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Disertaciones |
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1
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PAULO HENRIQUE DE SOUSA PAULINO
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Strategic Procedures for Improving the Conductivity of Poly(p-phenylene): A Theoretical Investigation
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Líder : CLEBIO SOARES NASCIMENTO JUNIOR
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MIEMBROS DE LA BANCA :
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CLEBIO SOARES NASCIMENTO JUNIOR
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GUILHERME FERREIRA DE LIMA
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LUCIANA GUIMARAES
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LUIZ GUSTAVO DE LIMA GUIMARAES
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Data: 07-oct-2021
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Resumen Espectáculo
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The goal of this master's dissertation was to carry out systematic theoretical investigations aiming to improve the electrical properties of poly(p-phenylene), via strategic procedures intrinsic to molecular electronics and supramolecular chemistry. In the first part, semi-empirical methods and the Density Functional Theory (DFT) were used to investigate the energetic, electronic and structural properties of pristine and push-pull substituted poly(p-phenylene), and their respective molecular wires formed by β-cyclodextrin (β-CD). ). From the results obtained, via PBE1PBE/6-31G(d,p)//PM3 calculations, it was possible to conclude: (i) the values of the HOMO-LUMO gap, for the pristine and substituted poly(p-phenylenes), decreases as the number of monomeric units increases; (ii) the insertion of push-pull groups leads to a reduction in the HOMO-LUMO gap values, being the NH2/NO2 set the best in this regard (iii) the encapsulation process of pristine and substituted poly(pphenylenes does not alter their electric conductivities. Therefore, the strategies used in this first step were effective in improving the electrical properties of poly(p-phenylene), from the theoretical point of view. In the second part, DFT and TD-DFT calculations, at the PBE1PBE/6-31G(d,p) level of theory, were performed in order to investigate the effect of doping process, implicit and explicit, by removing electrons and by different dopant atoms (Na, K and Cl), on the electronic, structural and spectroscopic properties of poly(p-phenylene). According to the results obtained, it was possible to conclude that: (i) the doping processes, whether implicit or explicit, led to a considerable reduction in the HOMO-LUMO gap energies; (ii) among the different dopants analyzed, Cl proved to be the most efficient for increasing the conductivity of poly(pphenylene); (iii) from the UV-Vis spectra it was possible to observe the formation of polarons and bipolarons, thus evidencing the success of the doping process
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2
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FILIPE SANTOS SOUSA
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Morphological Characterization of Quantum Dot Sensitized Photoanodes and Counterelectrodes of Solar Cells Using the Atomic Force Microscopy Technique
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Líder : WAGNER SOUZA MACHADO
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MIEMBROS DE LA BANCA :
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MARCO ANTONIO SCHIAVON
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THALITA CHIARAMONTE
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VIRGILIO CESAR SILVA E OLIVEIRA
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WAGNER SOUZA MACHADO
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Data: 15-oct-2021
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Resumen Espectáculo
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In an hour, the Sun provides the Earth with enough energy to meet global needs of electricity for a year. The electricity generated by the Sun provides only about 0.1 % of world demand. Thus, due to increasing global energy consumption, demand by generating alternative energy, such as low cost solar energy conversion is a great opportunity to remedy this problem. Quantum Dot Sensitized Solar Cells (CSSPQs) is a device with nanostructured electrodes in which a porous layer with specific (thermal, electrical and chemical) properties are required for the conversion of solar energy using low-cost nanostructures and involving a transfer of photogenerated carriers for a final stage of energy production. This project had as objective of preparing and characterizing electrodes for constrution of CSSPQs through atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), spectroscopy of electrochemical impedance (EIS) and current density vs voltage curve (J-V). From the studied electrodes, these were used in the construction of CSSPQs using the TiO2 as photoanode and the quantum dots of copper, indium and sulfur (CIS) as sensitizers in the photoanode. The studied counter electrode based on CuS was prepared at different concentrations and used in the cell construction with the polysulfide electrolyte (S2−/S2− n ). The study of the morphology and thickness of the TiO2 layers made it possible to obtain optimized values for the charge carrier transfer process, since their uniformity and homogeneity are important factors that act in these processes. The study of the morphology and electrical properties of the counter electrodes in relation to the concentration of reagents and temperature during the CuS synthesis allowed us to understand the limits for the best morphological configuration as a result of the optimization of the electrocatalytic activity of charge transport. With active and dispersive layer thickness set to approximately 6 mm for the photoanode and using a counter electrode with a rough morphology average of 83 nm for the counter electrode, it was possible to improve the transfer of charges at the electrolyte/counterelectrode interface eliminating the inter and intragrain transport resistance, leading to an efficiency of approximately 4 %. It is concluded that an adequate adjustment and control of the thickness and morphology of the layers that are part of the CSSPQ is of fundamental importance for a better understanding and optimization of these devices.
