The aim of the work was to develop an understanding of the phenomenon of rate enhancement observed when a heterogeneous catalytic reaction system is irradiated by ultrasound. The system under investigation was the catalytic hydrogenation of an a, B - unsaturated ketone, using zinc dust and aqueous nickel chloride as a source of hydrogen. When a slurry of zinc particles and aqueous nickel chloride is stirred or sonicated, nickel deposits in the form of patches on the surface of the zinc particles and simultaneously, zinc dissolves into the solution in the form of zinc ions, a process called pitting corrosion. Hydrogen atoms are formed when hydrogen ions diffuse from the bulk, adsorb onto the nickel surface and take up electrons generated by the dissolution of zinc. Once the atoms are formed on the surface, the atoms combine to form hydrogen molecules, which desorb in the form of hydrogen gas. When ketone is added to this slurry, the hydrogen atom formed on the surface of nickel is used as the source of hydrogen for the hydrogenation reaction. In these processes, nickel serves as catalyst. The ketone first has to diffuse to the bulk, adsorb onto the surface of nickel and undergo reduction by the hydrogen atoms to form the product. The product then has to desorb from the surface and diffuse into the bulk, in order to create vacant sites on the nickel surface for the adsorption of more ketone. Experiments dealing with measurements of hydrogen evolution rates pointed out that hydrogen is not a limiting reactant, since evolution was sustained for long periods of time. The evolution rates versus time data revealed that the nature of the plots for both, the stirred and sonicated systems were similar. These facts lead us to infer that the basic mechanism of nickel deposition, pitting corrosion, etc. was similar for the two cases. To study the hydrogenation reaction, experiments were first conducted keeping the nickel catalyst surface area constant. The results of these experiments showed that the hydrogenation reaction can be explained by a first order mechanism. Changing the speed of the stirrer did not effect the rate of the reaction; hence it was inferred that the reaction was not external mass transfer controlled. It was also seen that there was an no significant difference in reaction rates between the stirred and sonicated systems. Hence we conclude that sonication does not effect any process involved in the actual process of hydrogenation, i.e., adsorption, desorption, surface reaction, etc., do not get effected. It was concluded that the observed rate enhancements of similar compounds in the same system occur only when nickel catalyst is being continuously formed. This is possible only if irradiation with ultrasound enhances the rate of formation of the surface area of the nickel deposit. To study this phenomena, experiments were conducted with continuous formation of nickel catalyst. These experiments were conducted in three ways - stirring with zinc dust, sonication with zinc dust and stirring with presonicated zinc dust. For the first two kinds of experiments, the rates were low, increased to a maximum value and then decreased, but the nature of the third kind of experiments were different. The initial rates were very high as compared to either of the other two kinds of experiments but the rate rapidly reduces and becomes comparable to the rates obtained by stirring with zinc dust. We conclude that sonication creates many active sites on the surface of the zinc particles in the form of crystal defects, which are perhaps necessary for the deposition of nickel. When presonicated zinc particles are used, there are large numbers of these sites and these get consumed rapidly when stirred with aqueous nickel chloride solution. In this work, we do not deal with this case. In the case of sonication with zinc dust, these active sites are continuously created and are consumed by nickel deposition. For the stirred system, these sites are quite small to start with and new ones are not generated since there is no irradiation by ultrasound. Hence, the rates in the latter case are low for both nickel deposition and the hydrogenation reaction. In the model, it was assumed that the rate of increase of surface area of nickel, characterized by a specific rate term k z, was proportional to the amount of nickel in the bulk and also to the amount of free zinc surface area available. Similarly, nickel which deposits on previously deposited nickel (characterized by another specific rate constant, kn) was proportional to the amount of nickel in the bulk, the nickel area already deposited and also the free zinc surface area available. The model is in excellent agreement with the experimental data obtained. The model predicted higher values of kn and kz for the sonicated system, indicating that the rate of deposition of nickel is much higher in this case than for the stirred system. Moreover, the model also predicts that the deposit in the case of a sonicated system is thinner and flatter, since it was seen that the surface area created for the same amount of nickel deposited was much higher in this case than the stirred system.