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Filmes inorgânicos de ZrO2 e filmes híbridos orgânico-inorgânicos de ZrO2-PMMA, preparados pelo método sol-gel, foram estudados como protetores contra a corrosão de aço inoxidável em meio ácido. Os sóis foram preparados a partir de uma solução submetida à irradiação de ultra-som e contendo o alcóxito metálico correspondente como precursor, álcool como solvente e ácido acético glacial como agente quelante para modificar a reatividade do alcóxito metálico. Várias concentrações de PMMA foram adicionadas aos sóis e estes foram caracterizados através de reometria, espectroscopia na região do infravermelho (FTIR), calorimetria explanatória diferencial (DSC) visando estudar a evolução de suas características morfológicas durante o envelhecimento. Os filmes de ZrO2 e ZrO2-PMMA foram depositados, utilizando-se a técnica de imersão, sobre lâminas de aço inoxidável 316L (AISI 316L), densificados a 200&#176C e o tempo de tratamento térmico foi variado de 5 a 180 minutos. Os filmes foram caracterizados por espectroscopia de reflexão especular na região do infravermelho; a morfologia, composição e textura superficiais foram determinadas por microscopia eletrônica de varredura (MEV), dispersão de energia de raios X (EDS) e perfilometria, respectivamente. curvas de polarização potenciodinâmica a 1 mVs-1 foram usadas para estudar a eficiência dos diferentes recobrimentos na proteção do AISI 316L contra a corrosão em soluções de H2SO4 0,5 mol.L-1. Os resultados mostram que os filmes híbridos ZrO2-PMMA aumentam em média 30 vezes o tempo de vida do substrato em relação aos filmes puramente inorgânicos. / ZrO2 inorganic and ZrO2-PMMA hybrids organic-inorganic films, obtained by the sol-gel method, were studied in order to determine their properties as protective layers against corrosion of stainless steel in acid media. The sol was prepared from a sonocatalyzed solution containing the appropriate metal alkoxide as precursor, alcohol as solvent, and glacial acid acetic as chelant agent to modify the reactivity of the metal alkoxide and PMMA was added into these sols. Reology, infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were employed to determine the evolution of structural changes during aging time. The ZrO2 and ZrO2-PMMA films were deposited on stainless steel by dip-coating technique and heat treated at 200&#176C at times of heating ranging from 5 to 180 minutes. The films were characterized by FTIR reflection spectroscopy, scanning electronic microscopy, X-ray dispersive energy and profilometry to determine the surface morphology, composition and texture, respectively. Potentiodynamic polarization curves (PPC) at 1 mVs-1 were used to study the efficiency on the protection of AISI 316L against corrosion in H2SO4 0,5 mol.L-1, showing that ZrO2-PMMA increase in a factor up 30 the life time of substrate.

Filmes inorgânicos de ZrO2 e filmes híbridos orgânico-inorgânicos de ZrO2-PMMA, preparados pelo método sol-gel, foram estudados como protetores contra a corrosão de aço inoxidável em meio ácido. Os sóis foram preparados a partir de uma solução submetida à irradiação de ultra-som e contendo o alcóxito metálico correspondente como precursor, álcool como solvente e ácido acético glacial como agente quelante para modificar a reatividade do alcóxito metálico. Várias concentrações de PMMA foram adicionadas aos sóis e estes foram caracterizados através de reometria, espectroscopia na região do infravermelho (FTIR), calorimetria explanatória diferencial (DSC) visando estudar a evolução de suas características morfológicas durante o envelhecimento. Os filmes de ZrO2 e ZrO2-PMMA foram depositados, utilizando-se a técnica de imersão, sobre lâminas de aço inoxidável 316L (AISI 316L), densificados a 200&#176C e o tempo de tratamento térmico foi variado de 5 a 180 minutos. Os filmes foram caracterizados por espectroscopia de reflexão especular na região do infravermelho; a morfologia, composição e textura superficiais foram determinadas por microscopia eletrônica de varredura (MEV), dispersão de energia de raios X (EDS) e perfilometria, respectivamente. curvas de polarização potenciodinâmica a 1 mVs-1 foram usadas para estudar a eficiência dos diferentes recobrimentos na proteção do AISI 316L contra a corrosão em soluções de H2SO4 0,5 mol.L-1. Os resultados mostram que os filmes híbridos ZrO2-PMMA aumentam em média 30 vezes o tempo de vida do substrato em relação aos filmes puramente inorgânicos. / ZrO2 inorganic and ZrO2-PMMA hybrids organic-inorganic films, obtained by the sol-gel method, were studied in order to determine their properties as protective layers against corrosion of stainless steel in acid media. The sol was prepared from a sonocatalyzed solution containing the appropriate metal alkoxide as precursor, alcohol as solvent, and glacial acid acetic as chelant agent to modify the reactivity of the metal alkoxide and PMMA was added into these sols. Reology, infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were employed to determine the evolution of structural changes during aging time. The ZrO2 and ZrO2-PMMA films were deposited on stainless steel by dip-coating technique and heat treated at 200&#176C at times of heating ranging from 5 to 180 minutes. The films were characterized by FTIR reflection spectroscopy, scanning electronic microscopy, X-ray dispersive energy and profilometry to determine the surface morphology, composition and texture, respectively. Potentiodynamic polarization curves (PPC) at 1 mVs-1 were used to study the efficiency on the protection of AISI 316L against corrosion in H2SO4 0,5 mol.L-1, showing that ZrO2-PMMA increase in a factor up 30 the life time of substrate.

