Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As resinas fotocuradas são amplamente utilizadas em odontologia. Este processo de cura é assistido pela luz visível que promove ligações químicas que as endurecem. Nesta dissertação, as resinas odontológicas fotocuradas comerciais das marcas Opallis Flow A1, A2, AO 3,5, T, Opallis DA2, Natural Flow e Ebecryl 3720-TP25 foram caracterizadas empregando as técnicas de microbalança de cristal de quartzo (QCM) e espectroscopia fotoacústica (PAS) à temperatura ambiente. A espectroscopia fotoacústica foi utilizada para avaliar a região do espectro eletromagnético responsável pela fotocura das resinas odontológicas. Desta forma, conhecendo-se o comprimento de onda da absorção da resina, possibilitou realizar o processo de fotocura. Adicionalmente, foi possível monitorar o processo de fotocura com a técnica de microbalança. A frequência de ressonância do cristal da microbalança se modifica com a fotocura das resinas estudadas. Deste modo, foi possível estimar por QCM, o tempo de cura para os comprimentos de ondas caracterizados por PAS. / Photocured resins are largely used in dentistry. The curing process is visible light assisted provoking the chemical bonds that hardens the resin. In this dissertation, commercial photocured dentistry resins of brands Opallis Flow A1, A2, AO 3,5, T, Opallis DA2, Natural Flow and Ebecryl 3720-TP25 were characterized by quartz crystal microbalance (QCM) and photoacoustic spectroscopy (PAS) at room temperature. Photoacoustic spectroscopy was used to assess the region of the electromagnetic spectrum that is responsible for curing dental resins. Thus, knowing the absorption wavelength of the resin allowed the photocuring processes. Besides, the cure was monitored using microbalance technique. The ressonance frequency of the crystal microbalance changes during the photocuring processes. In this way, it was possible to evaluate by QCM the cure time for the wavelengths characterized by PAS.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As resinas fotocuradas são amplamente utilizadas em odontologia. Este processo de cura é assistido pela luz visível que promove ligações químicas que as endurecem. Nesta dissertação, as resinas odontológicas fotocuradas comerciais das marcas Opallis Flow A1, A2, AO 3,5, T, Opallis DA2, Natural Flow e Ebecryl 3720-TP25 foram caracterizadas empregando as técnicas de microbalança de cristal de quartzo (QCM) e espectroscopia fotoacústica (PAS) à temperatura ambiente. A espectroscopia fotoacústica foi utilizada para avaliar a região do espectro eletromagnético responsável pela fotocura das resinas odontológicas. Desta forma, conhecendo-se o comprimento de onda da absorção da resina, possibilitou realizar o processo de fotocura. Adicionalmente, foi possível monitorar o processo de fotocura com a técnica de microbalança. A frequência de ressonância do cristal da microbalança se modifica com a fotocura das resinas estudadas. Deste modo, foi possível estimar por QCM, o tempo de cura para os comprimentos de ondas caracterizados por PAS. / Photocured resins are largely used in dentistry. The curing process is visible light assisted provoking the chemical bonds that hardens the resin. In this dissertation, commercial photocured dentistry resins of brands Opallis Flow A1, A2, AO 3,5, T, Opallis DA2, Natural Flow and Ebecryl 3720-TP25 were characterized by quartz crystal microbalance (QCM) and photoacoustic spectroscopy (PAS) at room temperature. Photoacoustic spectroscopy was used to assess the region of the electromagnetic spectrum that is responsible for curing dental resins. Thus, knowing the absorption wavelength of the resin allowed the photocuring processes. Besides, the cure was monitored using microbalance technique. The ressonance frequency of the crystal microbalance changes during the photocuring processes. In this way, it was possible to evaluate by QCM the cure time for the wavelengths characterized by PAS.

