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1
Reinhard, Björn M. "Chemistry of microsolvated metal ions." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969739273.
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Phillips, Rosemary Helen. "Metal ions and Helicobacter pylori." Thesis, King's College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408125.
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Poteau, Xavier. "Fluorescent sensors for metal ions." Thesis, University of Central Lancashire, 2001. http://clok.uclan.ac.uk/21458/.
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The considerable current interest in the use of fluorescent molecules in molecular recognition is not new, but is one that has increased in importance in recent years due to their applications in many fields including trace analysis in chemistry and biochemistry. Using the "dual fluorescence" properties of TICT state compounds (Twisted Intramolecular Charge Transfer which gives an extra red-shifted emission band) and the key property of crown ether compounds which is their ability to complex ions, we designed and synthesised a range of new fluoroionophores and studied their photophysical behaviour towards a selection of alkaline and alkaline-earth metal ions. The new fluoroionophores (4-(i '-aza-4'-7'- 10 ,-i 3 '-tetraoxapentadecyl) benzonitrile, 4-( 1 '-aza-4'-7'- 10-i 3'-! 6'-pentaoxapentadecyl)benzonitrile, methyl-4- (1 '-aza-4'-7'-10'-13'-tetraoxapentadecyl)benzoate, 4'-N,N-(i "-aza-4",7",iO' ',l 3"- tetra oxapentadecyl)-3-hydroxyflavone and 4'-N,N-(l "-aza-4' ',7' ',lO", 13"- tetraoxapenta decyl)-3-methoxyflavone) have been shown to form TICT states upon excitation. The photophysics (absorption, emission, lifetimes) of these compounds are affected by the complexation of cations which reduce the donor character of the nitrogen belonging to the crown. The studied dications (Mg2 , Ca2 and Ba2') lead to larger spectral shifts and bigger values of the binding constant Ks than the studied monocations (Lie, Nat, K, CC) which can be interpreted in terms of a stronger electrostatic interaction between the nitrogen lone pair and the alkaline-earth metals than the alkali-metals. It appears that the selectivity demonstrated by these crown ethers towards the alkaline earth and alkali metals is not only explained by the "hole-size relationship" between the size of the crown ether cavity and the ionic mdii of the metal ions. The type of substituent on the phenyl of the azacrown ether has been shown to further influence the spectroscopic properties (shift of the absorption ansi emission bands). Nevertheless the photophysical properties of the azacrown ether derivatives studied does not show enhancement of the selectivity towards the studied metals on expansion of the delocalisation system. More complex mechanisms are in operation in flexible systems such as the azacrown derivatives used in this study geometry, conformation and rigidity all play roles in determining the binding strength and selectivity of these molecules.
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Ebreo, Darren. "The role of metal ions in metal-on-metal total hip replacement." Thesis, University of East Anglia, 2016. https://ueaeprints.uea.ac.uk/59343/.
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Metal-on-metal (MoM) total hip replacement (THR) offered theoretical advantages of decreased wear and increased functional outcomes. MoM bearings have been associated with sterile inflammatory masses and significant soft tissue destruction with poorer outcomes following revision surgery. The natural history of adverse reactions to metal debris (ARMD) is unknown, but may represent contributions from bearing surface wear, taper junction wear, and corrosion. Immunological and genetic factors may influence susceptibility to development of ARMD. Between 1997 and 2004, 652 Ultima TPS THRs (DePuy) were implanted in 545 patients who went on to experience a high rate of early implant failure (13.8%). Management of these patients has evolved beyond regular clinical follow up with plain radiographs to include surveillance monitoring of trends in levels of blood metal ions and staging of disease using metal artefact reduction (MAR) MRI. This study investigated: • The natural history of ARMD in 28mm MoM THR using MAR MRI. • The possibility of diurnal variation of cobalt (Co) and chromium (Cr). • Differences in gene expression profiles of patients undergoing revision of a metal-on-polyethylene (MoP) THR for aseptic loosening and those with ARMD arising from MoM THR. In patients whose MARS MRI staging on initial scan is normal or where mild evidence of disease is demonstrated, further deterioration is unlikely. Where it does occur, the rate of deterioration is slow and there may be a latent period of many years. There is no diurnal variation in levels of cobalt (Co) in plasma or urine. There is diurnal variation in levels of plasma chromium, but this is not clinically significant. Patterns of gene expression in patients with aseptic loosening of a metal-onpolyethylene (MoP) THR, and patients with ARMD from a MoM THR investigated by a microarray experiment were found to be similar on a genome-wide level suggesting that they may share common factors in their aetiologies. These studies have helped to describe the natural history of ARMD on a cellular and radiological level, and have provided a contribution to the evidence base that will inform as to the optimum strategy for monitoring these patients before they develop catastrophic complications.
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OGGIANU, MARIANGELA. "Luminescent platforms for metal ions sensing." Doctoral thesis, Università degli Studi di Cagliari, 2021. http://hdl.handle.net/11584/314054.
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This PhD thesis reports on the strategies for the design of novel luminescent chemosensors as valid alternative to conventional optical sensors, to recognize environmental pollutants, mainly heavy metal ions and nitroaromatics. Luminescent lab-on-chip platforms, molecular and Hybrid-based chemosensors, and luminescent Nanosheets are the three platforms developed for sensing applications. Fluorescent dyes of the family of Xhantenes, Rhodamine (RhO) and Fluorescein (Fluo), Diketopyrrolopyrroles (DPPs) and 2,5 -dihydroxy-1,4-benzoquinone derivatives are the old-fashioned and new building blocks selected, respectively, to fabricate these optical sensors, because of their unique luminescent properties.
Particularly, 2,3-dicyano-5,6-dichloro-1,4-benzoquinone, was selected for its capability i) to produce two dimensional (2D) Coordination Polymers/Metal-Organic Frameworks (CPs/MOFs) and ii) to act as a good antenna ligand towards NIR and Vis. emitting Lanthanide ions. 2D CPs/MOFs, based on this linker, were obtained and miniaturized to 2D Nanosheets (NS), as challenging sensing platforms.
