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Dissertations / Theses on the topic 'Luminescence spectroscopy'
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1
Kallir, Alan J. "Total luminescence spectroscopy /." [S.l.] : [s.n.], 1986. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=7960.
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Appelbaum, Ian 1977. "Ballistic electrons : microscopy, spectroscopy, devices and luminescence." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29612.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2003.Includes bibliographical references (leaves 139-147).
This thesis describes research to theoretically model and experimentally measure electronic systems which employ ballistic electron emission. First, a Monte-Carlo framework for simulating electron injection from a tunnel junction emitter into a semiconductor collector is presented in detail and a few applications of this theory are described. Second, a method of treating ballistic electron transport through nano-scale heterostructures by considering realistic, atomic-scale periodic potentials is examined. Third, experimental results toward development of a novel scanning-probe microscopy for the local study of buried luminescent heterostructure layers is presented. Finally, a number of future research directions suggested by these results are described.
by Ian Appelbaum.
Ph.D.
3
Alexeev, Evgeny. "Hot-carrier luminescence in graphene." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/18231.
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In this thesis, the effect of the sample properties on the characteristics of the hot carrier luminescence in graphene is investigated. The present work focuses on the two main issues described below. The first issue is the modification effects of near-infrared pulsed laser excitation on graphene. For excitation fluences several orders of magnitude lower than the optical damage threshold, the interaction with ultrafast laser pulses is found to cause a stable change in the properties of graphene. This photomodification also results in a decrease of the hot photoluminescence intensity. The detailed analysis shows that ultrafast photoexcitation leads to an increase in the local level of hole doping, as well as a change in the mechanical strain. The variation of doping and strain are linked with the enhanced adsorption of atmospheric oxygen caused by the distortion of the graphene surface. These findings demonstrate that ultrashort pulsed excitation can be invasive even if a relatively low laser power is used. Secondly, the variation of the hot photoluminescence intensity with the increasing charge carrier density in graphene is investigated. The electro-optical measurements performed using graphene field-effect transistors show a strong dependence of the photoluminescence intensity on the intrinsic carrier concentration. The emission intensity has a maximum value in undoped graphene and decreases with the increasing doping level. The theoretical calculations performed using a refined two-temperature model suggest that the reduction of the photoluminescence intensity is caused by an increase in the hot carrier relaxation rate. The modification of the carrier relaxation dynamics caused by photoinduced doping is probed directly using the two-pulse correlation measurements. The discovered sensitivity of the hot photoluminescence to the intrinsic carrier concentration can be utilised for spatially-resolved measurements of the Fermi level position in graphene samples, offering an advantage in resolution and speed.
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Hackenberg, Wolfgang. "Hot electron luminescence spectroscopy in GaAs and InP." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309213.
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Whitfield, Claire Margaret Frances. "Investigation of cavitating flow luminescence for analytical spectroscopy." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3464.
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Cavitating Flow Luminescence (CFL) is spontaneous photon emission associated with hydrodynamic cavitation which occurs when a flowing liquid passes through a Venturi.1 In this work, cavitation and micro-plasma generation in a flowing liquid, using a micro-Venturi, has been investigated. A bench-top system was designed and constructed to study CFL in a variety of liquids. The system comprised a high flow, liquid handling manifold and micro-Venturi with a variety of orifice sizes ranging from 160 – 220 μm i.d. The CFL was detected for the first time on a micro-scale using a PMT. The effect of various parameters such as temperature, flow rate (a proxy for the pressure differential) and orifice diameter were investigated to optimise the system. Studies were carried out using DDW and the effect of temperature, pressure and orifice size on CFL; it was found that low temperatures and high pressures resulted in more intense CFL. The effect of re-gassing with different noble gases was investigated and resulted in a large increase in CFL. Investigations in to the effect of solute concentration on CFL were performed using dimethylsulphoxide, polyethyleneglycol-200, isopropanol, diethyleneglycol and Triton X 100 & titanium sulphate nano-particles. Solutes with low vapour pressures resulted in an increase in CFL whereas solutes with a high vapour pressure supressed CFL, due to quenching effects. Low resolution spectra were produced using bandwidth filters to identify wavelength areas of strong emission from CFL.
6
Friis, Henrik. "Luminescence spectroscopy of natural and synthetic REE-bearing minerals." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/756.
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Paski, Edgar Francis. "Inorganic powder analysis by time-wavelength resolved luminescence spectroscopy." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29045.
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An investigation into the potential of time-wavelength resolved luminescence spectroscopy for the analysis of inorganic powders was performed. A time-wavelength resolved luminescence spectrometer consisting of an excimer laser, scanning monochromator, and gated integrator was constructed.
The spectrometer had wavelength coverage from 265 nm to 800 nm, it was capable of measuring lifetimes between 100 ns and 500 ms. Sample excitation was done at 193 nm and 248 nm.
A luminescence system model of first order decay in the time domain and a Gaussian function for the emission band was assumed. The time-wavelength resolved luminescence spectrum was described by the parameters: lifetime, peak maxima, peak halfwidth, and intensity factor. Parameter estimation was done with an algorithm employing a linear algebra construct and simplex optimization. The algorithm's performance on highly overlapped spectra was evaluated. For two component mixtures having a 1 % RSD noise level, overlaps greater than 0.3 halfwidths in the spectral domain and lifetime ratios greater than 1:1.3 were resolved with all parameter estimates having an error of less than ±2%.
The luminescence spectra of CaMo0₄, SrMo0₄, BaMo0₄, ZnMoO₄, CdMo0₄, PbMoO₄, CaWO₄, SrW0₄, BaWO₄, ZnWO₄, CdW0₄ and PbWO₄ consisted of broad featureless bands showing simple exponential decay. Mixed crystals of Ca(MOxW₁-x)O₄ and Sr(MOxW₁-x)0₄ were examined. Tungstate emission was quenched by molybdate, the molybdate emission dominated when x was greater than 0.15. The tungstate lifetime was found to be proportional to molybdate concentration.
The luminescence spectra of CaZrO₃, SrZr O₃, BaZr O₃ CaHfO₃ SrHfO₃, BaHfO₃, CaO, SrO, and BaO as pure compounds and doped with T1, Pb, Sb, and Bi were studied. The pure zirconates and hafnates showed short lived (<100 ns) luminescence
with 248 not excitation; no readily discernible luminescence was observed with
193 nm excitation. Doped compounds tended to show luminescence characteristic of the dopant ion.Science, Faculty of
Chemistry, Department of
Graduate
8
Lopinski, Stefan. "Circularly polarised luminescence spectroscopy of chiral europium (III) complexes." Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/2816/.
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Circularly Polarised Luminescence (CPL) spectroscopy detects the differential emission of left and right circularly polarised light from luminescent chiral species, and so can be thought of as the emission analogue of circular dichroism spectroscopy. The circularly polarised emission of chiral europium complexes derived from the 12-ane-4 macrocycle cyclen, (examples of which are shown below) have been recorded using this technique. (Fig. 10701) These and similar complexes have shown an ability to bind to biologically important anions such as carbonate and phosphate in aqueous media and are able to report this event by a change in luminescence. These interactions have been investigated by monitoring the emitted circularly polarised light using the technique described and the binding of the substrate is clearly signalled. Typical CPL spectra of the europium complexes will be presented as will the binding study results and a detailed account of how the spectra is obtained.
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Clark, Brian John. "Computer-aided studies on luminescence spectroscopy in pharmaceutical analysis." Thesis, Heriot-Watt University, 1985. http://hdl.handle.net/10399/1658.
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Bowmar, Paul. "Optical spectroscopy of novel materials." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259758.
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Jalkian, Rafi Diran. "The evaluation and the application of array detectors for analytical luminescence spectroscopy." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184782.
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The research described in this dissertation is the first evaluation and application of a new class of optical detectors, two-dimensional charge-coupled device (CCD), for low-light level chemiluminescence and other luminescence spectroscopies. This research conclusively demonstrates the superior qualitative and quantitative performance of spectrometric systems which employ these detectors. It is experimentally shown that a single detector element of a CCD has comparable or superior sensitivity to the most sensitive single channel detectors; photomultiplier tubes (PMT). The results from the application of the CCD detector system to molecular spectroscopies (fluorescence, chemiluminescence, fluorescence detection of high performance liquid chromatography (HPLC) effluents, and chemiluminescence detection of HPLC effluents) and atomic spectroscopies (spatially and spectrally resolved spark and direct current plasma are presented). The results of operating the CCD in specialized readout modes developed in this research termed charge dependent variable binning (CDVB), simultaneous variable binning (SVB), and continuous high speed spectral framing (CHSF) are described and applied. The CDVB and SVB techniques allow very sensitive quantitation of spectrally resolved and unresolved signals with very wide dynamic ranges without prior knowledge of the signal intensity. Finally, CHSF technique provides spectrally resolved temporal study of extended period luminescence emission with millisecond time resolution. The results of unique algorithms to restore the integrity of the image obtained with a two-dimensional CCD detector are described and applied. The algorithms implemented are for removing variations in detector sensitivity and responsivity and spectrometer efficiency, as well as providing digital image filtering.
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Williams, Mark. "Uranium(VI) uptake by geological materials, characterisation by luminescence spectroscopy." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/uraniumvi-uptake-by-geological-materials-characterisation-by-luminescence-spectroscopy(0220200d-b14b-4ef2-99e0-8d0342701576).html.
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Many of the wastes associated with the nuclear fuel cycle are toxic to the biosphere; advancing the use of high resolution spectroscopy applied to these materials will provide the chemical speciation of the interaction between nuclear waste and geological material, improving confidence in a permanent disposal method and informing clean-up operations. Luminescence spectroscopy of uranyl(VI) is a well-established technique for the molecular speciation of uranium-mineral interactions. This work explores the use of both micro- and macroscopic luminescence spectroscopy to expose uranyl(VI) speciative heterogeneity in a range of minerals which have been exposed to uranyl(VI) salt solutions. A comprehensive review of the available literature on the interaction of uranyl(VI) with a range of geological media is assessed and compared. The review finds considerable ambiguity in the speciation of uranyl(VI) at the mineral water interface. A database reporting the multi parametric luminescence properties of uranyl(VI) with silica gel, quartz, bayerite, boehmite, muscovite, kaolinite and montmorillonite (SWy-2 and STx-1b) is presented and discussed. Although some of the results are consistent with previously reported values, many newly identified species are reported and their identification speculated. Parallel factor analysis is used to deconvolute the excitationemission matrix of uranyl(VI) sorbed to silica gel between pH 3 and pH 10. The results are used to identify the spectroscopic properties of complexes >(SiO)2UO2 and >(SiO)2UO2OH and thus new complexation coefficients (log(K)) for their formation with the silica gel surface are determined, log(K1) = 9.22 ± 0.02 and log(K2) = 3.45 ± 0.01, respectively. The investigation also provides insight into the fundamental properties of uranyl(VI) excitation pathways, which are not yet fully understood. Confocal microscopy and phosphorescent lifetime image mapping (PLIM) is used to expose the sub-micron heterogeneity of uranyl(VI) sorption complexation across mineral surfaces of silica gel, bayerite and montmorillonite (STx-1b). The results suggest that changes in the uranyl(VI) lifetime can be used to observe and understand submicron changes in uranyl(VI) complexation at hitherto unknown temporal resolution.
