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1
Borghi, F. M. « ENGINEERING THE STRUCTURAL AND FUNCTIONAL PROPERTIES OF TRANSITION METAL OXIDE INTERFACES BY CLUSTER ASSEMBLING ». Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/278394.
Texte intégralRésumé :
Nanostructured materials are defined as systems composed of single or multiple
phases such that at least one of them has characteristic dimensions in the nanometer range
(1-100 nm). The strategic importance of nanostructured materials rely on the fact that their
structural, electronic, magnetic, catalytic, and optical properties can be tuned and controlled
by a careful choice and assembling of their nanoscale elemental building blocks.
Clusters, aggregations of a few atoms to a few thousands of atoms, are the building
blocks used to synthetize nanostructured materials. Low-Energy Cluster Beam Deposition (LECBD) is a technique of choice for the fabrication of nanostructured systems, since it allows the deposition on a substrate of neutral particles produced in the gas phase and maintaining their properties even after
deposition. This has been proven to be a powerful bottom-up approach for the engineering
of nanostructured thin films with tailored properties, since it allows in principle the control
of the physical and chemical characteristics of the building blocks. Among different approaches to LECBD, supersonic cluster beam deposition (SCBD) present several advantages in terms of deposition rate, lateral resolution compatible with planar microfabrication technologies and neutral particle mass selection by exploiting aerodynamic focusing effects. All these features make SCBD a superior tool
to synthesize nanostructured films and their integration on microfabricated platforms.
The morphology of cluster-assembled materials is characterized by a
hierarchical arrangements of small units in larger and larger features up to a certain critical
length-scale, in general determined by the duration of the deposition process. The cluster-assembled film morphology is characterized by high specific area and porosity at the nano
and sub-nanometer scale, extending in the bulk of the film. Surface pores and surface
specific area, as well as rms roughness, depend on film thickness, and increase with it.
All these morphological properties is of great relevance for the use of cluster-assembled
film in devices as gas sensor, (photo) catalysis, solar energy conversion and as biocompatible substrates.Recently it has been recognized that nanoscale surface morphology and nanopores play an important role in processes involving the interaction of biological entities (protein,
viruses, enzymes) with nanostructured surfaces, via the modulation of electric interfacial
properties. In particular, when the nanostructured material is used to produce electrodes
and substrates for operation in liquid electrolytes, with given pH and ionic strength, double
layer phenomena take place. An important parameter to describe these electrostatic
phenomena is the IsoElectric Point (IEP), which corresponds to the pH value at which the
net charge of the compact layer is zero. When two interacting surfaces approach to a
distance comparable or smaller than the typical screening length of the electrolytic solution
(the Debye length, determined by the ionic strength of the solution), the overlap of the
charged layers determines complex regulation phenomena that are difficult to describe
theoretically. While significant insights have been obtained on the properties of the electric
double layers formed between flat smooth surfaces, the case of rough surfaces still
represents a severe challenge, hampering analytical, yet approximate, solutions of the
double layer equations to be reliably obtained. Anyway, these phenomena have been
recently shown to be strongly influenced by the morphological properties of the surface.
The quantitative characterization of all these interfacial properties requires imaging
and force spectroscopy techniques with a resolution in and beyond the nanometer-scale.
Atomic Force Spectroscopy (AFM) is an excellent candidate, since it couples the possibility
of scanning with a z-resolution lower than fraction of nanometer and x-y resolution of 1
nm and also of performing very accurate force spectroscopy measurements.
The first aim of my PhD work is to characterize by AFM the evolution of
morphological properties of transition-metal oxides cluster-assembled materials (in
particular nanostructured Titania (ns-TiOx) and nanostructured Zirconia (ns-ZrOx), starting
from sub-monolayer regime to thin film, and especially to describe the influence of the
building-blocks dimensions on the growth mechanisms and on the final surface
morphology and topography. With this information, I have explored the influence of
nanoscale morphology on double layer interactions which takes place on these
nanostructured interfaces and on the wettability behaviour. The results have been used to
highlight the role of morphological and structural surface properties as biophysical signal
mediators for protein adsorption processes and cellular adhesion.
2
Zosiak, Lukasz. « Simulations of atomic and electronic structure of realistic Co and Pt based nanoalloy clusters ». Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAE038/document.
Texte intégralRésumé :
Cette thèse présente une étude théorique de la structure électronique et de la tendance à l'ordre dans les nanoalliages de métaux de transition en se référant au cas des systèmes à base de cobalt-platine (CoPt) qui présentent un intérêt particulier dans les domaines du magnétisme et de la catalyse. Il est ainsi important de décrire au mieux l'évolution de la structure électronique en lien avec la structure atomique ou l'arrangement chimique en fonction de la taille de tels nanoalliages en vue de prédire des propriétés potentielles pouvant différer fortement de celles du matériau massif correspondant. Dans ce contexte, des calculs systématiques de DFT ont été mis en œuvre sur des systèmes modèles simples, alliages massifs, surfaces et nanoparticules, qui ont permis de montrer qu'une règle de neutralité de charge locale, par site espèce et orbitale, s'applique au système CoPt massif et s'étend aux nanoalliages. Sur cette base, des calculs auto cohérents de liaisons fortes ont été développés et ont permis de proposer un moyen précis de prédire les caractéristiques de nanoalliages réalistes, en termes de redistribution des états électroniques et de tendance à l'ordre. Les grandeurs caractéristiques déduites de ces calculs, telles que le désordre diagonal et non diagonal, peuvent être en effet être déterminées à partir de lois simples linéaires de variations des centres et des largeurs de bandes sur les sites Co et Pt. Les valeurs issues de ces lois peuvent être placées sur des cartographies de domaines de tendance à l'ordre et l'ensemble de la méthodologie devrait être étendue facilement à d'autres systèmes binairesThe interest in alloys of late transition metals arises from their potential applications in high-density magnetic storage devices where they can be used as supported magnetic nanoparticle arrays and as stable, efficient and selective catalysts. The preparation of materials with optimal properties faces a number of technological and physical restrictions and requires an in-depth knowledge of the interplay between structural features on the atomic level and the desired macroscopic properties. In the thesis, after extensive discussion of Density Functional Theory and Tight Binding approaches the work focused on DFT calculations of bulk systems, surfaces and small clusters. The results allow to conclude on general validity of the method and especially to justify the local neutrality assumption in the case of low-coordinated sites in nanoparticles. Basic structural, magnetic and energetic properties were also studied and compared with the experimental data. Subsequently TB calculations were performed and verified with DFT results. The scope of the calculations was then extended for the case of nanoclusters of realistic sizes, unavailable in DFT. Local Densities of State on sites with different chemical environment and coordination numbers were analyzed. The observations prove that basic features of LDOS (d-band centre and d-band width) can be predicted by simple laws on the basis of two terms: a structural term represented by the linear function of the site coordination and a chemical term as a rigid shift which opens a new way to predict the ordering tendency (mapping of the ordering domains) for any transition metal nanoalloy as a function of its size
3
Taylor, Stephanie Merac. « Calixarene supported transition metal clusters ». Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7770.