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2016-09-23T20:44:49Z No. of bitstreams: 2 Dissertação - Maria Aparecida Bezerra dos Santos - 2016.pdf: 6679774 bytes, checksum: 89dea71508c554ec5524092cfac309bd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-09-26T11:48:23Z (GMT) No. of bitstreams: 2 Dissertação - Maria Aparecida Bezerra dos Santos - 2016.pdf: 6679774 bytes, checksum: 89dea71508c554ec5524092cfac309bd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-09-26T11:48:23Z (GMT). No. of bitstreams: 2 Dissertação - Maria Aparecida Bezerra dos Santos - 2016.pdf: 6679774 bytes, checksum: 89dea71508c554ec5524092cfac309bd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Rare earth hydroxides show optical and photocatalytic properties, and potential application as contrast agents and biomarkers. In this study, the start materials, samarium hydroxide (Sm(OH)3) and gadolinium hydroxide (Gd(OH)3), were synthesized at room temperature by precipitation method and using microwave-assisted hydrothermal (MAH) method for 20 minutes. Pure hexagonal phase with an anisotropic hexagonal nanotubes morphology was obtained, with dimensions of 200-350 nm x 30-40 nm to Sm(OH)3, and 570-990 nm x 90-245 nm for Gd(OH)3. Hydroxides doped and nanocomposites in the form of TR(OH) 3/TR(OH)3, were synthesized as hybrid systems. Nanocomposites Sm(OH) 3/Gd(OH)3 e Gd(OH)3/Sm(OH)3 were obtained in differents ratios by two step synthesis by MAH method, resulting in decorated nanotubes as nanocomposites the ordered/disordered type. The structural and morphological characterization of materials were carried out by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Atoms constituents of phases were confirmed by Energy Dispersive X-Ray Spectroscopy (EDS). Nanocomposites of Sm(OH)3 and Sm(OH)3 were also synthesized by sonochemical method, which enabled obtain both crystalline phases. The photoluminescent property of the materials was investigated by photoluminescence spectroscopy (PLS) in which was observed the broadband photoluminescence enhancement for both doped hydroxides as for nanocomposites. The latter provides the best results. The composite Sm/Gd-20-A showed photoluminescence up to seven times more intense than the pure precursor hydroxides due to interfacial defects. / Hidróxidos de Terras Raras (TR) apresentam propriedades ópticas, fotocatalíticas e exibem potencial aplicação como agentes de contraste e biomarcadores. Neste trabalho, os materiais de partida, hidróxido de samário (Sm(OH)3) e hidróxido de gadolínio (Gd(OH)3), foram sintetizados pelo método de precipitação à temperatura ambiente e utilizando o método hidrotérmico assistido por micro-ondas (HAM) por 20 minutos, obtendo-se fase pura hexagonal, com morfologia anisotrópica de nanotubos hexagonais, nas dimensões de 200-350 nm x 30-40 nm para o Sm(OH)3 e de 570-990 nm x 90-245 nm para o Gd(OH)3. Hidróxidos dopados e nanocompósitos, na forma de TR(OH) 3/TR(OH)3, foram sintetizados como sistemas híbridos destes dois hidróxidos. Os nanocompósitos Sm(OH) 3/Gd(OH)3 e Gd(OH)3/Sm(OH)3 foram obtidos em porcentagens variadas, por síntese em duas etapas, utilizando método HAM, na qual obteve-se nanotubos decorados, como nanocompósitos do tipo ordenado/desordenado. As caracterizações estrutural e morfológica dos materiais foram realizadas por Difração de raios X (DRX) e por Microscopias Eletrônicas de Varredura (MEV) e de Transmissão (MET). A presença dos elementos constituintes das fases foi confirmada por Espectroscopia de Energia Dispersiva de raios X (EDS). Nanocompósitos de Sm(OH) 3 e Sm(OH)3 também foram sintetizados por método sonoquímico, possibilitando a obtenção com ambas as fases cristalinas. A propriedade fotoluminescente dos materiais foi investigada por Espectroscopia de Fotoluminescência (EFL), na qual se observou o aprimoramento da fotoluminescência de banda larga tanto para os hidróxidos dopados quanto para os nanocompósitos. Estes últimos apresentaram os melhores resultados, onde o compósito Sm/Gd-20-A mostrou fotoluminescência até sete vezes mais intensa que os hidróxidos precursores puros, comportamento relacionado à formação de defeitos interfaciais.

