Spelling suggestions: "subject:"lanthanide"" "subject:"ianthanide""
81 |
Determinação da simetria de coordenação de alguns complexos de lantanídeos por difração de raios-x / Coordination symmetry studies in some lanthanide complex by X-ray diffractionCarlos de Oliveira Paiva Santos 16 August 1983 (has links)
lantanídeos, visando a determinação da simetria de coordenação ao redor dos íons e sua comparação com prévias previsões espectroscópicas. As medidas de difração foram realizadas com um difratômetro de quatro círculos de geometria Kappa. Os dados cristalinos relevantes são: [Eu (TMU)6] (AsF6)3, TMU = C5H12N2O. Fórmula química: EuC30H72N12O6As3F18; cela unitária é cúbica, a = 18,000 (3)Åe V = 5832 (3)޵ grupo espacial: F23 número - 196 da Internacional Tables For X-Ray Crystallography; número de moléculas por cela unitária: Z = 4; coeficiente de absorção de massa para radiação de molibdênio: µ (MoKα)=27,4 cm-1; densidade calculada: Dc = 1,60 g.cm-3 Para um cristal de tamanho aproximadamente 0,25 x 0,25 x 0,30mm foram medidas 2309 reflexões. A média das intensidades das reflexões equivalentes por simetria de Laue foi calculada obtendo-se um total de 841 independentes, das quais, apenas 277 resultaram maiores que três vezes o desvio padrão estimado de contagem estatística. A estrutura se mostrou altamente desordenada e o modelo proposto refinou a um fator-R final de 13.8%. Os átomos de európio e arsênio estão localizados em posições especiais de simetria pontual local 23 (T) O Eu3+ está hexacoordenado através dos oxigênios das moléculas de TMU formando um octaedro regular de simetria pontual Oh. A distância európio-oxigênio é de aproximadamente 2,28 Å. [Ln (H2O)9] (CF3SO3)3, Ln=Nd or Ho. Fórmula química: LnC3H18O18F9S3; cela unitária hexagonal a=13,851 (4)Å, c=7,460(3)Å e V=1240(1) ޵ para Ln = Nd, e a=13,570 (2)Å, c=7,577 (1)Å e V=1208,5 (9)޵ para Ln=Ho; grupo espacial: P63/m número 176 da Internacional Tables For X-Ray Crystalography; número de moléculas por cela unitária: Z=2; coeficiente de absorção de massa para radiação de molibdênio: µ (MoKα) = 23,2 cm-1(Nd) e 34,8 cm-1 (ho); densidade calculada: Dc=2,02 g.cm-3 e 2,13 g.cm-3 respectivamente para Ln = Nd e Ho. De um cristal de forma cilíndrica de diâmetro e altura aproximadamente de 0,20 mm foram medidas 2098 reflexões para o complexo de Nd e 2400 para o de Ho. Após o calculo de média das reflexões equivalentes de Laue, obteve-se para o caso de Nd 685 reflexoes independentes das quais 636 com I > 3σ(I) e o fator-R final foi 2,64%. Para o complexo de holmio as figuras foram: 763 reflexões independentes, 676 com I > 3σ(I) e fator-R de 2,18%. Em ambos os casos as estruturas foram resolvidas pelos métodos de Patterson e do átomo pesado. As estruturas se mostraram isomorfas com a única diferença significativa sendo a distância lantanídeo-oxigênio de 2,49 Å para Nd e 2,42 para Ho. O íon lantanídeo é nonacoordenado através dos oxigênios das moléculas de água formando um prisma trigonal triencapuçado de simetria pontual cristalografica D3h. Todas as distâncias interatômicas estão dentro da faixa esperada, com exceção das distâncias C-F em ambos os casos que são um pouco curtas (1,31 Å) / We describe here the X-ray determination of the crystal and molecular structures of three lanthanide complexes. The work is a contribution to the study of the coordination chemistry of lanthanide ions with organic ligands and in particular, it-aims to compare the observed point symmetry of the ion environment with spectroscopic predictions. The diffraction measurements were all performed on a four circle diffractometer of kappa geometry. The relevant crystal data are: Chemical formula: [Eu (TMU)6] (AsF6)3, TMU = C5H12N2O; cubic unit cell a = 18,000 (3)Åe V = 5832 (3)޵ space group: F23 number 196 from International Tables for X-ray Crystallography; number of molecules per unit cell: Z = 4; mass absorption coefficient for molybdenum radiation: (MoKα)=27,4 cm-1; calculated density: Dc = 1,60 g.cm-3. For a crystal of approximately 0.25 x 0.25 x 0.30 mm size, 2309 reflections were measured. After averaging the intensities of the Laue-equivalent reflection, 841 independent reflections were obtained, from which only 277 had intensities greater than three times the respective standard deviations estimated from counting statistics. The structure turn out to be highly disordered and the