Orientador: David Mendez Soares / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-06T09:05:00Z (GMT). No. of bitstreams: 1 Pinto_EdilsonMoura_M.pdf: 2421703 bytes, checksum: 4f88cfbf1bf972bc5ed1991a06982550 (MD5) Previous issue date: 2004 / Resumo: Neste trabalho, a QCM (Quartz Crystal Microbalan e) Microbalança de Cristal de Quartzo, como ténica alternativa para o estudo da corrosão /inibição do metal cobre. Estudamos a proteção anti-corrosão de superfícies de cobre mediante a adsorção de inibidores voláteis de corrosão (VCI-CHAB,Ciclohexilamina-Benzoato). Utilizamos uma QCM, composta de um cristal de quartzo de 6MHz, recoberto por um filme de ouro depositado por sputtering. Utilizamos Técnicas eletroquímicas para caracterizar a corrosão. Para isto, estudamos a corrosão do metal cobre em diferentes ambientes, básicos e ácidos, na presença e ausência dos inibidores. Aplicamos a QCM acoplada à um potenciostato (EQCM), como método de determinação de variação de massa e e carga de correntes da corrosão/inibição. A presença dos filmes VC I sobre a superfície de cobre, também foi demonstrada pela técnica Reflection-Absorption Infra-Red Spectros opy (RAIRS), através da Micros copia de infravermelho razante, esta técnica é indicada para situações em que os filmes formados são Ultra-finos. Baseado nos resultados das medidas feitas, propomos e des revemos um modelo para a dsorção dos filmes VCI sobre a superfície metálica, incluindo a formação da corrosão por pitting / Abstract: In this work we used the QCM (Quartz Crystal Microbalance) as an alternative technique for the studying of the corrosion/inhibition of cooper. We studied the protection of cooper surfaces due to the adsorption of a volatile corrosion inhibitor, (VCI-Cyclehexilamine-Benzoate). We used electrochemical techniques to characterize the corrosion in different environments. We applied the QCM together with the potentiostat as a method of determination of charge and mass variations. In this work the QCM has been used as a complementary technique for investigating the corrosion of copper with and without adsorbed inhibitors. The protection of copper surfaces due to the adsorption of a volatile corrosion inhibitor (VCI) ¿ Cyclohexylamine Benzoate ¿ has been studied by electro chemical techniques to characterise the corrosion in aqueous environments over a wide range of pH values. The presence of VCI films on the copper surface was also shown by Reflection-Absorption Infra-Red Spectroscopy (RAIRS), a technique indicated for situations when very thin films are formed. The EQCM, which used 6 MHz gold-sputtered quartz crystals coated with electrodeposited copper films, was applied to the simultaneous determination of the charge and frequency variations associated with the corrosion process, with and without adsorbed inhibitor. Based on the measurements, a model has been developed to describe the dynamics of adsorption of the VCI on the metalli surface, including the formation of pits on the surface / Mestrado / Superfícies e Interfaces ; Peliculas e Filamentos / Mestre em Física

Considerando a relevância dos trabalhos onde se utiliza eletrodos quimicamente modificados e o pequeno número de estudos envolvendo cocaína e seus interferentes (cafeína, teobromina e lidocaína), por técnicas eletroquímicas ou piezelétricas, este estudo tem como objetivo o desenvolvimento de eletrodos de ouro e platina quimicamente modificados com compostos da classe das cucurbiturilas (CB[5], CB[6] e CB[7]) para a detecção de cocaína. A técnica de microbalança de cristal de quartzo foi empregada a fim de se estudar cocaína padrão e seus interferentes, em fase gasosa. Os eletrodos de ouro foram quimicamente modificados com cucurbiturilas e o modificador CB[6] apresentou os melhores resultados. Medidas por voltametria cíclica foram realizadas utilizando-se um potenciostato Autolab III acoplado a um computador, com eletrodo de ouro e platina atuando como eletrodo de trabalho, Ag/AgCl como eletrodo de referência e eletrodo espiral de platina como eletrodo auxiliar, com velocidade de varredura de 0,1 V.s-1 (100 mV.s-1). Os parâmetros voltamétricos foram otimizados para tornar as análises mais rápidas e sensíveis sem perda de qualidade ou intensidade do sinal voltamétrico. O eletrodo de platina quimicamente modificado com filme de cucurbit[6]urila apresentou aumento da corrente de pico catódica quando estudado frente à cocaína, teobromina