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Dey, Gopal Ch. "Application of functionalised chelating resins for selective sorption of metal ions with special reference to heavy metals." Thesis, University of North Bengal, 2011. http://hdl.handle.net/123456789/1391.
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Ma, Yiu Wa. "Fixed bed removal of heavy metal ions by chelating ion exchange." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491880.
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Column runs with varied operation conditions of flowrate, feed concentration and particle size have been conducted to observe the sorption of nickel, copper and zinc by the chelating resin. They all show a typical constant-pattern, steep curve in the first part of the breakthrough curve and the slope would dramatically reduce at a breakpoint such that it would take extremely long time to reach 100% breakthrough level. ~ The Modified Bed Depth Service Time (BDST) model incorporated with a timedependent bed capacity has been used together with the Empty Bed Residence Time (EBRT) model to analyze the fixed bed performance under different operating conditions. The Homogeneous Surface Diffusion Model (HSDM) and the Shrinking Core Diffusion . Model (SCDM) have been applied to- model the fixed bed performance. Due to the dramatic change in the slope, the first and second parts of the breakthrough curves need to be modeled separately. Comparing the two models, SCDM is more appropriate to explain the sorption of metal ions into the chelating resin. The research has suggested the existence of a Na-loaded outer shell and a H-loaded inner core in the chelating resin. When the moving boundary progresses from the outer shell into the inner core, there is a remarkable change in the ion exchange process, resulting in different kinetics. This explains the sharp change in the slope of the experimental breakthrough curves. A new version of SCDM has been developed to model the progression of the moving boundary inside the resin for the successive resin layers along the whole resin column so as to predict the column' s solid and liquid phase concentration profiles. The new SCDM has. the flexibility of varying the portion of the outer shell so that the behavior of resins with different resin Na contents can be predicted.
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Kelly, Gregory J. "Negative ion production from positive ions incident in a metal vapour." Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/22416.
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Rejaldien, Moegamat Zain. "Base metal equilibrium prediction on ion exchange resin." Thesis, Cape Technikon, 2002. http://hdl.handle.net/20.500.11838/875.
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Thesis (MTech (Chemical Engineering)--Cape Technikon, Cape Town, 2002This study is the first phase of an investigation into an alternative process to recover base metals from solution, namely ion exchange. An identified ion exchange resin was employed to study the recovery of copper, nickel and cobalt from electrolytic solutions. The main focus of the investigation was the prediction of equilibrium conditions in this multi-component system using a batch configuration. In order to predict equilibrium conditions. existing multi-component isotherms such as Fritz and Schleunder were tested. It has been shown that traditional isothem15 did not accurately predict equilibrium conditions. hence the need for development of new isotherms. Essentially two approaches were followed in the development of new isotherms namely. an effective concentration approach as well as a heat transfer approach. Both yielded positive outcomes with the effective concentration approach proving to be the most accurate. In addition to these two approaches a thermodynamical approach was also tested which also showed favourable predictions for Cu loading
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Chen, Wan-Ru. "Interactions of tetracycline antibiotics with dissolved metal ions and metal oxides." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24698.
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Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Committee Chair: Huang, Ching-Hua; Committee Member: Kim, Jaehong; Committee Member: Pavlostathis, Spyros; Committee Member: Stack, Andrew; Committee Member: Yiacoumi, Sotira
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Bale, Simon J. "Retention-modification in HPLC using metal ions." Thesis, Loughborough University, 1988. https://dspace.lboro.ac.uk/2134/27578.
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The effects of transition metal ions as components of the mobile phase on the retentions in HPLC of 2-aminophenol and selected α-diketones were studied on both ODS-silica and porous polymer columns. The compounds were used as model compounds in an investigation which set out to derive a detailed understanding of the mechanisms Involved when metal ions are used to selectively modify the retention of compounds capable of interaction. This technique, which has parallels with ion-pair chromatography, provides another method by which the conditions of a separation may be altered and the selectivity adjusted to give better resolution.
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Ndifor-Angwafor, Nche George. "Analysis of metal ions in nanoparticle growth." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443661.
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Skipper, N. "The alkali metal ions in aqueous solutions." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379533.
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Irikura, Karl K. Beauchamp Jesse L. "Gas-phase chemistry of organotransition metal ions /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06202007-111048.
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Cheng, Jing. "Characterisation of wool treated with metal ions." Thesis, Queensland University of Technology, 1993. https://eprints.qut.edu.au/227117/1/T%28S%29%2025_Cheng_1993.pdf.
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The importance and complexity of the interactions of metal ions with wool
keratin have been well recognised. This work aims to add to the knowledge of
these interactions and to demonstrate the application of chemometrics.
A systematic study of wool fibres treated with lead metal ion was carried out
using various instrumental analyses in an attempt to investigate the binding
mechanism of the lead / wool interaction. The instrumental techniques applied
included Fourier Transform Infrared (FT-IR) spectroscopy, transmission
electron microscopy, energy dispersive X-ray microanalysis, scanning
electron microscopy and X-ray photoelectron spectroscopy. It was shown that
the carboxylate group acted as a binding site for the lead ion. The formation
of lead sulfide as a result of lead / keratin interaction in the aqueous acidic
solutions at elevated temperature was substantiated. Chemometrics was
employed to reveal the trend for the IR spectra of lead treated wool samples
with different treatment conditions.
