobs, Ian E, D’Avino, Gabriele, Lemaur, Vincent, Lin, Yue, Huang, Yuxuan, Chen, Chen, Harrelson, Thomas F, Wood, William, Spalek, Leszek J, Mustafa, Tarig, O’Keefe, Christopher A, Ren, Xinglong, Simatos, Dimitrios, Tjhe, Dion, Statz, Martin, Strzalka, Joseph W, Lee, Jin-Kyun, McCulloch, Iain, Fratini, Simone, Beljonne, David, and Sirringhaus, Henning

Subjects
Engineering, Macromolecular and Materials Chemistry, Materials Engineering, Chemical Sciences, General Chemistry, Chemical sciences
Abstract

Doped organic semiconductors are critical to emerging device applications, including thermoelectrics, bioelectronics, and neuromorphic computing devices. It is commonly assumed that low conductivities in these materials result primarily from charge trapping by the Coulomb potentials of the dopant counterions. Here, we present a combined experimental and theoretical study rebutting this belief. Using a newly developed doping technique based on ion exchange, we prepare highly doped films with several counterions of varying size and shape and characterize their carrier density, electrical conductivity, and paracrystalline disorder. In this uniquely large data set composed of several classes of high-mobility conjugated polymers, each doped with at least five different ions, we find electrical conductivity to be strongly correlated with paracrystalline disorder but poorly correlated with ionic size, suggesting that Coulomb traps do not limit transport. A general model for interacting electrons in highly doped polymers is proposed and carefully parametrized against atomistic calculations, enabling the calculation of electrical conductivity within the framework of transient localization theory. Theoretical calculations are in excellent agreement with experimental data, providing insights into the disorder-limited nature of charge transport and suggesting new strategies to further improve conductivities.

Published
2022

6. Structural and dynamic disorder, not ionic trapping, controls charge transport in highly doped conducting polymers

Author

Jacobs, Ian E., D'Avino, Gabriele, Lemaur, Vincent, Lin, Yue, Huang, Yuxuan, Chen, Chen, Harrelson, Thomas, Wood, William, Spalek, Leszek J., Mustafa, Tarig, O'Keefe, Christopher A., Ren, Xinglong, Simatos, Dimitrios, Tjhe, Dion, Statz, Martin, Strzalka, Joseph, Lee, Jin-Kyun, McCulloch, Iain, Fratini, Simone, Beljonne, David, and Sirringhaus, Henning

Subjects
Condensed Matter - Materials Science
Abstract

Doped organic semiconductors are critical to emerging device applications, including thermoelectrics, bioelectronics, and neuromorphic computing devices. It is commonly assumed that low conductivities in these materials result primarily from charge trapping by the Coulomb potentials of the dopant counter-ions. Here, we present a combined experimental and theoretical study rebutting this belief. Using a newly developed doping technique, we find the conductivity of several classes of high-mobility conjugated polymers to be strongly correlated with paracrystalline disorder but poorly correlated with ionic size, suggesting that Coulomb traps do not limit transport. A general model for interacting electrons in highly doped polymers is proposed and carefully parameterized against atomistic calculations, enabling the calculation of electrical conductivity within the framework of transient localisation theory. Theoretical calculations are in excellent agreement with experimental data, providing insights into the disordered-limited nature of charge transport and suggesting new strategies to further improve conductivities.

Published
2021
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7. Displacive Jahn–Teller Transition in NaNiO2.

Author

Nagle-Cocco, Liam A. V., Genreith-Schriever, Annalena R., Steele, James M. A., Tacconis, Camilla, Bocarsly, Joshua D., Mathon, Olivier, Neuefeind, Joerg C., Liu, Jue, O'Keefe, Christopher A., Goodwin, Andrew L., Grey, Clare P., Evans, John S. O., and Dutton, Siân E.

