京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第23536号 / エネ博第427号 / 新制||エネ||81(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 / (主査)教授 石原 慶一, 教授 佐川 尚, 准教授 奥村 英之 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

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The crystal structures of Co₃(AsO₄)₂, Co₂₄ٜ₂As₉O₄₈, Co₂As₂O₇ and Co₇As₃ٜ₆O₁₆ have been determined by x-ray diffraction methods. The crystal structure of Mg₃(VO₄)₂ have been refined using single crystal x-ray diffraction data. General structural relations between M₃(XO₄)₂ type compounds where M refers to a divalent cation with radius comparable to that of cobalt, and x = As or V, are discussed. The deviations from ideality in cation polyhedral groups in crystal structures are analysed. / Thesis / Doctor of Philosophy (PhD)

This work presents a joint theoretical and experimental investigation of the electronic structure of quasi one-dimensional cuprates and vanadates. Electron energy-loss spectroscopy in transmission was employed to measure the momentum-dependent loss function of Li2CuO2, CuGeO3, V2O5 and NaV2O5. The comparison between the experimental data and the results from bandstructure as well as cluster calculations allows an explanation of the mobility and correlations of the electrons in these systems. The investigation of the electronic structure of the structurally related cuprates Li2CuO2 and CuGeO3 is exemplary for the study of the transition from a quasi zero-dimensional to a quasi one-dimensional system. In contrast to Li2CuO2 where the electron transitions are strongly localized, the excited states in CuGeO3 can be assigned to the electron hopping to the nearest-neighboured CuO4 plaquettes. The shift of spectral weight from the high energy to the low energy region with increasing coupling between the plaquettes, observed in edge-sharing CuO2 chains, is confirmed by the applied cluster modell. The momentum dependent loss functions of NaV2O5 deliver information about the mobility and correlations of electrons in a quarter-filled ladder system which determine the transition from the charge ordered state into the unordered state at 34 K. Thcontributions of the 3d electrons to the EELS spectra of NaV2O5 are filtered by comparing these spectra with the loss functions of the structurally related V2O5 (d0 configuration). For NaV2O5 the picture of linear chains of V-O-V rungs containing a single d electron in a molecular orbital-like state is confirmed. The comparison of the experimentally determined optical conductivities and those derived from the bandstructrure calculations yield a good agreement upon adoption of an on-site Coulomb interaction U = 2-3 eV. In contrast to the strongly anisotropic hopping within the ladder plane the intersite Coulomb interactions V are about the same size. These interactions are the driving force for the transition from an unordered state at room temperature into a zigzag ordered state observed at low temperatures. / In einer Kombination aus experimentellen und theoretischen Methoden wurden in dieser Arbeit die Elektronenstrukturen von quasi-eindimensionalen Kupraten und Vanadaten untersucht. Dazu wurde die impulsabhängige Verlustfunktion mit Hilfe der Elektronen-Energieverlustspektroskopie in Transmission an Einkristallen von Li2CuO2, CuGeO3, V2O5 und NaV2O5 gemessen. Der Vergleich der experimentellen Daten mit Ergebnissen aus Bandstruktur- und Cluster-Rechnungen erlaubte Rückschlüsse auf die Beweglichkeit und Korrelationen der Elektronen in diesen Systemen. Die Untersuchung der elektronischen Anregungen in den strukturell sehr ähnlichen Kupraten Li2CuO2 und CuGeO3 ist beispielhaft für das Studium des Übergangs von einem quasi-nulldimensionalen zu einem quasi-eindimensionalen System. In Li2CuO2 finden die elektronischen Übergänge vorwiegend lokal auf der CuO4-Plakette statt. Dagegen findet man in CuGeO3 angeregte Zustände, die als das Hüpfen der Elektronen auf benachbarte Plaketten interpretiert werden können. Das angewandte Cluster-Modell bestätigt für eine zunehmende Kopplung zwischen den Plaketten die in eckenverbundenen Kupratketten beobachtete Verschiebung des spektralen Gewichts vom hoch- zum niederenergetischen Bereich. Die Verlustfunktionen von NaV2O5 liefern wertvolle Informationen über die Freiheitsgrade und Korrelationen der Elektronen in einem viertelgefüllten Leitersystem, die wesentlich den Phasenübergang zwischen geordneter und ungeordneter Ladung bei 34 K bestimmen. Die Beiträge der 3d-Elektronen von NaV2O5 zu den EELS-Spektren konnten durch eine vergleichende Studie der Verlustfunktionen des strukturell verwandten V2O5, das keine d-Elektronen besitzt, separiert werden. Die Beschreibbarkeit der Elektronenstruktur in NaV2O5 durch ein effektives Modell einfach besetzter, molekülähnlicher V-O-V-Sprossen wird bestätigt. Die Coulomb-Wechselwirkung U kann in diesem Modell auf den Wertebereich zwischen 2 und 3 eV eingeschränkt werden. Im Gegensatz zu den stark anisotropen Hüpfwahrscheinlichkeiten in der Leiterebene sind die Coulomb-Wechselwirkungen V zwischen Elektronen auf benachbarten Vanadiumplätzen nahezu von gleicher Größe. Diese Wechselwirkungen sind die treibende Kraft für den Übergang von einem ungeordneten Zustand bei Raumtemperatur in einen zickzackgeordneten Grundzustand bei tiefen Temperaturen.