e lidocaína. Análises com eletrodo de platina sem modificador químico apresentaram limite de detecção de 4,14.10-6 mol.L-1 e limite de quantificação de 1,38.10-5 mol.L-1 , para a cocaína, e na presença do modificador químico CB[6] apresentou limite de detecção de 1,36.10-6 mol.L-1 e limite de quantificação de 4,54.10-6 mol.L-1 . Eletrodos de ouro com ou sem a presença de modificadores químicos não apresentaram sinal para nenhum analito. / Considering the importance of chemically modified electrodes and the small amount of the cocaine study and their interfering (caffeine, theobromine and lidocaine) using electrochemical and piezoelectric techniques, this study aims to investigate the development of the gold and platinum electrodes chemically modified by cucurbiturils (CB[5], CB[6] and, CB[7]) in order to detect cocaine. The Quartz Crystal Microbalance technique was employed in order to study in gas phase the standard samples of cocaine and their interfering. Gold electrode was chemically modified with cucurbiturils films and the CB[6] modifier showed the best results. The cyclic voltammetric measurements were performed using a Autolab III potentiostat coupled to a computer, being gold and platinum as the working electrode, Ag/AgCl as the reference electrode and platinum wire as counter electrode, using a scan rate of 0,1 V.s-1 (100 mV.s-1). The voltammetric parameters were optimized in order to make the analysis faster and more sensitive without loss of intensity and quality of the voltammetric signal. The platinum electrode modified by cucurbit[6]uril film showed an increase of cathodic current peak when electrode was exposed to cocaine, theobromine and lidocaine. Analysis employed platinum working electrode without chemical modifier showed a detection limit of 4.14 . 10-6 mol.L-1 and quantification limit of 1.38 . 10-5 mol.L-1 for cocaine and with chemical modifier CB[6] showed a detection limit of 1.36 . 10-6 mol.L-1 and quantification limit of 4.54 . 10-6 mol.L-1 . Gold electrodes with or without chemical modifiers showed no response for any analyte.

Lithium-oxygen batteries, also known as Lithium-air batteries, could possibly revolutionize energy storage as we know. By letting lithium react with ambient oxygen gas very large theoretical energy densities are possible. However, there are several challenges remaining to be solved, such as finding suitable materials and understanding the reaction, before the lithium-oxygen battery could be commercialized. The scope of this thesis is focusing on the latter of these challenges. Efficient ion transport between the electrodes is imperative for all batteries that need high power density and energy efficiency. Here the mass transport properties of lithium ions in several different solvents was evaluated. The results showed that the lithium  mass transport in electrolytes based on the commonly used lithium-oxygen battery solvent dimethyl sulfoxide (DMSO) was very similar to that of conventional lithium-ion battery electrolytes. However, when room temperature ionic liquids were used the performance severely decreased. Addition of Li salt will effect the oxygen concentration in DMSO-based electrolytes. The choice of lithium salt influenced whether the oxygen concentration increased or decreased. At one molar salt concentration the highest oxygen solubility was 68 % larger than the lowest one. Two model systems was used to study the electrochemical reaction: A quartz crystal microbalance and a cylindrical ultramicroelectrode. The combined usage of these systems showed that during discharge soluble lithium superoxide was produced. A consequence of this was that not all discharge product ended up on the electrode surface. During discharge the cylindrical ultramicroelectrodes displayed signs of passivation that previous theory could not adequately describe. Here the passivation was explained in terms of depletion of active sites. A mechanism was also proposed. The O2 and Li+ concentration dependencies of the discharge process were evaluated by determining the reactant reaction order under kinetic and mass transport control. Under kinetic control the system showed non-integer reaction orders with that of oxygen close to 0.5 suggesting that the current determining step involves adsorption of oxygen. At higher overpotentials, at mass transport control, the reaction order of lithium and oxygen was zero and