proposed model refined to a final R-factor of 13.8%. The europium and arsenic atoms are sited on special positions of local point symmetry 23 (T). The Eu3+ is hexacoordinated to six TMU oxygen atoms, forming a regular crystallographic octahedron of point symmetry Oh. The europium oxygen distance is 2.28Å. [Ln (H2O)9] (CF3SO3)3, Ln=Nd or Ho. Chemical formula: LnC3H18O18F9S3 hexagonal unit a=13,851 (4)Å, c=7,460(3)Å and V=1240(1) ޵ for Ln = Nd, and a=13,570 (2)Å, c=7,577 (1)Å e V=1208,5 (9)޵ for Ln=Ho; spacial group: P63/m number 176 from International Tables for X-ray Crystallography number of molecules per unit cell: Z=2; mass absorption coefficient for molybdenum radiation: ܒ (MoKα) = 23,2 cm-1 for Ln=Nd and 34,8 cm-1 for Ln=Ho; calculated density: Dc=2,02 g.cm-3 e 2,13 g.cm-3 respectively for Nd and Ho. From a cylindrically shapped crystal of approximate diameter and height of 0.20 mm, 2098 reflections for the Nd and 2400 for the Ho complexes were measured. After averaging the intensi ties of the Laue-equivalent reflections we obtain for Nd 685 independent reflections of which 636 with I > 3σ(I) and agreement factor of 2.64%. For the holmium complexes the figures were 763 independent reflections, 676 with I > 3σ(I) and agreement factor equal to 2.18%. In both cases the structures were solved by the heavy-atom Patterson method. The structures turn out to be isomorphous with the only significant difference of the lanthanide oxygen distances which was 2.49Å for Nd and 2.42Å for Ho. The lanthanide ions are nine-coordinated to the oxygen atom of water molecules, which form a tricapped trigonal prism of crystallographic point symmetry D3h. All interatomic distances lie within the expected normal range except the C-F ones which are somewhat shorter (1,31 Å)
|
82 |
Síntese e caracterização de nanopartículas de óxido misto de estanho/titânio dopadas com lantanídeos para marcação biológica / Synthesis and characterization of tin / titanium mixed oxide nanoparticles doped with lanthanide for biomarkingPaula Pinheiro Paganini 06 December 2012 (has links)
Este trabalho apresenta a síntese, caracterização e estudo fotoluminescente de nanopartículas à base de óxido misto de estanho e titânio dopadas com európio, térbio e neodímio visando à utilização como marcadores luminescentes em sistemas biológicos. As sínteses foram feitas pelos métodos de coprecipitação, sol-gel proteico e Pechini e as partículas foram caracterizadas por espectroscopia de infravermelho, análise termogravimétrica, microscopia eletrônica de varredura, difração de raios X e espectroscopia de absorção de raios X. Os estudos das propriedades fotoluminescentes foram realizados para os luminóforos dopados com európio, térbio e neodímio, sintetizados pelo método de coprecipitação. Para o luminóforo dopado com európio foi possível calcular os parâmetros de intensidade e o rendimento quântico e este apresentou resultados satisfatórios. Tratando-se de uma marcação em sistemas biológicos fez-se necessário a funcionalização destas partículas para que as mesmas se liguem à parte biológica a ser estudada. Sendo assim, funcionalizou-se as nanopartículas pelos métodos de microondas e Stöber e caracterizou-se por espectroscopia de infravermelho, microscopia eletrônica de varredura, espectroscopia por dispersão de energia e difração de raios X, obtendo-se resposta qualitativa da eficácia da funcionalização. O método espectroscópico da ninidrina foi utilizado para a quantificação da funcionalização dos luminóforos. Os estudos fotoluminescentes das partículas funcionalizadas demonstram a viabilidade do uso destes luminóforos como marcadores luminescentes. / This work presents the synthesis, characterization and photoluminescent study of tin and titanium mixed oxide nanoparticles doped with europium, terbium and neodymium to be used with luminescent markers on biological systems. The syntheses were done by co-precipitation, protein sol-gel and Pechini methods and the nanoparticles were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction and X-ray absorption spectroscopy. The photoluminescent properties studies were conducted for luminophores doped with europium, terbium and neodymium synthesized by coprecipitation method. For luminophore doped with europium it was possible to calculate the intensity parameters and quantum yield and it showed satisfactory results. In the case of biological system marking it was necessary the functionalization of these particles to allow them to bind to the biological part to be studied. So the nanoparticles were functionalized by microwave and Stöber methods and characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction obtaining qualitative response of functionalization efficacy. The ninhydrin spectroscopic method was used for quantification of luminophores functionalization. The photoluminescent studies of functionalized particles demonstrate the potential applying of these luminophores as luminescent markers.