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Togay, Evren. "Design And Implementation Of A Luminescence Emission Spectrometer." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614144/index.pdf.
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Luminescence is the emission of light resulting from radiative transition of an atom from an excited state to a ground state. This radiative transition yields emission of photons and the luminescence is the general name which is used to classify &ldquocold emission&rdquo
other than the blackbody radiation. Spectroscopy involves the measurement of intensity of emitted, absorbed or scattered electromagnetic radiation as a function of wavelength. Thus, it is a valuable tool in the study of understanding the luminescence production mechanisms. Measurement of emission spectra gives information about the energy levels of transition and structure, geometry and composition of the sample. In this study, a versatile luminescence emission spectrometer was designed and developed with the main aim of measuring Photoluminescence (PL), Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) emission spectra of materials relevant for dosimetry. The spectrometer was constructed around a Littrow type monochromator by developing the necessary hardware, firmware and software. Wavelength calibration, measurement of spectral response and determination of resolution of the spectrometer were done using calibration lamps and a calibrated spectroradiometer. Finally the performance of the constructed spectrometer was tested by measuring the emission spectra of materials such as BeO, Al2O3 and CaF2 wherever possible the measured spectra were compared with the ones reported in the literature.
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Mather, Anne. "Applications of luminescence techniques to the analysis of multicomponent systems." Thesis, Heriot-Watt University, 1987. http://hdl.handle.net/10399/1048.
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Lucas, David M. "Luminescence studies of polymer behaviour in the solution and solid states." Thesis, Lancaster University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334750.
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Barrera, Bello Elixir William. "Lanthanide-based dielectric nanoparticles for upconversion luminescence." Doctoral thesis, Universitat Rovira i Virgili, 2013. http://hdl.handle.net/10803/108960.
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En esta tesis se ha estudia la luminiscencia y la emisión anti-stokes visible por excitación infrarroja a 980 nm, en iones lantánidos embebidos en nanoestructuras de Lu2O3 y KLu(WO4)2, en los cuales los iones lantánidos muestran interesantes propiedades ópticas. Se han producido tres tipos de nanoestructuras con alta cristalinidad a través del método Pechini modificado y síntesis hidrotermal. Se han descrito los mecanismos de fotoluminiscencia, catodoluminiscencia y eficiencia cuántica, en base a las especies adsorbidas en la superficie y la potencia de excitación.
Se han sintetizado nanobarras y partículas núcleo-capa que puede ser utilizadas como bloques de construcción de estructuras más complejas en aplicaciones fotónicas. Se ha logrado la generación de luz blanca en nanocristales de (Tm,Ho,Yb)KLu(WO4)2. Estas nanopartículas pueden formar parte de estructuras más complejas en dispositivos emisores de luz o como indicadores para visualización biológica de células.Nowadays especially attention has been given to materials capable of generating visible light by conversion of near infrared photons (upconversion) for save-energy technologies and reduction of photo-degradation caused by UV high energy photons. Nanoparticles using optically active Ln3+ have shown great potential for use as upconverting luminescent materials in bio-analysis applications, counterfeit fighting and back-lighting. However materials with nanometer dimensions may affect the luminescence dynamics of the Ln3+ ion modifying the emission lifetime, quantum yield, and concentration quenching. This thesis discusses the synthesis and upconversion emission of lanthanide doped nanostructures with Lu2O3 and KLu(WO4)2 as host because they posses high chemical stability; they offer favorable incorporation of Ln3+ ions and high absorption and emission cross sections. Er3+, Ho3+ and Tm3+ are used as emitting ions and Yb3+ as sensitizer. Luminescence dynamics of these ions into these nanostructures and the possibility of white light emission in KLuW nanocrystals are discussed.
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Potter, Mark David George. "Luminescence spectroscopy of CdTe/CdS based photovoltaic devices and associated materials." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4607/.
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This thesis contains primarily a study of CdTe/CdS heterojunction solar cells^ chiefly using photoluminescence spectroscopy. These solar cells show a good potential for commercial power generation in the near Aiture and are of interest to several major companies. A vital but little understood step in the manufacturing process is: annealing the cells in the presence of chlorine prior to back contact application. Studies are performed on a selection of thin film CdTe/CdS cells subjected to CdCl(_2) anneals of different duration. A chemical bevel etch was used to study the spectra at different depths into the sample and laser intensity arid sarhple temperature variations to identify the mechanisms behind the observed photoluminescence peaks. Evidence was found for the CdCl(_2) anneal promoting sulphur diffusion and subsequent grain boundary passivation in the CdTe, leading to increased minority carrier lifetimes and device efficiencies Attempts to obtain electroluminescence from the CdTe/CdS solar cells were madei By using current pulses electroluminescence was obtained in the 780-850nm range with discernible spectral features. Photoluminescence (PL) studies were also performed on a single crystal of CdTe grown to an unprecedented size of approx. 5 cm diameter at Durham university by a multi-tube seeded vapour method of crystal growth. Much higher resolution spectra were: obtained for this than for the solar cells. Several peaks were identified arid the mechanisms responsible were theorised. By taking slices of the crystal boule the PL spectra at different points-throughout the bulk of the crystal were determined. A series of high quality ion-implanted CdTe crystals were also studied! by intensity and temperature dependent PL in order to obtain a better understanding of the effects of known concentrations of known impurities on the PL spectra of CdTe. Specific PL features associated with certain dopants were observed.
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Gelamos, João Paulo [UNESP]. "Desenvolvimento e aperfeiçoamento de protocolos de conjugação de nanomarcadores luminescentes com sistemas biológicos para aplicação em imunoensaios." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/97762.
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gelamos_jp_me_sjrp.pdf: 2151806 bytes, checksum: 85d6f8deb1daa2021fbe2d398d6c62f7 (MD5)Universidade Estadual Paulista (UNESP)
Neste trabalho foram desenvolvidos e aprimorados protocolos de conjugação entre nanopartículas do luminóforo Y2O3:Er,Yb, aminofuncionalizadas e a proteína Streptavidina, para atuarem como marcador em imunoensaios. A streptavidina faz parte do sistema de auto-reconhecimento biotina-avidina mais aplicado em ensaios biológicos, sendo que, devido ao seu alto custo, a Albumina Sérica Bovina foi escolhida como proteína de trabalho em substituição à Avidina. Na etapa final, no entanto, utilizou-se a Streptavidina para comparativamente finalizar as discussões. Desta forma, o desenvolvimento do protocolo considerado padrão foi feito aplicando-se o crosslinker homobifuncional glutaraldeído, e a partir deste, estudou-se o comportamento da ligação luminóforo-proteína utilizando-se outros crosslinkers heterobifuncionais, no caso sulfo-N-succinimidil 4-maleimido- butirato sal de sódio (Sulfo-GMBS) e cloridrato de N-(3-dimetilaminopropil)-N'-etilcarbodiimida (EDC). Tal alteração teve como princípio o aperfeiçoamento do protocolo de conjugação, estabelecendo comparativos entres os dados experimentais já obtidos e as possíveis vantagens resultantes dos crosslinkers heterobifuncionais, já que neste caso a possibilidade de ocorrer autoconjugação, ligação cruzada intramolecular e/ou polimerização entre as nanopartículas aminofuncionalizadas pode ser nula. Com relação às nanopartículas, estas, antes da conjugação, foram caracterizadas por espectroscopia de luminescência, microscopia eletrônica de varredura e/ou transmissão, assim como titulação potenciométrica para quantificação dos grupos NH2 após funcionalização. No desenvolvimento e aperfeiçoamento dos protocolos de conjugação todas as etapas foram monitoradas por Espectroscopia de Absorção na Região...
In this work conjugation protocols between the aminofunctionalized nanophosphor Y2O3: Er, Yb, and the protein Streptavidin was developed and improved to be possible applied as markers in immunoassays. The Streptavidin is part of the biotin-avidin self-recognition system applied to most biological assays, and, due to its high cost, Bovine Serum Albumin protein was chosen to be used in most part of the developing protocol as a substitute for avidin. In the final step, however, the Streptavidin was used in comparison to the other results in order to finalize the study. Thus, the development of the standard protocol was done by applying the homobifunctional crosslinker glutaraldehyde, and from this, it was studied the behavior of protein-nanophosphors binding using the heterobifunctional crosslinkers N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and Sulfo-N-succinimidyl 4-maleimidobutyrate sodium salt (Sulfo-GMBS). Such a change had the challenge to improve conjugation protocol, establishing the comparison between experimental data already obtained and the possible advantages due to the use of heterobifunctional crosslinkers, considering that in this case the possibility of occurring self-conjugation, intermolecular crosslinking and/or polymerization between the aminofuctionalized nanoparticles can be null. With respect to the nanoparticles before the conjugation step, they were characterized by luminescence spectroscopy, scanning and/or transmission electron microscopy as well as potentiometric titration for NH2 groups quantification after functionalization. During the development and the improvement of the conjugation protocols all steps were monitored by UV-VIS absorption spectroscopy to verify the behavior of molecular species present before and after the reactions... (Complete abstract click electronic access below)
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Adegoke, Oluwasesan. "The design of quantum dots and their conjugates as luminescent probes for analyte sensing." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1010866.
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The design and applications of quantum dots (QDs) as fluorescent probes for analyte sensing is presented. Cadmium based thiol-capped QDs were employed as probe for the detection of analytes. Comparative studies between core CdTe and core-shell CdTe@ZnS QDs showed that the overall sensitivity and selectivity of the sensor was dependent on the nature of the capping agent and the QDs employed, hence making CdTe@ZnS QDs a more superior sensor than the core. To explore the luminescent sensing of QDs based on the fluorescence “turn ON” mode, L-glutathione-capped CdTe QDs was conjugated to 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT) to form a QDs-4AT conjugate system. The QDs-4AT nanoprobe was highly selective and sensitive to the detection of bromide ion with a very low limit of detection. Subsequently, metallo-phthalocyanines (MPcs) were employed as host molecules on the surface of QDs based on the covalent linking of the QDs to the MPc. Elucidation of the reaction mechanism showed that the fluorescence “turn ON” effect of the QDs-MPc probe in the presence of the analyte was due to axial ligation of the analytes to the Pc ring. Studies showed that the type of substituent attached to the MPc ring influenced the overall sensitivity of the probe. Additionally, a comparative investigation using newly synthesized phthalocyanine and triaza-benzcorrole complexes was conducted when these complexes were conjugated to CdSe@ZnS QDs for analyte sensing. Results showed that the triaza-benzcorrole complex can be employed as a host-molecule sensor but displayed a lower sensitivity for analyte sensing in comparison to the phthalocyanine complex.
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McCormick, James Patrick. "Computer-aided luminescence spectroscopy of some nitrogen heterocycles : the development of novel computer-aided techniques in luminescence spectroscopy, applied to nitrogen heterocycles of medicinal interest to maximise the specificity of analysis." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328026.
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Alexander, Sally Anne. "The stability of the remnant luminescence emissions of alkali feldspar." Thesis, Connect to e-thesis, 2007. http://theses.gla.ac.uk/1001/.