A comparative study was conducted for the wool keratin treated with Cr(III),
Cu(II), Fe(II), Ni(II) and Zn(II) ions. The order of structure modification at
the carboxyl group as a result of metal ion / wool interactions was obtained
using FT-IR spectroscopy combined with chemometric methods (PCA,
SIM CA and Fuzzy clustering). This order was found to contrast with the
similar ranking on the basis of uptakes alone. The treatment solution pH
changes were monitored to investigate the reaction schemes for metal /
carboxyl group interactions. The reaction schemes were found to be related to
the wool structure modification. FT-IR microscopic measurements of the
untreated and metal ion treated single wool fibres qualitatively agreed with the
results from normal FT-IR spectroscopy.
The Forosyn dyed wool / polyester fabric blends which are concerned with
metal - complex dyeing were analysed using diffuse reflectance FT-IR
spectroscopy with the aid of chemometric interpretation. The object of this
study was to attempt the matching and property prediction of these wool /
polyester blends.
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Granzotto, Alberto. "Role of metal ions dyshomeostasis in neurodegeneration." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423606.
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In the present study metal ions role in neurodegenerative processes has been investigated. Two major pathways have been developed: 1) metal ions role in β-amyloid (Aβ folding and deposition from in vitro to in vivo; 2) calcium dyshomeostasis in an in vitro model of neurodegeneration.
Firstly, metal ions role (aluminum, copper, iron, zinc) in Aβ folding and deposition was assessed. Aβ misfolding is, in fact, believed to play a critical role in Alzheimer’s disease pathogenesis. Our data confirm that Aβ folding is closely related to the conjugated metal ion, thereby following peculiar metal ion-dependent conformational changes. Strikingly, we report that aluminum, a non physiological metal ion, is the most efficient in “freezing” Aβ in its oligomeric and most toxic state.
Within this framework we investigated the mechanisms underlying Aβ and Aβ-metal conjugates toxicity. To that aim we employed two natural compounds (resveratrol and cholesterol) acting on two different Aβ mechanisms of toxicity: oxidative stress and membrane damage, respectively.
In both cases, in vitro analysis revealed that resveratrol and cholesterol do not influence Aβ and Aβ-metal conjugates folding processes, but are still effective in protecting a neuronal-like cell line against Aβ toxicity. We reported that resveratrol was able to significantly reduce the Aβ-triggered generation of reactive oxygen species, meanwhile physiological concentrations of cholesterol were effective in protecting cellular membrane structure against Aβ (especially Aβ-Al) lipid disrupting activity.
To further assess that differently shaped Aβ-metal conjugates result in different biological responses, we investigated Aβ-Cu and Aβ-Zn role in influencing/altering gene expression profile in a neuronal-like cell line. We found that these two conjugates are effective in modulating expression of transcripts involved in inflammatory processes, oxidative stress, and in apoptotic cell death.
Following these in vitro studies we decided to investigate whether expression of transcripts involved in metal ions homeostasis resulted affected in an in vivo model of the disease, represented by the 3xTg-AD mice. Our data highlight a significant overlapping between the expression profiles of young 3xTg-AD mice compared with aged wild type mice; this finding support the notion that Alzheimer’s disease can be interpreted as a boosted variant of otherwise naturally occurring age-driven changes. In our dataset we found several differentially expressed transcripts involved in calcium homeostasis, a key metal ion for the physiology of the cell.
Secondly, calcium dyshomeostasis in striatal neurons following excitotoxic challenge was assessed. Striatal neurons degeneration is involved in several pathologies showing motor and behavioral sequelae, such as Huntington’s disease (HD). We tried to determine why a subpopulation of striatal neurons results spared in HD striata, showing a peculiar resistance towards excitotoxic challenges. Our data demonstrate that the striking resistance of these cells may be due to boosted scavenging capabilities embedded in such neuronal subpopulation, resulting in lack of ROS generation upon excitotoxic insults.
Collectively, these findings highlight the pivotal role played by metal ions in the development of neurodegenerative disorders. Noteworthy, not only endogenous and biologically relevant metal ions (iron, copper, zinc and calcium) seem involved in the pathogenesis of neurodegenerative disorders, but also exogenous metals (i.e.: aluminum) could have a key and subtle, although less investigated, role in neuronal degenerationIl presente lavoro di tesi si è suddiviso in due filoni principali che hanno come filo conduttore la disomeostasi di ioni metallici nei processi neurodegenerativi. La prima parte riporta lo studio sul ruolo di alcuni ioni metallici (alluminio, ferro, rame e zinco) nel processo di folding della proteina β-amiloide (Aβ), ritenuta uno dei fattori eziopatogenici del morbo di Alzheimer. I dati ottenuti dimostrano come i complessi Aβ-metallo-ione acquistino una peculiare conformazione dipendente dal metallo legato, conferendo così all’Aβ particolari proprietà citotossiche. Tale citotossicità risulta particolarmente evidente per il complesso Aβ-Al che è in grado di aumentare, in maniera significativa, la tossicità data dalla sola Aβ o dalla stessa Aβ coniugata con metalli diversi dall’Al. All’interno di questo quadro sperimentale si è poi cercato di indagare più nel dettaglio i meccanismi con i quali Aβ, e i suoi complessi metallici, esercitassero la loro citotossicità. A questo scopo sono stati impiegati due composti quali il resveratrolo e il colesterolo, che vanno ad agire su due meccanismi che stanno alla base della tossicità dell’Aβ, come lo stress ossidativo e l’alterata fluidità delle membrane cellulari. Nel primo caso, i dati in vitro hanno permesso di dimostrare come, agendo in maniera selettiva sulla produzione di specie reattive dell’ossigeno (ROS) Aβ-mediata, sia possibile ridurre la tossicità di Aβ e dei suoi complessi con metalli redox (rame e ferro) mediante un meccanismo di scavenging dei ROS ad opera del resveratrolo, dalle spiccate proprietà anti-ossidanti e neuro-protettive. A