Texte intégralRésumé :
This thesis describes a series of calix[n]arene polynuclear transition metal and lanthanide complexes. Calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition metal and lanthanide centres. Surprisingly however, with only a few exceptions, the coordination chemistry of p-tBucalix[ 4]arene (TBC[4]), p-tBu-calix[8]arene (TBC[8]) and p-tBuhomotrioxacalix[ 3]arene (TBOC[3]) with paramagnetic transition metal ions for the purpose of making and studying magnetically interesting molecules is unknown. Chapter two describes the reaction of TBC[4] with manganese salts in the presence of an appropriate base (and in some cases co-ligand) resulting in the formation of a family of calixarene-supported [MnIII 2MnII 2] clusters (1-7) that behave as Single-Molecule Magnets (SMMs). These are: [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2MeOH (1), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(H2O)2]·4MeOH·2DMF (2), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2.8MeOH (3), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(EtOH)(H2O)] (4), [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6]·2MeOH·2DMSO (5) , [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6] (6) and [MnIII 2MnII 2(OH)2(C[4])2(MeOH)6]·4MeOH (7). Variation in the alkyl groups present at the upper-rim of the cone allows for the expression of a degree of control over the self-assembly of these SMM building blocks, whilst retaining the general magnetic properties. The presence of various different ligands around the periphery of the magnetic core has some effect over the extended self-assembly of these SMMs. Chapter three describes how the combination of complementary cluster ligands; sodium phenylphosphinate and the N,O-chelate 2-(hydroxy-methyl)pyridine (hmpH) with TBC[4] results in the formation of two new calixarene-supported clusters. This being an unusual [MnIIIMnII]2 dimer of dimers [MnIIIMnII(O2P(H)Ph)(DMF)2(MeOH)2]2 (8) and a ferromagnetic [Mn5] cage that displays the characteristic bonding modes of each support [MnIII 3MnII 2(OH)2(TBC[4])2(hmp)2(DMF)6](TBC[4]-H)·xDMF ·xH2O (9). Chapter four details how using oxacalix[3]arenes can tune the nature of the metal binding site, by introduction of ≥ 1 ethereal bridge. This results in Mn(II) rather than Mn(III) bonding in the phenolic pocket, and that these components self-assemble with additional Mn(II) and Mn(III) ions to form a [Mn10] supertetrahedron with an unusual oxidation state distribution, [MnII 6MnIII 4O4(TBOC[3])4(Cl)4(DMF)3]∙3.3H2O ∙ 1.5DMF (10). Chapter five introduces a family of lanthanide complexes formed using TBC[8]. Variation in the experimental conditions employed in the reaction of TBC[8] with lanthanide salts (LnX3) provides access to Ln1, Ln2, Ln4, Ln5, Ln6, Ln7 and Ln8 complexes, [Gd(TBC[8]-2H)Cl(DMSO)4]·MeCN·H2O·(DMSO)2·hex (11), [CeIV 4(TBC[8]-6H)2(μ3- O)2(DMF)4]·(DMF)5·hex·MeCN (12), [TbIII 5(TBC[8]-5H)(μ4-O)(μ3- OH)4Cl(DMSO)8(H2O)3]Cl3·(DMSO)2(hex)2 (13), [CeIV 6(TBC[8]-6H)2(μ4-O)2(μ2-OMe)4(μ2- O)2(DMF)4]·(DMF)6·hex (14), [Dy7(TBC[8]-7H)(TBC[8]-6H)(μ4-O)2(μ3-OH)2(μ2- OH)2(DMF)9]·(DMF)3 (15) and [Gd8(TBC[8]-7H)2(μ4-CO3)2(μ5-CO3)2(μ2-HCO2)2(DMF)8] (16), with all polymetallic clusters containing the common bi-nuclear lanthanide fragment. Closer inspection of the structures of the polymetallic clusters reveals that all but one (Ln8) are in fact based on metal octahedra or the building blocks of octahedra.
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Foster, D. F. « Stabilised transition metal carbonyl clusters ». Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354541.
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Hay, C. M. « Structural investigations of transition metal clusters ». Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234979.
Texte intégralRésumé :
The work described in this dissertation is concerned with structural aspects of the chemistry of transition metal cluster compounds, in particular with carbonyl clusters of the second and third transition series. The structures of a range of these complexes have been investigated, in the solid state, by single-crystal X-ray diffraction techniques, and in the solid and in solution, to a limited extent, by EXAFS spectroscopy. In Chapter One the basics of the single-crystal X-ray diffraction technique for determining the crystal and molecular structure of compounds in the solid state is described. The various steps of sample preparation, data collection, structure solution and refinement are discussed. Chapter Two is a review of the known structural chemistry of heterometallic cluster complexes which contain gold, or gold - phosphine units coordinated to the rest of the metal framework. The majority of complexes discussed in subsequent chapters are of this type. Simple 'electron counting' schemes which have been used to rationalise the structures of this class of compound are discussed critically. Chapter Three is divided up into five sections, each of which is concerned with a different class of heterometallic cluster containing an AuPR3 unit as a ligand. In section 1, the structure of [Os3(CO)10(AuPPh3)Cl], in which the Au atom bridges an Os-Os edge of the Os3 triangle, is described. In section 2, the structures of [HOs3Co(CO)13], [Os3Co(CO)13(AuPPh3)], and [HOs3Ru(CO)13(AuPEt3)] are described, and comment is made on the structural changes which occur when a bridging hydride ligand is replaced by a bridging AuPR3 group. In section 3 the structures of [Os4(CO)13(AuPEt3)], [Os4(CO)12(AuPPh2Me)2], and [Os4(CO)12(AuAsPPh3)2] are described, and a change in geometry is noted when a CO ligand is removed from the former complex and the level of unsaturation formally increased. In section 4 the structures of [Ru5C(CO)14(AuPEt3)2] and [Os6(CO)18P(AuPPh3)] are discussed. Both these clusters contain an interstitial atom which modifies the structural chemistry. Section 5 contains a description of the structures of [Os6(CO)16 lbraceP(OMe)3 rbrace (AuPEt4)2] and [Os6C(CO)20(OMe)Au]. The Os atom framework in these clusters is contrasted with a number of hexaosmium systems which do not contain gold. The structures of two hexaosmium 'raft' clusters, [Os6O(CO)18(PPh3)] and [H2Os6(CO)18(PPh)] are described in Chapter Four. The effect of the introduction of the capping O atom and the PPh group on to the previously planar metal system is discussed, and is related to molecular orbital calculations on the systems. In Chapter Five the introduction of heavy, main group metal atoms into a transition metal cluster system is discussed, with reference to the structures of [H3BiRu3(CO)9], [Bi2Os3(CO)9], and [Bi2Ru4(CO)12]. Both steric and electronic effects are shown to be of importance. Finally, in Chapter Six, the technique of EXAFS spectroscopy is described. The limitations of the technique when applied to transition metal cluster systems are discussed with reference to data obtained from two pentaosmium cluster complexes.
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Wang, John S. « Pseudocapacitive effects in nanostructured transition metal oxide materials ». Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1680034181&sid=11&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Harding, Daniel James. « Structure and reactivity of transition metal clusters ». Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527439.
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Hermes, A. C. « Structure and reactivity of transition metal clusters ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:91e9449f-8c1e-4955-8c08-d9f24e5bbe6a.