one, respectively. These results suggest that changes in oxygen concentration will influence the current more than that of lithium. During charging not all of the reaction product was removed. This caused an accumulation when several cycles was examined. The charge reaction pathway involved de-lithiation and bulk oxidation, it also showed an oxygen concentration dependence. / Litiumsyrebatteriet, även känt som litiumluftbatteriet, kan potentiellt revolutionera vårt förhållande till energilagring. Genom att låta litium reagera med syrgas från luften kan teoretiskt höga energitätheter uppnås. Dock så behöver många problem lösas, så som att hitta lämpliga elektrod- och elektrolytmaterial samt att få en ökad förståelse för reaktionsmekanismen, innan litiumsyrebatteriet kan kommersialiseras. Den här avhandlingen behandlar de sistnämnda av dessa problem. För att ett batteri ska kunna leverera hög effekttäthet och energieffektivitet krävs en effektiv jontransport mellan elektroderna. Här utvärderades masstransporten hos flera olika elektrolyter. Resultatet visade att masstransporten av litium i en litiumsyrebatterielektrolyt (baserad på dimetylsulfoxid (DMSO)) är likvärdig med en konventionell litiumjonbatterielektrolyt. När elektrolyter baserade på jonvätskor användes uppvisades väldigt stora energiförluster. När litiumsalt tillsattes påverkades lösligheten av syre i DMSO-baserade elektrolyter. Vilken sorts litiumsalt som användes påverkade om lösligheten av syre ökade eller minskade. Vid en saltkoncentration på en molar var den högsta syrelösligheten 68 \% större än den lägsta. Två olika modellsystem används för att studera den elektrokemiska reaktionen: En elektrokemisk kvartskristallmikrovåg och en cylindrisk ultramikroelektrod. Vid kombinerad användning av dessa system påvisades att löslig litiumsuperoxid bildades vid urladdningen. Följden av detta blev att endast delar av urladdningsprodukten hamnade på elektroden. Vid urladdning visade ultramikroelektroderna tecken på passivering som inte kunde beskrivas av tidigare teori. Här föreslås att passiveringen uppstår på grund av en blockering av de aktiva säten där reaktionen fortskrider. För denna process föreslås även en detaljerad mekanism. Urladdningsprocessens koncentrationsberoende utvärderades genom att bestämma reaktionsordningen för syre och litium under kinetisk- och masstransport kontroll. Under kinetisk kontroll fanns inga heltalsreaktionsordningar, för syre var reaktionsordningen nära 0.5 vilket föreslår att det reaktionssteg som bestämmer strömstorleken innefattar en adsorption av syre. Vid högre överpotentialer, då systemet var under masstransportkontroll, var reaktionsordningarna för litium och syre noll respektive ett. Detta föreslår att ändringar i syrekoncentration påverkar strömmen betydligt mer än vad det gör för litium. Under uppladdning kunde inte all reaktionsprodukt avlägsnas från elektroden. Detta ledde till en ackumulation då flera cykler studerades. Uppladdningens delsteg innefattade en delitiering följt av en oxidation av reaktionsproduktbulken. Denna process uppvisade även ett syrekoncentrationsberoende. / <p>QC 20171114</p>

Les multicouches de polyelectrolytes, systèmes auto-assemblés par adsorption successive de polycations et de polyanions, constituent un matériau d’intérêt pour la fonctionnalisation de surface. Ce type de revêtement possède toutefois quelques limitations majeures : leur construction est lente et fastidieuse ; leur tenue mécanique et chimique est faible. Récemment, une méthode basée sur l’auto-construction de films par l’utilisation d’un morphogène, i.e. un gradient de catalyseur généré depuis une surface, a été développé permettant ainsi une rapide construction de revêtements robustes. Cette technique reste toutefois limitée à des systèmes particuliers basés sur la chimie click ou sur des interactions hôtes-invités. Nos travaux ont permis de diversifier cette approche de construction tout-en-un par l’utilisation de morphogènes. Dans un premier temps, des brosses de polymères ont été construites en une étape depuis une surface par la réaction de polymérisation ATRP. Cette réaction a été catalysée par la formation d’ions Cu(I) (le morphogène) par électrochimie depuis la surface de travail. L’approche morphogénique a également été utilisée afin de construire des films de polyélectrolytes et de polyampholytes en une étape par la génération électrochimique d’un gradient de