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3
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Fernando Marques Lisboa
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TBAF supramolecular complexes / bulk alcohols as fluorinating agents
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Líder : JOSEFREDO RODRIGUEZ PLIEGO JUNIOR
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MIEMBROS DE LA BANCA :
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HEITOR AVELINO DE ABREU
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JOSEFREDO RODRIGUEZ PLIEGO JUNIOR
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MARCELO SIQUEIRA VALLE
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Data: 22-oct-2021
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Resumen Espectáculo
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Fluorine is a chemical element that was first discovered and isolated in 1986 by French chemist Henri Moissan. When fluorine is inserted into a carbon chain it adds several meaningful properties to this compound, which is now known as an organofluorinated compound. However, the production of these organofluorinated compounds currently requires the use of highly complex reagents or even reactions in extremely controlled environments in an attempt to overcome the difficulties in the fluorination processes, the low selectivity, which means that the elimination reactions compete with the nucleophilic substitution reactions, producing byproducts and decreasing the yield of the fluorinated product, as well as the amount of resources required to promote this type of reaction, since expensive reagents and time-consuming reactions are used. In the present work, theoretical calculations were used, at the DFT level with PBE, X3LYP and M06-2X functionals, of the fluorination reactions of ethyl bromide using supramolecular complexes of TBAF/bulky alcohols to understanding the role of controlled hydrogen bonds and increase the selectivity of the fluorination reactions, thus increasing the final yield, as well as understanding the influence of the volume of alcohol used in the formation of complexes with TBAF on the selectivity of the reaction. The calculations show that the use of supramolecular complexes of bulky TBAF/alcohols is a viable strategy despite the fact that the activation barrier for these reaction pathways higher than the activation barrier for nucleophilic fluorination using only TBAF. However, the activation barrier for the elimination reactions becomes even higher, providing better yields and higher selectivity of the organic compound fluorination process. The calculation of the global kinetics of the nucleophilic fluorination reactions, 4.39x10-6 mol L-1 s -1 , in toluene and 1.74x10-6 mol L -1 s -1 in acetonitrile, with the global kinetics of the elimination reactions, 9.20x10-9 mol L-1 s -1 in toluene and 5.53x10-7 mol L -1 s -1 in acetonitrile support this selectivity.
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4
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POLLYANNA PINTO MAIA
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THEORETICAL INVESTIGATION OF ENANTIO SELECTIVE SEPARATION AND MOLECULAR PRINT POLYMER FORMATION PROCESSES FOR ATENOLOL AND CARVEDILOL
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Líder : CLEBIO SOARES NASCIMENTO JUNIOR
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MIEMBROS DE LA BANCA :
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CLEBIO SOARES NASCIMENTO JUNIOR
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MARCELO SIQUEIRA VALLE
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LUIZ ANTONIO SODRE COSTA
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Data: 27-oct-2021
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Resumen Espectáculo
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In view of the incessant search for the improvement of research involving chemical separation of chiral drugs, it is necessary to develop enantioselective separation studies, as well as molecular imprinted polymers (MIPs), aiming at the selective extraction of analytes and their enantiomers from complex matrices, such as the biological ones. In the 1 st part of this dissertation, in order to understand, at the molecular level, the enantioselective separation of atenolol (ATL) and carvedilol (CVL) enantiomers, which are chiral β-blockers drugs, structural and energy calculations, via DFT methodology, were performed. The main goals in this 1st step were: (i) To analyze theoretically, by means of structural and energetic data, the chiral recognition mechanisms of the FEQs, amylose tris-(3,5- dimethylphenylcarbamate) and cellulose tris-(3,5-dimethylphenylcarbamate), for the enantioselective separation of ATL and CAR; (ii) To evaluate, at the molecular level, the inclusion complexes formed between the chiral selector (β-cyclodextrin) and ATL enantiomers, aiming to understand the chiral discrimination. Given the results obtained, it was possible to confirm and explain the enantiomeric elution and migration orders proposed experimentally for both ATL and CAR. The relative stabilities of the distinct diasteroisomeric complexes were explained by the formation of hydrogen bonds established between the β-blockers enantiomers and the chiral selectors, in addition to the establishment of π-π stacking interactions. In the 2nd part of the dissertation, it was investigated theoretically the formation process of a MIP for ATL, aiming to optimize some synthesis parameters. Through structural and energetic analyses, via DFT calculations, of the pre-polymerization complexes it was possible to obtain the theoretical synthesis protocol, regarding the choice of the most effective functional monomer, the best stoichiometry, and the most adequate solvent, which were APV, 1:5 and toluene, respectively. Moreover, through the molecular properties obtained, it can be evidenced the fundamental role of hydrogen bonds in the complex’s stability. Finally, one can highlight the role of computational chemistry as an extremely useful tool in studies, at the molecular level, involving the enantioselective separation of drugs and the formation process of MIPs.