Texte intégralRésumé :
A range of computational and experimental techniques have been applied to the study of four metal cluster systems. Decorated rhodium clusters Rh n O m (N 2 O) + ( n = 4 − 8, m = 0 − 2) have been investigated both experimentally by IR-MPD and computationally using DFT. The effect of cluster size as well as oxygen coverage on the spectroscopy of the N 2 O bend are analyzed. The infrared-induced decomposition of N 2 O on Rh n O + m is observed on all cluster sizes, with marked differences as a function of size and oxygen coverage, particularly in the case of Rh 5 (N 2 O) + . The oxidation of CO was studied on the surface of small platinum cluster cations Pt n O + m ( n = 3 − 7, m = 2 , 4) by IR-MPD at 400 – 2100cm −1 . Spectroscopically, oxygen is found to be bound both dissociatively and molecularly on the cluster surface, while the CO band is found to red shift in cluster size, and blue shift with oxygen coverage. Oxidation of CO proceeds on all cluster sizes, with a constant branching ratio of 40% : 60% . DFT calculations identified key stationary points and barriers on the Pt 4 O 2 CO + reaction pathway. The one-colour Ta 2 photodissociation is studied by photoionization and VMI in the range 23500 – 24000cm −1 , finding clear evidence of a fragmentation process producing Ta , which is interpreted as fragmentation of cationic Ta + 2 at the two photon level. A majority of the observed channels produce either atomic ( Ta( 4 F 3/2 ) ) or cationic ( Ta + ( 5 F 1 ) ) ground state. An improved value for the dissociation energy D 0 ( Ta + 2 ) is obtained, in agreement with computational predictions. The anisotropies observed show weak evidence of a perpendicular transition being involved in the photodissociation process. Finally, the photodissociation dynamics of Cu 2 are studied by spectroscopy in the range 36000 – 38200cm −1 as well as VMI. Clear evidence for resonant photolysis of Cu 2 is obtained, as a result of both direct dissociation of the Cu + 2 2 Π ion state as well as dissociation of doubly excited Cu 2 states, which leads to a determination of dimer dissociation energies. Finally, the production of Cu + 2 is interpreted as evidence of photolysis of Cu 3 , from which a Cu 3 dissociation energy is derived.
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Parry, Imogen Sophie. « Collisional and photoexcitation of transition metal clusters ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:b1f2fc37-97ff-4500-ab34-ceb7e515b9d2.
Texte intégralRésumé :
The properties of transition metal clusters differ from those of both atomic and bulk size regimes. Such clusters are incompletely understood and potentially useful, making them attractive targets for further study. The very smallest clusters studied in this thesis (CuO, Cu2 and Cu3) have been investigated with velocity map imaging. 1+1' photodissociation of CuO X 2Π3/2 was observed, via the C, D, E, F and H states of CuO. CuO* was photodissociated to form Cu(2D3/2) + O(1D2). D0(CuO) was determined to be 3.041±0.030 cm-1. Non-resonant three-photon Cu2 photodissociation occurred throughout the energy range studied to produce one ground-state and one highly-excited copper atom,Cu*. Cu* was ionised by a single additional visible photon. Nearly all Cu* atoms with internal energies between 41000 and 53000 cm-1 were observed. D0(Cu2) has been calculated to be 1.992±0.037 eV. Features arising from photodissociation of Cu3 were observed in the Cu+ and Cu2+ ion yield spectra and images. Their structure was ill-resolved due to uncertainties in the internal energy of both parent Cu3 and product Cu2. These features correspond to single-photon dissociation of Cu3 to produce metastable D-states of the copper atom and vibrationally excited Cu2. One series of features implies a previously-unobserved state of either Cu2 or Cu3. RhnN2O+ and RhnON2O+ (n=5, 6) were collisionally activated in collision-induced dissociation (CID) experiments with Ar and 13CO. These experiments were carried out in a Fourier Transform Ion Cyclotron Resonance(FT-ICR)spectrometer. Argon collisions induced both N2O desorption and N2O reduction. The branching ratios observed reproduced those seen in prior IR-MPD experiments. 13CO was observed to chemisorb to the cluster upon collision, activating not only N2O desorption and reduction but also CO oxidation. Formation of CO2 was noted to be particularly rapid on the n=5 cluster compared to the n=6 cluster. Reactions of RhnN2O+ (n=4-6) clusters were also activated by black body radiation. This technique is known as BIRD - black-body induced infrared radiative dissociation. These studies revealed that the N2O desorption barrier exceeds the N2O reduction barrier on all clusters studied, but that the entropic favourability of desorption increases its rate relative to reduction with increasing cluster internal energy. The BIRD rate was much reduced upon cooling the ICR cell to 100 K. A further test of the BIRD mechanism increased the number of N2O ligands and hence the absorption rate. An approximately linear increase in the dissociation rate of Rhn(N2O)m+ was observed with index m. Deviations from linearity were caused by variations in the N2O desorption rate. In the case of Rh5(N2O)m+, desorption rates corresponded closely to N2O binding energies calculated by density functional theory. The system was modelled using a master equation approach.
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Gu, Yanjuan, et 谷艳娟. « Nanostructure of transition metal and metal oxide forelectrocatalysis ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37774396.
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Gu, Yanjuan. « Nanostructure of transition metal and metal oxide for electrocatalysis ». Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37774396.
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Brown, D. B. « Studies of transition metal clusters with cyclic alkenes ». Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597013.
Texte intégralRésumé :
Chapter one outlines the role of organometallic transition metal clusters as models for chemisorption in surface chemistry. The factors which govern the applicability of the "surface-cluster analogy" are examined, and structural comparisons between organic species chemisorbed on the metal surface and similar ligands bound to metal clusters are used to develop these ideas. Particular reference is made to chemisorbed ethene since the bonding modes of this ligand are of most relevance to subsequent chapters. Chapter two commences with a brief discussion of the industrial importance of catalytic transformations of cyclic hydrocarbons. In an attempt to elucidate the mechanisms of such processes a detailed study of the reaction of unsaturated C8 ring systems with ruthenium carbonyl clusters was undertaken and the results are presneted in this chapter. Chapter three is primarily concerned with metal cluster interactions with the bicyclic alkene norbornene. It commences with a brief introduction illustrating the structure and bonding of norbornene to monometallic species and on a Pt(111) surface followed by the chemistry it subsequently undergoes. The limited chemistry of norbornene on transition metal clusters is also described. Following this a detailed description of the reaction of norbornene with ruthenium carbonyl clusters is provided. There is also a description of the reaction of norbornene with the activated cluster compound Os3(CO)10(MeCN)2. Chapter four is concerned with metal cluster interactions with the bicyclic diene norbornadiene. It begins by illustrating the mode of bonding of norbornadiene on a Pt(111) surface and the chemistry it subsequently undergoes. The limited cluster chemistry of norbornadiene that has been reported is also summarised. Following this a detailed description of the reaction of norbornadiene with ruthenium carbonyl clusters is provided. There is also a description of the reaction of norbornadiene with the activated cluster compound Os3(CO)10(MeCN)2.
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Sameera, W. M. C. « Electronic structure of transition metal ions and clusters ». Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/1389/.