In the first two chapters we presented the basics of density functional theory and semiempirical LSD+U approximation, which was implemented in the full-potential local-orbital (FPLO) minimal-basis calculation scheme. In the third chapter we tested the implemented version of LSDA+U on 3d transitional metal monoxides. Essential improvement of the spectroscopic properties was obtained. A simple model describing the value and direction of the magnetic moment of a transition metal ion was presented. The model visualizes the interplay of the spin-orbit coupling and crystal field splitting. In the fourth chapter we calculated the electronic spectrum of the single Zn impurity in CuO2 plane considered as a vacancy in Cu 3d states. The analytic solution for the states of different symmetry was obtained. Depending on the strength of perturbation induced by the impurity on the neighboring Cu ions, the states are either resonant or localized. The critical values of the perturbation were computed. In the fifth chapter we presented the calculations for three novel vanadates: MgVO3, Sb2O2VO3 and VOMoO4. The tight-binding parameters and the exchange integrals were computed. The magnesium and antimony vanadates appeared to be spin-½ one-dimensional systems, the latter having much stronger one-dimensional character and being probably the best realization of inorganic spin-Peierls system. The molybdenum vanadate was found to be two-dimensional spin-½ system. The Mo 4d orbitals play an important role in the electronic transfer.

This work presents a joint theoretical and experimental investigation of the electronic structure of quasi one-dimensional cuprates and vanadates. Electron energy-loss spectroscopy in transmission was employed to measure the momentum-dependent loss function of Li2CuO2, CuGeO3, V2O5 and NaV2O5. The comparison between the experimental data and the results from bandstructure as well as cluster calculations allows an explanation of the mobility and correlations of the electrons in these systems. The investigation of the electronic structure of the structurally related cuprates Li2CuO2 and CuGeO3 is exemplary for the study of the transition from a quasi zero-dimensional to a quasi one-dimensional system. In contrast to Li2CuO2 where the electron transitions are strongly localized, the excited states in CuGeO3 can be assigned to the electron hopping to the nearest-neighboured CuO4 plaquettes. The shift of spectral weight from the high energy to the low energy region with increasing coupling between the plaquettes, observed in edge-sharing CuO2 chains, is confirmed by the applied cluster modell. The momentum dependent loss functions of NaV2O5 deliver information about the mobility and correlations of electrons in a quarter-filled ladder system which determine the transition from the charge ordered state into the unordered state at 34 K. Thcontributions of the 3d electrons to the EELS spectra of NaV2O5 are filtered by comparing these spectra with the loss functions of the structurally related V2O5 (d0 configuration). For NaV2O5 the picture of linear chains of V-O-V rungs containing a single d electron in a molecular orbital-like state is confirmed. The comparison of the experimentally determined optical conductivities and those derived from the bandstructrure calculations yield a good agreement upon adoption of an on-site Coulomb interaction U = 2-3 eV. In contrast to the strongly anisotropic hopping within the ladder plane the intersite Coulomb interactions V are about the same size. These interactions are the driving force for the transition from an unordered state at room temperature into a zigzag ordered state observed at low temperatures. / In einer Kombination aus experimentellen und theoretischen Methoden wurden in dieser Arbeit die Elektronenstrukturen von quasi-eindimensionalen Kupraten und Vanadaten untersucht. Dazu wurde die impulsabhängige Verlustfunktion mit Hilfe der Elektronen-Energieverlustspektroskopie in Transmission an Einkristallen von Li2CuO2, CuGeO3, V2O5 und NaV2O5 gemessen. Der Vergleich der experimentellen Daten mit Ergebnissen aus Bandstruktur- und Cluster-Rechnungen erlaubte Rückschlüsse auf die Beweglichkeit und Korrelationen der Elektronen in diesen Systemen. Die Untersuchung der elektronischen Anregungen in den strukturell sehr ähnlichen Kupraten Li2CuO2 und CuGeO3 ist beispielhaft für das Studium des Übergangs von einem quasi-nulldimensionalen zu einem quasi-eindimensionalen System. In Li2CuO2 finden die elektronischen Übergänge vorwiegend lokal auf der CuO4-Plakette statt. Dagegen findet man in CuGeO3 angeregte Zustände, die als das Hüpfen der Elektronen auf benachbarte Plaketten interpretiert werden können. Das angewandte Cluster-Modell bestätigt für eine zunehmende Kopplung zwischen den Plaketten die in eckenverbundenen Kupratketten beobachtete Verschiebung des spektralen Gewichts vom hoch- zum niederenergetischen Bereich. Die Verlustfunktionen von NaV2O5 liefern wertvolle Informationen über die Freiheitsgrade und Korrelationen der Elektronen in einem viertelgefüllten Leitersystem, die wesentlich den Phasenübergang zwischen geordneter und ungeordneter Ladung bei 34 K bestimmen. Die Beiträge der 3d-Elektronen von NaV2O5 zu den EELS-Spektren konnten durch eine vergleichende Studie der Verlustfunktionen des strukturell verwandten V2O5, das keine d-Elektronen besitzt, separiert werden. Die Beschreibbarkeit der Elektronenstruktur in NaV2O5 durch ein effektives Modell einfach besetzter, molekülähnlicher V-O-V-Sprossen wird bestätigt. Die Coulomb-Wechselwirkung U kann in diesem Modell auf den Wertebereich zwischen 2 und 3 eV eingeschränkt werden. Im Gegensatz zu den stark anisotropen Hüpfwahrscheinlichkeiten in der Leiterebene sind die Coulomb-Wechselwirkungen V zwischen Elektronen auf benachbarten Vanadiumplätzen nahezu von gleicher Größe. Diese Wechselwirkungen sind die treibende Kraft für den Übergang von einem ungeordneten Zustand bei Raumtemperatur in einen zickzackgeordneten Grundzustand bei tiefen Temperaturen.

