12 results on '"Veronika Mocko"'
Search Results
2. Characterizing Polyoxovanadate‐Alkoxide Clusters Using Vanadium K‐Edge X‐Ray Absorption Spectroscopy
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Alexander S. Ditter, Samuel M. Greer, Stosh A. Kozimor, Samuel D. Weinstein, Scott R. Daly, Rachel L. Meyer, Feng Li, Veronika Mocko, Gerald T. Seidler, Samantha K. Cary, Benjamin W. Stein, Ellen M. Matson, and Anastasia V. Blake
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X-ray absorption spectroscopy ,Absorption spectroscopy ,010405 organic chemistry ,Organic Chemistry ,Vanadium ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Delocalized electron ,chemistry ,K-edge ,Alkoxide ,Physical chemistry ,Molecule - Abstract
A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron-functionalized and hexavanadium polyoxovanadate-alkoxide clusters, which we characterized here using V K-edge X-ray absorption spectroscopy. Substantial changes in the pre-edge peak intensities were observed that tracked with the V 3d-electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the FeIII cations were electronically isolated from the polyoxovanadate core.
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- 2020
3. A Solid-State Support for Separating Astatine-211 from Bismuth
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Eva R. Birnbaum, Yawen Li, Andrew C. Akin, David H. Woen, Kevin T. Bennett, Donald K. Hamlin, Veronika Mocko, Eric Dorman, D. Scott Wilbur, Stosh A. Kozimor, Nickolas H. Anderson, Frankie D. White, Elodie Dalodière, Cecilia Eiroa-Lledo, Mark Brugh, Laura M. Lilley, Sara L. Thiemann, Maryline G. Ferrier, and Anastasia V. Blake
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Inorganic Chemistry ,chemistry ,Radiochemistry ,Solid-state ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Astatine ,Bismuth - Abstract
Increasing access to the short-lived α-emitting radionuclide astatine-211 (211At) has the potential to advance targeted α-therapeutic treatment of disease and to solve challenges facing the medical...
- Published
- 2020
4. Preparation of an Actinium-228 Generator
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Laura M. Lilley, Benjamin W. Stein, Stosh A. Kozimor, Veronika Mocko, Kelly E. Aldrich, Cecilia Eiroa-Lledo, and Mila Nhu Lam
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Inorganic Chemistry ,Actinium ,Generator (computer programming) ,High specific activity ,Chemistry ,Radiochemistry ,Nuclear spectroscopy ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Volume concentration - Abstract
Advances in targeted α-therapies have increased the interest in actinium (Ac), whose chemistry is poorly defined due to scarcity and radiological hazards. Challenges associated with characterizing Ac3+ chemistry are magnified by its 5f06d0 electronic configuration, which precludes the use of many spectroscopic methods amenable to small amounts of material and low concentrations (like EPR, UV-vis, fluorescence). In terms of nuclear spectroscopy, many actinium isotopes (225Ac and 227Ac) are equally "unfriendly" because the actinium α-, β-, and γ-emissions are difficult to resolve from the actinium daughters. To address these issues, we developed a method for isolating an actinium isotope (228Ac) whose nuclear properties are well-suited for γ-spectroscopy. This four-step procedure isolates 228Ra from naturally occurring 232Th. The relatively long-lived 228Ra (t1/2 = 5.75(3) years) radioisotope subsequently decays to 228Ac. Because the 228Ac decay rate [t1/2 = 6.15(2) h] is fast, 228Ac rapidly regenerates after being harvested from the 228Ra parent. The resulting 228Ac generator provides frequent and long-term access (of many years) to the spectroscopically "friendly" 228Ac radionuclide. We have demonstrated that the 228Ac product can be routinely "milked" from this generator on a daily basis, in chemically pure form, with high specific activity and in excellent yield (∼95%). Hence, in the same way that developing synthesis routes to new starting materials has advanced coordination chemistry for many metals by broadening access, this 228Ac generator has the potential to broaden actinium access for the inorganic community, facilitating the characterization of actinium chemical behavior.