|
83 |
Introdução aos métodos de determinação de estrutura por difração de raio-x: aplicado a alguns complexos de lantanídeos / Introduction to x-ray crystal structure determination and its application to the study of some lanthanide complexesMarcos Alcantara de Oliveira 12 May 1986 (has links)
Este trabalho consta de uma introdução teórica tratando, do conceito de cristal, da interação entre o raio-X e o meio cristalino e dos fundamentos dos métodos de determinação de estruturas moleculares de pequeno porte aplicados na solução das estruturas cristalinas dos complexos: Praseodímio, Neodímio e Európio com Perrenato e Trans-l, 4-ditiano-l, 4-dióxido,(TDTD), tendo fórmula geral [Ln(H2O)4(η TDTD) (η ’ ReO4) (μ-┨-TDTD)]n (ReO4)2n • nTDTD onde, Ln= Eu, Pr, Nd e Metil-2,6-anhidro-3-azido-4-0-benzoil-3-deoxi-α-D-iodopiranosideo, um novo derivado de 2,5-dioxabiciclo [2,2,2] octano. Determinou-se que os complexos envolvendo íons latanídeos, tem estruturas isomorfas, que refinaram para os valores finais: R(eu)=0.067, R(Pr)= 0.074, R(Nd)= 0.061. As características principais das estruturas são as seguintes: a) sistema cristalino ortorrômbico; b) o íon Ln3+ é coordenado por nove átomos de oxigênio dos grupos TDTD, perrenato e H2O. Os átomos de oxigênio que coordenam o cátion formam formam uma configuração antiprisma quadrado de Arquimedes com chapéu; c) o íon de terra rara se encontra em posição especial de simetria C2; d) a estrutura possui uma desordem ocupacional com relação a três átomos de oxigênio descoordenados do perrenato que coordena o íon Ln3+ através de um oxigênio situado também em posição de simetria C2. Explica-se os resultados do espectro de emissão do Eu3+ à luz dos resultados estruturais obtidos, comparando estes resultados com outros descritos na literatura. A estrutura do complexo orgânico, com fórmula química C14H15N3O5, foi determinada utilizando métodos diretos. A conformação do anel de seis membros foi determinada como sendo aproximadamente um barco torcido. / This work consists of a theoretical introduction to the concept of a crystal, the interaction between X-ray and the crystalline medium and some aspects concerning the methods of structure determination, applied to the crystal structure of the complexes: Praseodymium, Neodymium and Europium Perrhenate with Trans-l,4-dithiane-l,4-dioxide (TDTD) of general formula: [Ln(H2O)4(η TDTD) (η ’ ReO4) (μ-┨-TDTD)]n (ReO4)2n • nTDTD, where Ln= Eu, Pr, Nd and Methyl-2,6-anhydro-3-azido-4-0-benzoyl-3-deoxy-α-D-iodopyranoside, a new 2,5-Dioxabicycle [2,2,2] octane derivative. It was determined that the complexes involving lanthanide ions are structurally isomorphous, the structures refined to the final values of: R(Nd)=0.061, R(Pr)=0.074, R(Eu)=0.067. The principal characteristics of these structures are: a) the crystal system is orthorhombic; b) the ion Ln3+ is coordinated by nine oxygen atoms of TDTD, perrhenate and water molecules. The coordinated oxygen have an approximate Antiprismatic Arquimedian Capped Square conformation; c) the rare earth atom is located on a crystallographic C2 position; d) the structure has an occupational disorder, with relation to three uncoordinated oxygen atoms of the perrhenate group that coordinates the cation by the oxygen located on the special position with exact point symmetry C2. The emission spectra of the Eu3+ ion is explained based on the structure information obtained from x-ray analysis. Also a comparison is traced with other coordination compounds, with the lanthanide ion Ln3+, revealing some important aspects of these structures. The structure of the compound with chemical formula C14H15N3O5 was determined using direct methods. The six member ring C(1)-O(5)-C(4)-C(3)-C(2) is in an approximate twist-boat conformation.