Sample preparation is the most error-prone step in chemical analysis. A great deal of efforts has been made to develop efficient techniques and protocols for sample preparation to accomplish important goals such as miniaturization and implementation of green analytical methodologies. Solid-phase microextraction (SPME) has successfully eliminated the use of hazardous organic solvents in extraction sampling, sample preparation, preconcentration and sample introduction to the analytical instrument in an effective manner. Ensuring thermal- and solvent-instability of traditional SPME extraction phases represented one of their main drawbacks. This was solved by the introduction of sol-gel SPME phases characterized by enhanced thermal-, solvent-, and stability over a wide pH range. Sol-gel SPME phases (sorbents) facilitated excellent preconcentration effects for a wide range of analytes. In this dissertation, hydrolytic and nonhydrolytic sol-gel routes were explored for the creation of zirconia-, titania-, and niobia-based novel hybrid organic-inorganic sorbents using sol-gel active polymeric ligands. These sorbents were prepared in the form of surface coatings for capillary microextraction and preconcentration of biologically important molecules such as catecholamine neurotransmitters and phosphopeptides. In comparison with other sorbents made only of inorganic transition metal oxides, the presented sol-gel sorbents facilitated efficient desorption of the extracted analytes by LC-MS compatible mobile phases. The sol-gel zirconia- and titania-based hybrid sorbents provided pH-stable (pH range: 0 - 14) and derivatization-free extraction media that effectively overcame the major drawbacks of traditional sorbents for the analysis of catecholamines (silica-based sorbents suffer from narrow operational pH window while polymer-based sorbents require additional sample derivatization steps). The modification of the terminal hydroxy groups in PPO with ZrCl4 or TiCl4 provided an enhanced sol-gel reactivity of the polymer modified-terminals. Such a modification procedure allowed for an efficient incorporation of the polymeric ligand into the evolving sol-gel network. The effectiveness of the PPO modification was also evaluated by a systematic thermogravimetric investigation exploring the loading of the ligand in sol-gel hybrid sorbents, which revealed an enhanced ligand-loading achieved via the nonhydrolytic sol-gel route used with modified-PPO. Sol-gel hybrid sorbents prepared by the nonhydrolytic sol-gel (NHSG) pathway provided excellent microextraction performance for catecholamines: low detection limits (5.6 – 9.6 pM), enhanced run-to-run reproducibility (RSD 0.6 – 5.1 %), excellent desorption efficiency (95.0 – 99.5 %) and high enrichment factors (EF) for epinephrine (EF ~ 1480) and for dopamine (EF ~ 2650) extracted from aqueous and synthetic urine samples at pH 10.5. Run-to-run and capillary-to-capillary reproducibility remained below 5 % when the peak area or the sorbent-mass was used as the reproducibility criterion. Niobia-based sol-gel sorbents prepared with and without organic ligand (polyethylenimine) were utilized as microextraction media for the enrichment of phosphorylated and nonphosphorylated tetrapeptide VYKA. Sol-gel niobia-based sorbents with covalently anchored polyethylenimine showed excellent selectivity toward the phosphopeptide compared to analogous titania-based sorbents. Specific extraction (SE) values were higher by 97.0 % when obtained by niobia-based sorbents. Excellent run-to-run peak area reproducibility (RSD < 5.1 %) and high EF of ~ 4000 were achieved. The sol-gel niobia-based coating facilitated excellent desorption efficiency (97.5 %), which suggests that the surface of the niobia sorbent possesses moderate-strength Lewis acid sites that avoided the need for special elution solvents that are conventionally used for the desorption of phosphorylated molecules from titania-based sorbents. The sol-gel pathway for the creation of microextraction phases is versatile and capable to provide unique control on the characteristics of the sorbents that are critically important for many sample preparation applications.