This dissertation describes a novel methodology to prepare, functionalize, and assemble polymer-coated ferromagnetic cobalt nanoparticles (PS-CoNPs) and cobalt oxide nanowires. This research demonstrated the ability to use dipolar nanoparticles as `colloidal monomers' to form electroactive 1-D mesostructures via self- and field-induced assembly. The central focus of this dissertation is in developing a novel methodology termed as `Colloidal Polymerization', in the synthesis of well-defined cobalt oxide nanowires as nanostructured electrode materials for potential applications in energy storage and conversion.Ferromagnetic nanoparticles are versatile building blocks due to their inherent spin dipole, which drive 1-D self-assembly of colloids. However, the preparation and utilization of ferromagnetic nanoparticles have not been extensively examined due to the synthetic challenges in preparing well-defined materials that can be easily handled. This dissertation has overcome these challenges through the hybridization of polymeric surfactants with an inorganic colloid to impart functionality, colloidal stability and improved processing characteristics. This modular synthetic approach was further simplified to prepare ferromagnetic nanoparticles in gram scale, which enabled further investigations to develop new chemistry and materials science with these materials. These polymer-coated magnetic nanoparticles self-assembled into extended linear chains due to strong dipolar attractions between colloids. Additionally, novel dipolar assemblies, such as, flux-closure nanorings and lamellae type mesostructures were demonstrated by controlling the interparticle of attractive forces (dipolar versus van der Waals).The research presented herein focused on utilizing polymer-coated ferromagnetic cobalt nanoparticles as `colloidal molecules' to form interconnected 1-D mesostructures via `Colloidal Polymerization'. This process exploited the magnetic organization of dipolar colloids into 1-D mesostructures followed by a facile oxidation reaction to form interconnected electroactive cobalt oxide nanowires. This facile and template free approach enabled the large scale synthesis of semiconductor cobalt oxide nanowires, in which the electronic and electrochemical properties were confirmed for potential applications for energy storage and conversion. This work served as a platform in fabricating a wide range of semiconductor heterostructures, which allowed for structure-property investigation of new nanostructured electrodes.

No description available.

Nowadays the ferroelectrics containing of several feroically active sublattices are very attractive, because interactions between these sublattices can caused novel phenomena. Antiferroelectrics, ferrielectrics and multiferoics belong to these materials. In this work new crystalline materials MNP2X6 (M = Cu, Ag; N=In, Cr, Bi; X=S, Se) were investigated, which have ferrielectric and multiferoic properties. The dielectric and electric properties of above mentioned materials have been investigated by broadband dielectric spectroscopy methods, which allows to analyze the collective processes related to order – disorder and displacive phase transitions, ions migration and freezing of dipoles (glassy state) in wide temperature (25 K - 500 K) and frequency (10-5 HZ - 3 GHz) ranges. By substitution or doping it becomes possible to tailor the ferroelectric materials to different properties. In this work is determined that the substitution of 10% Cu ions by Ag ions shifts the phase transition temperature of CuInP2S6 crystal toward lower temperatures while the addition of In ions shifts the phase transitions temperature toward the higher ones. The phase transition temperature difference is about 50 K for mentioned crystals. If the ferroelectric crystal CuInP2S6 is mixed with the antiferroelectric CuCrP2S6 the dipole glass phase occupies the middle of the phase diagram. The distribution of relaxation times has been calculated from the broadband dielectric spectra of dipolar glasses. The... [to full text] / Šiai dienai ypač populiarūs ferroelektrikai susidedantys iš kelių feroiškai aktyvių subgardelių, kurių persitvarkymas fazinio virsmo temperatūroje atskleidžia naujų, dar neaprašytų reiškinių. Prie šių medžiagų priskiriami antiferoelektrikai, ferielektrikai ir multiferoikai. Šiame darbe buvo tiriama nauja medžiagų šeimos MNP2X6 (M = Cu, Ag; N=In, Cr, Bi; X=S, Se ), kurios pasižymi ferielektrinėmis bei multiferoinėmis savybėmis, ir kurių dielektrines ir elektrines savybes galima efektyviai keisti įvedant priemaišas. Minėtų medžiagų dielektrinės ir elektrinės savybės buvo tiriamos dielektrinės spektroskopijos metodais, kurie leidžia tirti kristalų kolektyvinius reiškinius susijusius su tvarkos – netvarkos bei poslinkio tipo faziniais virsmais, jonų migracija bei dipolių užšalimu (stiklėjimu) plačiame dažnių (10-5 Hz iki 3 GHz) bei temperatūrų (25 K iki 500 K) intervaluose. Įvedus 10% Ag jonų vietoj Cu jonų ferielektriniame kristale CuInP2S6 fazinio virsmo temperatūra pasislenka į žemesnias temperatūras, o padidinus indžio koncentraciją fazinio virsmo temperatūra pasislenka į aukštesnes temperatūras. Minėtų kristalų fazinių virsmų temperatūrų skirtumas 50 K. Sumaišius skirtingomis proporcijomis feroelektriką (CuInP2S6) su antiferoelektriku (CuCrP2S6) stebima dipolinio stiklo fazė. Iš dielektrinių matavimų stiklo fazėje buvo paskaičiuota relaksacijos trukmių pasiskirstymo funkcija, kurios aprašymas dvigubos potencialinės duobės modeliu leido susieti mikroskopinius kristalo... [toliau žr. visą tekstą]