Published
2024
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8. Risperidone versus olanzapine among patients with schizophrenia participating in supported employment: Eighteen-month outcomes

Author

Noordsy, Douglas L, Glynn, Shirley M, Sugar, Catherine A, O'Keefe, Christopher D, and Marder, Stephen R

Subjects
Biological Psychology, Pharmacology and Pharmaceutical Sciences, Biomedical and Clinical Sciences, Psychology, Clinical Trials and Supportive Activities, Mental Health, Clinical Research, Brain Disorders, Schizophrenia, Serious Mental Illness, 6.1 Pharmaceuticals, Evaluation of treatments and therapeutic interventions, Mental health, Adult, Antipsychotic Agents, Benzodiazepines, Double-Blind Method, Employment, Supported, Female, Humans, Male, Middle Aged, Olanzapine, Outcome Assessment, Health Care, Risperidone, Weight Gain, Antipsychotic medication, Supported employment, BMI, Medical and Health Sciences, Psychology and Cognitive Sciences, Psychiatry, Clinical sciences, Clinical and health psychology
Abstract

This study compares the efficacy and tolerability of olanzapine versus risperidone among patients with schizophrenia who are established in outpatient psychiatric care and entering supported employment. A multicenter, randomized, double-blind trial was conducted among 107 outpatients with schizophrenia, who were cross-titrated to flexible dose risperidone or olanzapine over 2 weeks. Clinical endpoints included time to hospitalization and persistence on assigned medication. Weight, laboratory tests, psychopathology, neurologic side effects, social adjustment and role functioning were assessed at 3-6 month intervals. Data were analyzed first by randomized treatment, and then reassessed controlling for prior medication treatment. The proportion of patients on assigned medication at 18 months was 30.9% for risperidone and 37.3% for olanzapine. Mean doses were 6.4 ± 3.2 mg daily for risperidone, and 17.0 ± 5.0 mg daily for olanzapine. The groups did not differ significantly in time to medication discontinuation, first hospitalization or first employment. There were few differences in psychopathology, laboratory, or neurological assessments between groups at 18 months. Patients randomized to olanzapine gained modestly more weight. Controlling for pre-randomization medication suggested improvement in some aspects of psychopathology from switching medications; however, switching from olanzapine to risperidone was associated with more hospitalizations. Risperidone and olanzapine have similar efficacy and tolerability in patients with schizophrenia who are participating in supported employment. Randomization to olanzapine was associated with more weight gain, but randomization from olanzapine to risperidone appeared to be associated with a greater likelihood of hospitalization. Careful monitoring of metabolic effects and participation in supported employment may have contributed to minimal weight gain and metabolic effects.

Published
2017

9. Displacive Jahn–Teller Transition in NaNiO2

Author

Nagle-Cocco, Liam A. V., Genreith-Schriever, Annalena R., Steele, James M. A., Tacconis, Camilla, Bocarsly, Joshua D., Mathon, Olivier, Neuefeind, Joerg C., Liu, Jue, O’Keefe, Christopher A., Goodwin, Andrew L., Grey, Clare P., Evans, John S. O., and Dutton, Siân E.

Abstract

Below its Jahn–Teller transition temperature, TJT, NaNiO2has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO6and Jahn–Teller-distorted NiO6octahedra. Above TJTwhere NaNiO2is rhombohedral, diffraction measurements show the absence of a cooperative Jahn–Teller distortion, accompanied by an increase in the unit cell volume. Using neutron total scattering, solid-state Nuclear Magnetic Resonance (NMR), and extended X-ray absorption fine structure (EXAFS) experiments as local probes of the structure we find direct evidence for a displacive, as opposed to order–disorder, Jahn–Teller transition at TJT. This is supported by ab initiomolecular dynamics (AIMD) simulations. To our knowledge this study is the first to show a displacive Jahn–Teller transition in any material using direct observations with local probe techniques.

Published
2024
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11. Improving long-term capacity retention of NMC811 via lithium aluminate coatings using mixed-metal alkoxides.

Author

Riesgo-González, Víctor, O'Keefe, Christopher A., Grey, Clare P., and Wright, Dominic S.

