Orientador: Leandro Russovski Tessler / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-23T00:49:05Z (GMT). No. of bitstreams: 1 Bosco_GiacomoBizinotoFerreira_M.pdf: 3165188 bytes, checksum: 27e8ce40743de16593a21508898815d8 (MD5) Previous issue date: 2013 / Resumo: Neste trabalho estudamos a fotoluminescência (PL) do Eu3+ em filmes finos de subnitretos de silício amorfo hidrogenado (a-SiNx:H) dopados com európio. No total, 85 amostras do material foram preparadas por RF-sputtering reativo variando o conteúdo de nitrogênio e európio. A caracterização composicional foi feita por RBS (Rutherfod Backscattering Spectroscopy). Coeficientes de absorção, índices de refração e espessuras das amostras foram determinados por espectroscopia de transmitância ótica UV-VIS. A PL foi medida a temperatura ambiente e a 10K em função da temperatura de recozimento entre 250 e 1100°C sob atmosfera redutora de nitrogênio ou oxidante de oxigênio. Para as amostras recozidas em atmosfera de N2, não foi observada nenhuma PL proveniente dos íons Eu3+. Há, no entanto indicações da PL característica de íons Eu2+. Após quase um ano de tentativas frustradas de obter PL dos íons Eu3+ foram determinados os parâmetros das amostras que otimizam o processo: concentração de nitrogênio x em torno de 1,17, temperatura de recozimento de 1100oC em atmosfera de oxigênio e concentração de európio y = [Eu]/[Si] = 8,9 at%.. A emissão do Eu3+ em a-SiNx:H foi analisada pela teoria de campo cristalino usando um pacote de programas que otimiza os parâmetros de campo cristalino da camada f. Para isso, analisamos também o espectro do Eu2O3 em pó, usado como referencia. Assim confirmamos que os íons ativos de Eu3+ ocupam sítios de simetria pontual C2. A analise dos dados para a-SiNx:H sugere que nesse material os íons Eu3+ ocupam sítios com a mesma simetria encontrada em Eu2O3 mas muito mais suscetíveis aos efeitos de desordem. Considerando essa simetria e o tratamento térmico necessário, e razoável supor a formação de clusters de oxido de európio de dimensões nanométricas em torno dos íons Eu3+ / Abstract: In this work we studied the photoluminescence (PL) of Eu3+ in europium doped hydrogenated amorphous silicon subnitrides thin films (a-SiNx:H). In total, 85 samples of the material were prepared by reactive RF-sputtering varying the nitrogen and europium contents. Compositional characterization was obtained by RBS (Rutherford Backscattering Spectroscopy). Absorption coefficients, refraction indexes ans sample thicknesses were determined by UV-VIS optical transmittance spectroscopy. The PL was measured at room temperature and at 10K as a function of the sample annealing temperature between 250 and 1100°C under a reductive nitrogen atmosphere or an oxidant oxygen atmosphere. For the N2 annealed samples, we did not observe any PL from Eu3+ íons. There are, however, indications of Eu2+ characteristic emission. After almost a year of frustrated attempts to obtain PL from Eu3+ ions the parameters which optimize the process were determined: nitrogen content x around 1,17, annealing temperature of 1100oC under oxygen atmosphere and europium content y = [Eu]/[Si] = 8,9 at%. The Eu3+ emission in a-SiN1,17:H was analyzed using crystal field theory and a program suite to optimize f-shell crystal field parameters. We also analyzed the PL spectrum of powder Eu2O3 to use as a reference. The data analysis for a-SiNx:H suggests that in this material the Eu3+ active ions occupy sites with the same C2 point symmetry found in Eu2O3 but much distorted due to disorder. Considering this symmetry and the sample treatment necessary to obtain the PL, it is reasonable suppose the formation of europium oxide nanometer scale clusters around the Eu3+ ions / Mestrado / Física / Mestre em Física

A series of experiments were performed to study the sorption of humic acid and Eu3+ ion (at trace concentrations) on the minerals: montmorillonite, bentonite, diatomite and kaolinite in ternary systems. Humic acid and europium sorption were investigated as a function of humic acid concentration, ionic strength and pH. There was a strong uptake of humic acid on to the minerals with sorption increasing as humic acid concentration decreases. For montmorillonite, the uptake of discrete size fractions was also studied. It was found that the larger fractions were more strongly sorbing and were better able to retain Eu in solution.The ionic strength has an impact on Eu behaviour: in the absence of humic acid, sorption strength decreases, whilst in the