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- 2020
5. Advancing Chelation Chemistry for Actinium and Other +3 f-Elements, Am, Cm, and La
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Eva R. Birnbaum, Stosh A. Kozimor, Brian L. Scott, Veronika Mocko, Samantha K. Cary, Ping Yang, Kevin D. John, Amanda Morgenstern, Benjamin W. Stein, Maryline G. Ferrier, Enrique R. Batista, Sharon E. Bone, and Juan S. Lezama Pacheco
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Actinium ,Inorganic chemistry ,Binding pocket ,chemistry.chemical_element ,010402 general chemistry ,Ligands ,01 natural sciences ,Biochemistry ,Catalysis ,Coordination complex ,Colloid and Surface Chemistry ,Organophosphorus Compounds ,Coordination Complexes ,Lanthanum ,Molecule ,Chelation ,Chelating Agents ,chemistry.chemical_classification ,Americium ,Extended X-ray absorption fine structure ,Molecular Structure ,Extramural ,General Chemistry ,0104 chemical sciences ,chemistry ,Curium ,Radiopharmaceuticals - Abstract
A major chemical challenge facing implementation of 225Ac in targeted alpha therapy-an emerging technology that has potential for treatment of disease-is identifying an 225Ac chelator that is compatible with in vivo applications. It is unclear how to tailor a chelator for Ac binding because Ac coordination chemistry is poorly defined. Most Ac chemistry is inferred from radiochemical experiments carried out on microscopic scales. Of the few Ac compounds that have been characterized spectroscopically, success has only been reported for simple inorganic ligands. Toward advancing understanding in Ac chelation chemistry, we have developed a method for characterizing Ac complexes that contain highly complex chelating agents using small quantities (μg) of 227Ac. We successfully characterized the chelation of Ac3+ by DOTP8- using EXAFS, NMR, and DFT techniques. To develop confidence and credibility in the Ac results, comparisons with +3 cations (Am, Cm, and La) that could be handled on the mg scale were carried out. We discovered that all M3+ cations (M = Ac, Am, Cm, La) were completely encapsulated within the binding pocket of the DOTP8- macrocycle. The computational results highlighted the stability of the M(DOTP)5- complexes.
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- 2019
6. Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA–); Synthesis and Structure of MIVTTA4 (MIV = Zr, Hf, Ce, Th, U, Np, Pu) and MIII(TTA)4– (MIII = Ce, Nd, Sm, Yb)
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Samantha K. Cary, Benjamin W. Stein, Maksim Y. Livshits, Brian L. Scott, Stosh A. Kozimor, Veronika Mocko, Jeffrey J. Rack, Justin N. Cross, and Maryline G. Ferrier
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Highly skilled ,010405 organic chemistry ,Extraction (chemistry) ,chemistry.chemical_element ,Actinide ,Uranium ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Metal ,chemistry.chemical_compound ,chemistry ,visual_art ,visual_art.visual_art_medium ,Physical chemistry ,Physical and Theoretical Chemistry ,Thenoyltrifluoroacetone - Abstract
Thenoyltrifluoroacetone (HTTA)-based extractions represent popular methods for separating microscopic amounts of transuranic actinides (i.e., Np and Pu) from macroscopic actinide matrixes (e.g. bulk uranium). It is well-established that this procedure enables +4 actinides to be selectively removed from +3, + 5, and +6 f-elements. However, even highly skilled and well-trained researchers find this process complicated and (at times) unpredictable. It is difficult to improve the HTTA extraction—or find alternatives—because little is understood about why this separation works. Even the identities of the extracted species are unknown. In addressing this knowledge gap, we report here advances in fundamental understanding of the HTTA-based extraction. This effort included comparatively evaluating HTTA complexation with +4 and +3 metals (MIV = Zr, Hf, Ce, Th, U, Np, and Pu vs MIII = Ce, Nd, Sm, and Yb). We observed +4 metals formed neutral complexes of the general formula MIV(TTA)4. Meanwhile, +3 metals formed an...