Abstract

Ni-rich LiNixMnyCozO2 (NMC) materials such as NMC811 (80% Ni) are promising Li-ion battery cathodes due to their high energy density and low cost. However, their reactive surfaces pose a practical challenge for their handling and storage, due to their fast degradation under operation or storage in ambient air. To tackle these problems, lithium aluminum alkoxides are used here for the first time to coat NMC811 with lithium aluminate (Li1−xAl1+x/3O2). This method allows the controlled deposition of lithium aluminates on the surface of NMC811 by hydrolysis of the alkoxide precursor with transition metal TM(O)–OH surface groups. Of the series of alkoxides investigated, Li[Al(OtBu)4] was found to have the best coating/deposition properties in terms of solubility, thermal decomposition, phases formed and reactivity with NMC811. The effects of different NMC811 particle morphologies and surface treatments on the solution deposition of lithium aluminate were carefully evaluated by testing two different substrates: pristine polycrystalline NMC811 (PC-NMC811) and Al2O3-coated single-crystal NMC811 (SC-NMC811). A 17% increase in capacity retention at C/2 was seen for Li1−xAl1+x/3O2/Al2O3 coated SC-NMC811 compared to Al2O3 coated SC-NMC811 after 100 charge–discharge cycles. Furthermore, coating PC-NMC811 that was degraded by soaking in water led to an impressive recovery of 50% of its C/20 capacity retention after 300 charge–discharge cycles while also showing higher specific capacities (25 mA h g−1 more on the 2nd cycle) due to surface Li enrichment and regeneration of degraded surfaces. This coating method is a significant step forward in the scalable processing of new-generation battery cathodes with higher energy density and longer useful life. [ABSTRACT FROM AUTHOR]

Published
2024
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18. Sodium Borates: Expanding the Electrolyte Selection for Sodium-Ion Batteries

Author

Ould, Darren MC, Menkin, Svetlana, Smith, Holly E, Riesgo-Gonzalez, Victor, Jónsson, Erlendur, O'Keefe, Christopher A, Coowar, Fazlil, Barker, Jerry, Bond, Andrew D, Grey, Clare P, Wright, Dominic S, Menkin, Svetlana [0000-0003-3612-4542], Smith, Holly E [0000-0002-3389-6259], Riesgo-Gonzalez, Victor [0000-0002-2433-8562], Jónsson, Erlendur [0000-0002-7776-0484], O'Keefe, Christopher A [0000-0003-3115-0768], Bond, Andrew D [0000-0002-1744-0489], Grey, Clare P [0000-0001-5572-192X], Wright, Dominic S [0000-0002-9952-3877], and Apollo - University of Cambridge Repository

Subjects
Batteries, Electrolytes, SEI, Main Group Synthesis, Sodium-Ion Batteries
Abstract

Sodium-ion batteries (SIBs) are a promising grid-level storage technology due to the abundance and low cost of sodium. The development of new electrolytes for SIBs is imperative since it impacts battery life and capacity. Currently, sodium hexafluorophosphate (NaPF6 ) is used as the benchmark salt, but is highly hygroscopic and generates toxic HF. This work describes the synthesis of a series of sodium borate salts, with electrochemical studies revealing that Na[B(hfip)4 ]⋅DME (hfip=hexafluoroisopropyloxy, Oi PrF ) and Na[B(pp)2 ] (pp=perfluorinated pinacolato, O2 C2 (CF3 )4 ) have excellent electrochemical performance. The [B(pp)2 ]- anion also exhibits a high tolerance to air and water. Both electrolytes give more stable electrode-electrolyte interfaces than conventionally used NaPF6 , as demonstrated by impedance spectroscopy and cyclic voltammetry. Furthermore, they give greater cycling stability and comparable capacity to NaPF6 for SIBs, as shown in commercial pouch cells.

Published
2022

25. Sodium Borates: Expanding the Electrolyte Selection for Sodium‐Ion Batteries

Author

Ould, Darren M. C., primary, Menkin, Svetlana, additional, Smith, Holly E., additional, Riesgo‐Gonzalez, Victor, additional, Jónsson, Erlendur, additional, O'Keefe, Christopher A., additional, Coowar, Fazlil, additional, Barker, Jerry, additional, Bond, Andrew D., additional, Grey, Clare P., additional, and Wright, Dominic S., additional

Published
2022
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29. Formulation of Metal–Organic Framework-Based Drug Carriers by Controlled Coordination of Methoxy PEG Phosphate: Boosting Colloidal Stability and Redispersibility

Author

Chen, Xu, primary, Zhuang, Yunhui, additional, Rampal, Nakul, additional, Hewitt, Rachel, additional, Divitini, Giorgio, additional, O’Keefe, Christopher A., additional, Liu, Xiewen, additional, Whitaker, Daniel J., additional, Wills, John W., additional, Jugdaohsingh, Ravin, additional, Powell, Jonathan J., additional, Yu, Han, additional, Grey, Clare P., additional, Scherman, Oren A., additional, and Fairen-Jimenez, David, additional

Published
2021
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31. 2021 roadmap for sodium-ion batteries