presence of high concentrations of humic it increases. The sorption of Eu3+ increases from pH 2 to 5 in both the presence and absence of humic acid. Above pH 5, the Eu3+ showed different behaviour with and without humic acid, and as humic concentration became high (100 ppm), the Eu behaves in the same way as the humic. Bentonite is able to sorb humic acid and Eu3+ at any concentration expected in the environment, and shows the strongest sorption of any of the materials tested. Experiments confirmed that Eu is an excellent analogue for Am in these systems.The sorption of selected divalent and trivalent metal ions: Ni2+, Co2+, Zn2+, Cd2+, Eu3+ and Cr3+ on montmorillonite has been investigated in the micro-molar concentration range. In all cases, sorption strength increased with pH, and was consistently stronger for the tri-valent ions. In the presence of humic acid, there was some evidence for the enhancement of sorption. Uptake of metal ions (Co2+, Ni2+, Cd2+, Cr3+, Eu3+ and La3+) by natural and modified kaolinite was studied, and for all except Cr3+, it was found that kaolinite modified by manganese hydrothermal treatment gave the strongest sorption.A simple kinetic model was developed to simulate the experimental data for the sorption of humic acid and Eu3+ on the minerals. The model allows two humic binding sites on the mineral surface and two types of humic in solution, which can have different Eu3+ binding strengths. Metal ion surface complexation is modelled with a single kinetic equation. Ternary complexes are included in the model. The interaction of humic acid on the minerals can be fitted reasonably well. However, for the Eu3+ ion behaviour, although the model was able to give a reasonable fit to data for montmorillonite and bentonite, it could not reproduce the behaviour for kaolinite and diatomite.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-08-01T14:57:13Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação com a Data.pdf: 5044606 bytes, checksum: c09a234cd8ad3e6e1590e833910723e3 (MD5) / Made available in DSpace on 2017-08-01T14:57:13Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação com a Data.pdf: 5044606 bytes, checksum: c09a234cd8ad3e6e1590e833910723e3 (MD5) Previous issue date: 2017-03-28 / CNPQ / Inicialmente confirmamos a intensificação da luminescência em complexos de európio com ligantes não-iônicos mistos do tipo Eu(DBM)3(L, L’), onde DBM (1,3-difenilpropano-1,3diona) é o ligante iônico do tipo β-dicetonato e L são ligantes não-iônicos (DBSO (dibenzil sulfóxido), PTSO (ρ-toluil sulfóxido) e TPPO (óxido de trifenilfosfina)), quando comparados com complexos muito conhecidos do tipo Eu(DBM)3(L)2. A rota empregada no laboratório foi a partir da mesma metodologia de outros exemplos semelhantes de complexos mistos. Os rendimentos obtidos de cada etapa ficaram na faixa de 51-70%. Também, comprovamos experimentalmente que existe uma ordem ligantoquímica para os ligantes não-iônicos: TPPO>PTSO>DBSO>H2O. Esses dados foram corroborados a partir de cálculos teóricos do software MOPAC utilizando o modelo RM1 orbitais. As medidas de Arad obtidas para estes complexos fizeram a previsão da mesma conjectura usada anteriormente pelo nosso grupo de pesquisa: que o aumento da luminescência está relacionado com o aumento da assimetria dos complexos mistos sintetizados. Além disso, desenvolvemos uma nova metodologia de síntese, que denominamos síntese rápida (SR), para complexos do tipo Eu(β-dic)3(L)2 com diminuição no tempo de obtenção dos complexos puros (diminuição em 50% na média global) e aumento nos rendimentos globais de reação (aumento de 27% na média global). Este procedimento baseia-se na ordem de adição invertida dos ligantes (primeiramente não-iônicos e em seguida os iônicos) em relação à rota usualmente empregada na literatura. Sintetizamos também complexos de európio com ligantes iônicos mistos do tipo Eu(β’, β’’, β’’’)(TPPO)2 para comprovar que a assimetria de complexos com a utilização de ligantes iônicos também intensifica a luminescência. Os dados da luminescência obtidos comprovaram. Aperfeiçoamos a rota sintética anterior (SR) e aplicamos esta nova rota em complexos de európio que contêm ligantes iônicos mistos, realizando-a integralmente no balão de reação via One Pot. Isso proporcionou um menor tempo de reação, melhores rendimentos globais e redução na quantidade utilizada dos reagentes de partida. Foi possível também observar o efeito da triboluminescência em complexos mistos. Os complexos intermediários e finais obtidos