questo punto si è indagata la capacità dei vari complessi Aβ-metalloioni di alterare la struttura di membrane lipidiche attraverso l’uso di modelli di membrane cellulari. In precedenza si era dimostrato come il complesso Aβ-Al fosse l’unico complesso in grado di alterare significativamente la fluidità di layer lipidici. I dati ottenuti ci permettono di affermare che tale capacità è dovuta principalmente alla elevata idrofobicità superficiale del complesso Aβ-Al. Inoltre, agendo sulle membrane cellulari con concentrazioni fisiologiche di colesterolo è stato possibile ridurre l’”irrigidimento” delle membrane (lipidico) conseguente alla presenza di Aβ-Al, e ridurne la citotossicità. Si é quindi approfondito il ruolo geno-tossico dei succitati complessi Aβ-metalloioni andando ad indagare come questi siano in grado di modulare in maniera significativa (e metallo-dipendente) l’espressione genica di numerosi trascritti coinvolti nella patologia di Alzheimer. In particolare, il nostro interesse si è focalizzato sui complessi Aβ-Cu e Aβ-Zn, che si sono rivelati in grado di modulare selettivamente l’espressione di geni coinvolti in processi infiammatori, nello stress ossidativo e nella morte cellulare (apoptosi). Dopo questa serie di studi in vitro si è passati ad indagare l’espressione genica dell’intero genoma umano in un modello in vivo di patologia di Alzheimer. Lo scopo era quello di identificare il network o il pathway d’espressione coinvolti della disomeostasi cationica. I profili d’espressione del modello murino 3xTg-AD sono stati pertanto confrontati con quelli del controllo wild type. In questo contesto, si è scoperta una significativa sovrapposizione dei geni sovra- e sotto-espressi tra topi wild type anziani e topi 3xTg-AD giovani. Questo dato supporta l’idea che il substrato patologico dell’AD possa favorire un processo di invecchiamento precoce. All’interno del gruppo di geni trovati differenzialmente espressi, molti erano coinvolti nell’omeostasi del calcio, ione chiave per la fisiopatologia cellulare. Il secondo filone di ricerca ha riguardato lo studio del ruolo dello ione calcio nell’eccitotossicità dei neuroni dello striato. Tale fenomeno è particolarmente importante in alcune patologie neurodegenerative che hanno come segno caratteristico una progressiva e irreversibile perdita del controllo motorio, come ad esempio il morbo di Huntington. L’interesse si è focalizzato nel determinare il perchè una subpopolazione di neuroni striatali, caratterizzata dalla sovraespressione di nitrico-ossidosintasi, non vada incontro ad apoptosi in seguito a stress eccitotossico. I dati raccolti ci hanno permesso di stabilire che la resistenza di tale sottopopolazione al sovraccarico di calcio è dovuta principalmente ad una potenziata capacità di questi neuroni di detossificarsi rapidamente dalle specie ROS, di origine mitocondriale, specie che si generano durante fenomeni eccitotossici. Conclusione. Nel complesso i dati ottenuti sottolineano una volta di più un ruolo centrale degli ioni metallici nello sviluppo e/o nella progressione di alcune patologie a carattere neurodegenerativo. In particolare è importante notare come, a fianco di alcuni ioni metallici endogeni - che hanno un rilevante ruolo fisiologico (ferro, rame, zinco, calcio) -, anche altri ioni privi (apparentemente) di un ruolo biologico, ma coi quali ci interfacciamo quotidianamente, come ad esempio l’alluminio, sembrino svolgere un ruolo chiave in processi eziopatogenetici legati a fenomeni neurodegenerativi
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Dey, Benu Kumar. "A study on metal ion complexation with a macrocyclic ligand : a thermodynamic, kinetic, and mechanistic investigation." Title page, contents and abstract only, 1991. http://web4.library.adelaide.edu.au/theses/09SM/09smd528.pdf.
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Chow, Edith Chemistry Faculty of Science UNSW. "Peptide modified electrochemical sensors for the detection of heavy metal ions." Awarded by:University of New South Wales. Chemistry, 2006. http://handle.unsw.edu.au/1959.4/23354.
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In this research, the determination of trace concentrations of heavy metal ions was investigated using peptide modified electrochemical biosensors. The biosensor has several advantages over atomic absorption spectroscopy and inductively coupled plasma mass spectrometry by offering greater simplicity in use and the possibility of determining the bioavailability of heavy metals. Oligopeptides were modified on the electrode surface through the spontaneous self-assembly of thiols on gold. Firstly, 3-mercaptopropionic acid (MPA) was self-assembled onto the gold surface followed by activation of the carboxyl groups using a combination of carbodiimide and succinimide chemistry for coupling of the N-terminus of the peptide to occur. Using this generic strategy, Gly-Gly-His was used for the determination of copper ions. Cu2+ was accumulated at the MPA-Gly-Gly-His modified electrode at open circuit potential followed by electrochemical measurements. The reduction of Cu2+ to form underpotential deposited copper in the Osteryoung square wave voltammogram was used for quantification. The influence of various factors on the performance was investigated and after the optimal conditions had been identified, the biosensor was used for Cu2+ calibration and was applied to the analysis of a real sample. For Cd2+ detection, two different peptides covalently attached to MPA were investigated, g-Glu-Cys-Gly (GSH) and His-Ser-Gln-Lys-Val-Phe, with the latter sensor exhibiting a lower Cd2+ detection limit, higher sensitivity and greater selectivity. Although the success of MPA as a peptide linker to the gold surface had been shown for the detection of Cu2+ and Cd2+, a more viable approach was necessary for the stable detection of a wider range of metal ions. A more stable self-assembled monolayer of thioctic acid (TA) was identified in which human angiotensin I was attached. This alternate modification procedure was superior to MPA-angiotensin I for Pb2+ detection in terms of stability and reusability with the drawback being sensitivity. The newly identified strategy was also applied to the determination of Ag+ using TA-methionine enkephalin modified electrodes. A sensor array for Cu2+ was also investigated as well as an extension to the simultaneous determination of multianalytes using four different modified electrodes. Combining a soft-modelling approach, the responses of Cu2+, Cd2+ and Pb2+ could be deconvoluted.