protons (le morphogène) depuis la surface de travail. Ces films ont été fonctionnalisés pour présenter une activité enzymatique. / Polyelectrolyte multilayers, i.e. self-assembled systems based on successive polycation and polyanion adsorptions, constitute interesting materials for surface functionalization. These coatings possess several limitations: they are weak towards chemical and mechanical constraint and their buildup is long and tedious. Recently, a new method based on the self-construction of films by the means of a morphogen (a catalyst gradient generated from a surface) has attracted attention since it allows the quick self-assembly of robust films. Nevertheless, this technique was quite limited to peculiar systems based on click chemistry or on host-guest interactions.This present work generalize the one-pot morphogenic approach to other systems. In the first place, polymer brushes were built up from a surface by ATRP polymerization. The Cu(I) catalyst (the morphogen) was electrochemically generated at the interface.The morphogenic approach was later used to buildup polyelectrolytes and polyampholyte films in a one-pot manner by electrochemically generating protons (the morphogens) at the interface. These films exhibited an enzymatic activity.

In the adaptation to the oxidative environment on earth, metals played a crucial role for the evolution of life. The presence of metals also allowed access to advanced functions due to their unique coordination sphere and reactivity. This thesis focused on exploiting these unique properties for further development of the field of dynamic chemistry – a field in which adaptation plays a central role as well. The first part of the thesis aimed to create a better understanding of multivalent effects in carbohydrate-lectin interactions. By reversible ligand coordination to zinc ions one of the nanoplatforms, the Borromean rings, could be selectively obtained. After carbohydrate functionalization the binding events were monitored by quartz crystal microbalance technology and compared to glycosylated fullerenes and dodecaamide cages. Overall, this investigation indicated that statistical and polyelectrolyte effects play a considerable role in the observed multivalent effects. The second part of the thesis aimed to design and synthesize a new catalyst for application in aqueous olefin metathesis. This afforded a ruthenium based catalyst that was applied in the self- and cross-metathesis of highly functionalized substrates, such as carbohydrates. In addition, it was shown that addition of a small amount of acetic acid prevented undesired double bond isomerization. The last part of the thesis aimed to explore new methods to discover transition metal catalysts. Dynamic exchange of directing groups generated a pool of potential substrates for C-H activation. Combining this pool of substrates with a pool of potential catalysts resulted in amplification of a reactive substrate/metal combination. By iterative deconvolution in combination with mass spectrometry, this “intermediate” could be identified from the mixture, proving applicability of this alternative approach to catalyst discovery. / <p>QC 20170809</p>

Orientador: David Mendez Soares / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T00:49:55Z (GMT). No. of bitstreams: 1 Gomes_WyllersonEvaristo1983-_D.pdf: 5303870 bytes, checksum: ba3a86db4d3713f9b80b91fba5545795 (MD5) Previous issue date: 2015 / Resumo: Neste trabalho, pesquisamos o uso de filmes autoorganizados sobre o eletrodo de ouro da microbalança de cristal de quartzo eletroquímica, EQCM. Focamos a pesquisa na interação física da superfície sólida funcionalizada com o meio líquido. Desenvolvemos uma metodologia para compreender a dinâmica de variação dos parâmetros medidos, pela EQCM durante um experimento (perturbação) em meio líquido. Introduzimos a representação bidimensional da variação da freqüência de ressonância e da resistência de ressonância do cristal de quartzo da EQCM, ?f e ?R respectivamente, durante uma perturbação, usando o tempo como parâmetro. A metodologia foi utilizada para soluções aquosas de sais, álcool, líquidos apolares como ciclohexano, n-hexano, soluções de sacarose. Mostramos que líquidos reais apresentam viscoelasticidade. Também testamos a perturbação causada pela aplicação de campo elétrico nas interfaces sólido/soluções iônicas em condições em que o eletrodo é