Papers by Mark Allen Antonio
Bulletin of the American Physical Society, 2020
European Journal of Inorganic Chemistry, 2018
Keggin phosphotungstate heteropolyanions, PW12O40 3-, are known to interact via short-range attra... more Keggin phosphotungstate heteropolyanions, PW12O40 3-, are known to interact via short-range attraction and long-range repulsion (SALR) at moderate and high solution concentrations and low-pH (pH = 1). These interactions were identified through the observation of structure factor peaks in smallangle X-ray scattering (SAXS) data reported previously (J. Phys. Chem. C 2016, 120, 1317). Here we describe the interactions between the same heteropolyanions with extremely low concentrations at low (pH = 0) and high pH (pH = 4.7) conditions. The solution chemistry of Keggin heteropolyanions at these two pH values provides a unique way to change the charge of the cluster anions without changing the structure (from the perspective of SAXS) and, at the same time, changing the hydrogen bonding interactions. The structure factors obtained from concentration dependent SAXS data reveal that the change in pH changes the nature of SALR interactions, consistent with the presence of the plenary PW12O40 3anion at pH = 0 and the monovacant lacunary PW11O39 7anion at pH = 4.7. At the low pH condition, the attractive interactions dominate to provide a peak near = 0 Å-1 momentum transfer in the structure factors, whereas at pH = 4.7 the repulsive interactions dominate, thereby eliminating the peak near = 0 Å-1. The experimental results presented here are in agreement with the recent liquid state theory and computer simulation predictions on SALR interactions.
Le Journal de Physique Colloques, 1983
-L'intercalation de tétrathiafulvalène (TTF), tétraméthyl tétrathi afulvalène (TMTTF), tétrathiat... more -L'intercalation de tétrathiafulvalène (TTF), tétraméthyl tétrathi afulvalène (TMTTF), tétrathiatétracène (TTT), et tétrathi anaphtalène (TTN) dans FeOCl a produit une série nouvelle de composés à basse dimension, avec les conductivités' près de 10 2-10 3 plus grandes que celle de FeOCl.
Separation Science and Technology, 2017
The extraction of tetravalent cerium, Ce(IV), from aqueous nitric acid with tri-n-butyl phosphate... more The extraction of tetravalent cerium, Ce(IV), from aqueous nitric acid with tri-n-butyl phosphate (TBP) in n-dodecane was studied by varying the aqueous, initial cerium(IV) concentration, [Ce 4+ ] aq,init , up to and beyond the point of third phase formation, defined by the critical aqueous concentration (or CAC) and the limiting organic concentration (or LOC). The new chemistry elaborated here for the nearly-century-old Ce(IV)-20 % TBP system focuses on the phenomena of third phase inversion and the distribution of four solutes-Ce(IV), HNO 3 , H 2 O, and TBPbetween the aqueous and organic phases, which are of direct relevance to the PUREX process. We demonstrate that multinuclear Ce(IV) entities are present in the organic phases. A c c e p t e d M a n u s c r i p t Experiments Chemicals. Nitric acid (Optima TM) was obtained from Fisher Chemical and used as received. TBP (from Sigma-Aldrich) was distilled over CaH 2. The n-dodecane and Ce(III) nitrate hexahydrate, Ce(NO 3) 3 •6H 2 O, were used as received from Sigma-Aldrich. Cerium(IV) preparation and valence purity. Solutions of varying concentrations of Ce(IV) were obtained by bulk electrolysis (BE) of the corresponding initial solutions of Ce(NO 3) 3 •6H 2 O in 3
Physical Chemistry Chemical Physics, 2017
Macroscopic phase behaviors in the liquid–liquid extraction are explained by microscopic, reverse... more Macroscopic phase behaviors in the liquid–liquid extraction are explained by microscopic, reverse micellar fluid structures containing tetranuclear Ce(iv) clusters revealed by use of X-ray spectroscopy and scattering of the light and dense organic phases.