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Palla, Veladri. "Heterometallic Interactions of d8-d10 Metal Ions in the Presence of +2 Cations." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/PallaV2007.pdf.
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Lentz, Nicholas B. "Electrospray ionization mass spectrometry from cluster ions to toxic metal ions in biology /." [Ames, Iowa : Iowa State University], 2007.
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Oscarson, Karen Anna Martha. "Complexation of metal ions in aqueous solution by fluorescent ligands containing pyridyl groups /." Electronic version (PDF), 2004. http://dl.uncw.edu/etd/2004/oscarsonk/karenoscarson.html.
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Mendonça, Marília Assunção. "Reator contínuo com leito de lodo biológico anaeróbio para a remoção de íons metálicos em solução aquosa /." Jaboticabal, 2016. http://hdl.handle.net/11449/142849.
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Orientador: Roberto Alves OliveiraCoorientador: Allynson Takehiro Fujita
Banca: Mariana Carina Frigieri
Banca: Luciano dos Santos Rodrigues
Resumo: Reatores contínuos com leito de lodo biológico anaeróbio, in natura e seco em estufa, foram utilizados para a remoção de metais (Cu+2, Mn+2 e Zn+2) em solução aquosa. Com o lodo in natura avaliou-se o efeito conjunto da bioacumulação e biossorção; e com o lodo seco em estufa o efeito exclusivo da biossorção. Foram utilizadas baixas concentrações de Cu+2, Mn+2 e Zn+2 (0,01 a 5,00 mg L-1), tendo em vista que para a ocorrência de bioacumulação devem ser mantidas condições não tóxicas para os micro-organismos. Portanto, os resultados poderão ser aplicados para o pós-tratamento de efluentes com concentrações remanescentes desses metais, que necessitem de polimento para a disposição final, atendendo aos limites legais de qualidade de água do corpo receptor. Os lodos utilizados foram coletados de reatores anaeróbios horizontal (RAH) e de fluxo ascendente com manta de lodo (UASB) utilizados no tratamento de águas residuárias de suinocultura. A temperatura foi controlada a 20°C em todos os ensaios. Foram avaliadas vazões de 5, 10 e 15 mL min-1, valores de pH 4,0 e 6,0 e concentrações de 0,01, 0,5 e 1,0 mg L-1 de Cu2+ e Mn2+, e de 0,05; 2,5 e 5,0 mg L-1 de Zn2+. O pH ótimo para a remoção de Mn2+ e Zn2+ foi 4,0 e para o Cu2+ não foi verificada diferença. A maior eficiência foi encontrada quando utilizou-se os menores valores de concentração e fluxo para os três biossorventes avaliados. Foi verificado que os valores de concentração de metais utilizados demonstraram não serem tóxicos para... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Continuous reactors with anaerobic biological sludge bed, in nature and dry in an oven, were used for removal of metals (Cu+2, Mn+2 and Zn+2 ) in aqueous solution. With the sludge in natura it was evaluated the combined effect of bioaccumulation and biosorption; and the dry sludge in greenhouse sole effect of biosorption. It was used lower concentrations of Cu+2, Mn+2 and Zn+2 (0.01 to 5.00 mg L -1 ), considering that for bioaccumulation occurring should be kept non-toxic conditions for the micro-organisms. Therefore, the results can be applied to the posttreatment of effluents with remaining concentrations of these metals, which require polishing to final disposal, meeting the legal limits of quality of the receiving water body. The used sludges were collected from horizontal anaerobic reactors (RAH) and ascendant upflow sludge blanket (UASB) used in the treatment of swine wastewater. The temperature was controlled at 20°C in all tests. It was analyzed outputs of 5, 10 and 15 ml min-1, pH values 4.0 and 6.0 and concentrations of 0.01, 0.5 and 1.0 mg L- 1 Cu+2 and Mn+2, and 0.05; 2.5 and 5.0 mg L -1 Zn+2 . The optimum pH for the removal of Mn+2 and Zn+2 was 4.0 and the Cu+2 it was not verified difference. The highest efficiency was found when it was used the lowest values of concentration and flux for all three reviews biosorbents. It has been found that the metals concentration values used proved not to be toxic to cells of microorganisms present in the sludge in nature,... (Complete abstract click electronic access below)
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Balteanu, Iulia. "FT-ICR studies of transition metal cluster ions." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974430919.
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Smith, Alexis. "Coordination complexes of trivalent non-transition metal ions." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28400.
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Lathaxride(III) complexes of three potentially heptadentate Schiff base ligands were prepared by addition of lanthanide(III) salts to a solution containing a slight excess of ligand in the presence of poorly coordinating chloride ions or strongly coordinating nitrate ions. The complexes La(hatren), La(datren)(CH₃0H) and La(trac) were isolated in the presence of chloride ions, and were found to have the ligand bound in a hexadentate or heptadentate fashion. We were unable to isolate analogous complexes with the heavier lanthanides (Ln = Pr, Nd, Gd, Dy, Yb, Lu). The complexes Ln(H₃L)(NO₃)₃ (Ln = La, Pr, Nd, Gd, Dy, Yb; H₃L =
H₃hatren, H₃datren) and Ln(H₃trac)(NO₃)₃ (Ln = Pr, Nd, Gd, Dy, Yb) were isolated in the presence of nitrate ions, and were found to have the Schiff base ligand bound in a tridentate fashion ( where H₃datren = tris(2'-hydroxy-4',5'-dimethylacetopheniminoethyl)amine; H₃trac = tris(3-aza-4-methylhept-4-ene-6-one)amine; and H₃hatren = tris(2'-hydroxyacetophenirninoethyl)amine)
All products were characterized by infrared and mass spectroscopy, and by elemental analysis. ¹H-NMR spectroscopy indicated that the complexes were solution labile and dissociated in DMSO to yield free ligand and solvated lanthanide(III) ions.