|
84 |
Development of polyhipe chromatography and lanthanide-doped latex particles for use in the analysis of engineered nanoparticlesHughes, Jonathan Mark January 2013 (has links)
The aims of this thesis were two-fold: A) To use high internal phase emulsion (HIPE) templated materials to produce a chromatographic stationary phase for the size separation of engendered nanoparticles (NPs). B) To produce well characterised lanthanide doped polymer NPs with a potential use as analytical standards. Initially, silica materials were prepared from oil-in-water HIPEs by a two stage acid/base catalysed sol gel process. As well as presenting the expected macroporosity typical of HIPE templated materials, it was also found that micro- and meso-porosity could be influenced by surfactant choice and reaction with iron (III) chloride or copper (I) chloride which had been included in the HIPE. However, the resulting silica materials were deemed inappropriate for the desired chromatography. Monolithic columns were prepared from HIPE templated polymers (polyHIPEs) and incorporated into a HPLC system. Poly(styrene-co-divinylbenzene) and poly(ethylene glycol dimethacrylate) polyHIPE columns were able to separate sub-micron polystyrene latexes, detected by UV absorption, and dysprosium doped polystyrene latex particles and gold nanoparticles detected by inductively coupled plasma mass spectrometry (ICP-MS).Dysprosium, gadolinium and neodymium doped polystyrene NPs were prepared by micro-emulsion polymerisation. Particle size was controlled (over a 40 – 160 nm range) by tailoring of surfactant and initiator concentrations. Particles were characterised by dynamic light scattering, differential centrifugal sedimentation, transition electron microscopy and hydrodynamic chromatography (HDC)-ICP-MS. Also, particle surface change, lanthanide content and solids content were analysed. The latter two appear related to particle size. As far as the author is aware there are no cases of the use of polyHIPE columns size separation in the literature. Nor are there any cases of encapsulation of metals within polymer nanoparticles by micro-emulsion polymerisation reported.
|
85 |
Lanthanide Based Hydrogels in Sensing, Energy Transfer and Nanoparticle SynthesisGorai, Tumpa January 2016 (has links) (PDF)
Chapter 1: Luminescence property of lanthanide and its applications
Lanthanides are well-known for their unique luminescence property and have found widespread applications in sensing, bioimaging, lasers, optoelectronic devices, etc. Due to Laporte forbidden f-f transitions, lanthanides have very low intrinsic emission. The problem can be overcome by use of an ‘antenna’, which is an organic chromophore with excited state energy higher than the lanthanides’ emitting levels. Thereby it is possible to get highly emitting lanthanide complexes through energy transfer from the ‘antenna’. Due to long lifetime of lanthanides’ excited states, it's possible to perform time delayed measurement which is useful in bioassays and bioimaging since the short-lived background emission is effectively filtered.