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- 2018
7. A series of dithiocarbamates for americium, curium, and californium
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Brian L. Scott, Shane S. Galley, Samantha K. Cary, Ping Yang, Cayla E. Van Alstine, Stosh A. Kozimor, Frankie D. White, Veronika Mocko, Thomas E. Albrecht-Schmitt, Jing Su, Maryline G. Ferrier, and Enrique R. Batista
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Lanthanide ,Materials science ,Series (mathematics) ,Curium ,010405 organic chemistry ,Analytical chemistry ,chemistry.chemical_element ,Californium ,Americium ,Actinide ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry - Abstract
Characterizing how actinide properties change across the f-element series is critical for improving predictive capabilities and solving many nuclear problems facing our society. Unfortunately, it is difficult to make direct comparisons across the 5f-element series because so little is known about trans-plutonium elements. Results described herein help to address this issue through isolation of An(S2CNEt2)3(N2C12H8) (Am, Cm, and Cf). These findings included the first single crystal X-ray diffraction measurements of Cm-S (mean of 2.86 ± 0.04 Å) and Cf-S (mean of 2.84 ± 0.04 Å) bond distances. Furthermore, they highlight the potential of An(S2CNEt2)3(N2C12H8) for providing a test bed for comparative analyses of actinide versus lanthanide bonding interactions.
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- 2018
8. Covalency in Americium(III) Hexachloride
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Stosh A. Kozimor, Justin N. Cross, Brian L. Scott, Samantha K. Cary, Ping Yang, Enrique R. Batista, Cory J. Windorff, Benjamin W. Stein, William J. Evans, Jing Su, and Veronika Mocko
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X-ray absorption spectroscopy ,Americium ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Extramural ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Chlorides ,Chemical physics ,Computational chemistry ,Mixing (physics) - Abstract
Developing a better understanding of covalency (or orbital mixing) is of fundamental importance. Covalency occupies a central role in directing chemical and physical properties for almost any given compound or material. Hence, the concept of covalency has potential to generate broad and substantial scientific advances, ranging from biological applications to condensed matter physics. Given the importance of orbital mixing combined with the difficultly in measuring covalency, estimating or inferring covalency often leads to fiery debate. Consider the 60-year controversy sparked by Seaborg and co-workers ( Diamond, R. M.; Street, K., Jr.; Seaborg, G. T. J. Am. Chem. Soc. 1954 , 76 , 1461 ) when it was proposed that covalency from 5f-orbitals contributed to the unique behavior of americium in chloride matrixes. Herein, we describe the use of ligand K-edge X-ray absorption spectroscopy (XAS) and electronic structure calculations to quantify the extent of covalent bonding in-arguably-one of the most difficult systems to study, the Am-Cl interaction within AmCl
- Published
- 2017
9. Extraction chromatography of 225Ac and lanthanides on N,N-dioctyldiglycolamic acid /1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide solvent impregnated resin
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Mitchell T. Friend, Tara Mastren, T. Gannon Parker, Veronika Mocko, Mark Brugh, Michael E. Fassbender, and Eva R. Birnbaum
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Lanthanide ,Nuclear fission product ,Chromatography ,010401 analytical chemistry ,Organic Chemistry ,Extraction (chemistry) ,Thorium ,chemistry.chemical_element ,General Medicine ,010402 general chemistry ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,Analytical Chemistry ,chemistry.chemical_compound ,Adsorption ,chemistry ,Solvent impregnated resin ,Ionic liquid ,Imide - Abstract
The alpha-emitter 225Ac (t1/2 = 9.92 d) is currently under development for targeted alpha-particle therapy of cancer, and accelerator production of 225Ac via proton irradiation of thorium targets requires robust separations of 225Ac from chemically similar fission product lanthanides. Additionally, the lanthanide elements represent critical components in modern technologies, and radiolanthanides such as 140Nd (t1/2 = 3.37 d) also have potential application in the field of nuclear medicine. The ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][NTf2]), combined with the diglycolamide extractant, N,N-dioctyldiglycolamic acid (DODGAA), was adsorbed on macroporous resin support to produce a solvent impregnated resin (SIR) that was investigated for separations of 225Ac and lanthanides. The equilibrium distribution coefficients (Kd) of the rare earth elements (Sc(III), Y(III), Ln(III)), 225Ac(III), Th(IV), and U(VI) on the prepared DODGAA/[Bmim][NTf2]-SIR were determined from batch adsorption experiments in HCl and HNO3 media. The DODGAA/[Bmim][NTf2]-SIR exhibited preferential uptake of the heavier lanthanide elements while allowing for the separation of the lighter lanthanides. Column separations utilizing the DODGAA/[Bmim][NTf2]-SIR were effective at separating the lighter lanthanides from each other, and separating 225Ac from a mixture of lanthanides, 213Bi, and 225Ra without the need for additional complexing agents.