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Thesis (Ph.D.) - University of Glasgow, 2007.Ph.D. thesis submitted to the Department of Geographical & Earth Sciences, University of Glasgow, 2007. Includes bibliographical references. Print version also available.
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Hindson, Benjamin Joseph, and mikewood@deakin edu au. "The Chemistry, spectroscopy and analytical applications of certain chemiluminescent reactions." Deakin University. School of Biological and Chemical Sciences, 2001. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051017.114704.
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Chemiluminescence, the production of light from a chemical reaction, has found widespread use in analytical chemistry. Both tris (2, 2-bipyridyl) ruthenium (II) and acidic potassium permanganate are chemiluminescence reagents that have been employed for the determination of a diverse range of analytes. This thesis encompasses some fundamental investigations into the chemistry and spectroscopy of these chemiluminescence reactions as well as extending the scope of their analytical applications.
Specifically, a simple and robust capillary electrophoresis chemiluminescence detection system for the determination of codeine, O6-methylcodeine and thebaine is described, based upon the reaction of these analytes with chemically generated tris(2,2'-bipyridyl)ruthenium(III) prepared in sulfuric acid (0.05 M). The reagent solution was contained in a glass detection cell, which also held both the capillary and the cathode. The resultant chemiluminescence was monitored directly using a photomultiplier tube mounted flush against the base of the detection cell. The methodology, which incorporated a field amplification sample introduction procedure, realised detection limits (3a baseline noise) of 5 x 10~8 M for both codeine and O6-methylcodeine and 1 x 10~7 M for thebaine. The relative standard deviations of the migration times and the peak areas for the three analytes ranged from 2.2 % up to 2.5 % and 1.9 % up to 4.6 % respectively.
Following minor instrumental modifications, morphine, oripavine and pseudomorphine were determined based upon their reaction with acidic potassium permanganate in the presence of sodium polyphosphate. To ensure no migration of the permanganate anion occurred, the anode was placed at the detector end whilst the electroosmotic flow was reversed by the addition of hexadimethrine bromide (0.001% m/v) to the electrolyte. The three analytes were separated counter to the electroosmotic flow via their interaction with a-cyclodextrin. The methodology realised detection limits (3 x S/N) of 2.5 x 10~7 M for both morphine and oripavine and 5 x 10~7 M for pseudomorphine. The relative standard deviations of the migration times and the peak heights for the three analytes ranged from 0.6 % up to 0.8 % and 1.5% up to 2.1 % respectively. Further improvements were made by incorporating a co-axial sheath flow detection cell. The methodology was validated by comparing the results realised using this technique with those obtained by high performance liquid chromatography (HPLC), for the determination of both morphine and oripavine in seven industrial process liquors. A complimentary capillary electrophoresis procedure with UV-absorption detection was also developed and applied to the determination of morphine, codeine, oripavine and thebaine in nine process liquors. The results were compared with those achieved using a standard HPLC method.
Although over eighty papers have appeared in the literature on the analytical applications of acidic potassium permanganate chemiluminescence, little effort has been directed towards identifying the origin of the luminescence. It was found that chemiluminescence was generated during the manganese(III), manganese(IV) and manganese(VII) oxidations of sodium borohydride, sodium dithionite, sodium sulfite and hydrazine sulfate in acidic aqueous solution. From the corrected chemiluminescence spectra, the wavelengths of maximum emission were 689 ± 5 nm and 734 ± 5 nm when the reactions were performed in sodium hexametaphosphate and sodium dihydrogenorthophosphate or orthophosphoric acid environments respectively. The corrected phosphorescence spectrum of manganese(II) sulfate in a solution of sodium hexametaphosphate at 77 K, exhibited two peaks with maxima at 688 nm and 730 nm. The chemical and spectroscopic evidence presented strongly supported the postulation that the emission was an example of solution phase chemically induced phosphorescence of manganese(II). Thereby confirming earlier predictions that the chemiluminescence from acidic potassium permanganate reactions originated from an excited manganese(II) species.
Additionally, these findings have had direct analytical application in that manganese(IV) was evaluated as a new reagent for chemiluminescence detection. The oxidations of twenty five organic and inorganic species, with solublised manganese(IV), were found to elicit analytically useful chemiluminescence with detection limits (3 x S/N) for Mn(II), Fe(II), morphine and codeine of 5 x 10-8 M, 2.5 x 10-7 M, 7.5 x 10-8 M and 5 x 10-8M, respectively. The corrected emission spectra from four different analytes gave wavelengths of maximum emission in the range from 733 nm up to 740 nm indicating that these chemiluminescence reactions also shared a common emitting species, excited manganese(II). Whilst several analytical problems were addressed in this thesis and answers to certain questions regarding the fundamentals of acidic potassium permanganate chemiluminescence were proposed, there are several areas that would benefit from further research. These are outlined in the final chapter of this thesis.
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Duarte, Adriana Pereira [UNESP]. "Híbridos luminescentes à base de sílica e complexos de európio: ferramenta para análise em meio biológico." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/105791.
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duarte_ap_dr_araiq.pdf: 8458185 bytes, checksum: 4c4165ee9f06459dcc2e5293c42a8a1d (MD5)Este trabalho apresenta a síntese, caracterização e estudo das propriedades de fotoluminescência de híbridos à base de sílica e complexos európio (III). Estes híbridos, também, foram funcionalizados e testados como sondas ou biomarcadores. A associação do íon európio à matrizes inorgânicas (alumina, sílica) e orgânicas (PMMA), tem sido amplamente estudada. Entretanto, o estudo de diferentes metodologias de síntese são ainda necessárias para otimizar propriedades físico-químicas, incluíndo as propriedades luminescentes destes materiais. Neste sentido, a presente tese propõe a síntese de dois novos luminóforos à base de sílica, via ligação covalente de complexos de Eu3+ à matriz, impedindo, desta forma, processos indesejados de lixiviação. Estes novos complexos de európio (III) devem apresentar ligantes com função alcooxisilanos, e uma estrutura eletrônica que possibilite a eficiente transferência de energia não radiativa (“efeito de antena”) Ligante ® Eu3+, otimizando propriedades luminescentes. Além do ligante bipiridina (Bpy-Si) já conhecido na literatura, desenvolvido no CIRIMAT-Toulouse, o novo ligante alcoóxi modificado b-dicetona (TTA-Si) foi sintetizado nessa tese, gerando neste trabalho uma família composta de três complexos de európio (III): [Eu(TMHD)3(Bpy-Si)], [Eu (TTA)3(Bpy-Si)] e [Eu (TTA-Si)3], que serão citados no texto sob as siglas [Eu1], [Eu2] e [Eu3], respectivamente. A ancoragem dos complexos superficialmente à sílica foi realizada sobre duas matrizes diferentes: primeiro, nanopartículas de sílica densas, 24 ± 2 nm (Ludox AS-40), e segundo, matrizes de sílica mesoporosas. A sílica mesoporosa foi sintetizada pela metodologia de pirólise de aerossol, um método (one step) capaz de produzir partículas mesoporosas em poucos minutos, sem resíduos de surfactante e...
Ce travail décrit la synthèse, la caratérisation et l’étude des propriétés de photoluminescence d’hybrides à base de silice et de complexes d’europium(III). Ces hybrides sont ensuite organiquement modifiés pour illustrer leur application potentielle en tant que sondes ou biomarqueurs. Associer les très bonnes propriétés de luminescence des complexes de lanthanides avec les propriétés physico-chimiques d’une matrice inorganique telle que la silice est une voie prometteuse pour l’obtention de nouveaux outils d’analyse pour la biologie. La silice, SiO2, est une excellente matrice inorganique qui, sous forme de particules submicroniques voire même nanométriques, puisqu’elle permet à la fois de concentrer le luminophore tout en le protégeant des perturbations externes susceptibles d’inhiber le processus de luminescence. De plus la modification de la surface des particules de silice via une fonctionnalisation par voie chimique rend ces nouveaux hybrides biocompatibles, adaptés à leur mise en suspension en milieu aqueux et donc intéressants pour l’analyse des milieux biologiques. Dans cette optique l’obtention de particules dont la taille reste inferieure à 100 nm est une condition qui s’impose et qui nécessite de développer de nouveaux hybrides organique-inorganiques. C’est dans ce cadre que se situe ce travail de thèse. Les lanthanides voient leurs propriétés de luminescence exaltées par la présence dans leur sphère de coordination de chromophores organiques. Depuis une dizaine d’années l’association de chélates d’europium(III) dans des matrices inorganiques (silice, alumine) et organiques (PMMA) a fait l’objet d’un très grand nombre d’études pour lesquelles les conditions de synthèse ne sont pas bien contrôlées conduisant à des hybrides... (Complete abstract click electronic access below)
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Tyombo, Nolukholo. "Synthesis and Luminescence of Zinc Oxide Nanorods-Blended Thiopheno-Organosilicon Polymers." University of the Western Cape, 2017. http://hdl.handle.net/11394/6230.
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Magister Scientiae - MSc (Chemistry)The increasing cost of fossil fuel energy production and its implication in environmental pollution and climate change created high demand for alternative and renewable sources of energy. This has led to great interest in research in the field of photovoltaic or solar cells Due to the abundance of sunlight, the technology is sustainable, non-polluting and can be implemented at places where power demand is needed, for example in rural areas. Solar cell devices that have been commercialized are currently based on silicon technology, involving the use of monocrystalline, polycrystalline and amorphous silicon. Although they produce highly efficient solar cells, the cost of Si solar cells is too high. Second generation solar cell materials such as cadmium telluride and third generation materials such as perovskites and organic polymers have been receiving much attention recently. However, they lack the efficiency of Si solar cells. This research proposes the development of high energy conservation photovoltaic cells from novel low-cost organosilicon polymers. The aim was to develop novel highly branched organosilane polymers such as poly(3-hexythiophene), polydi(thien-2-yl)dimethylsilane, poly(3-hexyl- [2,2'] bithiophenyl-5-yl)-dimethyl-thiophen-2yl-silane) as electron donors along with zinc oxide nanorod as the electron acceptor which were able to bring the efficiency of the resultant photovoltaic cell close to that of current Si solar cell.
2021-08-31
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Balogh, Margareta Cristina. "New luminescent materials, bio-inspired and recyclabe, based on lanthanide complexes." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEN039.