The crystal structure of Gd(H₃trac)(NO₃)₃ was determined. The gadolinium(III) ion is nine coordinate. H₃trac is bound only through its three oxygen donor atoms, and the nitrate ions are bound in a bidentate fashion to the gadolinium center.
Aluminum (III) and gallium(III) complexes of 2-chloromethyl-5-hydroxy-4H-pyran-4-one (Hck) were isolated from a basic aqueous solution. The complexes Al(ck)₃ and Ga(ck)₃ were characterized by ¹H-NMR (CDCI₃), infrared and mass spectroscopy, as well as by elemental analysis. Al(ck)₃ was also characterized by ²⁷Al-NMR in CDCI₃.Science, Faculty of
Chemistry, Department of
Graduate
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Abbasi, Alireza. "Structural and Spectroscopic Studies of Solvated Metal Ions." Doctoral thesis, Stockholm : Structural Chemistry, Arrhenius Laboratory, Stockholm university, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-446.
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Cao, Yu. "Mass spectrometric study of alkali metal containing ions." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/27890.
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Gernert, Ina [Verfasser]. "Redox Chemistry of Hydrated Metal Ions / Ina Gernert." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1173163182/34.
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Low, Wan Li. "Lipsome encapsulated antimicrobial metal ions and essential oils." Thesis, University of Wolverhampton, 2012. http://hdl.handle.net/2436/219012.
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This study investigates the feasibility of using TTO and Ag+ alone and in combination either as free or liposome encapsulated agents. Based on the minimum lethal concentration (MLC), the fractional lethal concentration index (FLCI) showed that treatment with unencapsulated combinations of TTO and Ag+ exerted a synergistic effect against P. aeruginosa (FLCI = 0.263) and indifferent effects against S. aureus and C. albicans (0.663 and 0.880, respectively). Using polyvinyl alcohol (PVA) emulsified agents in combination, showed synergistic effects against P. aeruginosa and S. aureus (FLCI = 0.325 and 0.375, respectively), but C. albicans remained indifferent (FLCI = 0.733). Time kill experiments revealed that the combined agent concentrations and elimination time (to the lowest limit of detection, LOD) are as follows: C. albicans: 0.12%v/vTTO:2.5x10-4Ag+:1.5hrs, P. aeruginosa: 1%v/vTTO:3.2x10-4Ag+:15mins and S. aureus: 1.2%v/vTTO:3.2x10-4Ag+:30mins. Repeating these experiments with emulsified TTO encapsulated in liposomes (lipo-TTO:PVA30-70kDa) against P. aeruginosa and S. aureus reduced the effective amount of TTO required (compared to free TTO). However, this was not observed in C. albicans. The required effective concentration of Ag+ from liposome encapsulated Ag+ (lipo-Ag+) was shown to remain the same as free Ag+. The effective concentration and elimination time of liposomal agents in combination are as follows: C. albicans: 0.05%v/vTTO:PVA:8.9x10-5Ag:PVA:2.0hrs, P. aeruginosa: 0.25%v/vTTO:PVA:3.2x10-4Ag:PVA:30mins and S. aureus: 0.05%v/vTTO:PVA:6.0x10-4Ag:PVA:1.5hrs. These results showed the potential of using TTO and Ag+ in combination, along with liposome delivery systems to effectively lower the MLC. Scanning electron micrographs of microorganisms exposed to Ag+ showed a reduction in cell size when compared to untreated cells. Transmission electron micrograph of C. albicans showed the cell surface damaging potential of Ag+. Furthermore, this investigation also demonstrated the feasibility of using chitosan hydrogels as an alternative delivery system for TTO and/or Ag+. The development of these controlled release systems to deliver alternative antimicrobial agents may allow sustained targeted delivery at microbiocidal concentrations.
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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/.
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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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Crabtree, Elaine. "The role of metal ions in LDL peroxidation." Thesis, Birkbeck (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266211.
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Lloyd, Bryony Helen. "Bacterial resistance to tellurite and other metal ions." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333673.
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Xia, Baohui, and 夏寶輝. "Metal-metal interactions in homo- and hetero-metallic complexes containing d0, d8 and d10 metal ions: spectroscopic and theoretical studies." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B42577317.
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Xia, Baohui. "Metal-metal interactions in homo- and hetero-metallic complexes containing d0, d8 and d10 metal ions spectroscopic and theoretical studies /." Click to view the E-thesis via HKUTO, 2002. http://sunzi.lib.hku.hk/hkuto/record/B42577317.
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Liu, Haichuan. "Reactions in gaseous metal-organic complexes induced by the photoexcitation of the metal chromaphores /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202004%20LIU.
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Chen, Yongsheng. "Synthesis and properties of benzannulenes and their metal complexes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0013/NQ32706.pdf.
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Schilling, J. Bruce Goddard William A. Beauchamp Jesse L. "Experimental and theoretical aspects of hydrocarbon activation by transition metal ions in the gas phase." Diss., Pasadena, Calif. : California Institute of Technology, 1987. http://resolver.caltech.edu/CaltechTHESIS:11062009-094101367.
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Thesis (Ph. D.)--California Institute of Technology, 1987. UM #87-19,702.Advisor names found in the Acknowledgements pages of the thesis. Title from home page. Viewed 01/15/2010. Includes bibliographical references.
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Kirkwood, D. A. "Photo-dissociation of small metal/alcohol cluster ions confined within an ion trap." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321474.
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Cockrell, Gregory Mercer. "The highly preorganized ligand 2, 9-DI-(2'-PYRIDYL)-1, 10-Phenanthroline, and its complexation properties with metal ions /." Electronic version (PDF), 2007. http://dl.uncw.edu/etd/2007-1/cockrellg/gregorycockrell.pdf.