foram caracterizados por Espectroscopia de Infravermelho, Espectroscopia de Ressonância Magnética Nuclear (RMN) de 1H, Espectroscopia de RMN de 19F, Espectroscopia de RMN de 31P, Espectrometria de Massas MALDI-TOF e Análise Elementar. Por fim, apresentamos rotas eficientes de sintetizar e de intensificar a luminescência em complexos de európio para várias aplicações em ciência dos materiais. / Initially we confirmed that the intensification of the luminescence of mixed europium complexes of the type Eu(DBM)3(L,L’), where DBM (1,3-diphenylpropane-1,3-dione) is the ionic ligand and L or L’ are the non-ionic ligands: DBSO (dibenzyl sulphoxide), PTSO (ptolyl sulphoxide) and TPPO (triphenylphosphine oxide) when compared with known complexes of the type Eu(DBM)3(L)2. They were all synthesized by the same synthetic route mostly used in the literature. The reaction yields obtained ranged from 51% to 70%. It is important to mention that it was experimentally proved that there is a chemical bond order for the non-ionic ligand to attach to the central atom, as follows: TPPO>PTSO>DBSO>H2O. In addition, theoretical calculations performed with the MOPAC software, using the RMI orbitals model comproved this same behavior. Another interesting result that we achieved was concerning the Arad data obtained from these mixed europium complexes, they were able to predict the same conjecture used previously and it was in agreement to the quantum yield data determined for the other mixed L,L’ complexes: luminescence increasesment can be directly related to the assymmetry of the ligands in the europium mixed complex. Furthermore, we developed a new synthetic route named Fast Synthesis (FS), to obtain complexes of the type Eu(β-dic)3(L)2. The application of this methodology brought great advantages: significant decrease in reaction time to obtain the pure complexes (in average 50% decrease in reaction time); increase the global reaction yield (in average 27% of reaction yield increase). This synthetic procedure is based on the inverted order of addition of the ligands to the coordination atom or else, firstly the non-ionic ligands are added, followed by the ionic ones when compared to the synthetic route commonly employed by the inorganic chemists. Using the FS methodology we prepared assymmetric europium complexes coordinated with different ionic ligands like, Eu(β’, β’’, β’’’)(TPPO)2, envisaging to comprove that structure assymmetry enhances luminescence. The data of quantum efficiency obtained were in accodance with previous luminescence results. Another important step was introduced to improve our FS route in obtaining europium complexes with mixed ionic ligands, this time performing the experiment via One Pot procedure. The results of the synthesis One Pot was astonishing: much less reaction time, much better yields and pronounced reduction on initial reagents quantities. Unexpectedly, it was possible to observe the triboluminencence phenomenon, when crystals of the complex Eu(DBM,BTFA,TTA)TPPO2 were frictioned with a spatula and luminescent glares of light appeared. All the complex intermediates and final ones had their structures characterized by IR Spectroscopy, NMR Spectroscopy of 1H, 19F and 31P; Mass Spectrometry MALDI-TOF and Elemental Analysis. To conclude, we have developed two new synthetic routes, synthesized 23 new complexes, including a new class of luminescente europium complexes of the type Eu(β’, β’’, β’’’)(TPPO)2 , opening a new branch for application on Science of Materials.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18996号 / 工博第4038号 / 新制||工||1622(附属図書館) / 31947 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 田中 勝久, 教授 平尾 一之, 教授 三浦 清貴 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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Les fibres optiques dont on façonne la réponse spectrale incorporent des ions luminescents, des ions de terres rares (TR), dans des nanoparticules (NP) formées in situ dans un verre de silice par séparation de phase. Cette ingénierie nécessite de comprendre le lien entre la composition des NP et l’environnement des TR.En Dynamique Moléculaire, les potentiels interatomiques existants pèchent à reproduire la séparation de phase observée expérimentalement. Le mélange xMgO-(1-x)SiO2 présente un domaine où coexistent deux phases mixtes, riche en Mg ou en Si. Une telle séparation de phase ne se modélise qu’avec un potentiel interatomique prenant en compte la ionicité des liaisons, réalisé ici par l’ajustement des charges