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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Hydrides of Alkaline Earth–Tetrel (AeTt) Zintl Phases: Covalent Tt–H Bonds from Silicon to Tin

Auer, Henry, Guehne, Robin, Bertmer, Marko, Weber, Sebastian, Wenderoth, Patrick, Hansen, Thomas Christian, Haase, Jürgen, Kohlmann, Holger 28 February 2019 (has links)
Zintl phases form hydrides either by incorporating hydride anions (interstitial hydrides) or by covalent bonding of H to the polyanion (polyanionic hydrides), which yields a variety of different compositions and bonding situations. Hydrides (deuterides) of SrGe, BaSi, and BaSn were prepared by hydrogenation (deuteration) of the CrB-type Zintl phases AeTt and characterized by laboratory X-ray, synchrotron, and neutron diffraction, NMR spectroscopy, and quantum-chemical calculations. SrGeD4/3–x and BaSnD4/3–x show condensed boatlike six-membered rings of Tt atoms, formed by joining three of the zigzag chains contained in the Zintl phase. These new polyanionic motifs are terminated by covalently bound H atoms with d(Ge–D) = 1.521(9) Å and d(Sn–D) = 1.858(8) Å. Additional hydride anions are located in Ae4 tetrahedra; thus, the features of both interstitial hydrides and polyanionic hydrides are represented. BaSiD2–x retains the zigzag Si chain as in the parent Zintl phase, but in the hydride (deuteride), it is terminated by H (D) atoms, thus forming a linear (SiD) chain with d(Si–D) = 1.641(5) Å.
112

In situ hydrogenation of the Zintl phase SrGe

Auer, Henry, Wallacher, Dirk, Hansen, Thomas Christian, Kohlmann, Holger 28 February 2019 (has links)
Hydrides (deuterides) of the CrB-type Zintl phases AeTt (Ae = alkaline earth; Tt = tetrel) show interesting bonding properties with novel polyanions. In SrGeD4/3–x (γ phase), three zigzag chains of Ge atoms are condensed and terminated by covalently bound D atoms. A combination of in situ techniques (thermal analysis and synchrotron and neutron powder diffraction) revealed the existence of two further hydride (deuteride) phases with lower H (D) content (called α and β phases). Both are structurally related to the parent Zintl phase SrGe and to the ZrNiH structure type containing variable amounts of H (D) in Sr4 tetrahedra. For α-SrGeDy, the highest D content y = 0.29 was found at 575(2) K under 5.0(1) MPa of D2 pressure, and β-SrGeDy shows a homogeneity range of 0.47 < y < 0.63. Upon decomposition of SrGeD4/3–x (γ-SrGeDy), tetrahedral Sr4 voids stay filled, while the Ge-bound D4 site loses D. When reaching the lower D content limit, SrGeD4/3–x (γ phase) with 0.10 < x < 0.17, decomposes to the β phase. All three hydrides (deuterides) of SrGe show variable H (D) content.
113

Tetrasubstituierte Calix[4]arene mit gemischten Donorgruppen als selektive Liganden für Seltenerdelemente

Glasneck, Florian 19 April 2022 (has links)
folgt
114

Upconverting luminescent nanoparticles for bioimaging applications

Nsubuga, Anne 14 June 2019 (has links)
The synthesis and surface modification of upconverting nanoparticles (UCNPs) composed of a host lattice NaYF4 doped with sensitizers (Yb3+, Nd3+) and luminescent emitters (Er3+) were investigated for potential integration in biological applications.The fascination of NaYF4: Nd3+, Yb3+, Er3+ upconverting nanoparticles derives from their capacity to be excited in the biologically transparent window (650-950 nm) enabling deep tissue penetration. In particular, the ability to convert near infrared radiation into visible light (upconversion), which prevents autofluorescence and over-heating effect of biological tissues.In biological applications especially in vivo, morphology and size of the nanoparticles plays a crucial role in determination of cellular responses and fate in living organism. Heterogeneously sized nanoparticles, in contrast to uniform ones, might be distributed unevenly in the organism causing undesirable toxic side effects. Therefore, precise control of the nanoparticle size, distribution, and reproducibility were main tasks in the first part of this work. Colloidal upconverting nanoparticles were synthesized using coprecipitation method. Synthetic parameters such as reaction temperature (280-320 °C), and time (5-30 min) were used to tailor the nanoparticle morphology, crystal phase (cubic or hexagonal) and particle size (sub-10 - 20 nm). Integration of these nanoparticles in biological applications requires dispersibility in aqueous media. Hence hydrophobic UCNPs were surface-modified with low molecular weight ligands including O-phospho-L-threonine, alendronic acid, and PEG-phosphate ligands to generate water-dispersible UCNPs. Furthermore, in this work, photocrosslinking of diacetylenes is presented as an effective way to create robust UCNPs with a crosslinked shell. Finally, the protein corona formation on UCNPs coated with charged, zwitterionic and nearly neutral ligands was investigated. The composition of protein binding to UCNP is notably influenced by the surface charges of the UCNPs. Overall, the results obtained in the frame of this work show that the NaYF4: Nd3+, Yb3+, Er3+ UCNPS have the potential to replace conventional fluorophores in bioimaging applications due to their remarkable optical properties, as well as the derivatization flexibility of their surface
115