In the first two chapters we presented the basics of density functional theory and semiempirical LSD+U approximation, which was implemented in the full-potential local-orbital (FPLO) minimal-basis calculation scheme. In the third chapter we tested the implemented version of LSDA+U on 3d transitional metal monoxides. Essential improvement of the spectroscopic properties was obtained. A simple model describing the value and direction of the magnetic moment of a transition metal ion was presented. The model visualizes the interplay of the spin-orbit coupling and crystal field splitting. In the fourth chapter we calculated the electronic spectrum of the single Zn impurity in CuO2 plane considered as a vacancy in Cu 3d states. The analytic solution for the states of different symmetry was obtained. Depending on the strength of perturbation induced by the impurity on the neighboring Cu ions, the states are either resonant or localized. The critical values of the perturbation were computed. In the fifth chapter we presented the calculations for three novel vanadates: MgVO3, Sb2O2VO3 and VOMoO4. The tight-binding parameters and the exchange integrals were computed. The magnesium and antimony vanadates appeared to be spin-½ one-dimensional systems, the latter having much stronger one-dimensional character and being probably the best realization of inorganic spin-Peierls system. The molybdenum vanadate was found to be two-dimensional spin-½ system. The Mo 4d orbitals play an important role in the electronic transfer.

Lanthanide phosphate (LnPO4) and lanthanide vanadate (LnVO4) nanoparticles (NPs) are promising platforms for theranostic applications because of their chemical stability, low solubility, low toxicity, and unique luminescence and magnetic properties. Motivated by the high radiation resistance and ability to host actinides of naturally occurring lanthanide-based compounds, LnPO4 and LnVO4 NPs were studied as radionuclide carriers for targeted radionuclide therapy using in vivoα-generators, 223Ra, 225Ac, and 227Th. The implementation of these radionuclides has shown potential for the treatment of micrometastases and solid tumors as well as challenges in the retention of decay daughters at the target site to minimize unwanted radiotoxicity. LnPO4 and LnVO4 core-shell NPs doped with either 156Eu, a “cocktail” of 85, 89Sr and 156Eu, or in vivo α-generators 223Ra, 225Ac, and 227Th were synthesized in aqueous media. In vitro retention of radionuclides was investigated by dialyzing the radionuclide-doped NPs suspensions against deionized water and quantifying the activity in dialysate aliquots over time. The crystal structure, morphology, physical stability, luminescence and magnetic properties were evaluated. Partial retention of 156Eu (~70–95%) and 85, 89Sr (>80%) was evidenced in LnPO4 core NPs, while 227Th and decay daughters were quantitatively retained in LaPO4 core + 2 shells NPs (>99%). Gd0.8Eu0.2VO4 and GdVO4 core-shell NPs showed partial retention of 223Ra (~75%), 225Ac (75–95%), 227Th (>96%), and decay daughters. Radionuclide retention was influenced by the lanthanide concentration, crystal structure, and number of shells. The partial retention of radionuclides in both LnPO4 and LnVO4 core-shell NPs may enhance the treatment efficacy while minimizing unwanted toxicity. LnVO4 core and core-shell NPs have potential as carriers of short-lived radionuclides for both diagnostic and therapeutic applications. Emission intensities were higher for LnVO4 with respect to LnPO4 NPs, whereas no significant difference was observed in the magnetic susceptibilities. GdVO4 core NPs displayed enhancement of the signal intensity in T1-weighted images. This work evidences the promising application of both LnPO4 and LnVO4 NPs as platforms for targeted radionuclide therapy and multimodal molecular imaging.