des Oxygène selon l’environnement local. Ce modèle adaptatif, transférable, permet de suivre pour la 1ère fois la formation de NP amorphes de quelques nm. Mixtes et riches en Mg, elles se séparent d’une matrice riche en Si.Le dopage TR (Er3+ ou Eu3+) montre que leur voisinage dépend de la taille des NP les contenant : plus les NP sont grosses, plus les fractions de TR et de Mg augmentent. Ce voisinage riche en Mg permet à ces TR d’augmenter leur coordinence en Oxygène et elles n’ont plus besoin de s’agréger entre elles pour satisfaire cette tendance naturelle.Une simulation de l’étirage à chaud d’un verre de silice confirme l’existence d’une anisotropie dans la fibre optique, venant de l’orientation persistante des petits anneaux de silice, et se manifeste par une anisotropie élastique. Les effets que ces conditions extrêmes induisent sur les NP seront étudiés ultérieurement.La mise en œuvre d'un modèle de champ cristallin corrélera les modifications de l'environnement des TR avec leur réponse spectrale. / Optical fibers with tailored spectral response are doped with luminescent ions, rare-earth ions (re), embedded in nanoparticles (np) formed in situ in silica glass through a phase separation process. This engineering requires to understand the relation between the np composition and the re environment. In molecular dynamics, the existing interatomic potentials fail to reproduce the phase separation as experimentally observed. The system xmgo-(1-x)sio2 exhibits a domain inside of which two mixed phases coexist, mg-rich either si-rich. Such a phase separation can only be modeled by an interatomic potential that takes into account bond ionicity, and the transferability isEnabled here by the adaptation of oxygen charges according to the local environment. This adaptive model allows for the 1st time to track the formation of amorphous np of few nanometers. Mixed and mg-rich, they separate from a si-rich matrix. The re doping (er3+ or eu3+) shows that re environment depends on the size of the containing np: the bigger it is, the more the proportions of embedded re and mg increase. Thus, this mg-rich environment enables re ions to increase their oxygen coordination and to no more aggregate to each other to satisfy this natural trend. A simulation of the high-temperature drawing of silica-glass confirms the existence of an anisotropy in optical fiber, explained by the persistent orientation that small silica rings acquire in this fiber, and manifests itself by an elastic anisotropy. The nontrivial effects induced on np by these extreme conditions of temperature and stress can be studied later. The crystal-field model can be used to correlate the changes of the re environment with their spectral response.

Ce travail étudie le potentiel de l'électrophorèse capillaire couplée à la spectrométrie de masse à ionisation par plasma (ICP/MS) pour le criblage d'une bibliothèque de ligands en fonction de leur affinité pour l'europium en milieu hydro-organique. Cette méthode permet, d'une part, d'évaluer l'affinité des ligands phosphorés en moins de deux heures et en utilisant moins de 15 ng de ligand, et d'autre part, de déterminer les constantes de complexation. Les résultats sont en accord avec ceux obtenus par titrage spectrophotométrique.Parallèlement, une bibliothèque de copolymères pour l'extraction solide/liquide de l'europium a été étudiée. Le protocole d'extraction mis au point permet de les classer selon leur affinité pour celui-ci en milieu hydro-organique et en utilisant 60 mg de copolymère. Pour les plus prometteurs, les propriétés de reconnaissance et la sélectivité La3+/Eu3+/Lu3+ ont été évaluées. / This work investigates the potential of hyphenated capillary electrophoresis and inductively coupled mass spectrometry to classify different ligands according to their europium binding affinity in a hydro-organic medium. On the one hand, this method enables to evaluate the affinity of phosphorus-containing ligands in less than two hours and using less than 15 ng of ligand. On the other hand, complexation constants could be determined. The results are in excellent agreement with the values obtained by spectrophotometric titrations.Moreover, a library of copolymers for solid/liquid extraction of europium is investigated. The extraction protocol enables to classify copolymers according to their europium affinity in a hydro-organic medium. This screening requires 60 mg of copolymers. For the most promising recognition properties and selectivity La3+/Eu3+/Lu3+ are evaluated.