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L’objectif de ce projet a été de concevoir des matériaux émissifs recyclables à base de lanthanide, en vue de remplacer les oxydes contenus dans les lampes fluoro-compactes (CFLs). Les lanthanides, en particulier l’Eu¹¹¹ et le Tb¹¹¹ ont été les principaux « ingrédients » dans les phosphores à cause de leurs émissions fines dans le rouge et le vert. Les complexes tris-dipicolinate de lanthanides, solubles dans l’eau sont connus pour leurs excellentes propriétés de luminescence, ce qui en fait de bons candidats pour des applications dans le domaine de l’éclairage.Cette thèse décrit l’étude des complexes de tris-dipicolinate d’Eu¹¹¹ et de Tb¹¹¹ sous forme cristalline avec différents contre-cations, ainsi que des systèmes plus complexes comme des co-cristaux ou des de cristaux cœur/coquille. Ces complexes ont également été utilisés comme dopant dans des silices mésostructurées en utilisant une méthode dites de « incipient wet impregnation » (IWI). Les propriétés photophysiques de ces matériaux ont été étudiées en détail et une forte exaltation des propriétés d’émission a été mise en évidence dans les silices. En particulier, l’influence des oscillateurs O-X a été montrée et la détermination du rendement quantique intrinsèque nous a procuré une meilleure compréhension de cette exaltation.La recyclabilité des complexes de lanthanide dans la silice a pu être réalisée avec des bons rendements. Des matériaux, émettant de la lumière blanche ont pu être obtenus en mélangeant des émetteurs rouge, vert et bleu. Le naphtalimide a été choisi comme émetteur bleu. Ainsi, le mélange des complexes d’Eu¹¹¹ et de Tb¹¹¹ et de naphtalimide au sein d’une silice mésoporeuse a conduit à la première génération de matériaux émettant de la lumière blanche et pouvant être facilement recyclésThe objective of this project was to explore recyclable lanthanide based materials suitable for replacing the oxides from compact fluorescent lamps (CFLs). Lanthanides, particularly Eu¹¹¹ and Tb¹¹¹ have been the main “ingredients” in phosphors due to their colour purity and sharp emission in the red and green range of the visible spectrum. Lanthanide tris-dipicolinates are water soluble complexes, known for their excellent photophysical properties which makes them great candidates for lighting. The thesis describes the study of Eu¹¹¹ and Tb¹¹¹ tris-dipicolinate complexes in the crystalline form with different cations, as well as more complex systems like mixed co-crystals and core/shell crystals. The Eu¹¹¹ and Tb¹¹¹ complexes were also used as dopant in mesostructured silica materials via an incipient wetness impregnation method leading to homogeneous materials. The photophysical properties these different materials were thoroughly studied and a significant exaltation of the emission was evidenced in the silica. In particular, the influence of the O-X oscillators was explored and determination of the intrinsec quantum yield gave a clearer image on this exaltation. The recyclability of the lanthanide complexes from the material has been proven with high rates. Finally, white light emitting materials were obtained by mixing red, green and blue emitters. The naphthalimide moiety was chosen as blue emitter and white luminescence was successfully obtained in the solid state and for a silica material, representing a first generation of recyclable white light emitting materials based on lanthanide tris-dipicolinate complexes
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Jayaraj, Balaji. "Correlating microstructural development and failure mechanisms to photo stimulated luminescence spectroscopy and electrochemical impedance spectroscopy in thermal barrier coatings." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4948.
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Thermal barrier coatings (TBCs) are widely used for thermal protection of hot section components in turbines for propulsion and power generation. Applications of TBCs based on a clearer understanding of failure mechanisms can help increase the performance and life-cycle cost of advanced gas turbine engines. Development and refinement of robust nondestructive evaluation techniques can also enhance the reliability, availability and maintainability of hot section components in gas turbines engines. In this work, degradation of TBCs was non-destructively examined by photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) as a function of furnace thermal cycling carried out in air with 10-minute heat-up, 0.67, 9.6 and 49.6 - hour dwell duration at 1121[degree]C (2050[degree]F), and 10-minute forced-air quench. TBCs examined in this study consisted of either electron beam physical vapor deposited and air plasma sprayed yttria-stabilized zirconia (YSZ) on a variety of bond coat / superalloy substrates including bond coats of NiCoCrAlY and (Ni,Pt)Al, and superalloys of CMSX-4, Rene'N5, Haynes 230 and MAR-M-509. Detailed microstructural characterization by scanning electron microscopy and energy dispersive spectroscopy was carried out to document the degradation and failure characteristics of TBC failure, and correlate results of PSLS and EIS. Mechanisms of microstructural damage initiation and progression varied as a function of TBC architecture and thermal cycling dwell time, and included undulation of the interface between the thermally grown oxide (TGO) and bond coats, internal oxidation of the bond coats, and formation of Ni/Co-rich TGO. These microstructural observations were correlated to the evolution in compressive residual stress in the TGO scale determined by PSLS shift. Correlations include stress-relief and corresponding luminescence shift towards stress-free luminescence (i.e. v= 14402 cm[super-1] and v = 14432 cm[super]-1) associated with subcritical cracking of the TGO scale and stress-relaxation associated with gradual shift in the luminescence towards stress-free luminescence (i.e. v = 14402 cm[super-1] and v = 14432 cm[super-1]) is related to the undulation of TGO/bondcoat interface (e.g., rumpling and ratcheting). Microstructural changes in TBCs such as YSZ sintering, TGO growth, and subcritical damages within the YSZ and TGO scale were also correlated to the changes in electrochemical resistance and capacitance of the YSZ and TGO, respectively. With thermal exposure the YSZ/TGO resistance and capacitance increased and decreased as result of sintering and TGO growth. With progressive thermal cycling damages in the TGO was related to the TGO capacitance showing a continuous increase and at failure TGO capacitance abruptly increased with the exposure of bondcoat. Further correlations among the microstructural development, PSLS and EIS are documented and discussed, particularly as a function of dwell time used during furnace thermal cycling test, with due respect for changes in failure characteristics and mechanisms for various types of TBCs.ID: 029810158; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 213-217).
Ph.D.
Doctorate
Mechanical, Materials, and Aerospace Engineering
Engineering and Computer Science
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Kisand, Vambola. "Creation of free excitons in solid krypton investigated by time resolved luminescence spectroscopy." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961700092.
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Or, Chun-tat. "Optical characterization of defects in GaN /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23768770.
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Ledee, Ferdinand. "Cristallisation et fonctionnalisation de pérovskites hybrides halogénées à 2-dimensions pour le photovoltaïque et l’émission de lumière." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN045/document.
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Les pérovskites hybrides halogénées sont une nouvelle classe de semi-conducteurs polyvalents se proposant d'allier hautes performances, bas coût et processabilité en vue d'applications variées comme le photovoltaïque ou l'émission de lumière. Leur développement à grande échelle se heurte cependant à leur faible stabilité dans les dispositifs. Depuis quelques années, des groupes de chercheurs se sont particulièrement intéressés aux pérovskites hybrides à 2 dimensions (2D). Cette sous-catégorie de pérovskite est bien plus stable et offre une meilleure flexibilité chimique que leurs cousines 3D. Cependant, leurs performances restent limitées par la faible maitrise des méthodes de synthèses. En outre, de nombreux efforts sont encore à faire pour la compréhension de leurs propriétés intrinsèques, notamment via l'étude de monocristaux. Nous avons mis au point une méthode de synthèse par diffusion d’anti-solvant (AVC) permettant de synthétiser des monocristaux de pérovskites 2D telles que (PEA)2PbI4 et (PEA)2(MA)Pb2I7. Cette méthode a été de plus adaptée pour la synthèse de couches minces monocristallines. L’incorporation de ces couches minces dans des dispositifs pourrait permettre en théorie de se rapprocher des performances intrinsèques du matériau. Nous avons de plus synthétisé des nouvelles pérovskites 2D fonctionnalisées par des molécules de luminophore en tant que partie organique. L’étude spectroscopique de ces pérovskites met en évidence des probables transferts de charge entre les deux parties organique et inorganique. Ce type de pérovskite pourrait trouver un intérêt dans le photovoltaïque car il permettrait de séparer l’exciton fortement lié dans les pérovskites 2DHybrid halide perovskites are new class of high-end semiconductors that combine high performances, low cost and low temperature proccessability for different application such as photovoltaics or light-emitting devices. Their large-scale commercialization is however hindered by their poor stability. For a few years, many groups started to grow interest in 2-dimensional (2D) hybrid perovskites. This subclass of perovskite is much more stable than their 3D counterparts, and offers more chemical flexibility. Yet their performances are limited by the bad quality of the spin-coated layers. Moreover an increase in the understanding of their intrinsic properties is necessary. This last point could be solved by the study of single crystals. We developped therefore a new anti-solvant, vapor-assisted crystallization (AVC) method for the growth of (PEA)2PbI4 and (PEA)2(MA)Pb2I7. Furthermore, a capped AVC process (AVCC) was developped for the growth of 2D perovskites single crystalline thin films. These films might help getting closer to the intrinsic limits of the material. We also synthesized new 2D luminophore-functionalized perovskite systems. The spectroscopic studies of this material highlighted a possible charge transfer between the two moities of the perovskite. This kind of perovskite could help improving the photovoltaic performances of 2D perovskite thanks to the splitting of the strongly bounded exciton
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Gelamos, João Paulo. "Desenvolvimento e aperfeiçoamento de protocolos de conjugação de nanomarcadores luminescentes com sistemas biológicos para aplicação em imunoensaios /." São José do Rio Preto : [s.n.], 2011. http://hdl.handle.net/11449/97762.
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Orientador: Ana Maria PiresBanca: Marco Aurélio Cebim
Banca: Eduardo Alves de Almeida
Resumo: Neste trabalho foram desenvolvidos e aprimorados protocolos de conjugação entre nanopartículas do luminóforo Y2O3:Er,Yb, aminofuncionalizadas e a proteína Streptavidina, para atuarem como marcador em imunoensaios. A streptavidina faz parte do sistema de auto-reconhecimento biotina-avidina mais aplicado em ensaios biológicos, sendo que, devido ao seu alto custo, a Albumina Sérica Bovina foi escolhida como proteína de trabalho em substituição à Avidina. Na etapa final, no entanto, utilizou-se a Streptavidina para comparativamente finalizar as discussões. Desta forma, o desenvolvimento do protocolo considerado padrão foi feito aplicando-se o crosslinker homobifuncional glutaraldeído, e a partir deste, estudou-se o comportamento da ligação luminóforo-proteína utilizando-se outros crosslinkers heterobifuncionais, no caso sulfo-N-succinimidil 4-maleimido- butirato sal de sódio (Sulfo-GMBS) e cloridrato de N-(3-dimetilaminopropil)-N'-etilcarbodiimida (EDC). Tal alteração teve como princípio o aperfeiçoamento do protocolo de conjugação, estabelecendo comparativos entres os dados experimentais já obtidos e as possíveis vantagens resultantes dos crosslinkers heterobifuncionais, já que neste caso a possibilidade de ocorrer autoconjugação, ligação cruzada intramolecular e/ou polimerização entre as nanopartículas aminofuncionalizadas pode ser nula. Com relação às nanopartículas, estas, antes da conjugação, foram caracterizadas por espectroscopia de luminescência, microscopia eletrônica de varredura e/ou transmissão, assim como titulação potenciométrica para quantificação dos grupos NH2 após funcionalização. No desenvolvimento e aperfeiçoamento dos protocolos de conjugação todas as etapas foram monitoradas por Espectroscopia de Absorção na Região... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In this work conjugation protocols between the aminofunctionalized nanophosphor Y2O3: Er, Yb, and the protein Streptavidin was developed and improved to be possible applied as markers in immunoassays. The Streptavidin is part of the biotin-avidin self-recognition system applied to most biological assays, and, due to its high cost, Bovine Serum Albumin protein was chosen to be used in most part of the developing protocol as a substitute for avidin. In the final step, however, the Streptavidin was used in comparison to the other results in order to finalize the study. Thus, the development of the standard protocol was done by applying the homobifunctional crosslinker glutaraldehyde, and from this, it was studied the behavior of protein-nanophosphors binding using the heterobifunctional crosslinkers N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and Sulfo-N-succinimidyl 4-maleimidobutyrate sodium salt (Sulfo-GMBS). Such a change had the challenge to improve conjugation protocol, establishing the comparison between experimental data already obtained and the possible advantages due to the use of heterobifunctional crosslinkers, considering that in this case the possibility of occurring self-conjugation, intermolecular crosslinking and/or polymerization between the aminofuctionalized nanoparticles can be null. With respect to the nanoparticles before the conjugation step, they were characterized by luminescence spectroscopy, scanning and/or transmission electron microscopy as well as potentiometric titration for NH2 groups quantification after functionalization. During the development and the improvement of the conjugation protocols all steps were monitored by UV-VIS absorption spectroscopy to verify the behavior of molecular species present before and after the reactions... (Complete abstract click electronic access below)
Mestre
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Franke, Barbara. "Nondestructive Evaluation of Thermal Barrier Coatings with Thermal Wave Imaging and Photostimulated Luminescence Spectroscopy." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4088.