The emergence of verdazyl radicals as starting materials for organic synthesis is providing a unique opportunity to create a variety of distinctive heterocyclic scaffolds. These stable radicals have previously been used as spin probes, polymerization inhibitors, mediators of living radical polymerizations, and as substrates for molecular-based magnets. However, verdazyl radicals have never been employed to fulfill an organic synthetic role until recently. In an effort to pioneer the chemistry behind verdazyl radicals as novel organic substrates, our lab has been inspired to expand and explore the scope of reactions involving their synthetic utility. This thesis assesses the synthetic versatility of verdazyl radicals by constructing a library of structurally complex and diverse verdazyl-derived heterocycles in an approach called diversity-oriented synthesis. The synthetic versatility was further expanded to the preparation of a biphenyl-stacked biphenylophane, which exhibited interesting structural and conformational features as highlighted herein.

The emergence of verdazyl radicals as starting materials for organic synthesis is providing a unique opportunity to create a variety of distinctive heterocyclic scaffolds. These stable radicals have previously been used as spin probes, polymerization inhibitors, mediators of living radical polymerizations, and as substrates for molecular-based magnets. However, verdazyl radicals have never been employed to fulfill an organic synthetic role until recently. In an effort to pioneer the chemistry behind verdazyl radicals as novel organic substrates, our lab has been inspired to expand and explore the scope of reactions involving their synthetic utility. This thesis assesses the synthetic versatility of verdazyl radicals by constructing a library of structurally complex and diverse verdazyl-derived heterocycles in an approach called diversity-oriented synthesis. The synthetic versatility was further expanded to the preparation of a biphenyl-stacked biphenylophane, which exhibited interesting structural and conformational features as highlighted herein.

Šiai dienai ypač populiarūs ferroelektrikai susidedantys iš kelių feroiškai aktyvių subgardelių, kurių persitvarkymas fazinio virsmo temperatūroje atskleidžia naujų, dar neaprašytų reiškinių. Prie šių medžiagų priskiriami antiferoelektrikai, ferielektrikai ir multiferoikai. Šiame darbe buvo tiriama nauja medžiagų šeimos MNP2X6 (M = Cu, Ag; N=In, Cr, Bi; X=S, Se ), kurios pasižymi ferielektrinėmis bei multiferoinėmis savybėmis, ir kurių dielektrines ir elektrines savybes galima efektyviai keisti įvedant priemaišas. Minėtų medžiagų dielektrinės ir elektrinės savybės buvo tiriamos dielektrinės spektroskopijos metodais, kurie leidžia tirti kristalų kolektyvinius reiškinius susijusius su tvarkos – netvarkos bei poslinkio tipo faziniais virsmais, jonų migracija bei dipolių užšalimu (stiklėjimu) plačiame dažnių (10-5 Hz iki 3 GHz) bei temperatūrų (25 K iki 500 K) intervaluose. Įvedus 10% Ag jonų vietoj Cu jonų ferielektriniame kristale CuInP2S6 fazinio virsmo temperatūra pasislenka į žemesnias temperatūras, o padidinus indžio koncentraciją fazinio virsmo temperatūra pasislenka į aukštesnes temperatūras. Minėtų kristalų fazinių virsmų temperatūrų skirtumas 50 K. Sumaišius skirtingomis proporcijomis feroelektriką (CuInP2S6) su antiferoelektriku (CuCrP2S6) stebima dipolinio stiklo fazė. Iš dielektrinių matavimų stiklo fazėje buvo paskaičiuota relaksacijos trukmių pasiskirstymo funkcija, kurios aprašymas dvigubos potencialinės duobės modeliu leido susieti mikroskopinius kristalo... [toliau žr. visą tekstą] / Nowadays the ferroelectrics containing of several feroically active sublattices are very attractive, because interactions between these sublattices can caused novel phenomena. Antiferroelectrics, ferrielectrics and multiferoics belong to these materials. In this work new crystalline materials MNP2X6 (M = Cu, Ag; N=In, Cr, Bi; X=S, Se) were investigated, which have ferrielectric and multiferoic properties. The dielectric and electric properties of above mentioned materials have been investigated by broadband dielectric spectroscopy methods, which allows to analyze the collective processes related to order – disorder and displacive phase transitions, ions migration and freezing of dipoles (glassy state) in wide temperature (25 K - 500 K) and frequency (10-5 HZ - 3 GHz) ranges. By substitution or doping it becomes possible to tailor the ferroelectric materials to different properties. In this work is determined that the substitution of 10% Cu ions by Ag ions shifts the phase transition temperature of CuInP2S6 crystal toward lower temperatures while the addition of In ions shifts the phase transitions temperature toward the higher ones. The phase transition temperature difference is about 50 K for mentioned crystals. If the ferroelectric crystal CuInP2S6 is mixed with the antiferroelectric CuCrP2S6 the dipole glass phase occupies the middle of the phase diagram. The distribution of relaxation times has been calculated from the broadband dielectric spectra of dipolar glasses. The... [to full text]