L'analyse radiochimique est indispensable à de nombreuses étapes de la gestion des déchets nucléaires et du contrôle de l’environnement. Un protocole d’analyse comprend généralement plusieurs étapes de séparations chimiques longues, manuelles et difficiles à mettre en œuvre en raison de leur confinement en boite à gants. Il est nécessaire de proposer des solutions innovantes et robustes pour automatiser ces étapes mais aussi réduire le volume de déchets radioactifs et chimiques en fin de cycle analytique. Une solution consiste à miniaturiser les analyses en les réalisant en laboratoire sur puce.L’objectif de cette thèse est de proposer une approche raisonnée de la conception de microsystèmes séparatifs dédiés à l’extraction liquide-liquide de radionucléides. Pour cela le comportement hydrodynamique et les performances d’extraction dans un même microsystème ont été étudiés pour les systèmes Eu(III)-HNO3/DMDBTDMA, Eu(III)-AcO(H,Na)-HNO3/HDEHP et U(VI)-HCl/Aliquat® 336. Une méthodologie a été mise au point pour l’implémentation de l’extraction liquide-liquide en microsystème pour chaque système chimique d’extraction et la comparaison des résultats a permis de mettre en évidence l’influence du rapport des viscosités des phases sur les écoulements. Grâce à la modélisation à la fois de l’hydrodynamique et du transfert de masse en microsystème, les critères liés aux propriétés physiques et cinétiques des systèmes chimiques ont été dégagés afin de proposer une conception rationnelle de microsystèmes à façon. Enfin plusieurs exemples de mises en œuvre de l’extraction liquide-liquide en microsystème pour des applications analytiques applicables dans le domaine du nucléaire comme la séparation U/Co ou le couplage microextraction liquide-liquide/ICP-MS sont décrits. / Radiochemical analyses are necessary to numerous steps for nuclear wastes management and for the control of the environment. An analytical protocol generally includes different steps of chemical separations which are lengthy, manual and complicated to implement because of their confinement in glove boxes and because of the hostile chemical and radiochemical media. Thus there is a huge importance to propose innovative and robust solutions to automate these steps but also to reduce the volumes of the radioactive and chemical wastes at the end of the analytical cycle. One solution consists in the miniaturization of the analyses through the use of lab-on-chip.The objective of this thesis work was to propose a rational approach to the conception of separation microsystems for the liquid-liquid extraction of radionuclides. To achieve this, the hydrodynamic behavior as well as the extraction performances have been investigated in one chip for three different chemical systems: Eu(III)-HNO3/DMDBTDMA, Eu(III)-AcO(H,Na)-HNO3/HDEHP and U(VI)-HCl/Aliquat® 336. A methodology has been developed for the implementation of the liquid-liquid extraction in microsystem for each chemical system. The influence of various geometric parameters such as channel length or specific interfacial area has been studied and the comparison of the liquid-liquid extraction performances has led to highlight the influence of the phases viscosities ratio on the flows. Thanks to the modeling of both hydrodynamics and mass transfer in microsystem, the criteria related to physical and kinetic properties of the chemical systems have been distinguished to propose a rational conception of tailor-made chips. Finally, several examples of the liquid-liquid extraction implementation in microsystem have been described for analytical applications in the nuclear field: U/Co separation by Aliquat® 336, Eu/Sm separation by DMDBTDMA or even the coupling between a liquid-liquid extraction chip and the system of detection which is the ICP-MS.