Author

Tapia-Ruiz, Nuria, primary, Armstrong, A Robert, additional, Alptekin, Hande, additional, Amores, Marco A, additional, Au, Heather, additional, Barker, Jerry, additional, Boston, Rebecca, additional, Brant, William R, additional, Brittain, Jake M, additional, Chen, Yue, additional, Chhowalla, Manish, additional, Choi, Yong-Seok, additional, Costa, Sara I R, additional, Crespo Ribadeneyra, Maria, additional, Cussen, Serena A, additional, Cussen, Edmund J, additional, David, William I F, additional, Desai, Aamod V, additional, Dickson, Stewart A M, additional, Eweka, Emmanuel I, additional, Forero-Saboya, Juan D, additional, Grey, Clare P, additional, Griffin, John M, additional, Gross, Peter, additional, Hua, Xiao, additional, Irvine, John T S, additional, Johansson, Patrik, additional, Jones, Martin O, additional, Karlsmo, Martin, additional, Kendrick, Emma, additional, Kim, Eunjeong, additional, Kolosov, Oleg V, additional, Li, Zhuangnan, additional, Mertens, Stijn F L, additional, Mogensen, Ronnie, additional, Monconduit, Laure, additional, Morris, Russell E, additional, Naylor, Andrew J, additional, Nikman, Shahin, additional, O’Keefe, Christopher A, additional, Ould, Darren M C, additional, Palgrave, R G, additional, Poizot, Philippe, additional, Ponrouch, Alexandre, additional, Renault, Stéven, additional, Reynolds, Emily M, additional, Rudola, Ashish, additional, Sayers, Ruth, additional, Scanlon, David O, additional, Sen, S, additional, Seymour, Valerie R, additional, Silván, Begoña, additional, Sougrati, Moulay Tahar, additional, Stievano, Lorenzo, additional, Stone, Grant S, additional, Thomas, Chris I, additional, Titirici, Maria-Magdalena, additional, Tong, Jincheng, additional, Wood, Thomas J, additional, Wright, Dominic S, additional, and Younesi, Reza, additional

Published
2021
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32. 2021 roadmap for sodium-ion batteries

Author

Tapia-Ruiz, Nuria, Armstrong, A. Robert, Alptekin, Hande, Amores, Marco A., Au, Heather, Barker, Jerry, Boston, Rebecca, Brant, William R., Brittain, Jake M., Chen, Yue, Chhowalla, Manish, Choi, Yong-Seok, Costa, Sara I. R., Crespo Ribadeneyra, Maria, Cussen, Serena A., Cussen, Edmund J., David, William I. F., Desai, Aamod, V, Dickson, Stewart A. M., Eweka, Emmanuel, I, Forero-Saboya, Juan D., Grey, Clare P., Griffin, John M., Gross, Peter, Hua, Xiao, Irvine, John T. S., Johansson, Patrik, Jones, Martin O., Karlsmo, Martin, Kendrick, Emma, Kim, Eunjeong, Kolosov, Oleg, V, Li, Zhuangnan, Mertens, Stijn F. L., Mogensen, Ronnie, Monconduit, Laure, Morris, Russell E., Naylor, Andrew J., Nikman, Shahin, O'Keefe, Christopher A., Ould, Darren M. C., Palgrave, R. G., Poizot, Philippe, Ponrouch, Alexandre, Renault, Steven, Reynolds, Emily M., Rudola, Ashish, Sayers, Ruth, Scanlon, David O., Sen, S., Seymour, Valerie R., Silvan, Begona, Sougrati, Moulay Tahar, Stievano, Lorenzo, Stone, Grant S., Thomas, Chris, I, Titirici, Maria-Magdalena, Tong, Jincheng, Wood, Thomas J., Wright, Dominic S., Younesi, Reza, Tapia-Ruiz, Nuria, Armstrong, A. Robert, Alptekin, Hande, Amores, Marco A., Au, Heather, Barker, Jerry, Boston, Rebecca, Brant, William R., Brittain, Jake M., Chen, Yue, Chhowalla, Manish, Choi, Yong-Seok, Costa, Sara I. R., Crespo Ribadeneyra, Maria, Cussen, Serena A., Cussen, Edmund J., David, William I. F., Desai, Aamod, V, Dickson, Stewart A. M., Eweka, Emmanuel, I, Forero-Saboya, Juan D., Grey, Clare P., Griffin, John M., Gross, Peter, Hua, Xiao, Irvine, John T. S., Johansson, Patrik, Jones, Martin O., Karlsmo, Martin, Kendrick, Emma, Kim, Eunjeong, Kolosov, Oleg, V, Li, Zhuangnan, Mertens, Stijn F. L., Mogensen, Ronnie, Monconduit, Laure, Morris, Russell E., Naylor, Andrew J., Nikman, Shahin, O'Keefe, Christopher A., Ould, Darren M. C., Palgrave, R. G., Poizot, Philippe, Ponrouch, Alexandre, Renault, Steven, Reynolds, Emily M., Rudola, Ashish, Sayers, Ruth, Scanlon, David O., Sen, S., Seymour, Valerie R., Silvan, Begona, Sougrati, Moulay Tahar, Stievano, Lorenzo, Stone, Grant S., Thomas, Chris, I, Titirici, Maria-Magdalena, Tong, Jincheng, Wood, Thomas J., Wright, Dominic S., and Younesi, Reza