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Gas Turbine manufacturers strive for increased operating temperatures of gas turbine engines to improve efficiency and performance. One method of increasing the temperature beyond material limits is by applying thermal barrier coatings (TBCs) to hot section components. TBCs provide a thermal gradient between the hot gases and metallic substrate, and allow an increase in turbine inlet temperatures of 100-150ºC. However, spallation of TBCs can cause catastrophic failure of turbine engines by incipient melting of the substrate. To prevent such an occurrence, non-destructive evaluation (NDE) techniques are critical for quality control, health monitoring, and life assessment of TBCs. Two techniques in development for this purpose are thermal wave imaging (TWI) and photostimulated luminescence (PL) spectroscopy. TWI is a promising NDE technique with the ability to detect integrity and thickness of TBCs. In this study, TWI was employed as an NDE technique to examine as-coated TBCs with varying thicknesses, and thermally-cycled TBCs for initiation and progression of subcritical-subsurface damage as a function of thermal cycling. TWI and thermal response amplitude were correlated to the microstructural characteristics and damage progression of TBCs based on phenomenological expressions of thermal diffusion. The TBC specimens examined consisted of air plasma sprayed ZrO2 - 7wt.% Y2O3 on NiCoCrAlY bond coats with Haynes 230 superalloy substrate. As-coated specimens of varying thicknesses were evaluated by TWI to examine its applicability as a thickness measurement tool. It was found that heat dissipation through the TBC following pulsed excitation by xenon flash lamps initially followed the 1-D law of conduction and deviated from it as a function of thickness and time. The deviation resulted from quick dissipation of heat into the conductive metallic substrate. Therefore, with calibration, TWI can be used as a tool for YSZ thickness measurements of APS TBCs in the as-coated condition for quality control measures. Specimens of uniform thickness were evaluated as a function of thermal cyclic oxidation for subcritical-subsurface damage detection. Thermal cycling was carried out in air with 30-minute heat-up, 10-hour dwell at 1150°C, 30-minute air-quench and 1-hour hold at room temperature. During thermal cycling, TBC specimens were evaluated non-destructively by TWI at room temperature every 10 to 20 thermal cycles, and selected specimens were removed from thermal cycling for microstructural analysis by scanning electron microscopy (SEM). Higher thermal response amplitude associated with disrupted heat transfer was observed where localized spallation at or near the YSZ/TGO interface occurred. The health of the TBC was monitored by a rise in thermal response amplitude which may indicate a coalescence of microcracks to a detectable level. PL has been developed to measure stress, and detect subsurface damage and polymorphic transformation within the thermally grown oxide (TGO) of TBCs. PL was employed in this study as an NDE technique for TBCs to correlate subsurface damage as a function of thermal cyclic oxidation. The TBCs consisted of ZrO2 – 7 wt.% Y2O3 applied by electron beam physical vapor deposition with an as-coated (Ni,Pt)Al bond coat on a CMSX-4 superalloy substrate. Specimens were thermally cycled with a 10 minute ramp to a peak temperature of 1121°C, 40 minute hold at peak temperature, and 10 minute forced air quench. The TBCs were periodically removed from thermal cycling for NDE using PL until failure. Two specimens were removed from thermal oxidation after 10% and 70% of the average lifetime for microstructural analysis by SEM. During initial thermal cycling, metastable phases and polymorphic transformations of the Al2O3 scale were examined by PL. The polymorphic transformation from a metastable phase to equilibrium a-Al2O3 was detected. Since metastable phases are thought to be detrimental to coating lifetime, detection of these phases by PL can be used as a quality control tool. Nearing end-of-life, relief of the TGO from the compressive residual stress arising from thermal expansion mismatch was detected with PL and confirmed with microstructural analysis that revealed damage initiation (e.g. microcracking within the TGO scale parallel to the interfaces.) Rise in luminescence near the R-line frequency for polycrystalline a-Al2O3 without any residual stress (i.e. n = 14402 cm-1 and n = 14432 cm-1) corresponded to regions where cracked TGO was adhered to YSZ and not exposed to compressive stresses from thermal expansion mismatch upon cooling.M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Charles, Steven John. "Characterisation of irradiation damage and dopant distribution in synthetic diamonds by luminescence micro-spectroscopy." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393876.
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Legrand, Marie. "Advanced imaging of transient and spectral luminescence for optoelectronic characterization of photovoltaic materials." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS066.pdf.
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La photoluminescence des absorbeurs photovoltaïques permet de connaître les phénomènes de transport de charges et les propriétés optoélectroniques dont dépendent leurs performances. Cependant, son analyse repose sur des modèles physiques qui peuvent nécessiter des hypothèses non contrôlées et des paramètres inconnus. Cette thèse explore comment l'acquisition de cartographies de photoluminescence résolues spectralement en excitation pulsée peut contribuer à la caractérisation des matériaux, tout en limitant les connaissances préalables nécessaires et en contrôlant les hypothèses et modèles sous-jacents. D'une part, nous avons développé des systèmes d'imagerie décrivant l'intensité émise en quatre dimensions : 2D spatiale, temporelle et spectrale. D'autre part, nous avons réalisé des études de variation de longueur d'onde d'excitation et discuté leur relation avec l'absorption de la lumière. Les montages déjà mis en place illustrent l’intérêt de l’analyse des différentes dimensions de la lumière. Un imageur hyperspectral, fournissant le spectre dans chaque pixel, permet de caractériser les propriétés du matériau et les porteurs de charge générés. En complément, l'imagerie résolue en temps donne un aperçu des mécanismes de transport. Nous passons en revue et proposons différentes techniques pour obtenir des données 4D correspondant à l'évolution temporelle du spectre dans chaque pixel d'une image I_PL (x,y,énergie,temps). Parmi elles, l’imagerie monopixel utilise la modulation spatiale de la lumière pour reconstruire des cartographies spatiales. Trois techniques de mesure ont été développées sur le principe de l'imagerie à pixel monopixel. Elles correspondent à différents schémas d'échantillonnage dans l'espace 4D, en se concentrant sur les dimensions temporelles et spectrales qui sont atteintes avec de hautes résolutions. Leur mise en œuvre a été un défi car la photoluminescence correspond à des conditions de faible luminosité, et plus les résolutions sont élevées, plus la sensibilité est faible. Chaque dimension de la lumière impliquée doit être reconstruite avec précision tout en étant intriquée dans le processus d'acquisition. En particulier, l'impact de la diffraction et des interférences dues au modulateur spatial de lumière a été étudié. Ce travail instrumental a tout d'abord donné lieu à un système d’imagerie multimodale résolue temporellement et spectralement (2x3D). Il a été appliqué au suivi des mécanismes induits par la lumière dans les pérovskites, et qui conduisent à des changements dans de spectre et de dynamique. En second lieu, nous avons réalisé un outil d’imagerie 4D, illustré sur un échantillon d'arséniure de gallium. L'évolution conjointe de la photoluminescence dans les dimensions temporelle, spatiale et spectrale est observée en raison du remplissage des bandes et de la diffusion. Enfin, une méthode basée sur des algorithmes de segmentation d’image est proposée. Une cartographie spatiale est obtenue par imagerie mono-pixel, à partir de laquelle les zones d'intérêt sont déterminées avant d’y mesurer le déclin avec de hautes résolutions temporelles et spectrales. Un échantillonnage de la photoluminescence est obtenu avec un rapport signal/bruit élevé permettant son application à une variété d’échantillons et de conditions d'injection. Ces deux dernières approches sont uniques à notre connaissance et permettent d'obtenir une variation du PL dans les domaines combinés spatial, temporel et spectral. De plus, nous avons mis en place une méthodologie pour réaliser des études de longueur d'onde d'excitation sur l'imageur hyperspectral. Ainsi, l'absorptivité relative locale d’un échantillon de pérovskite inhomogène est obtenue sur une large gamme spectrale à partir d’une analyse combinée des spectres d'émission et d'excitation. Les mesures de réflectivité complétant cette étude fournissent des informations optiques et topologiques permettant d'affiner l'interprétation des cartographies de photoluminescencePhotoluminescence characterization of photovoltaic absorbers provides the charge transport phenomena and the optoelectronic properties on which their performance relies. However, their obtention is based on physical models and may require uncontrolled assumptions and unknown parameters. This thesis explores how acquiring spectrally resolved maps of photoluminescence in pulsed excitation can contribute to material characterization while limiting the necessary prior knowledge and controlling underlying hypotheses and models. On the one hand, we developed imaging systems describing the emitted intensity in four dimensions: 2D spatial, temporal and spectral. On the other hand, we performed excitation wavelength variation studies and investigated their relationship with light absorption. Maps of intensity can be acquired by pixelated detectors or non-imaging detectors, as in Single-pixel imaging. This approach employs spatial light modulation to reconstruct images and is particularly relevant to obtain multidimensional images. It is thus of interest for photoluminescence as each dimension brings information, as demonstrated by the setups already in use. A hyperspectral imager, providing the spectrum in each pixel, allows the characterization of material properties and the charge carriers generated. Complementarily, time-resolved imaging gives an insight into the transport mechanisms. We review and propose different techniques to obtain 4D data corresponding to the temporal evolution of the spectrum in each pixel of an image I_PL (x,y,energy,time). It provides the correlation between temporal and spectral dimensions, which was not available in the lab previously. Three measurement approaches were developed based on the principle of single-pixel imaging. They correspond to different sampling schemes in the 4D space, focusing on temporal and spectral dimensions that are reached with high resolutions. Their implementation was challenging as photoluminescence corresponds to low light conditions, and the higher the resolutions, the lower the sensitivity. Each dimension of light involved must be accurately reconstructed while entangled in the acquisition process. Particularly, the impact of diffraction and interferences due to the spatial light modulator has been investigated. This instrumental work allowed, first of all, combined time and spectrally resolved imaging (2x3D) of perovskite. It allowed monitoring of light-induced mechanisms that modify the photoluminescence spectrum and dynamics. Secondly, it has led to the characterization in 4D of the emission of a gallium arsenide wafer. The joint evolution of the signal in temporal, spatial, and spectral dimensions is observed due to band-filling and diffusion. At last, a workflow based on pixel clustering algorithms is proposed. A spatial map is obtained by single-pixel imaging, from which areas of interest are determined before the decay is obtained with high temporal and spectral resolutions. It allows an original sampling of photoluminescence with a high signal-to-noise ratio enabling its application to various samples and injection conditions. These last two approaches are unique to the best of our knowledge and provide photoluminescence variation in the combined spatial, temporal, and spectral domains. In addition, we have set up a methodology to perform excitation wavelength studies on the hyperspectral imager. It was demonstrated on an inhomogeneous perovskite sample from which the local relative absorptivity is obtained on a wide spectral range by combined analysis of the emission and excitation spectra. Reflectivity measurements completing this study provide optical and topological information allowing us to refine the interpretation of photoluminescence maps
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Fau, Amaury. "Spectroscopies Raman et de luminescence résolues en temps pour l'exploration de Mars." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS101.