Dendrimere als vielseitige, nano-skalige Objekte für biomimetische, biomedizinische und katalytische Fragestellungen

Appelhans, Dietmar, Voit, Brigitte 29 August 2007 (has links)
With their three-dimensional macromolecular structure and shape, and with their tuneable properties in both the inner and outer spheres, dendrimers are ideal model compounds in the nanometre range between 1 and 10 nm. The possibility to combine different properties within one macromolecule destines them for use in various high-end research fields such as medicine, pharmacy, biology, supramolecular chemistry, nanotechnology and material sciences. On the basis of their high end-group density and a compact, highly branched molecular structure, dendrimers are successfully investigated as carrier systems for active substances and metal ions (e.g. contrast agents for the visualisation of blood vessels), as templates for metal nanoparticles, as artificial enzymes with defined functions, and as materials for catalysis. / Dendrimere sind aufgrund ihrer dreidimensionalen Makromolekülstruktur und -form und ihrer steuerbaren Eigenschaften sowohl an der Oberfläche als auch im Molekülinneren ideale Modellverbindungen im Nanometerbereich – sie sind zwischen 1 und 10 nm groß –, die vorzugsweise in der Medizin, Pharmazie, Biologie, Supramolekularen Chemie, Nanotechnologie und den Materialwissenschaften eingesetzt werden. Aufgrund ihrer hohen Endgruppendichte und der kompakten, stark verzweigten Molekülform werden Dendrimere unter anderem als Trägermaterialien und Transportsysteme für Wirkstoffe und Metallionen, zum Beispiel als Kontrastmittel zur Visualisierung von Organen und Blutgefäßen, als Template für metallische Nanopartikel, zur Erzeugung künstlicher Enzymfunktionen und in der Katalyse erfolgreich untersucht.
116

On Design for Electrochemical Energy Storage Materials

Sakaushi, Ken 19 December 2013 (has links)
In this dissertation, diverse strategic designs of energy storage materials were explored. The main aims were: affordability and high-performances. I) on eco-efficient synthesis of 1D intercalation compounds was described; a low-temperature aqueous solution synthesis of nanostructured 1D (molybdenum trioxide) MoO3 was developed. Subsequent self-assembly of the fibers to form large-scale freestanding films in paper-like structure was achieved without any assistance of organic compounds. Indeed, the whole processes, from synthesis to assembly of obtained materials, do not require toxic organic solvents. As an example of the application of our synthesized materials, 1D MoO3, having the width in 50−100 nm, with the length in micro scale, and with thickness in ~10 nm, and the macroscopic oxide papers consisting of 1D MoO3 and carbon materials were applied as the cathode and anode to lithium-ion batteries, respectively. As a cathode material, the 1D MoO3 showed a high rate capability with a stable cycle performance up to 20 A/g due to a short Li+ diffusion path along [101] and less grain boundaries which were achieved by the precise nanostructure control. As an anode material, the composite paper showed the first specific discharge capacity of 800 mAh/g. These findings above indicate not only an affordable, eco-efficient synthesis and assembly of nanomaterials but also show a new attractive strategy towards a possible whole aqueous process for a large-scale fabrication of freestanding oxide papers without any toxic organic solvent. II) a new energy storage principle using polymeric frameworks was investigated. The new energy storage concept can deliver both high power and high energy. This is because of the novel energy storage nature of designed artificial polymeric frameworks which is different from classical energy storage mechanisms. The main novel discovery was as follows; since CTF-1 is linear stepwise p- and n-dopable polymer, therefore, this framework can store energy as a cathode in the wide working potential with both cation below 3 V versus Li/Li+ and anion above 3 V versus Li/Li+ by Faradaic reaction. Due to this feature, CTF-1 can store high specific capacity of 540 mAh/g. As the result the new energy storage concept which can deliver both high power and high energy was discovered by using a novel polymeric cathode. Unlike typical organic electrodes in sodium battery systems, the CTF-1 has a high specific power of 10 kW/kg, specific energy of 500 Wh/kg, and over 7,000 cycle life retaining 80 % of its initial capacity in half-cells. Indeed, all-organic energy storage devices based on CTF-1 suggested a possibility towards an extremely affordable energy storage device. Recent research on such artificial polymeric frameworks suggests their huge variability to utilize different functional structures which could even further increase power and energy even further when using different starting monomers. This would significantly extend the possibilities of electrical energy storage devices for a sustainable society based on our result. From this point of view, our research strategy which combined the experimental and theoretical study would be a model for further development of this field.
117