Texte intégralRésumé :
This thesis uses density functional theory (DFT) to explore the electronic structure and reaction mechanisms of open-shell transition metal ions and clusters. The early part of the thesis (Chapters 2 and 3) is devoted to high-valent metal-oxo species, both mono- and bimetallic, while Chapter 4 describes some aspects of copper-catalysed carbon-carbon bond formation. Finally, Chapter 5 highlights the role of DFT in computing magnetic and spectroscopic properties of exchange-coupled iron clusters. Whilst the chemistry contained in the thesis is rather diverse, the underlying theme of open-shell transition metal ions is common to all chapters. Moreover, we are primarily concerned with the ways in which interactions between two or more adjacent open-shells (either two metals or a metal and a ligand radical) control structure and reactivity. After a brief introduction to relevant theoretical aspects in Chapter 1, we use Chapter 2 to establish a link between the electronic structure of the high-valent Mn(V)=O porphyrin monomer species and their ability to perform oxidation reactions. The reaction profiles for oxidation of a range of substrates depend critically on the electronic structure of the isolated oxidant. Where the electronic ground state is genuinely best described as Mn(V)=O, the interaction between oxidant and substrate is repulsive at large separations, only becoming attractive when the incoming nucleophile approaches close enough to drive an electron out of oxide p manifold. In contrast, where the ground state is better described as an oxyl radical form, Mn(IV)-O.+, the oxidation occurs in sequential one-electron steps, the first of which is barrierless. In Chapter 3, we extend these ideas to bimetallic systems, where the presence of two high-valent manganese centres allows the system to oxidise water. Specifically, we focus on two model systems which have been shown to oxidise water, a Mn-porphyrin-based system synthesised by Naruta and a Mn-based system reported by McKenzie where the ligands contain a mixture of pyridine and carboxylate donors. In both cases, we again find that the emergence of oxyl radical character is the key to the reaction chemistry. However, the radical character is ‘masked’ in the electronic ground states, either by transfer of an electron from the porphyrin ring (Naruta) or by formation of a di-μ-oxo bridge (McKenzie system). In Chapter 4 we turn our attention to copper chemistry, and the role of copper complexes in catalysing atom transfer radical additions (Kharasch additions). In this reaction, the copper cycles between Cu(I) and Cu(II) oxidation states, and the result is the formation of a new C-C bonds. This Chapter makes extensive use of hybrid QM/MM techniques to model the environment of the copper centre in the target polypyrazolylborate-copper complexes (TpxCu). Finally, in Chapter 5 we consider the electronic structure, magnetic and spectroscopic properties of a pair of exchange-coupled Fe3 clusters, [Fe3(μ3-O)(μ-4-O2N-pz)6X3]2- (where pz = pyrazolato, X = Cl, Br). Our primary goal was to establish how well broken-symmetry DFT is able to reproduce the observed Mössbauer spectroscopic parameters, which are extensively used to identify the chemical environments of iron species and, in the case of mixed-valence clusters, to establish the degree of delocalisation of the additional electrons. In recent years DFT has proved able to compute these parameters with encouraging accuracy, but it is not clear to what extent the known deficiencies in broken-symmetry wavefunctions will compromise this ability. Our work suggests that neither the isomer shift nor the quadrupole splitting are strongly influenced by the nature of the coupling between the metal ions, suggesting that broken-symmetry solutions can be used as a basis for computing these parameters in more complex clusters.
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Clucas, J. A. « Synthesis and structural characterisation of transition metal clusters ». Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383429.
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Brown, Alisdair James. « Functionalised transition metal clusters of cobalt and osmium ». Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/12847.
Texte intégralRésumé :
In Chapter One, a review of the chemistry of the tricobalt nonacarbonyl methylidyne cluster is presented. The concept of organic polymeric species containing inorganic moieties is introduced and methods of synthesis and characterisation are discussed. The importance of these compounds as potentially homogenised heterogeneous catalysts is highlighted, and some examples of these species are given. Finally, the catalytic cross linking of alkyd polymers is considered. In the second chapter, the synthesis and characterisation of some tricobalt clusters and their derivatives is presented. Reaction of [(CO)9Co3(μ3-CCO)]+ [AlCl4-] with nucleophiles ROH produced the compounds [(CO)9Co3(μ3-CCOOR)], where R= CH2CH=CH2 (1) and CH2CH2O(CO)CH=CH2 (2). The crystal structure of (1) is presented, and whilst it does not undergo polymerisation, compound (2) is readily polymerised by free radical initiation in both solution and emulsion systems with acrylic comonomers. The polymeric systems were characterised by infrared and ultra violet spectroscopy, as well as by gel permeation chromatography. However, neither the polymeric or monomeric cluster systems were found to catalyse the cross linking of alkyd polymers as they exhibit no redox properties under the ambient conditions studied. Chapter Three describes the synthesis and characterisation of triosmium clusters which contain functionalised alkynes. The crystal structure of [Os3(CO)8(μ-CO)(HOCH2C=CCHOCCHCCH2) is reported. Attempts to make polymeric and multicluster derivatives of these functionalised compounds are described. Chapter Four details the synthesis and characterisation of a novel amide linked di-cluster. Reaction of [(CO)9Co3(μ3-CCO+)][PF6-] with [(CO)9Co3(μ3-C)(p-C6H4NH2)] produced the species [(CO)9Co3(μ3-CCON(H)-p-C6H4(μ3-CCo3(CO)9], which has been characterised by X Ray crystallography, as well as by IR, NMR, FABMS and electrochemical techniques.
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Schooler, Paul. « Linked arene clusters : the interaction of transition metal clusters with the cyclophanes ». Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624962.
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Li, Yin. « Catalysis of colloidal transition metal nanoparticles in aqueous medium ». Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/30541.
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Whitton, Alan John. « Preparation and characterisation of mixed bismuth-transition metal clusters ». Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293876.
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Upward, Martin David. « Fullerenes, transition metal clusters and organometallics on silicon surfaces ». Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267153.
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Cooper, Graham Alastair. « Spectroscopy and imaging of gas-phase transition metal clusters ». Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:9db3727c-4246-4d39-95b3-83936265dfad.
Texte intégralRésumé :
The field of transition metal clusters has proven to be fertile ground for study in recent years due to their interesting properties and reactivity. In this thesis, Velocity Map Imaging (VMI) has been used alongside spectroscopic techniques to study a range of diatomic metal-containing molecules which have relevance to cluster chemistry. The photodissociation of Ag-RG complexes (RG = Ar, Kr, Xe), as well as AgO, have been studied in the 29900-31700 cm⁻¹1 spectral region using VMI. The electronic states of the fragments produced have been assigned in each case and new values for the dissociation energies determined. These are presented as an update to the most recent experimental values for each molecule, about which doubts have been expressed. VMI has also been used to study the photodissociation dynamics of isotopically-selected 98MoO and 52CrO in multiple spectral regions. Assignments have been proposed for the processes generating the observed features, and values for the dissociation energies of these species determined which are consistent with literature values from other, older experimental techniques, or indirect measurements. Finally, a comparison has been made of different image reconstruction algorithms in order to determine which is best suited to analysing the data recorded in our group. The experimental data from the rest of this thesis have been reanalysed using various approaches, and it is demonstrated that recently-developed maximum entropy programs produce better results than the onion peeling algorithm previously used.