Physical chemistry chemical physics : PCCP, Jan 16, 2016
Redox-driven ion transfer between phases underpins many biological and technological processes, i... more Redox-driven ion transfer between phases underpins many biological and technological processes, including industrial separation of ions. Here we investigate the electrochemical transfer of nitrate anions between oil and water phases, driven by the reduction and oxidation of cerium coordination complexes in oil phases. We find that the coordination environment around the cerium cation has a pronounced impact on the overall redox potential, particularly with regard to the number of coordinated nitrate anions. Our results suggest a new fundamental mechanism for tuning ion transfer between phases; by 'trapping' the migrating ion inside the coordination sphere of a redox-active complex. This presents a new route for controlling anion transfer in electrochemically-driven separation applications.
Dalton transactions (Cambridge, England : 2003), Jan 24, 2017
The coordination of the trivalent 4f ions, Ln = La(3+), Dy(3+), and Lu(3+), with neutral and acid... more The coordination of the trivalent 4f ions, Ln = La(3+), Dy(3+), and Lu(3+), with neutral and acidic organophosphorus reagents, both individually and combined, was studied by use of X-ray absorption spectroscopy. These studies provide metrical information about the interatomic interactions between these cations and the ligands tri-n-butyl phosphate (TBP) and di-n-butyl phosphoric acid (HDBP), whose behavior are of practical importance to chemical separation processes that are currently used on an industrial scale. Previous studies have suggested the existence of complexes involving a mixture of ligands, accounting for extraction synergy. Through systematic variation of the aqueous phase acidity and extractant concentration and combination, we have found that complexes with Ln and TBP : HDBP at any mixture and HDBP alone involve direct Ln-O interactions involving 6 oxygen atoms and distant Ln-P interactions involving on average 3-5 phosphorus atoms per Ln ion. It was also found that L...
ChemPlusChem, 2011
Upon solvent extraction of the colorless solution 0.1 M Ce (NO 3) 3⋅ 6H 2 O in 3 M HNO 3 with DMD... more Upon solvent extraction of the colorless solution 0.1 M Ce (NO 3) 3⋅ 6H 2 O in 3 M HNO 3 with DMDBTDMA (N, N′-dimethyl-N, N′-dibutyltetradecyl malonamide) at a concentration of 0.5 M in n-dodecane (also a colorless solution), a yellow third phase is formed. In ...
Journal of the American Chemical Society, Jun 15, 2016
Although the analytical simplicity of the one-step classical theory of nucleation facilitates its... more Although the analytical simplicity of the one-step classical theory of nucleation facilitates its use to understand crystallization processes, recent experiments and simulations have shown that many occur via multiple steps. According to the contemporary two-stage theory of nucleation, the onset of crystallization in a solution is preceded by large density fluctuations in the mother liquor that results in the formation of dense liquid-like correlated structures of the constituent solute particles. Here we report the observation of dense liquid-like correlated structures of heteropolyacid salts of α-Keggin anions (heteropolyanions) in aqueous solutions as volume is decreased long before the onset of crystallization by in situ time-dependent small-angle X-ray scattering measurements. Experiments were performed on drying drops of solutions of heteropolyacids to monitor their ordering before and during the onset of their crystallization. A continuous change in the density of the correla...
Scientific reports, Jun 21, 2016
We report the discovery of an electrochemical process that converts two dimensional layered mater... more We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and M...
Bulletin of the American Physical Society, Mar 6, 2015
of physical, chemical and biological processes. The dynamic nature of water surface and the surfa... more of physical, chemical and biological processes. The dynamic nature of water surface and the surface fluctuations created by thermally excited capillary waves have always limited measurement of near surface ionic-distributions. We demonstrate that this limitation can be overcome by using macro-ions of sizes larger than the capillary wave roughness ∼3Å. Our attempts to measure distributions of inorganic macro-ions in the form of Keggin heteropolyanions (HPAs) of sizes ∼10Å have unraveled novel charge-dependent condensation of macro-ions beneath air-water interfaces. Our results demonstrate that HPAs with-3 charges condense readily beneath air-water interfaces. This is in contrast to the absence of surface preference for HPAs with-4 charges. The similarity of HPA-HPA separations near air-water interfaces and in bulk crystal structures suggests the presence of the planar Zundel ions (H 5 O + 2), which interact with HPAs and the water surface to facilitate the charge dependent condensation beneath the air-water interfaces.