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5
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GIORDANE LADEIRA
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Synthesis of Graphited Chitosan Nanogel with 3,4-methylenedioxycinnamic Acid for Encapsulation of Monoterpenes with Antifungal Properties
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Líder : LUIZ GUSTAVO DE LIMA GUIMARAES
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MIEMBROS DE LA BANCA :
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ARNALDO CESAR PEREIRA
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EVERTON LUIZ DE PAULA
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LUIZ GUSTAVO DE LIMA GUIMARAES
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Data: 07-dic-2021
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Resumen Espectáculo
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Dermatophytosis is a type of infection caused by dermatophyte fungi, a specialized group of keratinophilic fungi that are lodged in the nails, skin and hair. Many kinds of treatments have been developed, however, side effects or resistance to drugs are frequently reported. Essential oils have several biological activities, including bactericidal, antiviral, antifungal, among others. In general, essential oils have greater antifungal activity due to their constituents, such as monoterpenes. The great challenge of applying essential oils is to protect them from degradation, evaporation, improve their dispersions in an aqueous medium and obtain a controlled release. Encapsulation using modified chitosan-based materials is a possible alternative to overcome this problem. In this work, the synthesis of a graphitized chitosan nanogel with 3,4-methylenedioxycinnamic acid (MDCA) was carried out with the objective of encapsulating the monoterpenes carvacrol and thymol, aiming at preservation and better dispersion in aqueous medium, with the aim of developing a material that can be used to control the fungus Microsporum canis. Material characterizations were performed by FTIR, 13C-NMR, TGA, SEM and DLS. To assess the antifungal potential, the minimum inhibitory concentration (MIC) and the inhibition of M. canis mycelial growth (MIC/2, MIC, 2xMIC) of chitosan nanogel and MDCA encapsulated with monoterpenes analysis were performed. The results obtained by FTIR and NMR for the nanogel revealed the formation of a bond between chitosan and MDCA. The encapsulation efficiency calculation showed that the nanogel encapsulated with the monoterpenes carvacrol and thymol presented an encapsulation capacity between 12.9 and 13.3%, respectively. The DLS studies showed that the nanogel particles in aqueous medium presented nanometric sizes and good stability, before and after the encapsulation of monoterpenes. From the results obtained by SEM, differences in the morphology of the materials obtained can be observed in relation to the morphology presented by chitosan, in addition to well-defined spherical cavities being visualized in cross-sections of the chitosan nanogel graphited with MDCA, resulting from the presence of incorporation of monoterpenes. The QT-g-MDCA-Ca and QT-g-MDCA-Ti nanogels showed antifungal potential against the fungus Microsporum canis, being able to inhibit mycelial growth by 100.00 and 93.13%, respectively.
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6
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LILIAN CHRISTINA ZIN
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Enantioselective Separation and Molecular Impression Polymer for Oxybutynin: A Theoretical Investigation
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Líder : CLEBIO SOARES NASCIMENTO JUNIOR
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MIEMBROS DE LA BANCA :
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ARNALDO CESAR PEREIRA
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CLEBIO SOARES NASCIMENTO JUNIOR
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LUCIANA GUIMARAES
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MATEUS FERNANDES VENÂNCIO
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Data: 17-dic-2021
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Resumen Espectáculo
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Since Chemistry is an ever-changing science, it requires a constant need for developing techniques capable of covering the demand required from time to time. An example in this regard is the research involving selective materials, which allows both the creation of new materials - such as molecular imprinted polymers (MIPs) - and the enantioselective separation of drugs. Such studies can be developed in two ways: on the laboratory bench, through experiments; and on computers, through simulations. In the first chapter of this dissertation, a theoretical study, via DFT calculations, of the enantioselective separation process of oxybutynin (OXI), an antimuscarinic drug widely used in the treatment of overactive bladder, was performed. Firstly, the optimized structures for the OXI enantiomers, for the reduced model of the selected chiral selector - amylose tris-(3,5-dimethylphenylcarbamate), also called MRADMPC - and for the diastereoisomeric complexes formed between them were analyzed. From the hydrogen bonds formed between both species and the stability conferred to each of the complexes, it was possible to determine their enantiomeric elution order - being the complex (R)-OXI...[MR-ADMPC] the first one, followed by the complex (S)-OXI...[MR-ADMPC] - corroborating previous results obtained experimentally. In the 2nd step of the work, a theoretical protocol was proposed, based on four main parameters, aiming at the synthesis of a MIP for OXI. The fundamental idea of this type of study is to minimize the large reagent consumption inherent to the MIP synthesis at the laboratory. As a result, hydrogen bonds played, once again, a very important role, being the main responsible for the stability of the prepolymerization complexes formed. Taking into account the structural and energetic properties obtained, it was possible to obtain the following protocol: (i) functional monomer - acrylic acid (AA); (ii) stoichiometry - 1:4; (iii) solvent - toluene; (iv) cross-linking agent - ethylene glycol dimethacrylate (EGDMA).