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-05-03T20:30:01Z No. of bitstreams: 2 Dissertação - Douglas Carlos de Sousa Silva - 2017.pdf: 3036182 bytes, checksum: c02aa9da97c239bf3b1954923b5ee8a0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-05-04T11:06:57Z (GMT) No. of bitstreams: 2 Dissertação - Douglas Carlos de Sousa Silva - 2017.pdf: 3036182 bytes, checksum: c02aa9da97c239bf3b1954923b5ee8a0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-05-04T11:06:57Z (GMT). No. of bitstreams: 2 Dissertação - Douglas Carlos de Sousa Silva - 2017.pdf: 3036182 bytes, checksum: c02aa9da97c239bf3b1954923b5ee8a0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-04-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Nanostructured materials, such as: Ag2MoO4 and ZnO are of great importance because they have unique characteristics and properties, and can be applied in sensors, catalysis, photoluminescence, among other applications. In this work, the Ag2MoO4 and ZnO powders were synthesized separately and in the form of heterostructures, by two different routes, coprecipitation (CP), at room temperature and coprecipitation with subsequent microwave assisted hydrothermal treatment (CPMAHT), at 130 ° C for 30 min, with a heating rate of 10 ° C / min. The heterostructures composed of both materials, Ag2MoO4 and ZnO present in molar proportions ranging from 0.25-2.00%, were synthesized by coprecipitation with subsequent sonochemical processing (CPSP). The Ag2MoO4 samples were obtained with pure cubic phase of spinel type with crystallite size of 143 nm for the sample obtained by CP and 90 nm for the sample obtained by CPTHAM. For the ZnO the hexagonal phase of the wurtzite type, with crystallite sizes of 19 and 49 nm, was obtained for the samples obtained by CP and CPTHAM, respectively. The phases of both Ag2MoO4 and ZnO were observed for the heterostructures obtained by CPSP. The structural and morphological characterization of the obtained materials was performed using X-ray diffraction (XRD) techniques and scanning electron microscopy (SEM). The diffusion reflectance UV-Vis spectroscopy (DRS) was performed to determine the band gap values of the materials. The photoluminescent property was investigated by means of the photoluminescence spectroscopy (PHS) technique, with an improvement in the photoluminescent property of broadband for all the obtained heterostructures. It was also observed that the synergism of the Ag2MoO4 and ZnO materials in the heterostructures resulted in an improvement in the photocatalytic property, leading to a 90% discoloration of the rhodamine B dye in 90 min for the photocatalysis using the Ag2MoO4: 2 ZnO heterostructure. / Materiais nanoestruturados, tais como: o Ag2MoO4 e o ZnO são de grande importância por apresentarem características e propriedades únicas, podendo ser aplicados em sensores, catálise, fotoluminescência, dentre outras aplicações. Neste trabalho, os pós de Ag2MoO4 e ZnO foram sintetizados na sua forma pura por duas rotas diferentes, coprecipitação (CP) a temperatura ambiente e coprecipitação com posterior tratamento hidrotérmico assistido por microondas (CPTHAM), a 130 °C durante 30 min, com taxa de aquecimento de 10 °C/min. Heteroestruturas compostas por ambos os materiais, Ag2MoO4 e ZnO foram obtidas com proporções de 0,25; 0,50; 1 e 2 mols de ZnO para 1 mol de Ag2MoO4. Estas heteroestruturas foram sintetizadas por coprecipitação com posterior processamento sonoquímico (CPPS). As amostras de Ag2MoO4 foram obtidas com fase cúbica pura do tipo espinélio com tamanho de cristalito de 143 nm para a amostra obtida por CP e 90 nm para a amostra obtida por CPTHAM. Para o ZnO foi obtida a fase hexagonal do tipo wurtzita, com tamanhos de cristalito de 19 e 49 nm, para as amostras obtidas por CP e CPTHAM, respectivamente. Foram observadas ambas as fases, tanto do Ag2MoO4 quanto do ZnO para as heteroestruturas obtidas por CPPS. A caracterização estrutural e morfológica dos materiais obtidos foi realizada utilizando das técnicas de difração de raios X (DRX) e microscopia eletrônica de varredura (MEV). A espectroscopia de UV-Vis por reflectância difusa (ERD) foi realizada para determinação dos valores de “band gap” dos materiais. A propriedade fotoluminescente foi investigada por meio da técnica de espectroscopia de fotoluminescência (EFL), sendo observado uma melhora na propriedade fotoluminescente de banda larga para todas as heteroestruturas obtidas. Foi observado também que a sinergia dos materiais Ag2MoO4 e ZnO nas heteroestruturas resultou em uma melhora na propriedade fotocatalítica, levando a uma descoloração do corante rodamina B de 90 % em 90 min para a fotocatálise usando a heteroestrutura Ag2MoO4: 2 ZnO.