Strukturaufklärung gehört zu den wichtigsten Gebieten der Grundlagenforschung, da sie direkte Einblicke in biologische Systeme und ihre Mechanismen liefert. Der NMR Spektroskopie kommt dabei eine besondere Bedeutung zu, denn sie ermöglicht Forschung unter physiologischen Bedingungen. Dementsprechend ist die Entwicklung neuer Techniken zur Verbesserung dieser Methode weiterhin ein zentrales Forschungsgebiet. Paramagnetische Markierung von Biomolekülen ermöglicht die Bestimmung von NMR Parametern, wie z.B. residuale dipolare Restkopplungen (RDCs) oder Pseudokontaktverschiebungen (PCSs), die für die Strukturaufklärung wertvolle Winkel- und Abstandsinformationen über das Zielmolekül beinhalten. In diesem Zusammenhang wurden Lanthanoidionen-koordinierende Tags entwickelt und erfolgreich an Proteinen angebracht. Durch die paramagnetischen Eigenschaften der Lanthanoidionen wird eine partielle Ausrichtung des Zielmoleküls im Magnetfeld des NMR Spektrometers induziert und somit das Messen residualer dipolarer Kopplungen ermöglicht. Zusätzlich werden die NMR Signale durch eine Dipol-Dipol-Wechselwirkung zwischen dem Lanthanoidion und den Kernen verschoben (PCS). In der konventionellen NMR Spektroskopie werden diese Effekte, aufgrund der Brownschen Molekularbewegung und dem Fehlen eines Metallions, nicht beobachtet. In der Fachliteratur ist ein Transfer dieser Methode auf Oligonukleotide nicht bekannt, obwohl DNA und RNA zu den wichtigsten Biomolekülen überhaupt zählen. In dieser Arbeit wurde mit Hilfe des kürzlich entwickelten Cys-Ph-TAHA Tags ein Protokoll zur Bestimmung von paramagnetischen Effekten in der DNA entwickelt. Dafür wurde eine modifizierte Nukleobase synthetisiert, die eine passende Bindungsstelle für den Tag aufweist. Mit der neu entwickelten Methode wurden zwei paramagnetische und eine diamagnetische Referenzprobe hergestellt. Mittels hochauflösender NMR Spektroskopie konnten paramagnetisch-induzierte PCSs und RDCs gemessen werden. Die Auswertung zeigte eine hohe Qualität der gemessenen PCSs in beiden paramagnetischen Proben. Die RDCs wiesen einen signifikanten Fehler auf. Die in der NMR Spektroskopie übliche Isotopenmarkierung (13C/15N) ist bei im DNA-Synthesizer hergestellten Oligonukleotiden auf Grund der teuren Ausgangsmaterialien nicht möglich, sodass die hergestellten NMR Proben eine natürliche Isotopenhäufigkeit aufwiesen. In den NMR Spektren zur Bestimmung der RDCs ist damit das Verhältnis von Signal-zu-Rausch relativ niedrig, was zusammen mit der paramagnetischen Relaxationsverstärkung zu einem größeren Messfehler führt. Dennoch konnten die erhaltenen paramagnetischen Daten mit einem Ensemblemodell beschrieben werden. In der vorliegenden Arbeit wurde die Methode der paramagnetischen Markierung erfolgreich auf die Stoffklasse der Oligonukleotide übertragen. Dabei wurde ein reproduzierbares Protokoll entwickelt, mit dem eine Bindungsstelle in einen DNA Strang eingebaut und das Zielmolekül anschließend mit dem Cys-Ph-TAHA Tag markiert wurde. Die erfolgreiche Anwendung der Methode konnte durch die erhaltenen paramagnetischen Messwerte von hoher Qualität verifiziert werden.