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Dinescu, Adriana Cundari Thomas R. "Metals in chemistry and biology computational chemistry studies /." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3678.
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Martinez, Ortega Maria Eugenia. "Lipid metal organic networks." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Dietrich, Theo Henry. "The removal of heavy metals from dilute aqueous streams by the use of ion exchange resins." Thesis, Cape Technikon, 1998. http://hdl.handle.net/20.500.11838/887.
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Thesis (MTech (Chemical Engineering)--Cape Technikon, Cape Town, 1998Ion exchange resins are widely used to remove or concentrate heavy metals from aqueous solutions or slurries.This thesis attempts to properly evaluate the interaction between ion exchange resins and heavy metals at trace metal concentrations.The durability of the resins and their effectiveness in real slurries were also investigated. In this study, a chelating resin, as well as a cation, and anion exchange resin was contacted with aqueous solutions of heavy metals in both free and complexed form. Zinc, nickel and copper cyanide complexes were adsorbed onto the anion exchange resin, while the chelating and cation exchange resins were contacted with zinc and nickel nitrates, and cupric sulphate. All the tests were conducted in batch stirred tank reactors. All the metal cyanide complexes behaved in a similar manner when contacted with the anion exchange resins. These tests were p~rf0nned under variations in temperature, stirring speed, pH., ionic strength and . initial metal 90E~entrations. Fitting of a dual resistance model to the profiles for thetlptllk:e" of the complexes, show that both film diffusion and intraparticle diffusion rates were improved with an increase in temperature, and that film diffusion rates improved with an increase in stirring speed. A high ionic strength negatively affected equilibrium loading as well as diffusional rates.It was found that at these low concentrations, the diffusional rates improves with a decrease in the external metal concentration. A comparative study involving the chelating and cation·exchange resins were performed, during which the resins were contacted with the metals in free fonn. It was found that at high metal concentrations, the chelating resin induced a rate limiting effect, but at trace concentrations, this effect is virtually negated. Whereas the cation exchange resin exhibited little selectivity in adsorbing the metals, it was found that the chelating resin prefers the metals in the eu > Ni > Zn. The chelating resin proved to be no less durable then the cation exchange resin, and both slightly lost their ability to adsorb the metal cations as a result of the effects of an inert coarse sand slurry.Tests performed with a real ore leachate, showed the cation exchange resin to be efficient at a low pH , but also relatively non selective, since the adsorption of copper from the leachate was greatly reduced due to the presence of other heavy metals.
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Mayr, Torsten. "Optical sensors for the determination of heavy metal ions." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964444569.
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Hetzer, Adrian. "Sequestration of metal and metalloid ions by thermophilic bacteria." The University of Waikato, 2007. http://hdl.handle.net/10289/2642.
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This Ph. D. thesis presents results and conclusions from studies 1) investigating the interaction between metal and metalloid ions and thermophilic bacteria, and 2) characterizing microbial populations in a geothermally active habitat with relatively high concentrations of metalloid ions and compounds. In initial cadmium ion toxicity assays, the minimal inhibition concentration for 46 thermophilic bacteria of the genera Aneurinibacillus, Anoxybacillus, Bacillus, Brevibacillus, Geobacillus, and Thermus were determined. The highest tolerances to cadmium ions (Cd2+) in the range of 400 to 3200 micro;M were observed for species belonging to the genus Geobacillus. The thermophilic Gram-positive bacteria Geobacillus stearothermophilus and G. thermocatenulatus were selected to describe further biosorption reactions between cadmium ions and chemically reactive functional groups (potential ligands) within and onto the bacterial cell walls. Data obtained from electrophoretic mobility, potentiometric titration and cadmium ion adsorption experiments were used to quantify the number and concentrations of ligands and to determine the thermodynamic stability constants for the ligand-cation complexes. The first reported surface complexation models (SCMs) quantifying metal ion adsorption by thermophilic microorganisms predicted cadmium adsorption and desorption by both studied Geobacillus strains over a range of pH values and for different biomasses. The results indicated the functional group, with a deprotonation constant pK value of approximately 3.8, to be more dominant in cation biosorption accounting for 66 and 80% of all titrable groups for G. thermocatenulatus and G. stearothermophilus, respectively. The generated SCMs are different from model parameters obtained from mesophilic species that have been studied to date and might indicate a different biosorption behavior for both studied Geobacillus strains. Another objective of this thesis was to characterize microbial populations in the hot spring Champagne Pool, located in Waiotapu, New Zealand. The thermal spring is approximately 65 m in diameter and discharges water at 75eg; C and pH 5.5, which is oversaturated with arsenic and antimony compounds that precipitate and form orange deposits. Recovered nucleic acids and adenosine 5'-triphosphate (ATP) concentrations obtained for Champagne Pool water samples indicated low microbial density and were in good agreement with relatively low cell numbers of 5.6 plusmn; 0.5 x10^6 cells per ml. Denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene clone library analyses revealed the abundance of Sulfurihydrogenibium, Sulfolobus and Thermofilum-like populations in Champagne Pool. Two novel bacteria and one novel archaeon were successfully isolated with a distant phylogenetic relationship to Sulfurihydrogenibium, Thermoanaerobacter, and Thermococcus, respectively. Genotypic and metabolic characteristics differentiated isolate CP.B2 from described species of the genus Sulfurihydrogenibium. CP.B2 represents a novel genus within the Aquificales order, for which the name Venenivibrio stagnispumantis gen. nov., sp. nov. is proposed. V. stagnispumantis is a thermophilic, chemolithothrophic bacterium, that utilizes molecular hydrogen as electron donor and oxygen as electron acceptor and displayed growth in the presence of up to 8 mM NaAsO2 (As3+) and more than 20 mM Na2HAsO4.7H2O (As5+). However, growth was not observed when Na2HAsO4.7H2O and NaAsO2 were provided as the sole electron acceptor and donor pair. Arsenic resistance was conferred by the genes arsA and arsB
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Seo, Jin Seog. "Hydrolyzing phosphates with metal ions : di and trinuclear approach." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq30381.pdf.