Abstract

Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid-electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology.

Published
2021
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38. Correction: A revised mechanistic model for sodium insertion in hard carbons

Author

Au, Heather, primary, Alptekin, Hande, additional, Jensen, Anders C. S., additional, Olsson, Emilia, additional, O’Keefe, Christopher A., additional, Smith, Thomas, additional, Crespo-Ribadeneyra, Maria, additional, Headen, Thomas F., additional, Grey, Clare P., additional, Cai, Qiong, additional, Drew, Alan J., additional, and Titirici, Maria-Magdalena, additional

Published
2021
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42. A revised mechanistic model for sodium insertion in hard carbons

Author

Au, Heather, primary, Alptekin, Hande, additional, Jensen, Anders C. S., additional, Olsson, Emilia, additional, O’Keefe, Christopher A., additional, Smith, Thomas, additional, Crespo-Ribadeneyra, Maria, additional, Headen, Thomas F., additional, Grey, Clare P., additional, Cai, Qiong, additional, Drew, Alan J., additional, and Titirici, Maria-Magdalena, additional

Published
2020
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43. New Route to Battery Grade NaPF6 for Na‐Ion Batteries: Expanding the Accessible Concentration.

Author

Ould, Darren M. C., Menkin, Svetlana, O'Keefe, Christopher A., Coowar, Fazlil, Barker, Jerry, Grey, Clare P., and Wright, Dominic S.

Subjects
SODIUM ions, STORAGE batteries, FLUOROETHYLENE, AMMONIUM acetate, ELECTROLYTES, SODIUM, SOLVENTS, ELECTRIC batteries
Abstract

Sodium‐ion batteries represent a promising alternative to lithium‐ion systems. However, the rapid growth of sodium‐ion battery technology requires a sustainable and scalable synthetic route to high‐grade sodium hexafluorophosphate. This work demonstrates a new multi‐gram scale synthesis of NaPF6 in which the reaction of ammonium hexafluorophosphate with sodium metal in THF solvent generates the electrolyte salt with the absence of the impurities that are common in commercial material. The high purity of the electrolyte (absence of insoluble NaF) allows for concentrations up to 3 M to be obtained accurately in binary carbonate battery solvent. Electrochemical characterization shows that the degradation dynamics of sodium metal‐electrolyte interface are different for more concentrated (>2 M) electrolytes, suggesting that the higher concentration regime (above the conventional 1 M concentration) may be beneficial to battery performance. [ABSTRACT FROM AUTHOR]

Published
2021
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44. Multinuclear Solid-State NMR Investigation of Structure, Dynamics, and Formation of Porous Materials