High Energy and Power Density Dual-ion Batteries with Graphite as Cathode: Key Challenges and Strategies

Sabaghi, Davood 23 May 2024 (has links)
In summation, this thesis provides a panoramic view of the prevailing challenges and potential solutions associated with achieving unparalleled energy and power densities in GDIBs where graphite reigns supreme as the cathode material of choice. By comprehensively tackling these challenges and integrating the recommended strategies, there lies a promising path ahead for the evolution of advanced dual-ion batteries. Such advancements could redefine benchmarks in en-ergy storage, heralding an era of more efficient and versatile applications.
118

In-Plane Oriented Two-Dimensional Conjugated Metal-Organic Framework Films for High-Performance Humidity Sensing

Park, SangWook, Zhang, Zhe, Qi, Haoyuan, Liang, Baokun, Mahmood, Javeed, Noh, Hyuk-Jun, Hambsch, Mike, Wang, Mingchao, Wang, Mao, Ly, Khoa Hoang, Wang, Zhiyong, Weidinger, Inez M., Zhou, Shengqiang, Baek, Jong-Beom, Kaiser, Ute, Mannsfeld, Stefan C. B., Feng, Xinliang, Dong, Renhao 02 October 2024 (has links)
Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have emerged as a new generation of conduct-ing MOFs for electronics. However, controlled synthesis of thin-film samples with high crystallinity and defined layer orientation, which is beneficial for achieving high-performance devices and reliable structure-property relationship, has remained a challenge. Here we develop a surfactant-directed two-step synthesis of layered 2D c-MOF films based on benzene and triphenylene ligands linked by copper-bis(diimino) complexes (HIB-Cu and HITP-Cu, respectively). The achieved layered 2D c-MOF films are featured as free-standing, in-plane oriented, and polycrystalline films with domain size up to ~ 8000 nm2 and a tunable thickness in the range of 8 - 340 nm. Benefiting from the intrinsic elec-trical conductivity and quasi-one-dimensional pore channels, a HIB-Cu film based chemiresistive sensor is construct-ed, displaying effective humidity sensing with a response as fast as ~ 21 s, superior to the reported MOF-powder-based chemiresistive sensors (in the orders of minutes).
119

Synthese neuartiger siliciumorganischer Pharmaka und Riechstoffe sowie siliciumhaltiger Synthesebausteine / Synthesis of New Silicon-based Drugs and Odorants and Silicon-containing Building Blocks

Büttner, Matthias Werner January 2007 (has links) (PDF)
Siliciumhaltige Analoga bekannter Pharmaka sowie Derivate diverser Riechstoffe wurden dargestellt. Darüber hinaus wurden neue siliciumhaltige Synthesebausteine für weitere Wirkstoffsynthesen synthetisiert. / Silicon-containing analogs of well-known drugs and derivatives of several odorants were prepared. Furthermore, new silicon-containing building blocks for the syntheses of drugs and odorants have been synthesized.
120

Synthese von Liganden muscarinerger Rezeptoren - Allostere Modulatoren, bivalente Agonisten und Antagonisten / Synthesis of ligands of muscarinic receptors - Allosteric modulators, bivalent agonists and antagonists