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Tesis |
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1
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BRUNA CARNEIRO PIRES
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"Síntese de materiais adsorventes à base de polipirrol e sua aplicação em estudos de adsorção e em preparo de amostras de compostos orgânicos ácidos, neutros e básicos”
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Líder : KEYLLER BASTOS BORGES
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MIEMBROS DE LA BANCA :
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ARNALDO CESAR PEREIRA
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KEYLLER BASTOS BORGES
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LUIZ GUSTAVO DE LIMA GUIMARAES
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MARIA DO CARMO HESPANHOL
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RENATA PEREIRA LOPES MOREIRA
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Data: 26-ene-2021
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Resumen Espectáculo
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The main purpose of this work was to synthesize different materialsbased on polypyrrole (PPy) and verify their potential in adsorption studies and sample preparation using analytes with different pKa values.The mesoporous magnetic PPy (MMPPy) was developed to be used in studies of adsorption of the following adsorbates:ibuprofen (acid), caffeine (neutral) and bupropion (basic) present in aqueous solutions.For this, parameters such as pH of the aqueous solution, contact time/kinetics, concentration/isotherm and temperature were evaluated.Subsequently, MMPPy was double coated with hydrophilic monomers and casein, obtaining RA-MMPPy-HM-CAS.The coated material aims to exclude macromolecules present in complex matrices, facilitating sample preparation and analysis.RA-MMPPy-HM-CAS was used in magnetic solid phase extraction (MSPE) for simultaneous determination of diclofenac (acid), fipronil(neutral) and febantel (basic) in milk samples.Another PPy-based material developed was mesoporous PPy double coated with hydrophilicmonomers and bovine serum albumin, called RA-MPPy-HM-BSA.It was used in dispersive solid phase extraction (DSPE) and pipette-tip solid phase extraction (PT-SPE), in order to compare which of these two techniques was more efficient for simultaneous determination of pyriproxifen (acid), progesterone (neutral) and deltamethrin (basic) in chicken egg samples.In sample preparation techniques, the following parameters were optimized: pH and volumesample, washing solvent, amount of material, type and volume of elution solvent and contact time (MSPE and DSPE).The methods were validated including performance criteria such as linearity, limit of quantification (LOQ), precision, accuracy, robustness and stability and applied to milk (MSPE) and egg samples(PT-SPE)
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2
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DANIELA RIBEIRO SILVA
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Theoretical Study of Alpha Arylation to Carbonyls, Investigation of Organocatalyst Potentials and Catalysis with Organometallic Palladium Complexes
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Líder : JOSEFREDO RODRIGUEZ PLIEGO JUNIOR
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MIEMBROS DE LA BANCA :
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ATAUALPA ALBERT CARMO BRAGA
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JOSEFREDO RODRIGUEZ PLIEGO JUNIOR
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MARCELO SIQUEIRA VALLE
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STELLA MARIS RESENDE
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WAGNER BATISTA DE ALMEIDA
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Data: 05-feb-2021
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Resumen Espectáculo
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The α-arylation reactions of carbonyl compounds creates new C-C bonds through nucleophilic aromatic substitution reactions (SNAr). The α-aryl carbonyl products are fundamental intermediates in the synthesis of bioactive compounds, drugs and natural products. SNAr reactions with inactive substrates are difficult to occur and the inclusion of electron withdrawing groups is suggested to activate the aromatic ring. However, the solvent effect may have a fundamental role in the reactivity of these reactions. At theoretical level, the arylation reactions are little explored and most of the studies use organometallic catalysts. In this thesis, α-arylation reactions of carbonyls with aryl compounds were analyzed using organocatalysts, phase transfer and organometallic catalysts. The reactions were investigated using electronic structure methods. The minimum geometries and transition states (TS) were obtained employing the Density Functional Theory (DFT) including the functionals X3LYP, B3LYP or PBE and the base sets 6-31(+)G(d) or def2-SVP, followed by harmonic frequency calculations. Additional single point calculations were made using the functionals M06-2x, M08-SO or mPW2-PLYP to get more accurate electronic energies. The solvation free energies of the reagents and TS were calculated using the SMD and PCM methods including MeOH, DMSO and toluene solvents. The SNAr reactions of inactive aromatic rings with anionic nucleophiles exhibit high values of activation free energy showing high solvent effects in solution. Only reactions with hydroxide and methoxide ions in DMSO should be observed. It is proposed that an approach based on supramolecular catalysis may make this reaction viable. The acetaldehyde α-arylation reactions with aryl compounds were investigated via