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En 2021, le rover Mars 2020 de la NASA déploiera l’instrument SuperCam dans le cratère Jezero sur Mars. Cet instrument franco-américain multi-techniques d'analyse à distance sera équipé notamment d’un LIBS (analyse chimique) et d’un spectromètre Raman et de luminescence résolu en temps (analyse minéralogique). Après étude de paramètres environnementaux ainsi que de facteurs intrinsèques à l’échantillon cible, la spectroscopie Raman résolue en temps s’avère très puissante et permet la réalisation de spectres Raman dépourvus de signaux parasites (e.g. luminescence) pour de nombreux minéraux (carbonates, phosphates, silicates) parfois non analysables en Raman conventionnel. Une base de données de spectres Raman résolu en temps a ainsi été élaborée. Les effets de tirs laser LIBS sur la structure et la signature Raman de nombreux minéraux ont été étudiés sur la base d’expériences et de modélisations thermiques simples. Les résultats montrent un effet majeur (vitrification voire transition de phase) pour des minéraux opaques à fort coefficient d'absorption optique alors que les effets sont minimes, voire non détectables, pour des phases plus transparentes. Ces résultats sont discutés en termes de contraintes opérationnelles pour les instruments du rover Mars2020. L’étude de la luminescence des terres rares dans des apatites synthétiques dopées et naturelles montre que la luminescence est un outil pertinent de détection de ces éléments. En revanche, l’étude des temps de décroissance met en évidence des phénomènes complexes de transferts d’énergie entre centres émetteurs et limite l’utilisation de ces temps de décroissance pour une éventuelle quantification des terres raresIn 2021, the NASA Mars 2020 rover will deploy the SuperCam instrument in the Jezero crater on Mars. This franco-american multi-tool instrument for remote analysis will be equiped with LIBS (chemical analysis) and with a time-resolved Raman and luminescence spectrometer (mineralogical analysis). After investigating various environmental parameters as well as intrinsic factors from the target sample, time-resolved Raman spectroscopy appears as a powerful tool to obtain high-quality Raman spectra free of parasitic signal (e.g. luminescence) for many mineral phases (carbonates, phosphates, silicates), even in the case of minerals hardly analysable with conventional Raman. A database of time-resolved Raman spectra has been elaborated. The effects of LIBS laser shots on the mineral structure and Raman fingerprint have been studied experimentally and through simple thermal modeling. Results show a major structural effect (vitrification and/or phase transition) in the case of opaque minerals with high optical absportion coefficient whereas the effects are minimal, or even non detectable, for more transparent and less absorbing minerals. Implications of these results for the operation of the Mars 2020 instruments are discussed. The study of Rare-Earth Elements (REE) luminescence in synthetic doped and natural apatites shows that luminescence is powerful to detect and characterize REEs. However, due to strong transfer energy among emission centers, the possible use of luminescence lifetime appears to be impossible to quantify REE in natural apatites
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Jones, Debbie. "Fluorescence spectroscopy and microscopy as tools for monitoring redox transformations of uranium in biological systems." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/fluorescence-spectroscopy-and-microscopy-as-tools-for-monitoring-redox-transformations-of-uranium-in-biological-systems(e5420e94-b96e-4ee1-be63-1a3363672014).html.
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The immobilisation of uranium is an important issue within the nuclear industry due to contaminated land from accidental spillage, weapons testing or mining activities. Within the environment uranium is most commonly found in the +VI oxidation state as the mobile uranyl cation [UO2]2+. Alternatively, the +IV oxidation state can also be found in the environment, forming either an insoluble crystalline uraninite phase, or a more soluble molecular uranium(IV) species. Many endogenous subsurface bacteria can bind and accumulate actinide ions through biosorption and can reduce mobile uranyl(VI) species down to immobile uranium(IV) compounds and mineral phases. This work presents an investigation into the bioreduction process by two anaerobic Gram-negative bacteria, Geobacter sulfurreducens and Shewanella oneidensis MR-1. Luminescence spectroscopy is used to monitor the intensity of uranyl(VI) emission in situ over the course of a 24 hour bioreduction experiment with uranyl(VI) acetate as the electron acceptor and either acetate or lactate as the electron donor. An increase in intensity of the emission around hour three or four during the reduction, followed by an overall decrease, is attributed as the disproportionation of an unstable uranyl(V) intermediate. The role of inner and outer membrane c-typecytochromes as well as flavin secretion is also investigated using three deletion mutants of the S. oneidensis bacteria, which shows that in their absence, the reduction of uranyl(VI) does not occur over the course of 24 hours. The emission of uranium(IV) is also investigated during bioreduction in phosphate media and results show that emission can be observed in aqueous solutions at pH 7 pointing to the presence of a molecular product. One photon confocal and two photon fluorescence microscopy has been utilised for the very first time to directly optically image the bioreduction of uranyl(VI) in combination with luminescence lifetime mapping. The sorption of uranyl(VI) onto the surface of the bacteria with differing lifetimes indicates a direct interaction between uranyl(VI) and surface bound c-type cytochromes, since this variation was not observed in mutant S. oneidensis strains where the cytochromes were not present. Combined, these results have established the applicability of optical spectroscopy and microscopyin tracking the bioreduction of uranium in situ.
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Duarte, Adriana Pereira. "Híbridos luminescentes à base de sílica e complexos de európio : ferramenta para análise em meio biológico /." Araraquara : [s.n.], 2012. http://hdl.handle.net/11449/105791.
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Orientador: Sidney José Lima RibeiroOrientador: Marie Joelle Menu
Banca: Oscar Manoel Loureiro Malta
Banca: Jean Olivier Durand
Banca: Luís Antonio ferreira Martins Dias Carlos
Banca: Eric Benoist
Resumo: Este trabalho apresenta a síntese, caracterização e estudo das propriedades de fotoluminescência de híbridos à base de sílica e complexos európio (III). Estes híbridos, também, foram funcionalizados e testados como sondas ou biomarcadores. A associação do íon európio à matrizes inorgânicas (alumina, sílica) e orgânicas (PMMA), tem sido amplamente estudada. Entretanto, o estudo de diferentes metodologias de síntese são ainda necessárias para otimizar propriedades físico-químicas, incluíndo as propriedades luminescentes destes materiais. Neste sentido, a presente tese propõe a síntese de dois novos luminóforos à base de sílica, via ligação covalente de complexos de Eu3+ à matriz, impedindo, desta forma, processos indesejados de lixiviação. Estes novos complexos de európio (III) devem apresentar ligantes com função alcooxisilanos, e uma estrutura eletrônica que possibilite a eficiente transferência de energia não radiativa ("efeito de antena") Ligante ® Eu3+, otimizando propriedades luminescentes. Além do ligante bipiridina (Bpy-Si) já conhecido na literatura, desenvolvido no CIRIMAT-Toulouse, o novo ligante alcoóxi modificado b-dicetona (TTA-Si) foi sintetizado nessa tese, gerando neste trabalho uma família composta de três complexos de európio (III): [Eu(TMHD)3(Bpy-Si)], [Eu (TTA)3(Bpy-Si)] e [Eu (TTA-Si)3], que serão citados no texto sob as siglas [Eu1], [Eu2] e [Eu3], respectivamente. A ancoragem dos complexos superficialmente à sílica foi realizada sobre duas matrizes diferentes: primeiro, nanopartículas de sílica densas, 24 ± 2 nm (Ludox AS-40), e segundo, matrizes de sílica mesoporosas. A sílica mesoporosa foi sintetizada pela metodologia de pirólise de aerossol, um método (one step) capaz de produzir partículas mesoporosas em poucos minutos, sem resíduos de surfactante e... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Ce travail décrit la synthèse, la caratérisation et l'étude des propriétés de photoluminescence d'hybrides à base de silice et de complexes d'europium(III). Ces hybrides sont ensuite organiquement modifiés pour illustrer leur application potentielle en tant que sondes ou biomarqueurs. Associer les très bonnes propriétés de luminescence des complexes de lanthanides avec les propriétés physico-chimiques d'une matrice inorganique telle que la silice est une voie prometteuse pour l'obtention de nouveaux outils d'analyse pour la biologie. La silice, SiO2, est une excellente matrice inorganique qui, sous forme de particules submicroniques voire même nanométriques, puisqu'elle permet à la fois de concentrer le luminophore tout en le protégeant des perturbations externes susceptibles d'inhiber le processus de luminescence. De plus la modification de la surface des particules de silice via une fonctionnalisation par voie chimique rend ces nouveaux hybrides biocompatibles, adaptés à leur mise en suspension en milieu aqueux et donc intéressants pour l'analyse des milieux biologiques. Dans cette optique l'obtention de particules dont la taille reste inferieure à 100 nm est une condition qui s'impose et qui nécessite de développer de nouveaux hybrides organique-inorganiques. C'est dans ce cadre que se situe ce travail de thèse. Les lanthanides voient leurs propriétés de luminescence exaltées par la présence dans leur sphère de coordination de chromophores organiques. Depuis une dizaine d'années l'association de chélates d'europium(III) dans des matrices inorganiques (silice, alumine) et organiques (PMMA) a fait l'objet d'un très grand nombre d'études pour lesquelles les conditions de synthèse ne sont pas bien contrôlées conduisant à des hybrides... (Complete abstract click electronic access below)
Doutor
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Cousseau, Fabien. "Structuration et étude de luminescence à l’échelle du nano-objet unique." Thesis, Angers, 2018. http://www.theses.fr/2018ANGE0053.