The Journal of Physical Chemistry C, 2016
Figure: Typical SAXS/SANS structure factor showing two distinct peaks corresponding to different ... more Figure: Typical SAXS/SANS structure factor showing two distinct peaks corresponding to different correlations in the solution of particles interacting via short-range attractions and long-range repulsions. The coexistence of non-associated monomers and randomly percolated monomers are conclusively justified in the present work.
Angewandte Chemie International Edition, 2015
Physical Review B, 1994
ABSTRACT A variety of experimental techniques are employed to probe the electronic state of Tb in... more ABSTRACT A variety of experimental techniques are employed to probe the electronic state of Tb in the supeconductor Y0.9Tb0.1Ba2Cu3O7-δ. An analysis of neutron-diffraction data reveals that Tb is incorporated into the sample, replacing Y. There are no anomalies observed in the lattice constants or the planar oxygen thermal parameters determined from the neutron data, but the low concentration of Tb prohibits the determination of Tb oxidation state from these data alone. A comparison of experimentally determined magnetic susceptibilities with those calculated from single-ion, crystal-field models assuming either Tb3+ or Tb4+ shows a close agreement between the Tb3+ model and experiment. The presence of Tb3+ is confirmed by x-ray absorption near-edge spectroscopy. L3-edge data are used to argue that the Tb ions are not significantly hybridized in Y0.9Tb0.1Ba2Cu3O7-δ.
Angewandte Chemie (International ed. in English), Jan 23, 2015
Ceric ammonium nitrate (CAN) is a single-electron-transfer reagent with unparalleled utility in o... more Ceric ammonium nitrate (CAN) is a single-electron-transfer reagent with unparalleled utility in organic synthesis, and has emerged as a vital feedstock in diverse chemical industries. Most applications use CAN in solution where it is assigned a monomeric [Ce(IV) (NO3 )6 ](2-) structure; an assumption traced to half-century old studies. Using synchrotron X-rays and Raman spectroscopy we challenge this tradition, converging instead on an oxo-bridged dinuclear complex, even in strong nitric acid. Thus, one equivalent of CAN is recast as a two-electron-transfer reagent and a redox-activated superbase, raising questions regarding the origins of its reactivity with organic molecules and giving new fundamental insight into the stability of polynuclear complexes of tetravalent ions.
Langmuir : the ACS journal of surfaces and colloids, Jan 24, 2015
Despite long-standing efforts, there is no agreed upon structural model for electrolyte solutions... more Despite long-standing efforts, there is no agreed upon structural model for electrolyte solutions at air-liquid interfaces. We report the simultaneous detection of the near-surface and bulk coordination environments of a trivalent metal cation (europium) in an aqueous solution by use of X-ray absorption spectroscopy. Within the first few nanometers of the liquid surface the cations exhibit oxygen coordination typical of inner-sphere hydration of an aquated Eu(3+) cation. Beyond that, outer-sphere ion-ion correlations are observed that are otherwise not present in the bulk electrolyte. The combination of near-surface and bulk sensitivities to probe metal ion speciation in electrolyte solutions is achieved by detecting electron-yield and X-ray fluorescence signals from an inverted pendant drop. The results provide new knowledge about the near-surface chemistry of aqueous solutions of relevance to aerosols and ion transport processes in chemical separations and biological systems.
The Journal of Physical Chemistry, 1995
... Mark R. Antonio Argonne National Laboratory, Chemistry Division, Argonne, Illinois 60439-4831... more ... Mark R. Antonio Argonne National Laboratory, Chemistry Division, Argonne, Illinois 60439-4831 Violeta Z. Leger and George E. Blomgren Technology Laboratory, Eveready Battery Company, Inc., Westlake, Ohio 44145 Received: November 10, 199P ...
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Papers by Mark Allen Antonio