polarizável. Mostramos a possibilidade de formação de nanoestruturas gasosas, nanobolhas. Estendemos a pesquisa para a superfície do ouro funcionalizado com filmes de tiol, S-layers (proteínas de membrana de bactéria), e adsorção de lipossomos zwiteriônicos. A interface sólido/líquido também foi estudada relativamente às características hidrofóbicas da funcionalidade devido à sua microestrutura superficial (superfície superhidrofóbica). Usamos as técnicas de microscopia de força atômica, AFM, e de Raman confocal, paralelamente às nossas pesquisas com a EQCM. Para complementar o estudo de campos elétricos aplicados a interfaces, estudamos também os efeitos macroscópicos da aplicação desses campos a líquidos dielétricos como a água. Pesquisamos o fenômeno da ponte líquida usando líquidos dielétricos isolantes apróticos / Abstract: In this work, we have studied the use of self-assembling films onto gold electrode of the electrochemical quartz crystal microbalance, EQCM. The main objective is to understand the physical interaction of the functionalized solid surface with the liquid medium. We have developed a methodology to understand the dynamics of variation of the parameters measured by the EQCM in liquid medium. We also have introduced the two-dimensional representation of the variation of resonance frequency and resonance resistance of the quartz crystal of the EQCM, ?f and ?R respectively. The measurements were taken during a perturbation, using time as parameter. The methodology was used for aqueous salt solutions, alcohol, nonpolar liquids such as cyclohexane, n-hexane and sucrose solutions. We showed that real liquids exhibit viscoelasticity. We also tested the perturbation caused by the application of electric field at solid interfaces/ionic solutions, under conditions in which the electrode is polarizable. We showed the possibility of formation of gaseous nanostructures, nanobubbles. We extended the study to gold electrode thiol-functionalized surfaces, gold surfaces covered by S-layers films (membrane proteins of bacteria), and then adsorption of zwitterionic liposomes. The solid/liquid interface was also studied in relation to hydrophobic functionality due to its surface microstructure (superhydrophobic surface). We use the atomic force microscopy, AFM, and confocal Raman techniques, parallel to our research with EQCM. In addition to the study of electric fields applied to interfaces, we also studied the macroscopic effects of the application of these fields to the dielectric liquids like water. We researched the phenomenon of liquid bridge using insulating dielectric aprotic liquids / Doutorado / Física / Doutor em Ciências / 2010/140031-3 / CNPQ

Electrochromic devices are based on the intercalation processes to the active layer mostly WO3. The optical properties of active layer are changed by intercalation ions from the electrolyte. For that purpose are used Li ions. The mass of thin layer can be observed by the QCM method. This method is based on the changes of the resonance frequency of a quartz crystal resonator. The investigated substance is deposited on the surface of the resonator. Various metals (Pt, Au, Ag) and their compounds should be plated on the resonator. Most frequently, the resonators for the frequency 5,0 MHz are used. This frequency change is used for the detection of chemical changes of the electrode surface and is very sensitive.

This dissertation work deals with analysis of nickel hydroxide phases, their oxidation compounds, their stability and degradation mechanisms of electrochemically more active alpha phase on standard beta phase. The active material was prepared by both methods, electrodeposition and chemical precipitation. Main analysis method was Electrochemical Quartz Crystal Microbalance in combination with common analytical methods (cyclic voltammetry, potenciometry) can resolute between alpha and beta phases and quantitatively describe differences in main reaction by monitoring mass changes in the active material. Poor stability of the ?-Ni(OH)2 were improved by adding cations with valence two three and four into the structure instead of Ni atoms. The most important role plays cobalt and its hydroxide. Totally new way is to use titanium in combination with other cations. In electrolyte the most significant addition is LiOH, which has beneficial influent on cycle ability, stability in strong alkaline medium and cycle life.