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La photo-isomérisation de l’azopolymère cause des mouvements de masse permettant d'inscrire des figures d'interférences à la surface de films minces. Les films sont répliqués sur un substrat en PDMS transparente t étirable. Il forme des réseaux de phase. Les figures de diffraction décrivent les surfaces, elles sont utilisées pour modéliser numériquement les réseaux, quelles que soient les contraintes.Le projet WOLF vise à fabriquer des nano lasers blancs à colorants organiques. Un montage complexe de caractérisation est développé. Le module d’excitation permet d’illuminer les nanotubes un à un. Le pompage tente de maximiser l’émission laser d’un unique nano objet. La collection du signal repose pricipalement sur l’utilisation d’une fibre optique ouvrant la porte de la microscopie confocale. La spectroscopie associée au montage révèle la formation de cavités au sein des nano bâtonnets organiques. Malgré la faible puissance du signal, les modes sont étudiés,mettant en évidence des nano-cavités. Les nano-objets sont parfois étudiés dans des liquide. La micro-fluidique est développée au laboratoire. Sans salle blanche une méthode photolithographique est développée à bas coûts. Les puces nouvellement créées sont testées dans le mélange de deux fluides et lors de la caractérisation de nanoparticules en suspension par leur mouvement Brownien. Cette thèse à permis de mettre en place les outils d’observation de nano-objets uniquesAzopolymer photo-isomerization causes matter motion. This phenomena is responsible for the inscription of the interference pattern on surface of thin films. The films are replicated by pouring PDMS on it. PDMS is a transparent and stretchable polymer. The diffraction pattern of these gratings describes the surface. These informations are used to numerically simulate the surface irrespective of the mechanical constraints.The WOLF project try to synthetize white lightorganic nanolasers. For that purpose, a complex setup has been realised. The excitation part of the setup illuminates a single nano-laser or a few. The pump source is designed to optimise the amplified emission of the nanolasers. The collection of the signal is based on an optical fiber.This fibre has given us the chance to use confocal microscopy. Spectroscopy combined with our setup show the existence of nanocavities among nanotubes. In spite of the low signal power, the emitting modes are studied and show the cavity effect of these lasers. In another context, nano-objets are sometimes studied in solution. For that reason, a new experiment has been setup, namely, microfluidic. Without the use of a clean room, a low cost photolithograpic method is developped. The microfluidic chips are tested during the mixing of to liquids and during the obsevation of the brownian motion of particules. This PhD thesis has given the tools needed for the characterization of single nano-objects
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Curry, Richard James. "Luminescence characterisation of aluminium and erbium tris (8-hydroxyquinoline)." Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312173.
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Xia, Ruidong. "Spatial resolved luminescence spectroscopy investigation of defect emission and degradation of III-V semiconductor devices." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272880.
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Williams, Diane Keith. "Particle Size Dependence on the Luminescence Spectra of Eu3+:Y2O3 and Eu3+:CaO." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/29719.
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Since the Eu3+ ion can occupy different cation sites in a host material, it can serve as a useful probe of nanocrystalline structures to gain more insight into the structural changes that can occur when the particle size is reduced from the bulk to nanometer regime. The use of laser spectroscopy to probe two nanocrystalline structures, Eu3+:Y2O3 and Eu3+:CaO, was investigated. The nanocrystalline structures were prepared by the laser-vaporization-gas-phase condensation of the bulk oxides. The particle size distribution and dominant particle diameters of the nanocrystals were determined by transmission electron microscopy.
The particle size dependency results of Eu3+:Y2O3 revealed three distinct phases: (1) the sharp lines of the monoclinic Y2O3 were dominant in the larger particles; (2) the C2 site of the cubic phase, which appears in the smaller particles; and (3) the amorphous phase that increases in intensity as the particle size decreases. The observation of distinct spectral lines from the monoclinic phase confirms the presence of a crystalline phase for all of particle sizes studied.
The site-selective results of various concentrations of 13-nm Eu3+:CaO showed that the laser-vaporization-gas-phase condensation method of preparation produced two europium-containing phases at most concentrations: cubic CaO and monoclinic Eu2O3. Results showed that the monoclinic Eu2O3 phase could be reduced by 95% by annealing at 800 0C for 30 minutes without particle growth.
Since the Eu3+ ion and the Y3+ ion are isovalent, the substitution of a Eu3+ ion into Y2O3 is considered a trivial case of extrinsic disorder since the impurity is neutral relative to a perfect crystal1. As a result, it is not necessary to have any other defects present in the crystals to maintain charge neutrality. With Eu3+:CaO, the dopant and host cation charges are different and therefore the dopant distribution can be investigated by site-selective spectroscopy.
Since the experimental dopant distribution results for nanocrystalline Eu3+:CaO were inconclusive, a model to predict the theoretical change in the dopant distribution in Eu3+:CaO as a function of particle size was developed. The model predicts that the defect chemistry is affected when the particle size is approximately 50 nm and smaller.Ph. D.
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Lannes, Anthony. "Chimie de coordination de radicaux nitronyl-nitroxyde pontants pour l’élaboration de matériaux magnétiques moléculaires : synthèse, structures cristallines, propriétés magnétiques et spectroscopie électronique." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10173/document.
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Au cours des dernières décennies, l'électronique s'est développée de manière à répondre au besoin grandissant de stocker et traiter toujours plus d'information, et elle a évolué de manière incessante vers une miniaturisation extrême. Dans ce contexte, les molécules-aimants, qui sont des entités moléculaires magnétiques, présentent une bistabilité magnétique permettant de stocker l'information dans des unités de la taille d'une molécule. Le principal frein aux applications tient aux basses températures auxquelles ces molécules présentent de telles propriétés (< 15K). Il est donc important de comprendre les mécanismes mis en jeu au sein de ces entités afin d'augmenter les températures de fonctionnement. Un moyen prometteur est de ponter deux ions de lanthanides par un ligand radicalaire. Cette approche a conduit à la conception de la molécule-aimant ayant à ce jour la plus haute température de blocage (14 K). Ce travail de thèse est dédié à la conception et à la caractérisation des structures, ainsi qu'à l'étude des propriétés magnétiques et des relations magnéto-structurales par spectroscopie électronique de molécules aimants et d'aimants à base moléculaires. Ces systèmes sont élaborés à partir d'ions de lanthanides(III) ou de manganèse(II) et de radicaux libres organiques de types nitronyl-nitroxyde. Une attention particulière sera dirigée vers la réalisation de complexes dinucléaires de lanthanides pontés par un ligand radicalaire, et sur l'étude de la brique monomérique. Nous avons exploré la possibilité d'utiliser le radical NITBzImH comme ligand radicalaire pontant des briques moléculaires de type [Ln(β- dicétone)3] et [Ln(NO3)3]. Nous nous sommes intéressés au comportement magnétique inhabituel d'un polymère de coordination de manganèse(II) pontés par les radicaux NITIm, parent de NITBzImH, puis nous avons commencé à nous intéresser à l'effet produit en remplaçant les manganèses(II) par des lanthanides(III)For the past decades, electronics have been developed in order to meet the increasing need of information storage, always evolving to the constant upgrade of their components: better, faster, smaller. Twenty-five years ago, the recently created field of molecular magnetism allowed designing entities responding to the aforementioned requirements: Single- Molecule-Magnets (SMMs). On the one hand, those are compounds showing magnetic bistability affording to stock information and on the other hand, they are the smallest entities available to design any information support. In spite of those remarkable qualities, they require very low temperature (< 15 K) to display their properties. Thus, it is of primary importance to understand underlying mechanisms in order to increase this temperature range. One promising route is to connect lanthanide dimer by a radical bridge. This method has led to the discovery of a SMM, whose blocking temperature is the highest known to date (14 K). This thesis work has been dedicated to the conception of SMMs and molecular-based magnets, as well as the characterization of their structures and magnetic properties, and their magneto-structural relationships by electronic spectroscopy. Those systems were mostly based on lanthanide(III) or manganese(II) ion and nitronyl-nitroxide organic free radicals. A special focus was made to the synthesis of dinuclear lanthanide complexes bridged by an organic free radical, and to the study of their mononuclear complex. We have studied the potential of NITBzImH radical as a bridge for [Ln(β-diketonate)3] and [Ln(NO3)3] molecular bricks. We also took interest to the unusual magnetic behavior of a manganese(II) coordination polymer, where each metal center is bridged by a NITIm radical, closely related to NITBzImH radical. Finally, we started to explore the changes induced by switching manganese(II) to lanthanide(III)
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Yang, Sen. "Characterization of low voltage cathodo-luminescent phosphors for field emission displays." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/30859.
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Dai, Xuemin, and 戴學敏. "Experimental and theoretical studies of defects related emissions in ZnO crystals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B4163388X.
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Dai, Xuemin. "Experimental and theoretical studies of defects related emissions in ZnO crystals." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B4163388X.
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Partl, Michal. "Total fluorenscence spectra of resorufin and anthracene : applications of singular-value decomposition in total luminescence spectroscopy /." Zürich, 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10785.
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Mühlenberend, Svenja [Verfasser]. "Metals and organic adsorbates on GaAs(110) : a scanning tunneling microscopy, spectroscopy and luminescence study / Svenja Mühlenberend." Kiel : Universitätsbibliothek Kiel, 2016. http://d-nb.info/1096220903/34.
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yu, shenjiang. "NEW DEVELOPMENTS ON HIGH-RESOLUTION LUMINESCENCE SPECTROSCOPY AND THEIR APPLICATION TO THE DIRECT ANALYSIS OF ORGANIC POLLUTANTS." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4075.
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Polycyclic aromatic compounds (PACs), which comprise a complex class of condensed multi-ring benzenoid compounds, are important environmental pollutants originating from a wide variety of natural and anthropogenic sources. PACs are generally formed during incomplete combustion of pyrolisis of organic matter containing carbon and hydrogen. Because combustion of organic materials is involved in countless natural processes or human activities, PACs are omnipresent and abundant pollutants in air, soil, and water. Chemical analysis of PACs is of great environmental and toxicological importance. Many of them are highly suspect as etiological agents in human cancer. Because PACs carcinogenic properties strongly depend on molecular structure and differ significantly from isomer to isomer, it is of paramount importance to determine the most toxic isomers even if they are present at much lower concentrations than their less toxic isomers. Gas chromatography (GC), high-resolution GC, and high-performance liquid chromatography (HPLC) are the basis for standard PACs identification and determination. Many cases exist where GC, HPLC, and even HR-GC have not been capable to provide unambiguous isomer identification. The lack of reliable analytical data has lead to serious errors in environmental and toxicological studies. This dissertation deals with the development of novel instrumentation and analytical methods for the analysis of PACs in environmental samples. The developed methodology is based on two well-known high-resolution luminescence techniques, namely Shpol'skii Spectroscopy (SS) and Fluorescence Line Narrowing Spectroscopy (FLNS). Although these two techniques have long been recognized for their capability in providing direct determination of target PACs in complex environmental samples, several reasons have hampered their widespread use for the problem at hand. These include inconvenient sample freezing procedures; questions about signal reproducibility; lengthy spectral acquisition, which might cause severe sample degradation due to prolonged excitation; broadband fluorescence background that degrades quality of spectra, precision of measurements and detection limits; solvent constrains imposed by the need of optically transparent media; and, most importantly, the lack of selectivity and sensitivity for unambiguous determination of closely related PACs metabolites. This dissertation presents significant advances on all fronts. The analytical methodology is then extended to the analysis of fluoroquinolones (FQs) in aqueous samples. FQs are one of the most powerful classes of antibiotics currently used for the treatment of urinary tract infections. Their widespread use in both human and animal medicine has prompted their appearance in aquatic systems. The search for a universal method capable to face this new environmental challenge has been centered on HPLC. Depending on the FQ and its concentration level, successful determination has been accomplished with mass spectrometry, room-temperature fluorescence (RTF) or UV absorption spectrometry. Unfortunately, no single detection mode has shown the ability to detect all FQ at the concentration ratios found in environmental waters. We provide a feasible alternative based on FLNS. On the instrumentation side, we present a single instrument with the capability to collect multidimensional data formats in both the fluorescence and the phosphorescence time domains. We demonstrate the ability to perform luminescence measurements in highly scattering media by comparing the precision of measurements in optically transparent solvents (Shpol'skii solvents) to those obtained in "snow-like" matrixes and solid samples. For decades, conventional low-temperature methodology has been restricted to optically transparent media. This restriction has limited its application to organic solvents that freeze into a glass. In this dissertation, we remove this limitation with the use of cryogenic fiber-optic probes. Our final efforts deal with low-temperature absorption measurements. Recording absorption spectra via transmittance through frozen matrixes is a challenging task. The main reason is the difficulty to overcome the strong scattering light reaching the detector. This is particularly true when thick samples are necessary for recording absorption spectra of weak oscillators. In the case of strongly fluorescent compounds, additional errors in absorbance measurements arise from the emission reaching the detector, which might have comparable intensity to that of the transmitted light. We present a fundamentally different approach to low-temperature absorption measurements as the sought-for-information is the intensity of laser excitation returning from the frozen sample to the intensified-charge coupled device (ICCD). Laser excitation is collected with the aid of a cryogenic fiber optic probe. The feasibility of our approach is demonstrated with single-site and multiple-site Shpol'skii systems. 4.2K absorption spectra show excellent agreement to their literature counterparts recorded via transmittance with closed cycle cryogenators. Fluorescence quantum yields measured at room-temperature compare well to experimental data acquired in our lab via classical methodology. Similar agreement is observed between 77K fluorescence quantum yields and previously reported data acquired with classical methodology. We then extend our approach to generate original data on fluorescence quantum yields at 4.2K.Ph.D.