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Ouyang, Hui. "Calmodulin interactions with peptides, hormones, drugs and metal ions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0025/NQ49528.pdf.
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Ager, Patrick. "Mobilizationpurging of aqueous metal ions into supercritical carbon dioxide." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20553.
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The technology of supercritical fluid extraction (SFE) offers the opportunity to efficiently extract both relatively non-polar analytes as well as ionic materials (such as metal ions) that can be mobilized with the addition of complexing reagents. The nebulizer of a conventional flame atomic absorption spectrometer (FAAS) was modified to extend the range of metals amenable to on-line detection. The flow injection thermospray-FAAS (FI-TE-FAAS) interface provided efficient detection for a variety of less volatile elements (Co, Cr(III), Cr(VI), Fe, Ni, Mn and Al) present as ions in aqueous media or as complexes in the supercritical fluid (SC-CO2) carrier phase. The range of possible metal analytes that can be monitored has been increased over the nine elements (Ag, As, Cd, Cu, Hg, Mn, Pb, Se and Zn) that could be detected with an all-silica interface. The acetylacetonate complexes offered considerable potential for metal detection in an SC-CO2 carrier phase. Limits of detection (LODs) were used to compare the instrument responses to different metals. (Abstract shortened by UMI.)
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Tobin, John M. (John Michael). "The uptake of metal ions by rhizopus arrhizus biomass /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73999.
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Taylor, T. M. C. "Modified phospholipids : Oxidation promoted by vesicle-bound metal ions." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382664.
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Shackleford, Stephen. "Development of an EQCM-based sensor for metal ions." Thesis, University of Central Lancashire, 2002. http://clok.uclan.ac.uk/8090/.
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A series of fundamental studies are presented of the components of a prototypical electrochemical quartz crystal microbalance (EQCM)-based sensor for metal ions. Designed for use in the nuclear industry, the sensor consists of a gold (Au) piezoelectrode modified by a Nafion® polymer layer impregnated with a cationic hydroxainic acid (HA), a ligand showing oxidation state specific selectivity towards actinide 4+ ions and a non-radioactive demonstrator ion, Fe3+ In its final configuration, the polymer layer will also contain a redox mediator, methylene blue (MB), to facilitate electrochemical conditioning of the analyte. The following results have been obtained from EQCM and microelectrode voltammetry studies of each of the component parts. The Gold Piezoelectrode - The dissolution and redeposition processes of Au in HNO3 solution at pH I & 0 were investigated as a function of sweep rate (v). At pH I and v < 10 mV s-1 , Au dissolves through a 3e’ oxidation at E > +1.00 V (vs. SCE), a process that, at v ≤ 10 mV s-1, is kinetically hindered with respect to under potential deposition (UPD) of OH surface sublattices and subsequent 2-D-phase oxide formation. The inhibition arises from a closed packed layer of nitrate ions at the gold surface, although the layer is disrupted and the inhibition removed by the gold dissolution and reprecipitation processes that occur during potential cycling at low v. The Hydroxamic Acid Ligand - Study of the oxidation of acetohydroxamic acid (AHA) in nitric acid revealed that three processes occur at Au electrodes at potentials in the vicinity of AHA oxidation at pH 0 & I: (a) oxidation of the Au surface; (b) oxidation of the AHA; (c) complexation of the AHA with electrogenerated Au3+ . The last process inhibits oxide formation and associated electrode passivation, so promoting the occurrence of the first two. The two current peaks associated with AHA oxidation show no associated mass change, indicating that AHA oxidation is controlled by semi-infinite diffusion. The waves correspond to I and 2 electron processes with current onsets of +0.55 V and ̴̴̴+0.80 V (vs. SCE) respectively. Oxidation of AHA appears to be irreversible and blocked at electrodes with minimal microscopic roughness by close packing of nitrate ions at the surface. The Polymer Layer and the Demonstrator Ion, Fe 3+ - Microelectrogravimetric studies of the Fe2+/3+ couple were conducted at bare Au, Nafion® modified Au and Nafion® modified Au impregnated with the hydrophobic cationic HA ligand, desferrioximine (DFA+) electrode. In background nitric acid (pH 1 & 0), the electrochemistry of Nafion ® layer partitioned Fe 2+/3+ ions exhibits thin layer cell behaviour with the polymer layer increasing in mass during reduction of Fe(III) due to an influx of highly hydrated H+ ions necessary to maintain electroneutrality. Studies on Nafion® layers impregnated with DFA+ and Fe3+ show that while Fe3+ complexes with DFA+, Fe2+ does not and that, upon reduction of the complexed ferric ion, the resultant Fe(II)-DFA+ complex dissociates suggesting that electrochemical expulsion of the analyte is possible. The Redox Mediator - At pH 7.9, the reduction of methylene blue (MB) to leucomethylene blue (LMB), occurs in two steps: (i) a reversible net 1.5 e transfer to form a solid charge transfer complex (LMB/LMB+) (ii) an irreversible reduction of LMB/LMB+ to LMB, the onset of which can be directly observed as an inflection in the voltamassogram, the first time that this has been reported. The reversibility of the MB to LMB reduction within the context of charge transfer complex electrogeneration suggests that MB may be a suitable mediator for actinide cation reduction within the polymer layer of the proposed sensor. It is known that the pendular amino-groups of LMB are protonated below pH 1, so rendering the resultant LMBH22+ soluble in aqueous solution. This means (a) difficulties associated with the irreversibile reoxidation of the solid LMB generated at pH 7.9 will be obviated at pH I; and (b) being a large cation, we could expect LMBH22+ to be retained within the Nafion® layer.
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Dobson, Matthew Peter. "Studies of singly and doubly charged solvated metal ions." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321352.
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