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Dogbevia, Moses K. « Gas phase transition metal-cluster catalysis / ». abstract and full text PDF (free order & ; download UNR users only), 2005. http://0-wwwlib.umi.com.innopac.library.unr.edu/dissertations/fullcit/3209128.
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Thesis (Ph. D.)--University of Nevada, Reno, 2005."August, 2005." Includes bibliographical references. Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm.
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Mott, Derrick M. « Synthesis, characterization, and catalysis of metal nanoparticles ». Diss., Online access via UMI:, 2008.
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Figueras, Valls Marc. « Nanostructured transition metal carbides as potential catalysts for greenhouse gases conversion ». Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673020.
Texte intégralRésumé :
Over the recent decades, several studies revealed the precarious climate situation which is threatening all Life forms on earth, including mankind, even if sometimes we tend to ignore the actual fragility of our situation. Ironically, the human species is at the origin of the rapid change on climate, mostly by practicing unsustainable activities, such as the unregulated consumption of fossil fuels, excessive deforestation, extensive agriculture, and intensive livestock. All these practices have increased the concentration of greenhouse gases in the atmosphere, producing a rapid increase in the average Earth temperature with noticeable consequences in our lifetime. Nevertheless, several efforts have been conducted by the scientific community in order to revert the actual climate situation, even if society acts delayed.
One of the actual work routes implies the use of catalysts to capture and convert greenhouse gases into less harmful and more useful chemicals. This route has found in transition metal carbides (TMCs) proficient candidates that could have an important impact in the aforementioned matter. An interesting aspect of TMCs is their capacity to catalyse such transformation reactions at low temperatures and to withstand several reaction cycles without degrading. Precisely, the present Thesis unveils and discusses several reaction mechanisms involved in the greenhouse gases transformation reactions held by TMCs, particularly, focusing on MoCy nanoparticles, a largely unexplored field. This Thesis combines experimental and theoretical approaches to explain the observed experimental evidences, where custom synthetized MoC nanoparticle supported on Au(111) are able to activate methane at room temperature, hydrogenate CO2, and act as superior H2 sponges with respect to clean MoC extended surfaces. Moreover, other important findings are revealed, such as the reconstruction held by some transition metal carbides and nitrides surfaces and the intrinsic nature of clean MoC nanoparticles towards hydrogenation reactions. Overall, the present dissertation intends to encourage further efforts on developing TMC based catalyst able to be used at industrial levels.
The experimental section of this thesis has been carried out at the Brookhaven National Laboratory by the group of Prof. J. A. Rodriguez, while the computational part and results analysis has been carried out in the present institution, the Universitat de Barcelona. The results obtained have led to several joint publications.En els darreres dècades, diversos estudis han revelat la precària situació climàtica que està amenaçant totes les formes de vida a la terra, inclosa la humanitat, encara que de vegades tendim a ignorar la fragilitat de la nostra situació. Irònicament, l’espècie humana és l’origen del ràpid canvi climàtic, principalment per practicar activitats insostenibles, com el consum no regulat de combustibles fòssils, la desforestació excessiva, l’agricultura extensiva i la ramaderia intensiva. Totes aquestes pràctiques han augmentat la concentració de gasos d’efecte hivernacle a l’atmosfera, produint un ràpid augment de la temperatura mitjana de la Terra amb conseqüències notables fins i tot durant la nostra vida. No obstant això, la comunitat científica està realitzant diversos esforços per revertir la alarmant situació climàtica, fins i tot si la societat actua amb retard. Una de les rutes de treball implica l’ús de catalitzadors per capturar i convertir els gasos d’efecte hivernacle en productes químics menys nocius i més útils. Aquesta ruta ha trobat en els carburs de metalls de transició (TMC) candidats competents que podrien tenir un impacte important en la reactivitat esmentada. L’aspecte més interessant dels TMCs és la seva capacitat per catalitzar aquestes reaccions de transformació a baixes temperatures i per suportar diversos cicles de reacció sense degradar-se. Precisament, aquesta Tesi revela i analitza diversos mecanismes de reacció implicats en les reaccions de transformació dels gasos d’efecte hivernacle catalitzades pels TMC, concretament, centrant-se en les nanopartícules de MoCy, que encara romanen inexplorades. Aquesta tesi combina enfocaments experimentals i teòrics per explicar les evidències experimentals observades, on les nanopartícules de MoC sintetitzades suportades sobre Au (111) són capaces d’activar el metà a temperatura ambient, hidrogenar CO2 i actuar com a esponges H2 superiors respecte a les superfícies netes de MoC. A més, altres descobriments importants han estat revelats, com ara la reconstrucció d’algunes superfícies de TMC/TMN i la naturalesa química intrínseca de les nanopartícules de MoC netes pel que fa a les reaccions d’hidrogenació. En general, la present dissertació té la intenció de fomentar nous esforços en el desenvolupament de catalitzadors basats en TMCs que puguin ser utilitzats a nivell industrial. La secció experimental d’aquesta tesi s’ha dut a terme al Brookhaven National Laboratory pel grup del professor J. A. Rodriguez, mentre que la part computacional i l’anàlisi de resultats s’ha dut a terme a la present institució, la Universitat de Barcelona. Els resultats obtinguts han donat lloc a diverses publicacions conjuntes.
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Nordlander, Hans Ebbe. « Some chemistry of transition metal carbonyl clusters containing phosphorus ligands ». Thesis, University of Cambridge, 1990. https://www.repository.cam.ac.uk/handle/1810/272946.
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Morewood, Catherine Alexandra. « π-complexes of osmium and ruthenium organometallic clusters ». Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/272792.
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Bienati, Massimiliano. « Ab initio study of the chemical reactivity of metal clusters and metal oxide clusters ». Doctoral thesis, [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96444237X.
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Lee, Yui-bing. « The chemistry of osmium-silver and osmium-iridium mixed-metal clusters ». Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40987632.
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Walker, Nicholas R. « Gas-phase studies of multiply-charged transition metal complexes ». Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299030.
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Davies, S. J. « Synthesis and reactivity of metal chain and ring complexes ». Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233632.
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Rashid, Haroon. « Synthesis of novel heteroleptic stannylenes and reactions with transition-metal carbonyl clusters ». Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388466.
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Kinzer, Raymond Edward. « Fourier transform infrared spectroscopy study of small transition-metal carbide clusters ». [Fort Worth, Tex.] : Texas Christian University, 2009. http://etd.tcu.edu/etdfiles/available/etd-10152009-103514/unrestricted/kinzer.pdf.
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Irele, Patricia Taiwo. « Some chemistry of triosmium clusters with P- and N- ligands ». Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254120.
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Jund, Rodolphe. « Electrochimie de clusters mixtes tetrametalliques ». Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13175.
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Pedersen, David B. « The reactivity of gas-phase neutral transition-metal clusters, reactions of W clusters with cyclopropane and Ta clusters with alkanes ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0007/NQ38324.pdf.
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Wong, Wing Tak. « The chemistry of high nuclearity carbonyl clusters of osmium ». Thesis, University of Cambridge, 1991. https://www.repository.cam.ac.uk/handle/1810/271928.