Research in supramolecular metallogels has grown rapidly in recent years, and already proven to have potential for designing advanced materials for a variety of applications, such as sensing, optoelectronics, catalysis, nanoparticle synthesis, biomedicine etc. A supramolecular gel where a lanthanide is an integrated part of it can combine the advantages of the supramolecular gel along with the unique property of lanthanide luminescence and thus such materials can be explored for potential applications. This chapter discusses the background information on the unique luminescence of lanthanides, and some examples of the applications of lanthanide complexes and lanthanide based gels.
Chapter 2: Lanthanide luminescence based enzyme sensing in hydrogels
This chapter describes the use of Tb/Eu luminescence in the sensing of biologically important enzymes. We discovered the sensitization of Eu(III) in Eu-cholate gel by 1-hydroxypyrene, and of Tb(III) in Tb-cholate gel by 2,3-dihydroxynaphthalene. These two sensitizers were covalently modified and sensitizer-appended hybrid (artificial) enzyme substrates were prepared for a few biologically important hydrolases. The covalently modified sensitizer
termed as “pro-sensitizers”, didn't sensitize Tb(III)/Eu(III) in the hydrogel and no photoluminescence was observed. In the presence of the appropriate enzyme in the hydrogel, the pro-sensitizer was cleaved to liberate the sensitizer, which led to an enhancement of luminescence with time. Alkaline phosphatase and β-lactamase were assayed using pyrene phosphate and pyrene-oxo-cephalosporanic acid derivatives, respectively, in Eu-cholate hydrogel (Figure 1). β-Galactosidase was assayed using Tb(III) luminescence in Tb-cholate gel. The enzyme detection was based on red/green luminescence response from the gel. To understand the behaviour of the enzymes in the hydrogel, kinetic parameters were determined. The detection of different enzymes was also demonstrated in natural/biological samples like blood serum, milk and almond extract.
Figure 1. Three different pro-sensitizers used for alkaline phosphatase, β-lactamase and β-galactosidase assays
Chapter 3: Enzyme sensing on paper discs using lanthanide luminescence
Developing a user-friendly biosensor is of considerable importance in clinical and analytical chemistry. Paper based biosensor design is an emerging field of research and paper based point of care (PoC) testing devices have already found applications in clinical, veterinary, environmental, food safety, security etc. Paper is made out of natural cellulose fibres, and has advantages of low cost, biodegradability, biocompatibility, and user friendliness. Paper based sensors have been used for the detection of ions, glucose, proteins, nucleic acids, antigens etc., with mostly colorimetric, fluorescent, electrochemical, chemiluminescence and
Electrochemiluminescence readouts. In this work, the non luminescent Tb(III) and Eu(III) were embedded on paper as their cholate hydrogels and were used for detecting different hydrolases. Pro-sensitizers, as reported in Chapter 2, were immobilized on paper for the detection of a specific enzyme. The “pro-sensitizer” released the sensitizer upon enzyme action and led to luminescence enhancement from the gel coated paper disc. By this way, four different hydrolase enzymes detection were carried out using Tb(III)/Eu(III) luminescence as the readout (Figure 2) and the practical utility was demonstrated by the detection of specific enzymes in natural/biological samples. This paper disc based enzyme sensing provides a simpler and user friendly approach over the contemporary approach of enzyme sensing typically carried out in solution.
Figure 2. Paper based biosensors for hydrolase enzymes
Chapter 4: Luminescence resonance energy transfer in self-assembled supramolecular hydrogels
Luminescence resonance energy transfer is a phenomenon of energy transfer between a FRET (Förster resonance energy transfer) pair, where a lanthanide is the donor. Lanthanides have attracted attention for the last several decades for their unique luminescence properties. LRET is a FRET process along with added advantages of Lanthanides, i.e. long lifetime of
the lanthanides and characteristics emission spectra. LRET has been used for studying interaction of biomacromolecues, immunoassay, bioassays, etc. LRET in either a supramolecular organogel or a hydrogel is still an unexplored field. In this work we showed the energy transfer from Tb(III) to two different red emitting dyes in Tb-cholate hydrogel (Figure 3). The self assembly processes during hydrogelation assisted the energy transfer process without any need for laborious synthesis. The energy transfer was confirmed by time delayed emission, excitation spectra and lifetime measurement in the hydrogels. Energy transfer was observed both in the gel and the xerogel states. These luminescent materials may find applications in optoelectronics.