formation of enol, enamine and sodium enolate. All reactions were unfeasible due high values of activation free energy in solution, all above 35 kcal mol1. The adding of organocatalysts, piperidine, hydroxylamine and aminothiourea, did not decreased the activation barrier of this reactions. When potassium enolate ion pairs were present in solution, the formation of aggregates was highly favored. However, the reactions of these aggregates with aryl compounds should not occur, due the high activation free energy in solution, all bigger than 35 kcal mol-1. The inclusion of hydro-crown phase transfer catalyst increases the activation energies reaching values above 37 kcal mol-1. The scenario becomes different when the catalyst used in the reaction of potassium enolate with bromobenzene is the Pd[P(tBu)3]2 complex. The monophosphine pathway appear to be the most favorable, with activation free energy in solution of 5.4 and 6.9 kcal mol-1 for the oxidative addition and reductive elimination steps, respectively. The reaction is viable and must be kinetically fast. The mechanism for the catalytic cycle and the free energy profile were obtained for the reaction of an aldehyde with aryl halide, this kind of data is difficult to find in the literature. These results are important for the development of new catalysts and more efficient processes.
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3
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ADRIANA SOUZA DE OLIVEIRA
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Synthesis and optical-structural characterization of yttrium and calcium silicates with apatite-like structure doped with Eu3+, Dy3+ and Tb3+ ions for application in solid-state lighting systems
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Líder : JEFFERSON LUIS FERRARI
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MIEMBROS DE LA BANCA :
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BRUNO HENRIQUE SACOMAN TORQUATO DA SILVA
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JEFFERSON LUIS FERRARI
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MARCO ANTONIO SCHIAVON
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MÁRCIO DE SOUSA GÓES
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PATRICIA BENEDINI MARTELLI
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THALITA CHIARAMONTE
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Data: 24-feb-2021
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Resumen Espectáculo
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Ca2Y8-x-y-z(SiO4)6O2: xEu3+ , yDy3+ , zTb3+ luminescent materials were prepared by the sol-gel method, followed by a solid-state reaction carried out at 1100 °C. Syntheses with simple doping, only with Eu3+, Dy3+ or Tb3+ ions, and codoping, with the combination of Eu3+/Dy3+or Eu3+/Tb3+ ions, were performed by varying, in all cases, the concentrations of these ions. The structural characterization of the materials, carried out by X-ray diffraction, infrared spectroscopy (IR) and Raman spectroscopy, proved the formation of oxyapatite-type silicates, with hexagonal type unit cell, belonging to the space group P63/m. In Raman and IR spectra, bending and stretching modes of [SiO4] 4- tetrahedral groups, characteristic of apatite-like structures was identified. The excitation and emission spectra of the synthesized materials showed bands referring to the 4f-4f interconfigurational transitions characteristic of each doping ion. In agreement with the emission bands displayed in the spectra of Eu3+ -doped apatites, these materials showed chromaticity coordinates in the red region, with high color purity, differing only in the emission intensity. Doping with Dy3+ ions resulted in color emissions in the blue, cyan, and white regions. The materials doped with Tb3+ ions exhibited emissions that varied from blue to green. Among single-doped materials, only Dy3+ -doped showed suppression of luminescence due to the increase in the concentration of doping ions inserted in the matrix. Spectroscopic measurements as a function of temperature proved the high thermal stability of apatites doped with Tb3+, Dy3+ and Eu3+ ions, in the face of minor changes in photoluminescent emission with increasing temperature. The energy transfer process in the codoped apatites was investigated by analyzing the excitation and emission spectra and the life-state curves of the excited state. Among the parameters that fundamentalized the efficiency of the energy transfer processes Dy3+→Eu3+ and Tb3+→Eu3+, we highlight a spectral overlap between the excitation spectrum of the activating ion, Eu3+, and the emission of the sensitizing ion, Dy3+ or Tb3+, in addition to the decrease in the lifetime of the co-doped materials with the increase in the concentration of the activator, in which the curves were monitored at the emission and excitation wavelengths of the sensitizing ion. The simultaneous incorporation of the Dy3+ and Eu3+ ions and the Tb3+ and Eu3+ ions resulted in emission spectra with characteristics of both doping ions, enabling the adjustment of the luminescent emission of each ion from the concentration and excitation wavelength. As a result of the combinations of ion emissions, there is a wide range of colors emitted in the visible region: green, red, orange, yellow, pink, cyan, white. The potential application of synthesized materials in solid-state lighting, especially white LEDs, is promising. This is justified due to its high luminescent intensity; diversity of emission colors, especially the single-phase white emission, and color temperatures, which expands the application possibilities; and the feasibility of associating these materials with UV-LED and blue LED chips, whose emission wavelengths can efficiently excite the synthesized apatites.