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Gam, Franck. « Modelization of stable metal clusters containing Group 11 elements ». Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S048/document.
Texte intégralRésumé :
Les travaux décrits dans ce mémoire portent sur le calcul de la structure électronique de clusters homo- ou hétéro-nucléaires de métaux du groupe 11, afin d’en interpréter leur stabilité, leur structure et éventuellement leurs propriétés. Nous nous sommes tout d’abord intéressés au fait que, contrairement à leurs homologues de l’or et de l’argent, les superatomes de cuivre sont très rares. Nos calculs montrent que ces derniers sont plus stables que les superatomes d’argent. Néanmoins, les méthodes de synthèse de superatomes par réduction de complexes de Cu(I) par le borohydrure conduisent préférentiellement à la formation de polyhydrures de Cu(I) en raison de leur grande stabilité. Nous nous sommes de plus intéressés à la stabilité de clusters contenant un cœur tétraédrique M16, analogue à celui contenu dans le cluster emblématique [Au₂₀]. Notre étude des clusters organométalliques à 20 électrons. [M₁₆Ni₂₄(CO)₄₀]⁴⁻ (M = groupe 11) indiquent que les quatre entités périphériques Ni₆(CO)₁₀ font partie intégrante du superatome, suggérant que [M₁₆]⁴⁻ n’est pas viable. Des calculs sur plusieurs séries de systèmes homo- ou hétéro-nucléaires nus proposent de contourner cet écueil soit en réduisant le nombre d’électrons à 18, soit en incorporant un élément encapsulé au centre de l’entité tétraédrique. Dans une autre étude, nous avons exploré la possibilité de dopage du cluster icosaèdrique à 18 électrons [WAu₁₂] par des atomes de platine (donneurs de 0 électron), soit [WAu₁₂Pdₓ] (x = 1-4). Le calcul indique que certains isomères sont viables et présentent un large spectre d’absorption UV-vis leur conférant des applications potentielles. Enfin, nous avons étudié la structure électronique de clusters organométalliques apparemment très déficitaires en électrons, [Cu₃Zn₄Cp*5] et [Cu₂Zn₅Cp*₅]⁺ et montré que ce déficit n’est aussi important qu’il n’apparaîtThe work described in this manuscript concerns electronic structure calculations of homo- and hetero-nuclear clusters made of group 11 metals, in order to rationalize their stability, structure and in some cases properties. We have first looked at the fact that copper superatoms are very scarce, contrarily to their gold and silver counterparts. Our calculations indicate that copper superatoms are more stable than silver superatoms. However, the synthetic process based on the reduction of Cu(I) complexes by borohydride leads preferentially to the formation of very stable Cu(I) polyhydrides. On the other hand, we have looked at the stability of clusters containing a tetrahedral M₁₆ core similar to the one contained in the emblematic [Au₂₀] cluster. Our investigation of the 20-electron organometallic clusters [M₁₆Ni₂₄(CO)₄₀]⁴⁻ (M = group 11) showed that the four peripheral Ni₆(CO)₁₀ units are full part of the superatom entity, suggesting that the [M₁₆]⁴⁻ entity is not viable. Calculations on several homo- and hetero-nuclear series of bare species indicate that this instability can be avoided either in reducing the electron count to 18, or in incorporating a supplementary element in cluster center. In another investigation, we explored the possibility of doping the icosahedral 18-electron [WAu₁₂] cluster by 0-electron donor platinum atoms, namely [WAu₁₂Pdₓ] (x = 1-4). Calculations indicate that some isomers are stable and have a large spectrum of UV-vis absorption, providing them potential applications. Finally, we have investigated the electronic structure of organometallic clusters, [Cu₃Zn₄Cp*5] and [Cu₂Zn₅Cp*₅]⁺, which are apparently extremely electron-deficient and showed that this deficiency is not as large as it appears
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Bradd, Kerry J. « Rhodium compounds and clusters containing N-donor ligands ». Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366947.
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Cartwright, Peter C. « Mass selective laser photoionisation spectroscopy of copper dimer ». Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/13333.
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Fahlquist, Henrik. « Transition Metal Hydride Complexes and Hydrogenated Gallium Clusters : Synthesis and Structural Properties ». Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89760.
Texte intégralRésumé :
Synthesis and structural characterisation of metal hydrides in two important systems are presented. The first system presented is low valent cobalt and nickel complex hydrides with the compositions BaMg5Co2H10, RbMg5CoNiH10, SrMg2CoH7and Sr4Mg4Co3H19 featuring nickel with oxidation state of 0 and cobalt with oxidation state +I and -I. The second system presented is polyanionic gallium complex hydrides with the compositions RbGaH2, RbxK(1−x)GaH2 (0.5≤x≤1), CsxRb(8−x)Ga5H15 (0≤x≤8) and Cs10Ga9H25 featuring novel hydrogenous polyanionic gallium hydride clusters mimicking common hydrocarbons. The syntheses of the compounds were performed at elevated temperatures and at moderate hydrogen pressures (50-100 bar). The structural investigations were mainly done by X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD). The metal-hydrogen bond was investigated by vibrational spectroscopy using Fourier Transform IR-spectroscopy (FTIR) and Inelastic Neutron Scattering (INS).By subtle changes in the compositions of the hydrides it was possible to induce major changes in band gaps, oxidation states and structures.At the time for the doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Manuscript; Paper 2: Accepted; Paper 5: Manuscript
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Yoshida, Yuichiro. « Energy Surface Explorations of Clusters, Transition-Metal Complexes, and Self-Assembled Systems ». Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263681.
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Randtke, Jie Min. « Rotational Spectroscopy of Simple Metal Carbon Clusters : Resolving the Beauty of Fine and Hyperfine Interactions in Metal Monoacetylides and Metal Carbides ». Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/603492.
Texte intégralRésumé :
Pure rotational spectra of simple metal carbon clusters that relevant to transition metal synthesis and catalysis have been obtained using Fourier transform microwave (FTMW) techniques combined with millimeter-wave direct-absorption methods. Rotational spectra of metal acetylides (CuCCH, ZnCCH, Li/Na/KCCH, MgCCH, AlCCH, CrCCH), diatomic metal monocarbide (CrC) and T-shape metal dicarbides (YC₂ and ScC₂) were recorded in the 4–650 GHz frequency regime. Measurements of weaker isotoplogues including ⁶⁶ZnCCH, ⁶⁸ZnCCH, Zn¹³C¹³CH, ZnCCD, Li/Na/KCCD, CrCCD, Y¹³C¹²C, Y¹³C¹³C, Sc¹³C¹³C, were also studied to aid in structural determinations. This work is the first study of ZnCCH and ScC₂ by any type of spectroscopic technique. Hyperfine splittings in MgCCH and Li/Na/KCCH have also been resolved and the weak isotoplogues of YC₂ have been measured for the first time. Potential interstellar molecules ScO and FeCN were studied using the FTMW techniques in the 4–62 GHz frequency regime. Spectra of the zinc insertion product ClZnCH₃ were additionally recorded in the 10–30 GHz (FTMW) and 260–296 GHz (direct absorption) frequency ranges, along with weaker isotopologues Cl⁶⁶ZnCH₃ and Cl⁶⁸ZnCH₃. This works is the first measurement of zinc insertion products using the FTMW-DALAS techniques. The data were analyzed implementing an effective Hamiltonian, allowing for accurate spectroscopic parameters to be established. From rotational constants, the molecular geometries were accurately determined. Electronic properties were also assessed, including the degree of covalent vs ionic character in a chemical bond, and the molecular orbital composition. The fundamental physical and chemical properties of these benchmark species were obtained in order to gain insight into their role in larger molecular systems, test theoretical calculations, and, in certain cases, provide accurate rest frequencies for astronomical searches.