Department of Chemistry
Sciences
Chemistry: Ph.D.
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Schneider, Julia. "Characterisation of Single and Multibubble Cavitation Through Analysis of Molecular, Atomic and Ionic Line Emissions." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20011.
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La cavitation acoustique (formation, croissance et effondrement de bulles de gaz dans un liquide soumis aux ultrasons) est à l'origine de réactions chimiques (sonochimie) via la génération de conditions extrêmes lors de l'effondrement des bulles. Des températures de 103-104K et des pressions de l'ordre de 1000 atm sont atteintes au cœur des bulles [1]. Dans ces conditions, les liaisons chimiques des molécules volatiles présentes dans les bulles peuvent être rompues, formant, dans le cas de solutions aqueuses, des radicaux OH et H. Par ailleurs, l'effondrement violent des bulles de cavitation peut être accompagné par l'émission de lumière, sonoluminescence (SL), qui est le sujet d'étude de ce travail. Cette émission lumineuse est formée d'un continuum, de l'UV au proche IR, similaire à l'émission d'un corps noir, sur lequel peuvent se superposer des lignes d'émission atomiques ou moléculaires.On distingue deux types de SL: la SL mono-bulle (SBSL) et la SL multibulle (MBSL). En général, les spectres de MBSL se différencient de ceux de SBSL par la présence de lignes d'émission (d'atomes alcalins, de radicaux hydroxy… [2]), si bien que les mécanismes d'émission ainsi que la nature des conditions à l'intérieur des bulles lors de leur effondrement ont longtemps été considérés comme différents pour les systèmes mono- et multi-bulles. Un pont a été érigé entre les deux systèmes par le travail de Liang et al. [3] qui mit en évidence les conditions expérimentales permettant l'apparition de lignes dans le spectre de SBSL. Dans ce contexte, l'objectif de ce travail était de comparer les émissions de SBSL (27 kHz) et MBSL à haute et basse fréquences (20, 203, 607 kHz) pour différentes solutions aqueuses. Un sonoréacteur monobulle a été développé, dans lequel la température, la nature et la pression de gaz dissous ainsi que la pression acoustique sont contrôlés. Les électrolytes étudiés étaient : NaCl et les chlorures de lanthanides luminescents Ce3+, Tb3+, Eu3+ et Gd3+. Ces derniers peuvent être excités soit par absorption de photons dans l'UV soit par collisions avec des particules énergétiques [4].Dans la première partie de ce travail, les conditions à l'intérieur d'une monobulle lors de son effondrement ont été estimées via un fit du continuum par l'équation de Planck du corps noir. Les températures du corps noir obtenues sont de l'ordre de 104K, en accord avec des études précédentes. Elles sont indépendantes de la présence de NaCl et de la pression acoustique alors que l'intensité de SL y est très sensible. Les résultats obtenus remettent en question l'utilisation du modèle du corps noir en SL. Des lignes d'émission atomique et moléculaire se superposent parfois au continuum de SL : en MBSL, et en SBSL dans certaines conditions particulières (pression d'argon suffisante, faible pression acoustique) [3, 5]. Ce travail met en évidence la similarité entre la forme de l'émission de OH en SBSL et en MBSL à 20kHz, ce qui indique des conditions intrabulles très proches dans les conditions expérimentales étudiées [6]. En SBSL sous 70mbar d'Ar, l'intensité des lignes diminue lorsque la pression acoustique augmente, jusqu'à leur disparition dans le continuum. Cette évolution peut apparaître comme un lien entre SBSL et MBSL.Par ailleurs, cette étude confirme que la concentration en sodium à l'interface bulle-liquide, qui peut être enrichie par l'utilisation d'un contre-ion tensioactif, est le paramètre clé de l'observation de l'émission du sodium en SBSL, suggérant que l'excitation du sodium a lieu soit à l'interface de la bulle, soit en son cœur, après injection de gouttelettes. La seconde partie de cette étude concerne l'effet de la fréquence ultrasonore et de la puissance acoustique sur l'intensité de luminescence des ions lanthanides en MBSL. La luminescence des ions Tb3+, Ce3+ et Eu3+ est ainsi observée. La comparaison des rendements de SL et de photoluminescence indique qu'à l'exception de Ce3+, l'excitation par photons est minThe importance of acoustic cavitation, i.e., the formation, growth and collapse of gaseous cavities in liquid exposed to ultrasound, in sonochemistry is based on the generation of extreme conditions upon bubble collapse. Temperatures and pressures inside the collapsing bubble are approximated to reach 104 K and 1000 atm, respectively [suslick-1999]. Under such conditions chemical bonds of the solvent vapour or volatile solutes present in the bubble core are easily cleaved, which in the case of aqueous systems, leads to the formation of chemically reactive OH and H radicals. These primary radicals either recombine leading to chemiluminescence, or diffuse into solution, where they are liable to react with other species. Of particular importance in this work is the light emission that accompanies cavitation, termed sonoluminescence (SL). This emission is a broad continuum ranging from 200nm to 900 nm, resembling the emission of a blackbody, which can be superimposed with atomic or molecular emission lines comparable to bremsstrahlung. It is necessary to distinguish two forms of SL, single-bubble (SBSL) and multibubble (MBSL). In general, MBSL spectra differ from SBSL spectra in that they contain emission lines, e.g., from alkali atoms or hydroxyl radicals [matula-1995]. Consequently, it was, until recently considered that the mechanisms of light emission, and the nature of the bubble interior upon collapse were fundamentally different for the single and multibubble systems. Considering that MBSL is a cloud of single bubbles a bridging theory is desired.With this background the objective of the present work was to conduct a comparative spectroscopic analysis of SBSL, driven at 27 kHz, and MBSL generated from low and high ultrasonic frequencies (20, 203 and 607 kHz) of aqueous electrolyte solutions. Therefore a single bubble sonoreactor was developed, where the temperature, gas content and type, as well as the acoustic pressure could be controlled. The electrolytes of choice were: sodium chloride and chlorides of the luminescent lanthanide ions, Ce3+, Tb3+, Eu3+ and Gd3+, which can be excited by UV light absorption and collisions with energetic particles [kulmala-1995]. In the first part of this work the conditions upon bubble collapse were approximated by fitting the broad-band continuum of SBSL spectra of water with 70 mbar of argon and a 0.5 M NaCl solution with 70 mbar of argon using Planck's law of blackbody radiation. The obtained blackbody temperatures are in the range of 104 K, which is in good agreement with previous studies, but with the discrepancy of being independent of the presence of NaCl and the acoustic pressure, whereas the SL intensity increased by a factor of more than 10 upon increased acoustic pressure. The different trends followed by SL intensity and blackbody temperatures question the blackbody model. Another observation questioning the blackbody model is the appearance of atomic and molecular emission lines in MBSL and as recently observed also in SBSL [liang-2007, young-2001]. The present work proofed that the key factors for line emission in SBSL are small amounts of argon and low acoustic pressure. Moreover, the work revealed that the shape of the OH• radical emission is very similar to that in MBSL spectra, indicating the strong similarity of intrabubble conditions in MBSL and SBSL under certain experimental conditions [schneider-2011]. An increase of the acoustic pressure caused the continuum to overlap the lines until they become indistinguishable giving the usually in SBSL observed featureless continuum. This advance is a big step toward bridging the gap between SBSL and MBSL. Furthermore this study reveals that the concentration of the sodium ion at the interface of a single bubble can be enriched with a surface active counterion and the concentration is crucial for the observation of the sodium line in SBSL, suggesting that excitation of sodium either takes place at the interface of the
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柯俊達 and Chun-tat Or. "Optical characterization of defects in GaN." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31226607.
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Milori, Debora Marcondes Bastos Pereira. "Caracterização do LiNbO3:Er+3 como meio ativo para lasers de estado sólido através dos espectros de absorção/emissão polarizada e medida dos tempos de vida de luminescência." Universidade de São Paulo, 1989. http://www.teses.usp.br/teses/disponiveis/54/54131/tde-19052009-104534/.
Full textAbstract:
Este trabalho consiste na caracterização ótica de monocristais de LiNbO3: Er+3, visando a possibilidade deste sistema ser meio ativo para laser. Os resultados obtidos para absorção e emissão foram satisfatórios, sendo bastante compatíveis com os do modelo teórico adotado. O tempo de vida de luminescência das transições 4S3/2 - 4I15/2 e 4F9/2 - 4I15/2 foi medido, à temperatura ambiente e de nitrogênio líquido, mostrando que elas são possíveis candidatas a transições laser. Também foi feito um estudo sobre o comportamento das concentrações das impurezas indesejáveis OH- e Fe2+, através de tratamento térmico. O controle dessas concentrações foi feito através das técnicas de RPE e absorção ótica e os resultados mostraram que é perfeitamente possível eliminar tais impurezas de uma forma totalmente controlada.This work consists in the optical characterization of LiNbO3:Er3+ single crystals, aiming to verify the possibility of this system being an active media for laser. The absorption and emission results were satisfactory, being compatible enough with the theoretical model adopted. The luminescence lifetime of the 4S3/2 - 4I15/2 e 4F9/2 - 4I15/2 transitions was measured at the ambient and liquid nitrogen temperature, showing that they are possible candidates for laser transitions. The behavior of the undesirable OH- and Fe2+ impurities was also studied through thermal treatment. The control of these concentrations was done using the EPR and optical absorption techniques and the results showed it is possible to eliminate such impurities in a totally controlled way.