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4
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LÍVIA AVILA DE OLIVEIRA
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Development and Characterization of Sandwich-Type Structural Composites Containing Aluminum Blades and Bamboo Rings
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Líder : TULIO HALLAK PANZERA
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MIEMBROS DE LA BANCA :
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GILBERTO GARCIA DEL PINO
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JUAN CARLOS CAMPOS RUBIO
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KURT STRECKER
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LEANDRO JOSE DA SILVA
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RODRIGO TEIXEIRA SANTOS FREIRE
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TULIO HALLAK PANZERA
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Data: 18-jun-2021
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Resumen Espectáculo
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Sandwich panels are lightweight structures with high resistance and excellent structural performance, widely used in several areas, ranging from sports materials to components in the aerospace industry. In the last decades, extensive research has been carried out to investigate their behaviour and optimise their use under different loadings and conditions by testing different materials and core geometries. However, the increasing demand for sandwich panels highlights the need for sustainable components, focusing on biodegradability and reducing the post-disposal environmental impacts. Thus, this research project aims to investigate the feasibility of using renewable and abundant natural resources in Brazil, such as bamboo and castor, to obtain alternative and sustainable materials for structural engineering applications. This research is divided into four distinct stages. The first stage investigates the physical and mechanical properties of two different types of aluminium alloys and bamboo species to be used as faces and core of the sandwich panels, respectively. The second stage explores the adhesive efficiency of the panel components through the apparent shear test of single lap joints by varying the type of polymeric adhesive and the surface treatment of their constituents. In the third stage, the panels made of aluminium faces, the circular core of bamboo rings and epoxy adhesive are manufactured by varying the diameter and the packing of the core cells. The characterisation is performed through quasi-static loading to obtain flexural and shear properties. In addition to the failure mode, specific properties are determined for comparison with commercial structures. Finally, the fourth step investigates the impact properties of sandwich panels through drop-tower test by varying the diameter of the bamboo rings and the type of polymeric adhesive. In addition to the traditional epoxy adhesive, the use of biopolymeric adhesive based on castor oil is also investigated in this stage. In general, panels with hexagonal packaging and 30 mm bamboo rings have the best specific properties in bending and shearing, being competitive even with commercial structures. The impact properties are not affected by the variation in the bamboo rings diameter; however, biopolymeric adhesive results in structures with high energy absorption. Finally, the results obtained reveal that the proposed panels are feasible and promising for the future of sustainable structural engineering
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5
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BRENER RODRIGO DE CARVALHO VALE
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Exciton and Charge Carrier Dynamics in Colloidal Semiconductor Nanocrystals
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Líder : MARCO ANTONIO SCHIAVON
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MIEMBROS DE LA BANCA :
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MARCO ANTONIO SCHIAVON
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HORACIO WAGNER LEITE ALVES
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MARCOS JOSE LEITE SANTOS
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MARCELO GONCALVES VIVAS
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LAZARO AURELIO PADILHA JUNIOR
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Data: 16-ago-2021
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Resumen Espectáculo
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Semiconductors are materials of great interest to scientific human activities because many available technologies nowadays use these materials. In addition, the miniaturization of semiconductors on the nanoscale (10-9 m) opened, even more, the use of semiconductors in our growing demands for technology. However, the control of optoelectronic properties of semiconductors nanocrystals is not trivial being necessary a better comprehension of their photophysics, since many of these processes occur at very short timescales. In order to study and characterize them, it is suitable to use time-resolved spectroscopy techniques on the ultrafast timescale (10-15 -10-6 s). These generally rely on pulsed lasers with ultrashort pulses (10-15s). Two of these techniques are known as transient absorption and broadband fluorescence upconversion spectroscopies. In this