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Njoki, Peter Njunge. « Metal and alloy nanoparticles synthesis, properties and applications / ». Diss., Online access via UMI:, 2007.
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Abreu, Marissa B. « Electronic Principles Governing the Stability and Reactivity of Ligated Metal and Silicon Encapsulated Transition Metal Clusters ». VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3732.
Texte intégralRésumé :
A thorough understanding of the underlying electronic principles guiding the stability and reactivity of clusters has direct implications for the identification of stable clusters for incorporation into clusters-assembled materials with tunable properties. This work explores the electronic principles governing the stability and reactivity of two types of clusters: ligated metal clusters and silicon encapsulated transition metal clusters. In the first case, the reactivity of iodine-protected aluminum clusters, Al13Ix- (x=0-4) and Al14Iy- (y-0-5), with the protic species methanol was studied. The symmetrical ground states of Al13Ix- showed no reactivity with methanol but reactivity was achieved in a higher energy isomer of Al13I2- with iodines on adjacent aluminum atoms – complementary Lewis acid-base active sites were induced on the opposite side of the cluster capable of breaking the O-H bond in methanol. Al14Iy- (y=2-5) react with methanol, but only at the ligated adatom site. Reaction of methanol with Al14- and Al14I- showed that ligation of the adatom was necessary for the reaction to occur there – revealing the concept of a ligand-activated adatom. In the second case, the study focused heavily on CrSi12, a silicon encapsulated transition metal cluster whose stability and the reason for that stability has been debated heavily in the literature. Calculations of the energetic properties of CrSin (n=6-16) revealed both CrSi12 and CrSi14 to have enhanced stability relative to other clusters; however CrSi12 lacks all the traditional markers of a magic cluster. Molecular orbital analysis of each of these clusters showed the CNFEG model to be inadequate in describing their stability. Because the 3dz2 orbital of Cr is unfilled in CrSi12, this cluster has only 16 effective valence electrons, meaning that the 18-electron rule is not applicable. The moderate stability of CrSi12 can be accounted for by the crystal-field splitting of the 3d orbitals, which pushes the 3dz2 orbital up in energy. CrSi14, on the other hand, has 18 effective valence electrons on Cr, minimal 3d-orbital splitting, and does follow the 18-electron rule. A repetition of these calculations with WSin (n=6-16) showed similar results, except WSi12 shows all the markers of a magic cluster, due to the greater crystal-field splitting of 5d orbitals.
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Curtis, H. « Synthesis, characterisation and reactivity of transition metal carbido-carbonyl cluster and other organometallic compounds ». Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377825.
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Schulman, Cheryl Lutins. « Synthesis, Structure, and Solution Dynamics of Co₄(CO)₈(dmpe)(mu₄-PPh)₂ ». Thesis, University of North Texas, 1990. https://digital.library.unt.edu/ark:/67531/metadc501095/.
Texte intégralRésumé :
Reaction of the tetracobalt cluster Co4(CO)10(t 4-PPh)2 with 1,2-bis(dimethylphosphino)ethane
(dmpe) affords the bis-substituted cluster Co4(CO)8(dmpe)(t 4-PPh)2. The bidentate dmpe ligand is
shown to bind to the cluster in a chelating fashion by IR, NMR, and X-ray diffractions analyses.
The fluxional nature of the ancillary carbonyl groups has been studied by variable temperature 13C
NMR measurements which reveal two distinct carbonyl scrambling pathways. The stability of the
phosphine-ligated cluster has been examined using in situ Cylindrical Internal Reflection (CIR)
Spectroscopy. The effect of the dmpe ligand on the cluster polyhedron will be discussed with
respect to the observed crystallographic and spectroscopic results
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Gandubert, Aurore. « Nanomatériaux hybrides luminescents à clusters d'éléments de transition ». Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S101/document.
Texte intégralRésumé :
Mon travail au sein de l'équipe Chimie du Solide et Matériaux (CSM) à l'Institut des Sciences Chimiques de Rennes a porté sur la synthèse et la caractérisation de nouveaux composés hybrides à clusters, en particulier des clustomésogènes. Depuis leur publication en 2010, les clustomésogènes représentent une nouvelle famille de cristaux liquides, combinant les propriétés physiques des clusters, en particulier la luminescence, avec les propriétés de mise en forme et d'organisation des cristaux liquides. La première partie de ce manuscrit est consacrée à la synthèse, aux études de luminescence, d'oxydo-réduction et aux calculs DFT d'un nouveau composé à clusters, K4[Re6Sei8(N3)a6]·4H2O, précurseur de briques moléculaires pour l'élaboration de nanomatériaux hybrides. La deuxième partie porte sur la synthèse et l'étude de trois clustomésogènes (CL3, CL6 et CL9) présentant différentes densités en unités mésogéniques grâce à la modulation d'un espaceur entre le coeur inorganique et l'unité mésogénique. LC3, LC6 et LC9 possèdent respectivement une chaine aliphatique de 3, 6 et 9 carbones entre le cluster et les unités mésogéniques de type cyanobiphényls. Finalement, une prospective de simulation par dynamique moléculaire a été menée dans le but de comprendre les interactions entre ces macromolécules cristal-liquides, les clustomésogènes, afin de comprendre et prévoir les processus d'auto-assemblage de ces composés hybrides. Ce travail est une première étape pour le développement futur de clustomésogènes de structures contrôlées pour des applications dans les domaines de l'affichage et de l'éclairageMy work took place in the material and solid chemistry team (CSM) from the institute of chemical Sciences of Rennes. It dealt with the synthesis and characterisation of new hybrid compounds : the clustomesogens, which generate luminescent properties assigned to the cluster and self-organisation from liquid-crystal material. The first chapter describes the state of art of the cluster chemistry and the basic knowledge to understand liquid-crystal and in particular clustomesogen material. The second chapter describes the synthesis, characterisation, luminescence and redox analysis and finally DFT calculations of a new inorganic cluster compound K4[Re6Sei8(N3)a6]·4H2O, precursor of molecular building block for the development of hybrid materials. The third chapter deals with the synthesis and study of three specific clustomesogens. Differing by the density in mesogenic units around the cluster core, the compound LC3, LC6 and LC9 have respectively an aliphatic chain of 3, 6 and 9 carbons between the cluster and the mesogenic cyanobiphenyl units. The fourth chapter presents a prospective of molecular dynamic simulations in order to understand the interaction between the clustomesogen supermolecular systems and anticipate the selfarrangement processes. This work is a first step for the future development of new and specific building blocks based on clustomesogens for applications in the field of display or lighting
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Lima, Francisco Anderson de Sousa. « Application of transition-metal-oxide-based nanostructured thin films on third generation solar cells ». reponame:Repositório Institucional da UFC, 2015. http://www.repositorio.ufc.br/handle/riufc/14584.