Author

O'Keefe, Christopher Andrew

Subjects
NMR, Porous materials, Solid-state NMR
Abstract

The work described herein demonstrates the utility of solid-state nuclear magnetic resonance (SSNMR) spectroscopy for the characterization of molecular-level structure and dynamics in porous materials, including the determination of the reaction pathways involved in the formation of porous solids made via solid-state synthetic techniques, a study of the motion of dynamic components of metal-organic frameworks (MOFs) that are prototypes for future molecular machines, and the structural characterization of a surface-supported catalyst. In Chapters 2 and 3, accelerated aging and mechanochemical reactions are used to synthesize cadmium-containing zeolitic imidazolate frameworks (ZIFs). These techniques provide a means for clean and efficient syntheses of these materials; however, little is known about the reaction kinetics and mechanisms underlying their production. First, the structure of a new cadmium-imidazolate framework (CdIF) is determined using a combination of powder X-ray diffraction (PXRD) and SSNMR, a methodology known as NMR-assisted crystallography. SSNMR experiments are also used to monitor the formation of ZIFs made using mechanochemical synthesis, providing information on the intermediates and products of the reactions. It is revealed that the initial mechanochemical ball milling provides the activation energy for the formation of ZIFs, but aging reactions within the milling jars drive the reaction to completion. As demonstrated here, milling times as short as five seconds provide enough energy for the initiation of the reactions, allowing for extremely low-energy synthesis of these materials. In Chapter 4, series of metal-organic frameworks (MOFs) with dynamic, interlocked crown ether rings are investigated to determine the factors that influence the motion of the rings. It is demonstrated that the size of the rings and the framework structure affect the motion. 13C variable temperature SSNMR is used to confirm the shuttling motion of rings between recognition sites on an axle that is incorporated into a MOF. Next, a study on a series of simple inorganic molecular rotors is described. It is shown that some of these compounds act as rotors with very low energy barriers that exhibit random rotational dynamics at temperatures below 75 K, while other structurally similar compounds do not display any motions over a wide range of temperatures. It is posited that steric and electronic effects from the coordinating ligands are responsible for the observed dynamics. 2H SSNMR is shown to be essential for classifying and understanding the dynamics of these low-energy molecular rotors Finally, 35Cl SSNMR is used to elucidate the structure of a transition-metal compound bound to the surface of a porous silica material. It is demonstrated that ultra-wideline (UW) 35Cl SSNMR spectra for transition-metal complexes can be rapidly acquired using a combination of high magnetic fields and specialized pulse sequences. These spectra allow for the differentiation of different Cl bonding environments (i.e., bridging, terminal axial, and terminal equatorial). Density functional theory (DFT) calculations and an accompany molecular-orbital analysis allow for an understanding of the origin of the observed 35Cl electric field gradient (EFG) parameters, which influence the 35Cl quadrupolar interactions. The structure of a surface-supported complex is then proposed, demonstrating the applicability of these techniques to the study of very dilute catalytic species.

Published
2018

47. Resolving the full spectrum of human genome variation using Linked-Reads

Author

Marks, Patrick, primary, Garcia, Sarah, additional, Barrio, Alvaro Martinez, additional, Belhocine, Kamila, additional, Bernate, Jorge, additional, Bharadwaj, Rajiv, additional, Bjornson, Keith, additional, Catalanotti, Claudia, additional, Delaney, Josh, additional, Fehr, Adrian, additional, Fiddes, Ian T., additional, Galvin, Brendan, additional, Heaton, Haynes, additional, Herschleb, Jill, additional, Hindson, Christopher, additional, Holt, Esty, additional, Jabara, Cassandra B., additional, Jett, Susanna, additional, Keivanfar, Nikka, additional, Kyriazopoulou-Panagiotopoulou, Sofia, additional, Lek, Monkol, additional, Lin, Bill, additional, Lowe, Adam, additional, Mahamdallie, Shazia, additional, Maheshwari, Shamoni, additional, Makarewicz, Tony, additional, Marshall, Jamie, additional, Meschi, Francesca, additional, O'Keefe, Christopher J., additional, Ordonez, Heather, additional, Patel, Pranav, additional, Price, Andrew, additional, Royall, Ariel, additional, Ruark, Elise, additional, Seal, Sheila, additional, Schnall-Levin, Michael, additional, Shah, Preyas, additional, Stafford, David, additional, Williams, Stephen, additional, Wu, Indira, additional, Xu, Andrew Wei, additional, Rahman, Nazneen, additional, MacArthur, Daniel, additional, and Church, Deanna M., additional

Published
2019
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50. Dividend Growth Better Performance Indicator Than Dividend Yield.

Author

O’KEEFE, CHRISTOPHER P.

Subjects
DIVIDEND yield, DIVIDENDS, PETROLEUM sales & prices, BUSINESS enterprises, STOCK repurchasing, VALUATION of corporations
Abstract

An interview with Christopher P. O'Keefe of Logan Capital Management, who manages primarily a dividend growth strategy that invests only in companies that consistently increase dividends over time, is presented. He mentions that the company focuses on companies that have a strong business model generating strong free cash flow, underpinned by strong margins, good market share that gives them strong cash flows over long periods of time that can defend that dividend.

Published
2023

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