Figure 3. Energy transfer from DHN to Tb3+ and then to red emitting dyes (Rhodamine B & Sulforhodamine 101) in the Tb-Cholate hydrogel
Chapter 5: Room temperature synthesis of Lanthanide phosphate nanoparticle using a gel as a soft template
Lanthanide orthophosphates are an important class of rare earth compounds, and have widespread applications in laser materials, optical sensors, heat resistance materials, solar cell etc. There are several methods in the literature for the synthesis of rare earth phosphate nanoparticles. Most of these are based on hydrothermal, microwave assisted, micro emulsion, arrested precipitation etc., which invariably dependent on stringent conditions such as (i) high temperatures and pressures, (ii) inert atmosphere and (iii) the use of external capping agents as stabilizers. Synthesis of such nanoparticles under milder conditions would always be preferable. In this context, the preparation of nanoparticles using hydrogel as template can be a possible alternative approach.
The LnPO4 nanoparticle synthesis was done by diffusion of Na3PO4 in Ln-cholate hydrogels. The particles were characterized by transmission electron microscopy (TEM) and powder XRD analysis. TEM showed the formation of 3-4 nm size particles with an ordered arrangement on the gel fibre. This work demonstrated that the lanthanide cholate gels have high potential for the synthesis, and immobilization of lanthanide phosphate nanoparticles at room temperature to produce new types of composite materials.
(For structural formula pl see the abstract pdf file)
|
86 |
Development of a simplified soft-donor technique for trivalent actinide-lanthanide separationsLangford Paden, Madeleine Hilton January 2015 (has links)
The necessity of reprocessing spent nuclear fuel has arisen from increasing awareness and concern for the environment, in addition to the potential of minimising proliferation. A number of different reprocessing techniques are currently being developed around the world to allow useful spent nuclear fuel (SNF) to be recycled and reused and the remaining waste to be treated. One such technique, currently being developed in the USA is the TALSPEAK process, an advanced reprocessing method for the separation of trivalent lanthanide (Ln3+) and minor actinide (MA3+) components. This process, developed in the 1960s at Oak Ridge National Laboratory, uses DTPA to act as a holdback reagent for MA3+, in a lactate buffered aqueous phase at pH 3.6, allowing Ln3+ to be selectively extracted by organophosphate HDEHP into an organic phase of DIPB or dodecane. TALSPEAK is one of the most promising techniques being researched due to its numerous advantages, particularly its relative resistance to radiolysis and its ability to be carried out without the need for high reagent concentrations. Additionally it gives high separation factors, in the region of ~50-100, comparable to other advanced reprocessing methods under development. The chemistry of the process is very complex and not particularly well understood so it would be advantageous to simplify the process by removing the need for a separate holdback reagent and buffer. In collaboration with colleagues at the Idaho National Lab, the use of amino acids as a potential combined buffer and soft donor was investigated. Although it was found that amino acids do not act as holdback reagents in their own right, optimisation of an L-alanine buffered TALSPEAK system with DTPA was found to allow the process to be carried out effectively at a lower pH of 2, which is more preferable for industrial application. As an extension of this, separation studies were carried out using the tripeptide L-glutathione (GSH) to determine its potential for use as a combined buffer and soft-donor. As with the studies with amino acids, it was found that GSH also does not act as a holdback reagent in its own right, however it does interact with Ln-DTPA complexes at pH 4. When optimised at this pH, separation factors of up to 1200 were achieved for Eu3+/Am3+, whilst still maintaining low MA3+ partitioning. However, further studies by ICP-MS and luminescence spectroscopy showed that a GSH buffered system was not effective for extraction of heavier lanthanides, although the results show the potential for further investigation into other short and longer chain peptide buffered systems and possibly lanthanide-lanthanide separations. Further studies were carried on amino acid appended DTPA ligands which were synthesised in a one step reaction in order to create a combined buffer and soft donor. The ligands were found to self-buffer at around pH 2 and allow successful separation of Eu3+/Am3+ (SF ~ 100). The results from initial investigations by luminescence spectroscopy and solvent extraction are promising and are presented here. Further work is needed on these systems in order to optimise their extraction capability and minimise Am3+ partitioning. In the future this work could promote studies for better understanding of TALSPEAK chemistry that could be used in industrial partitioning processes.