Texte intégralRésumé :
LIMA, F. A. S. Application of transition-metal-oxide-based nanostructured thin films on third generation solar cells. 2015. 225 f. Tese (Doutorado em Ciência de Materiais) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2015.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2015-12-17T12:45:41Z No. of bitstreams: 1 2015_tese_faslima.pdf: 24015209 bytes, checksum: a66470eb7a55b6b3c2a5e8544c6d4d32 (MD5)
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One of the greatest challenges of our time is to devise means to provide energy in a sustainable way to attend an exponentially growing demand. The energy demand is expected to grow 56% by 2040. In this context, the use of clean and sustainable sources of energy is imperative. Among these sources, solar energy is the only one which can meet the total world energy requirement even considering such large growth in demand. The solar power incident on the Earth's surface every second is equivalent to 4 trillion 100-watt light bulbs. Photovoltaic solar cells are one of several ways to harness solar energy. These cells convert solar energy directly into electricity. Commercial photovoltaic devices are already a reality, but their share of the world energy matrix is still quite small, mainly due to the high costs. Next generation photovoltaics open a number of new possibilities for photovoltaic energy applications that can potentially decrease the overall cost of energy production. Transition metal semiconductor oxides are promising materials that can be produced by low cost methods and o er interesting new features. The use of these materials in next generation photovoltaics is therefore a very promising and interesting application. In this thesis work zinc, titanium and vanadium oxides were used in next generation solar cells. Thin lms of zinc oxide were synthesized by the low cost and environmentally friendly techniques of electrodeposition and hydrothermal synthesis and applied as working electrodes in highly e cient dye sensitized solar cells (DSSCs). The lms were characterized by structural and optical techniques while the cells were tested by current vs: voltage and quantum e ciency measurements. The e ciencies of these cells were as high as 2.27% using ZnO thin lms without any post deposition treatment. Moreover, natural dyes extracted from plants of northeastern Brazil were applied as sensitizers in DSSCs assembled with commercial available TiO 2 as working electrode. The natural dyes were extracted employing very simple methods and were characterized by XPS and UPS techniques. Their band alignments were shown to be compatible with the TiO 2 as well as with the mediator electrolyte. The e ciency of DSSCs sensitized with natural dyes were as high as 1.33%. Finally, water based V 2 O 5 was used as hole transport medium (HTM) in conventional organic solar cells (OSCs) and ITO-free, plastic OSCs. The results obtained with V 2 O 5 were compared with the results obtained from cells assembled with PEDOT:PSS, which is the most used HTM. This comparison showed that the use of V 2 O 5 as HTM can lead to more e cient OSCs. The stability of these devices were evaluated by tests applying the ISOS standards ISOS-D-1, ISOS-L-1 and ISOS-O-1. A UV- lter and a protective graphene oxide (GO) layer were employed seeking to improve the stability of OSCs. The combination of both UV- lter and GO protective layer was shown to be the most e ective way to improve the stability of these devices
Um dos maiores desa os do nosso tempo e desenvolver formas para fornecer energia de forma sustent avel para atender uma demanda que cresce exponencialmente e que dever a crescer 56% at e 2040. Neste contexto, o uso de fontes limpas e sustent aveis de energia e um imperativo. Entre essas fontes, a energia solar e a unico que pode satisfazer a ne- cessidade total de energia do mundo, mesmo considerando o crescimento na demanda. A pot^encia solar incidente na superf cie da Terra a cada segundo e equivalente a 4 trilh~oes de l^ampadas de 100 watts. C elulas solares fotovoltaicas s~ao uma das v arias maneiras de aproveitar a energia solar, convertendo-a diretamente em eletricidade. Dispositivos com- erciais fotovoltaicos j a s~ao uma realidade, mas a sua participa c~ao na matriz energ etica mundial ainda e muito pequena, principalmente devido aos seus custos elevados. C elulas fotovoltaicas de nova gera c~ao abrem uma s erie de novas possibilidades para aplica c~oes de energia fotovoltaica que pode diminuir o custo total de produ c~ao de energia. Oxidos semicondutores de metais de transi c~ao s~ao materiais promissores que podem ser produzi- dos atrav es de m etodos de baixo custo e que possuem caracter sticas interessantes. Por conseguinte, o uso destes materiais em energia fotovoltaica de pr oxima gera c~ao se apre- senta com uma aplica c~ao promissora. Nesta tese de doutorado oxidos de zinco, tit^anio e van adio foram utilizados em c elulas solares de pr oxima gera c~ao. Filmes nos de oxido de zinco foram sintetizados por eletrodeposi c~ao e s ntese hidrot ermica. Os lmes foram apli- cados como eletrodos de trabalho em c elulas solares sensibilizadas por corante (DSSCS) altamente e cientes. Os lmes foram caracterizados por t ecnicas estruturais e oticas en- quanto que as c elulas foram testadas por medidas de corrente vs: voltagem e de e ci^encia qu^antica. A e ci^encia dessas c elulas atingiu 2,27% utilizando lmes nos de ZnO sem qualquer tratamento p os-deposi c~ao. Al em disso, corantes naturais extra dos de plan- tas do nordeste do Brasil foram aplicados como sensibilizadores em DSSCs montadas com TiO 2 comercial utilizado como eletrodo de trabalho. Os corantes naturais foram extra das empregando m etodos simples e foram caracterizados por espectroscopia de fotoel etrons excitados por raios X e por radia c~ao ultravioleta, XPS e UPS respectivamente. Seus alin- hamentos de banda se mostraram compat veis com o TiO 2 e com o eletrodo de regenera c~ao. A e ci^encia das DSSCs sensibilizadas com corantes naturais chegou a 1,33%. Finalmente, V 2 O 5 a base de agua foi usado como material transportador de buracos (HTM) em c elulas solares org^anicas (OSCs) convencionais e OSCs de pl astico constru das sem ITO. Os re- sultados obtidos com V 2 O 5 foram comparados com os resultados de c elulas constru das com PEDOT:PSS, que e o HTM mais utilizado. Esta compara c~ao revelou que o uso de V 2 O 5 como HTM pode levar a OSCs mais e cientes. A estabilidade destes dispositivos foi avaliada por testes aplicando os padr~oes ISOS-D-1, ISOS-L-1 e ISOS-O-1. O uso de ltros ultravioleta e de uma camada protetora de oxido de grafeno reduzido foi testado com o intuito de melhorar a estabilidade desses dispositivos. O uso de uma combina c~ao de ambos se mostrou a forma mais efetiva de melhorar a estabilidade das OSCs
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Cheng, Kai-wing. « Polymers with pendant transition metal complexes for photovoltaic applications and nanofabrications ». Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39707544.
Texte intégral
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何毅雯 et Ngai-man Emmie Ho. « The chemistry of ruthenium carbonyl clusters containing nitrene and nitrido ligands ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B3124029X.
Texte intégral
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Ho, Ngai-man Emmie. « The chemistry of ruthenium carbonyl clusters containing nitrene and nitrido ligands / ». Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21982351.
Texte intégral