Les halopéroxydases à vanadate (vHPO) seraient des enzymes clés du métabolisme iodé des algues brunes en assurant la captation de l'iode et en participant à la biosynthèse de composés volatils iodés. Pour vérifier ces hypothèses, nous avons mis en place une stratégie de génétique chimique inverse dans le but d'étudier in vivo les effets de l'invalidation des vHPOs. A cette fin, nous avons réalisé un test de criblage à haut-débit sur la bromopéroxydase à vanadate d'Ascophyllum nodosum pour identifier des inhibiteurs de cette enzyme. Les tests secondaires ont montré que les molécules sélectionnées ne sont pas des inhibiteurs mais qu'elles sont très réactives envers les espèces oxydées de l'iode générées par l'enzyme. Un test in vivo a permis de montrer que ces molécules inhibent l'influx des iodures par Laminaria digitata, ce qui corrobore l'implication d'une vHPO dans ce mécanisme. Nous avons étudié la distribution tissulaire et subcellulaire de l'iode chez L. digitata par microsonde nucléaire et par microsonde SIMS. Cette étude a mis en évidence que l'iode est principalement stocké au niveau du tissu périphérique dans le compartiment apoplastique et non au sein de structures intra-cellulaires. Cette découverte remet en cause le modèle de captation des iodures proposé dans la littérature et ouvre de nouvelles perspectives de recherche. Parallèlement à ces études, nous avons poursuivi les travaux concernant les inhibiteurs de la captation des iodures chez des modèles cellulaires exprimant le symporteur Na+/I- en mettant au point leur synthèse, en validant leur activité et en initiant la recherche de leur protéines cibles par photomarquage d'affinité.

In this work I present a 23Na/51V-NMR study of sodium vanadate as pure compound, and the influence of very small amounts of Sodium substitution by Calcium and Lithium is reported and discussed. The measurements of spin-lattice relaxation for 23Na and 51V are also presented. The sodium vanadate is found to have a double phase transition. The two transitions are close together and take place around 34 K. Above the transition temperature there is one V site in the mixed oxidation state 4.5+ and there is one Na site. A consistency for a number of un-doped and very slightly doped samples of three vanadium valences is argued, confirming a charge ordering transition at transition temperature, in good qualitative agreement with Bernert’s model and as well in quantitative and qualitative agreement with Sawa’s monoclinic structure. Below the transition temperature sodium is found to have ten sites. The number of the Na site is continuously developed with decreasing the temperature below transition temperature. This continues development of the Na sites demonstrates that the second transition is continues. The detailed spin-lattice relaxation rate for 23Na in both, the pure and the doped samples, in transition region, provided evidence for a non-symmetric and complex transition peak structure which we relate to the onset of more than one transition occurring at slightly different temperatures. This scales with the transition temperature reduction provided by lithium and calcium doping. The two transitions (i.e. dimerization and charge ordering) are intimately related. We investigated the spin-gap by means of Vanadium and Sodium spin-lattice relaxation temperature dependence well below transition temperature. The analysis of the single crystal data reveals a significant anisotropy in the nature of the gap, which is sensitive to Calcium and Lithium doping, indicating that is constrained to the ladder plane.