|
87 |
Tailoring Crystalline Phase and Surface of Lanthanide-Based Nanoparticles for MRI ApplicationsLiu, Nan 22 November 2019 (has links)
Lanthanide-based nanoparticles (Ln3+-based NPs) are promising candidates as magnetic resonance imaging (MRI) contrast agents. The present thesis aims to investigate the effect of the crystalline phase of Ln3+-based NPs on their MRI contrast performance. Understanding the phase-dependent MRI contrast behaviour of Ln3+-based NPs will provide insights into the development of brighter MRI contrast agents for future in vivo biomedical applications. A set of NaGdF4 NPs (6-8 nm) in cubic and hexagonal phases in the same size range was synthesized by employing a microwave-assisted approach, allowing the influence of host crystallinity on MRI T1 relaxivity to be investigated (chapter 4). The results showed that cubic NaGdF4 NPs exhibited superior performance as MRI T1 contrast agents than their hexagonal analogues, irrespective of the chosen surface modification, e.g. small citrate groups or longer chain poly(acrylic acid). NaDyF4 NPs (3 nm) were synthesized in both phases to assess whether phase-dependent MRI contrast behaviour consistently exists in other Ln3+-base NPs of the NaLnF4 family (chapter 5). Again, it was demonstrated that cubic NaDyF4 NPs had a better contrast performance as T2 contrast agents than the hexagonal NPs. Alternatively, cubic NaEuF4 NPs, exhibiting additional optical properties (e.g. red emission under UV excitation), were prepared as potential candidates for the preparation of chemical exchange saturation transfer (CEST) contrast agents (chapter 5). Chapter 6 introduces preliminary dispersion stability studies of cubic NaGdF4 NPs dispersed in different buffer solutions, the obtained hydrodynamic diameters indicated that NaGdF4 NPs possessed better dispersity in saline than that in PBS solution.
|
88 |
Quantum Chemistry Calculations of Energetic and Spectroscopic Properties of p- and f-Block MoleculesSouth, Christopher James 08 1900 (has links)
Quantum chemical methods have been used to model a variety of p- and f-block chemical species to gain insight about their energetic and spectroscopic properties. As well, the studies have provided understanding about the utility of the quantum mechanical approaches employed for the third-row and lanthanide species. The multireference ab initio correlation consistent Composite Approach (MR-ccCA) was utilized to predict dissociation energies for main group third-row molecular species, achieving energies within 1 kcal mol-1 on average from those of experiment and providing the first demonstration of the utility of MR-ccCA for third-row species. Multireference perturbation theory was utilized to calculate the electronic states and dissociation energies of NdF2+, providing a good model of the Nd-F bond in NdF3 from an electronic standpoint. In further work, the states and energies of NdF+ were determined using an equation of motion coupled cluster approach and the similarities for both NdF2+ and NdF were noted. Finally, time-dependent density functional theory and the static exchange approximation for Hartree-Fock in conjunction with a fully relativistic framework were used to calculate the L3 ionization energies and electronic excitation spectra as a means of characterizing uranyl (UO22+) and the isoelectronic compounds NUO+ and UN2.
|
89 |
Solubility Studies on Lanthanide Oxides, Hydroxides, and Their Solid Solutions / 希土類酸化物、水酸化物およびそれらの固溶体の溶解度に関する実験的研究Moniruzzaman, Mohammad 24 November 2021 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第23576号 / 工博第4931号 / 新制||工||1770(附属図書館) / 京都大学大学院工学研究科原子核工学専攻 / (主査)教授 佐々木 隆之, 教授 横峯 健彦, 准教授 小林 大志 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
|
90 |
Spectroelectrochemical Real-Time Monitoring of f-block Elements during Nuclear Fuel ReprocessingSchroll, Cynthia A. 30 September 2013 (has links)
No description available.
|
Page generated in 0.0581 seconds