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- 2020
10. Ferromagnetic quantum critical point in CePd2P2 with Pd → Ni substitution
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David Graf, Alexander S. Ditter, Stosh A. Kozimor, Veronika Mocko, Sharon E. Bone, Stefan G. Minasian, W. Potter, You Lai, K. Huang, Thomas E. Albrecht-Schmitt, Yu-Che Chiu, Ryan Baumbach, M. G. Ferrier, Juan S. Lezama-Pacheco, Gerald T. Seidler, and W. L. Nelson
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Physics ,Valence (chemistry) ,Absorption spectroscopy ,Condensed matter physics ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cerium ,chemistry ,Ferromagnetism ,Quantum critical point ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Ferromagnetic order ,Quantum ,Phase diagram - Abstract
Author(s): Lai, Y; Bone, SE; Minasian, S; Ferrier, MG; Lezama-Pacheco, J; Mocko, V; Ditter, AS; Kozimor, SA; Seidler, GT; Nelson, WL; Chiu, YC; Huang, K; Potter, W; Graf, D; Albrecht-Schmitt, TE; Baumbach, RE | Abstract: An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1-xNix)2P2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration (T-x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, and the introduction of disorder through alloying. Near the critical region at xcr≈ 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium f valence crosses over from trivalent to a noninteger value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd2P2 has a purely trivalent cerium f state, CeNi2P2 has a small (l10 %) tetravalent contribution. In a broad region around xcr, there is a breakdown of Fermi-liquid temperature dependences, signaling the influence of quantum critical fluctuations and disorder effects. Measurements of clean CePd2P2 furthermore show that applied pressure has an initial effect similar to alloying on the ferromagnetic order. From these results, CePd2P2 emerges as a keystone system to test theories such as the Belitz-Kirkpatrick-Vojta model for ferromagnetic quantum criticality, where distinct behaviors are expected in the dirty and clean limits.
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- 2018
11. Isolation of 163Ho from dysprosium target material by HPLC for neutrino mass measurements
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W. A. Taylor, Todd E. Barnhart, Gerd Joachim Kunde, Michael W. Rabin, Francois M. Nortier, Robert J. Nickles, Jonathan W. Engle, Veronika Mocko, Anthony D. Pollington, and Eva R. Birnbaum
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Matrix (chemical analysis) ,Aqueous solution ,chemistry ,Isotope ,Radiochemistry ,Dysprosium ,Analytical chemistry ,chemistry.chemical_element ,Fraction (chemistry) ,Physical and Theoretical Chemistry ,Holmium ,High-performance liquid chromatography ,Dissolution - Abstract
The rare earth isotope 163Ho is of interest for neutrino mass measurements. This report describes the isolation of 163Ho from a proton-irradiated dysprosium target and its purification. A Dy metal target was irradiated with 16 MeV protons for 10 h. After target dissolution, 163Ho was separated from the bulk Dy via cation-exchange high performance liquid chromatography using 70 mmol dm –3 α-hydroxyisobutyric acid as the mobile phase. Subsequent purification of the collected Ho fraction was performed to remove the α-hydroxyisobutyrate chelating agent and to concentrate the Ho in a low ionic strength aqueous matrix. The final solution was characterized by MC-ICP-MS to determine the 163Ho/165Ho ratio, 163Ho and the residual Dy content. The HPLC purification process resulted in a decontamination factor 1.4E5 for Dy. The isolated Ho fraction contained 24.8 ± 1.3 ng of 163Ho corresponding to holmium recovery of 72 ± 3%.
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- 2015
12. Coordination Chemistry of +3 Actinium
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Kevin D. John, Benjamin W. Stein, Amanda Morgenstern, Laura M. Lilley, Veronika Mocko, Enrique R. Batista, Stosh A. Kozimor, and Eva R. Birnbaum
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chemistry.chemical_classification ,Actinium ,Radiological and Ultrasound Technology ,chemistry ,Computational chemistry ,chemistry.chemical_element ,Radiology, Nuclear Medicine and imaging ,Coordination complex - Published
- 2019
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