thesis, we have used these both techniques to study the photohysical processes of full-inorganic perovskites CsPbBr3 colloidal nanoplatelets (CNPls) and, we have also used transient absorption spectroscopy to study quaternary quantum dots (QDs) based on Cu-In-Zn-S (CZIS). This thesis was written in five chapters to cover this subject. Chapters 1 and 2 are introductories. The former introduces the relevant theory for the following chapters, which will allow the readers to be familiarized with the main concepts and properties of semiconductors. Meanwhile, the second one gives a detailed explanation of ultrafast spectroscopy, including the setup description and data analysis. Chapter 2 also describes time-resolved spectroscopy applied in the carried out study. The following chapters placed in increasing complexity present the main results obtained for both kinds of nanoparticles. Chapter 3 consists of a review of the recent literature of perovskite nanocrystals contrasting their properties under strong and weak quantum confinement regimes. Chapter 4 presents a time-resolved photophysical study of CsPbBr3 CNPls. These materials are interesting because of their unique blue emission, strong exciton binding energy, large absorption cross-section, and fast hot exciton relaxation. These properties make them attractive for light-emitting devices. We synthesized these CNPLs by using a simple methodology at room temperature. The exciton, biexciton, and hot exciton dynamics were studied by means of fluorescence upconversion and transient absorption spectroscopies. Chapter 5 describes a timeresolved photophysical study of CZIS QDs. These materials are promising for a variety of applications because they are composed of less toxic elements. Here, we have studied three different samples in which we introduced more Zn2+ in the crystalline lattice of CZIS. Using transient absorption spectroscopy, we could study hole and electron trapping processes in these 9 nanoparticles as function of different concentrations of Zn. The Introduction of Zn increased the bandgap of the material and decreased the hole and electron trapping process.
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6
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Tienne Aparecida do Nascimento
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SYNTHESIS AND CHARACTERIZATION OF MAGNETIC ADSORBING MATERIALS BASED ON CONDUCTING POLYMERS APPLIED IN SAMPLE PREPARATION TECHNIQUE AND ADSORPTION STUDIES FOR THE DETERMINATION OF ORGANIC COMPOUNDS
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Líder : KEYLLER BASTOS BORGES
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MIEMBROS DE LA BANCA :
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EDUARDO COSTA DE FIGUEIREDO
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KEYLLER BASTOS BORGES
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LUIZ GUSTAVO DE LIMA GUIMARAES
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MARIA CRISTINA SILVA
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RENATA PEREIRA LOPES MOREIRA
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Data: 01-dic-2021
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Resumen Espectáculo
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Magnetic conducting polymers based on polypyrrole (PPy) and polythiophene (PTh) were synthesized and applied in sample preparation using the technique of magnetic solid phase microextraction (MSPE) and in adsorption studies. The adsorbent materials were characterized by DRX, FTIR, TGA, MEV and EDS, in order to evaluate the main characteristics of the studied solid phases. Firstly, the magnetic molecularly imprinted polypyrrole (MMIPPy) was developed for selective determination of praziquantel (PZQ) in milk samples. In the optimization of MSPE, the parameters of elution solvent, amount of adsorbent, sample volume and eluent and pH were studied, reaching a recovery of PZQ enantiomers above 80%. The selectivity study of MMIPPy demonstrated that the adsorbent has greater affinity for the (S)-(+)-PZQ enantiomer, when compared to the (R)-(-)-PZQ enantiomer, as well as other drugs that may act as interfering agents. The validation of the analytical method was performed in accordance with the recommendations established by ANVISA, evaluating the parameters of selectivity, linearity, LOD, LOQ, precision, accuracy, robustness and stability. The method was linear in the studied concentration range (0.01 to 10 µg mL-1 ), with a LOQ of 0.01 µg mL-1 for both enantiomers. Precision and accuracy were evaluated at concentrations of 1.70, 5.00 and 8.40 µg mL-1 , obtaining values of RSD% in the range of 1.28 to 10.21 for intraday and 0 .66 to 6.69 for the inter-day. Furthermore, the RE% values were between -9.74 and 9.72 (intra-day) and between -11.8 and 12.3 (inter-day). The robustness of the analytical method was also verified from small variations in the proportion of the mobile phase, flow rate, injection volume and HPLC model. Stability was observed by comparing the sample of interest with a fresh sample, prepared and analyzed on the same day. When applying the method, no PZQ was found in the ewe milk samples evaluated. Finally, from the adsorption studies it was observed that MMIPPy had a high adsorption capacity, with Q equal to 1322 and 1508 mg g-1 , for (R)-(-)-PZQ and (S)-(+)-PZQ, respectively, based on the Langmuir model that assumes a homogeneous and monolayer adsorption mechanism, from