Schmitz, Jens January 2008 (has links) (PDF)
Die vorliegende Arbeit befasst sich mit der Synthese von Liganden muscarinerger Rezeptoren, die zur Superfamilie der G-Protein-gekoppelten Rezeptoren gehören. Die fünf Muscarinrezeptor-Subtypen weisen im Bereich der orthosteren Bindungsstelle, an die u. a. der endogene Ligand Acetylcholin bindet, einen hohen Konservierungsgrad der Aminosäuresequenz auf. Alle Muscarinrezeptoren weisen neben der orthosteren Bindungsstelle auch eine oder mehrere allostere Bindungsstellen auf. Da diese sich im weniger konservierten extrazellulären Bereich des Rezeptors befinden, ist es möglich subtypspezifische Liganden zu entwickeln. Allostere Modulatoren binden an diese topographisch andere Stelle des Rezeptors und sind in der Lage, gezielt die Bindung eines orthosteren Agonisten oder Antagonisten zu modulieren. Dies bedeutet, dass sie die Assoziation und die Dissoziation orthosterer Agonisten und Antagonisten beeinflussen können. Die Gleichgewichtsbindung des Orthosters kann erhöht (d. h. positive Kooperativität), erniedrigt (d. h. negative Kooperativität) bzw. nicht beeinflusst (d. h. neutrale Kooperativität) werden. Das Ziel der Arbeit bestand zunächst darin, die Synthese allosterer Modulatoren des M2-Rezeptors vom Bis(ammonium)alkan-Typ, wie W84 und Naphmethonium, zu optimieren. Da die Synthesen dieser bisquartären Verbindungen zeitaufwändig sind, wurden die Synthesen durch Einsatz einer Synthesemikrowelle optimiert, um neue Bis(ammonium)alkan-Verbindungen effizienter synthetisieren zu können. Der Vergleich beider Synthesemethoden (konventionell bzw. Mikrowellen-unterstützt) zeigt sehr deutlich, dass die Reaktionszeiten durch Einsatz einer Synthesemikrowelle drastisch verkürzt werden konnten, insbesondere bei Verbindungen, die sehr lange Reaktionszeiten beanspruchen. Zusätzlich konnten die Ausbeuten aller synthetisierten Verbindungen durch Mikrowellen-unterstützte Synthese z. T. deutlich gesteigert werden. Im Verlauf der Arbeit wurden unsymmetrisch und symmetrisch nitrosubstituierte Bisnaphthalimide hergestellt. Durch Mikrowellen-unterstützte Hydrierung unter Palladium/Kohle-Katalyse wurden anschließend die analogen aminosubstituierten Derivate erhalten. Ein weiteres Ziel der Arbeit bestand darin, ein Naphmethonium-Derivat herzustellen, das über einen Spacer mit einem geeigneten Fluoreszenzfarbstoff gekoppelt werden kann. Ein Farbstoff-markierter allosterer Modulator könnte als ein wichtiges pharmakologisches Werkzeug zur direkten Charakterisierung allosterer Interaktionen und zur Verfolgung des „Rezeptor-Traffickings“ mittels Fluoreszenzkorrelations-spektroskopie genutzt werden. Als Spacer diente eine Alkylkette mit endständiger primärer Aminofunktion, die mit Alexa-Fluor 532 gekoppelt werden sollte. Zur Einführung des Spacers wurden verschiedene Strategien verfolgt. Schließlich konnte Verbindung 3h über eine Chlorzwischenstufe hergestellt werden, über deren freie primäre Aminogruppe der Fluoreszenzfarbstoff in weiteren Arbeiten gekoppelt werden kann. Ein weiteres Ziel der Arbeit war die Syntheseoptimierung des hochpotenten unselektiven Agonisten Iperoxo, das eine für akademische Zwecke wichtige Substanz in der pharmakologischen Testung und ein wichtiges Zwischenprodukt in der Synthese bivalenter Agonist/Alloster-Hybridverbindungen ist. Die Ausbeuten aller Stufen konnten erhöht und die Gesamtausbeute signifikant von 13% auf 22% gesteigert werden. Außerdem wurden neue Agonisten hergestellt, die sich im Heterozyklus unterscheiden. Ein weiteres Ziel der Arbeit war die Synthese bivalenter Hybridverbindungen nach dem Nachrichten-Adressen-Modell von Schwyzer. Zum einen sollten Agonist/Alloster-Hybridverbindungen synthetisiert werden, wobei die in der Literatur beschriebene Hybridverbindung Hybrid 1 (W84 und Iperoxo) als Leitstruktur diente. So wurde im ersten Schritt eine auf der allosteren Seite verkürzte Substanz ohne Phthalimidopropyl-Rest hergestellt (Hexamethonium und Iperoxo). Danach wurden verschiedene Funktionalitäten an der lateralen quartären Ammoniumfunktion eingeführt. Daneben wurden erstmals Antagonist/Alloster-Hybridverbindungen hergestellt, die aus einem M2-selektiven allosteren Modulator (W84, Naphmethonium bzw. Hexamethonium) und einem subtypunspezifischen Antagonisten (Atropin bzw. Scopolamin) bestehen. Im ersten Schritt wurde der allostere Molekülteil nach der optimierten Mikrowellen-unterstützten Synthese hergestellt. Die erhaltenen Zwischenstufen 2 wurden im Anschluss mit Atropin und Scopolamin in Acetonitril umgesetzt und die Antagonist/Alloster-Hybridverbindungen 34 und 35 erhalten. Die pharmakologische Testung der synthetisierten Verbindungen erfolgte durch Radioligandbindungsstudien an Herzventrikelgewebe des Hausschweins. Der allostere Effekt der Testsubstanzen wurde indirekt über die Verzögerung der Dissoziation des radioaktiv