Inelastic collisions between dipolar molecules, assumed to be trapped in a static electric field at cold (> 10−3K) temperatures, are investigated and compared with elastic collisions. For molecules with a Λ-doublet energy-level structure, a dipole moment arises because of the existence of two nearly degenerate states of opposite parity, and the collision of two such dipoles can be solved entirely analytically in the energy range of interest. Cross sections and rate constants are found to satisfy simple, universal formulas. In contrast, for molecules in a Σ electronic ground state, the static electric field induces a dipole moment in one of three rotational sublevels. Collisions between two rotor dipoles are calculated numerically; the results scale simply with molecule mass, rotational constant, dipole moment, and field strength. It might be expected that any particles interacting only under the influence of the dipole-dipole interaction would show similar behavior; however, the most important and general result of this research is that at cold temperatures inelastic rate constants and cross sections for dipoles depend strongly upon the internal structure of the molecules. The most prominent difference between the Λ-doublet and rotor molecules is variation of the inelastic cross section with applied field strength. For Λ-doublet dipoles, cross sections decrease with increasing field strength. For rotor dipoles, cross sections increase proportionally with the square of field strength. Furthermore, the rate constants of the two types of molecules depend very differently on the angular orientations of the dipoles in the electric field.

DE LA TESI:L'exposició dels estudis realitzats segueix el següent esquema:- En el primer capítol es calcula el moment dipolar de la molècula d'àcid malònic lliure i amb ell el valor de l'efecte dioxà en la mesura experimental d'aquesta propietat. Per a portar a cap aquest càlcul hom ha estudiat les possibilitats que ofereixen els diversos mètodes d'estudi de propietats de molècules no rígides, per a acabar proposant-ne un de més adequat al tipus de molècules que ens ocupen.S'efectua, també, el càlcul del moment dipolar dels àcids succínic, glutàric i adípic mitjançant un dels mètodes que podriem anomenar pobres. I, prèviament a tot càlcul, s'analitza el concepte de molècula no rígida i es justifica la necessitat de conèixer propietats com el valor mig del moment dipolar per a obtenir informació estructural de la mateixa molècula.- En el segon capítol es planteja l'estudi del líquid dioxà pur mitjançant simulació Monte Carlo, des de l'anàlisi del potencial d'interacció més adequat fins a la definició del sistema simulador passant per la descripció de les tècniques a tenir en compte en la construcció del programa d'ordinador. Aquests càlculs són un pas previ a la simulació de la dissolució malònic-dioxà, i els resultats que s'hi obtenen són una referència per a saber si el model que es construeix està ben encaminat o no, a la vegada que tenen interès en si mateixos com a font d'informació sobre el comportament del líquid dioxà.- Finalment, en el tercer capítol, s'empren la simulació de la dissolució diluida d'àcid malònic en dioxà, per a averiguar si aquest canvia l'equilibri conformacional del diàcid. Es planteja la problemàtica característica d'aquest tipus de simulació, la seva resolució, el nou potencial malònic-dioxà a incorporar en el procés de càlcul, i s'efectúa l'estudi per a dos sistemes simuladors diferents. Els resultats, allà mateix analitzats, són significatius.En aquest procés, repartit en tres capítols, hom pot observar la repetició d'un mateix esquema teòric: l'estudi de la dinàmica d'un sistema de partícules en interacció. La dinàmica intramolecular dels diàcids pot ser vista, com la d'un sistema de partícules (àtoms) que es mouen sota unes forces de tipus enllaçant i no enllaçant.En la simulació del líquid dioxà les partícules del sistema són les molècules, les quals interaccionen entre si d'acord a unes forces intermoleculars. En analitzar la influencia del líquid dioxà sobre l'equilibri conformacional de l'àcid malònic es produeix un contacte entre els dos sistemes descrits anteriorment. Depèn de la importància de les forces que s'estableixin entre les particules-molécules del sistema-dissolució per a que les partícules-àtoms del sistema-molecula vegin afectada la seva dinàmica.En conjunt, tres estudis que poden ser vistos independentment però que estan íntimament relacionats, no només pel fet de basar-se sobre un esquema teòric similar sinó també per formar part d'un treball global que intenta subministrar noves dades sobre el comportament de la matèria a nivell molecular, tant en estat gasós com en l'encara poc conegut estat líquid.