a spontaneous and endothermic process. In the second work, magnetic polythiophene (MPTh) was synthesized and also applied iv T. A. Nascimento Tese de Doutorado to MSPE for the determination of propoxur, a pesticide, in water, using an optimized method which showed recovery above 90%, including for other pesticides such as diazinon and ethofenprox. From the analytical validation, the method for determining propoxur was linear in the concentration range from 0.01 to 10 µg mL-1 , with a LOQ of 0.01 μg mL-1 . Precision and accuracy were evaluated at concentrations of 1.70, 5.00 and 8.40 µg mL-1 , obtaining RSD% values in the range of 1.23 to 8.30 for intraday and 0.45 to 1.36 for the inter-day. By the stability test, comparing the sample of interest with a fresh sample, values of RSD% below 15% and p values are higher than 0.05 were obtained, showing that the samples are stable even with oscillating the working temperature. The application of the method was performed using water samples collected from the Rio das Mortes, in São João del-Rei, which did not show residuals of the pesticide propoxur. Through adsorption studies, it was possible to determine that the interaction process between MPTh and propoxur is better represented by the Langmuir model, which describes a homogeneous adsorption in terms of energy and surface interactions, with high sorting capacity (Q = 1723 mg g-1 ). Furthermore, the thermodynamic study indicated that the process is spontaneous and endothermic
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FLÁVIA VIANA AVELAR DUTRA
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POLYMERIC MATERIALS BASED ON POROUS POLYANILINE APPLIED IN DIFFERENT TECHNIQUES FOR SOLID PHASE EXTRACTION OF DRUGS IN BIOLOGICAL MATRICES.
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Líder : KEYLLER BASTOS BORGES
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MIEMBROS DE LA BANCA :
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MARIANE GONÇALVES SANTOS
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KEYLLER BASTOS BORGES
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LEANDRO AUGUSTO CALIXTO
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LUIZ GUSTAVO DE LIMA GUIMARAES
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WANDERSON ROMAO
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Data: 10-dic-2021
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Resumen Espectáculo
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This work aimed to develop polymeric materials based on porous polyaniline double coated with restricted access materials to be applied in different solid phase extraction techniques of drugs in biological matrices, which aims to exclude macromolecules present in complex matrices, facilitating sample preparation and analysis. In the first study, magnetic mesoporous polyaniline coated with hydrophilic monomers and bovine serum albumin (RA-MMPAni-HMBSA) was synthesized and, from the results obtained in the characterization techniques, it can be seen that the objective of synthesizing an adsorbent material with magnetic characteristics and with the ability to exclude proteins was successfully achieved, because by EDS, it is possible to prove the composition of the material at each step, by XRD it can be seen that the magnetic property was maintained and, by the results of TG , FTIR, wettability and protein exclusion it can be concluded that the material was coated with the restricted access materials. Furthermore, RA-MMPAni-HM-BSA was applied as an adsorbent material in the magnetic solid phase extraction (MSPE) of two coumarins, 4,7-dimethylcoumarin (DMC) and 7- methoxy-4-methylcoumarin (MMC) , present in rat plasma, showing good adsorptive and also magnetic capacity. For the optimization of the analytical method, some parameters were evaluated, such as pH and sample volume, washing solvent, amount of material, type and volume of elution solvent and contact time. Thus, the optimized conditions were: 500 µL of sample with pH equal to 2, 20 mg of adsorbent material, stirring for 1 min, water as washing solvent, acetonitrile as elution solvent (750 µL), obtaining recovery 72.9% for MMC and 98.0% for DMC. The method was validated and applied to a plasma samples from rat and then showed good results in terms of accuracy and precision, in addition to being reproducible for the identification and quantification of the analytes under study. In the second study, the mesoporous polyaniline coated with hydrophilic monomers and bovine serum albumin, called RA-MPAni-HM-BSA, was used in dispersive solid phase extraction (DSPE) and microextraction by packed sorbent (MEPS). In order to compare which of the two techniques would be more efficient for the extraction of two antiallergics, loratadine (LRT) and cetirizine (CTZ) in human urine. The DSPE method showed better recovery results (71.9% for CTZ and 79.1% for LRT) compared to the MEPS method (46.9% for CTZ and 85.8% for LRT). Therefore, the DSPE method was chosen to be validated and applied. The validation obtained results in accordance with the current standard and was successfully applied to real samples, finding concentrations equal to 0.111 and 0.041 µg mL-1 of two volunteers. Finally, the materials were efficient to be used as adsorbents in extraction techniques and from the characterizations you can see that the syntheses were carried out successfully.
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