markierten orthosteren Antagonisten [3H]N-Methylscopolamin. / The present work focussed on the synthesis and characterisation of ligands of muscarinic receptors belonging to the superfamily of G-protein-coupled receptors. The five known subtypes of muscarinic receptors (M1-M5) are located ubiquitary in the mammalian organism and participate in many physiological procedures. The endogenous ligand acetylcholine and classical antagonists bind to the orthosteric binding site, which is located deeply in the receptor channel and exhibit a highly conserved amino acid sequence. Allosteric modulators bind to a topographically different site than classical orthosteric ligands. The allosteric binding sites are located in the external loops of the receptor protein. Since these regions exhibit a less conserved structure it is possible to design allosteric modulators capable of binding selectively to specific subtypes and modulating the efficiency of the orthosteric ligand. An allosteric modulator has the ability to affect equilibrium binding of the orthosteric agonist or antagonist: equilibrium binding can either be increased (= positive cooperativity), decreased (= negative cooperativity) or left unaltered (= neutral cooperativity). One intention of this work was to optimize the synthetic pathway to bis(ammonio)alkane-type allosteric modulators of the M2-receptor, like W84 or naphmethonio. The syntheses to these bisquaternary compounds are time consuming. In order to obtain new potent bis(ammonio)alkane-compounds the syntheses were optimized by using a microwave oven. Comparing the conversion times of conventional and microwave-assisted heating revealed a substantially speed up in the synthetic pathway particularly for the reactions which took the longest under conventional reflux conditions. Additionally, the yields of all synthesized compounds could be increased by means of microwave-assisted synthesis. In this work symmetrical and non-symmetrical nitro-substituted bisnaphthalimides were synthesized and the analogue amino-substituted compounds were obtained by microwave-assisted hydrogenation afterwards. A further aim of this work was to synthesize a naphmethonio-derivative which is suitable for a connection to a fluorescent dye. A fluorescent naphmethonio-derivative may help to characterize allosteric interactions directly and trace receptor trafficking by means of fluorescence correlation spectroscopy. Firstly, a primary amino group should be connected via an alkyl-spacer to the allosteric modulator and secondly, this intermediate should be combined with the fluorescent dye alexa-fluor-532. Several strategies were prosecuted. Finally, the synthesis of compound 3h via a chloride-intermediate was successful. Another intention of this work was to optimize the synthetic pathway to the non-selective muscarinic agonist iperoxo, which is an important reference compound in the pharmacological testing and an intermediate in the synthetic pathway of bivalent agonist/allosteric modulator hybrid compounds. The yields in each reaction step were enhanced and the total yield was increased from 13 % to 22 %. Furthermore, other muscarinic agonists differing in the substitution pattern of the heterocycle were synthesized. A further aim of this work was to synthesize bivalent hybrid compounds combining an orthosteric and an allosteric ligand in one molecule. Following Schwyzer´s concept of hybrid compounds containing an “address” skeleton that binds selectively to a receptor subtype and a non-selective “message” moiety inducing agonism or antagonism, a group of hybrid hexamethonio-type derivatives has been designed as subtype selective agonists and antagonists. Hybrid 1 served as a lead for the agonist/allosteric modulator-hybrid compounds synthesized in this work. Firstly, the goal was to combine the agonist iperoxo with hexamethonio and secondly, to introduce a different substitution pattern at the lateral quaternary ammonio-group in the obtained iperoxo/hexamethonio-hybrid compound 27a. Another aim of this work was to synthesize antagonist/allosteric modulator hybrid compounds. Therefore, the classical antagonists atropine and scopolamine were connected with the allosteric agents W84, naphmethonio and hexamethonio via hexyl-spacer. The pharmacological testing of all compounds was accomplished by radioligand binding studies in homogenates of porcine heart ventricles. The resulting allosteric effect was determined by measuring the inhibition of the dissociation of the radioactive marked orthosteric antagonist [3H]N-methylscopolamine ([3H]NMS). In equilibrium binding studies information about the affinity of the allosteric modulators to the free receptor and about the cooperativity between the allosteric and the orthosteric ligand was obtained.

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