In this thesis we study the effects of the dipole-dipole interaction on the physics of ultracold quantum gases, both bosonic and fermionic, within the theoretical framework provided by the mean-field regime. This kind of interaction takes place in ultracold atomic gases (for instance 52Cr or 164Dy) due to their atomic magnetic dipole moment, and in ultracold molecular gases due to the magnetic or electric dipole moment. In the case of quantum gases of bosonic atoms, or Bose-Einstein condensates, the dipole-dipole interaction can be studied within mean-field approximation using the Gross-Pitaevskii equation, which now contains a new non-linear term due to the dipole-dipole interaction. We investigate, on the one hand dipolar condensates confined in harmonic traps, and on the other dipolar condensates confined in toroidal traps. In the harmonic geometry, our focus is on the study of the ground state and the quantized vortex state, where the density profile is characterized as well as some properties leading to the process of vortex formation, such as the critical frequency and the energy barrier that has to be overcome to bring the vortex from the surface to the centre of the gas. We finish the study of dipolar condensates in harmonic traps by dynamically simulating the precession frequency of an off-center vortex in a non-rotating condensate. In the toroidal geometry the dipolar effects are strongly magnified when the polarization axis of the dipoles is perpendicular to the trap symmetry axis. In this case, the anisotropic structure of the density can be understood as the response of the system to the double-well effective potential along the ring. We have studied the dynamics of this system when the initial number of atoms in the left and right wells is imbalanced, predicting Josephson and self-trapping oscillations depending on the initial condition. This has led us to name this new system as Self-induced Josephson Junction. We have studied in detail the self-trapping regime and we have seen that the particle flux inversion is closely related to the crossing of vortices across the Josephson junctions. This result opens the door to establishing a more direct connection between the phase-slip regime, widely addressed in superfluid helium, and the self-trapping regime of condensates. In the case of quantum gases of fermionic dipolar particles, we have studied how the radial quadrupole mode allows one to distinguish between hydrodynamic and collisionless regimes. We have analytically calculated the frequency of this mode in the mean-field approximation, generalizing the results from the Thomas-Fermi approximation for trapped ideal Fermi gases. On the one hand, we observe that the frequency in the hydrodynamic regime is smaller than in non-dipolar Fermi gases, while in the collisionless regime the frequency is larger or smaller than that corresponding to the non-interacting system depending on the geometry of the harmonic trap. On the other hand, we predict that reducing the trap deformation (aspect ratio) an observable jump in the frequency of the radial quadrupole mode would take place, which would correspond to the transition between the collisionless and hydrodynamic regimes, for instance when the gas undergoes the transition to the superfluid state. / En aquesta tesi s’estudien els efectes de la interacció dipol-dipol en la física dels gasos qu`antics ultrafreds, tant de caràcter bosònic com fermiònic, i dins del marc teòric del règim de camp mig. En el primer cas considerem condensats de Bose-Einstein dipolars confinats tant en trampes harmòniques com toroidals, descrivint-ne la geometria de l’estat fonamental i de l’estat de vòrtex quantitzat.En la geometria toroidal els efectes dipolars es veuen fortament magnificats quan l’eix de polarització dels dipols és perpendicular a l’eix de simetria de la trampa. Aquesta configuració ens permet introduïr el concepte de Junció de Josephson Autoinduïda (Self-induced Josephson Junction), en la qual hem predit oscil•lacions de Josephson i d’autoatrapament (self-trapping) depenent de la condició inicial. Estudiant en detall el règim d’autoatrapament hem vist que la inversió del flux de partícules està fortament lligada al creuament de vòrtexs quantitzats a travès de les unions de Josephson. Aquest resultat obre les portes a establir una relació més directa entre el règim dinàmic de salts de fase (phaseslips), àmpliament estudiat en heli superfluid, i el règim d’autoatrapament propi dels condensats. Finalment, en el cas de gasos quàntics de partícules dipolars fermiòniques, hem estudiat com les excitacions col•lectives, en concret el mode quadrupolar radial, permeten distingir entre els règims hidrodinàmic (que pot ser tant degut a la rapidesa de les interaccions com a la superfluidesa) i nocol•lisional (que té lloc quan les interaccions són a tan baixa freqüència que efectivament es poden negligir).