Le marché de l’éclairage est un marché de masse à diffusion large en pleine mutation face aux nouvelles contraintes environnementales. Il s’inscrit dans une démarche de préservation de l’environnement avec une volonté européenne de voir sa consommation énergétique réduite de 20% d’ici 2020. Les luminophores jouent un rôle prépondérant dans les performances des systèmes d’éclairage utilisant comme sources d’excitations des LEDs bleues ou UV, ou encore un plasma (Xe-Ne), où ils permettent de convertir les photons incidents (VUV, UV ou bleus) en lumière visible. Dans le cadre de cette thèse, nous nous sommes intéressés à la production de lumière blanche. Pour obtenir une couleur la plus proche du blanc idéal et répondant aux mieux au cahier des charges de l’éclairage domestique, une amélioration des performances des luminophores utilisés classiquement est nécessaire. Au cours de ces travaux nous avons porté notre attention sur deux aluminates de formulations Y3Al5O12 dopé Ce3+ (YAG :Ce) et BaMgAl10O17 dopé Eu2+ (BAM :Eu). L’aspect novateur repose d’une part sur la synthèse de ces luminophores sous forme de nanoparticules par des voies de synthèse originales (la voie solvothermale et la combustion assistée par micro-ondes respectivement) et d’autre part sur leur mise en forme (revêtements composites « luminophores/polymère »). Plusieurs techniques expérimentales (DRX, IR, Mössbauer, aimantation, MEB, MET,…) ont été utilisées afin de caractériser leurs propriétés structurales et morphologiques. L’étude des performances optiques de ces luminophores enregistrées sous excitations bleue, UV et/ou VUV nous a permis de mettre en évidence leur utilisation potentielle dans les nouveaux dispositifs d’éclairage : associés à d’autres luminophores (rouge pour le YAG :Ce; rouge et vert pour le BAM :Eu) en proportions adéquates, il est possible de générer de la lumière blanche présentant les propriétés escomptées. / Lighting market is a widespread distribution mass market undergoing radical transformation faced with new environmental restrictions. It fits into an environmental protection approach with a European will to reduce by 20% its energy consumption by 2020. Phosphors play a key role on performances of lighting devices where, combined with LEDs (blue or UV) or plasma (Xe-Ne) excitations, they provide visible light. In this work, we have focused on the generation of white light. In order to obtain a color closest to ideal white and meeting with the specifications of domestic lighting, it is necessary to improve the performances of traditional phosphors. Two aluminates have been investigated: Ce3+ doped Y3Al5O12 (YAG :Ce) and Eu2+ doped BaMgAl10O17 (BAM :Eu). On the one hand, innovation is based on unconventional synthesis methods allowing the preparation of nanostrutured phosphors (solvothermal and microwave induced solution combustion syntheses respectively) and on the other hand on their shaping (composite coatings « phosphors/polymer »). Structural and morphological features have been studied by means of several tools (XRD, IR, Mössbauer, magnetization, SEM, TEM,…). Finally, the optical properties of phosphors recorded upon blue, UV and/or VUV excitations have evidenced that they are suitable for applications in new lighting devices: their combination with other phosphors (red for YAG:Ce; red and green for BAM:Eu) in appropriate proportions allows producing white light with the required specifications.

Studies of Lanthanide Complexes by a Combination of Spectroscopic Methods Monika Krupová (Department of Physical and Macromoecular Chemistry, Faculty of Science, Charles University in Prague) Since conventional structural analysis offers rather limited means for the chirality detection, a series of lanthanide tris-(β-diketonates) are investigated as effective receptors for a better chirality sensing in biomolecular substrates. These lanthanide complexes containing β-diketonate ligands are electrically neutral; they can further coordinate with various small organic molecules such as chiral alcohols, amino alcohols or amino acids in organic solvents and produce a strong chiral signal. Previously, a resonance in Raman scattering was observed in the studied systems due to the correspondence of europium electronic transition energy to the laser excitation wavelength, about a 100-fold signal enhancement if compared to non-resonant vibrational ROA was observed. This enabled shorter detection times as well as lower sample concentrations. In the current work, interaction of the Eu(FOD) complex with (R)- and (S)- enantiomer of 1-phenylethanol in n-hexane was studied using IR spectroscopy, Raman spectroscopy and Raman optical activity (ROA), UV-Vis spectroscopy and ultraviolet circular dichroism (UVCD). Only...