Semiconductor nanostructures have attracted considerable research interest due to their unique physical and chemical properties at nanoscale which open new frontiers for applications in electronics and sensing. Zinc oxide nanostructures with a wide range of applications, especially in optoelectronic devices and bio sensing, have been the focus of research over the past few decades. However ZnO nanostructures have failed to penetrate the market as they were expected to, a few years ago. The two main reasons widely recognized as bottleneck for ZnO nanostructures are (1) Synthesis technique which is fast, economical, and environmentally benign which would allow the growth on arbitrary substrates and (2) Difficulty in producing stable p-type doping. The main objective of this research work is to address these two bottlenecks and find a solution that is inexpensive, environmentally benign and CMOS compatible. To achieve this, we developed a Sonochemical method to synthesize 1D ZnO Nanorods, core-shell nanorods, 2D nanowalls and nanoflakes on arbitrary substrates which is a rapid, inexpensive, CMOS compatible and environmentally benign method and allows us to grow ZnO nanostructures on any arbitrary substrate at ambient conditions while most other popular methods used are either very slow or involve extreme conditions such as high temperatures and low pressure. A stable, reproducible p-type doping in ZnO is one of the most sought out application in the field of optoelectronics. Here in this project, we doped ZnO nanostructures using sonochemical method to achieve a stable and reproducible doping in ZnO. We have fabricated a homogeneous ZnO radial p-n junction by growing a p-type shell around an n-type core in a controlled way using the sonochemical synthesis method to realize ZnO homogeneous core-shell radial p-n junction for UV detection. ZnO has a wide range of applications from sensing to energy harvesting. In this work, we demonstrate the successful fabrication of an electrochemical immunosensor using ZnO nanoflakes to detect Cortisol and compare their performance with that of ZnO nanorods. We have explored the use of ZnO nanorods in energy harvesting in the form of Dye Sensitized Solar Cells (DSSC) and Perovskite Solar Cells.

Cette thèse porte sur l'intensification de l'extraction de polyphénols à partir de produits à base de pomme (chair, peau et marc) par ultrasons (US) et sur la purification d'extraits de peau de pomme par adsorption/désorption et technologie membranaire. L'extraction sélective des polyphénols issus des produits de la pomme a été analysée. Les données obtenues ont démontré la possibilité d’une régulation fine de l’extraction sélective de la matière soluble, de la catéchine et des composés polyphénoliques totaux en utilisant différentes températures, protocoles UAE, mélanges éthanol/aqueux. La sélectivité de l'extraction de la catéchine dépendait également du type de tissu (chair, peau ou marc) et de la variété de pomme (verte ou rouge). Le phénomène de cavitation généré par les ultrasons pourrait augmenter l'extraction de composants précieux des pelures de fruits en endommageant les membranes cellulaires des échantillons et en accélérant ainsi le transfert de chaleur et de masse. D’autre part, les solvants eau-gaz pourraient améliorer l'efficacité d'extraction des polyphénols des peaux de pomme en renforçant le phénomène de cavitation généré par les ultrasons. L'efficacité de la purification de polyphénols d'extraits de pelure de pomme par adsorption/désorption assisté par ultrasons (adsorbant polyaromatique Amberlite XAD-16) et par électrofiltration sur membrane a été mise en évidence. Les données obtenues ont démontré que la sonication facilitait significativement la cinétique d’adsorption, la capacité d’adsorption accrue et augmentation de l’énergie d’activation de l’adsorption des polyphénols. En outre, le taux de désorption a été positivement affecté par la sonication au cours de l'étape d'adsorption. Par ailleurs, les résultats ont montré que l’électrofiltration sur membrane permettait de purifier les polyphénols dans l’espace anodique (+) et d’obtenir un volume plus important de filtrats. / This thesis focuses on the intensification of polyphenols extraction from apple products (flesh, peel, and pomace) by ultrasound (US) and the purification of apple peel extracts by adsorption/desorption and membrane technology. The selective extraction of phenolic contents from apple products has been analyzed. The obtained data evidenced the possibility of fine regulation of selective extraction of soluble matter, catechin and total polyphenolic compounds using different temperatures, ultrasound-assisted extraction (UAE) protocols, ethanol/aqueous mixtures. The selectivity of catechin extraction was also depended on the type of the tissue (flesh, peel or pomace) and apple variety (green or red). The cavitation phenomenon generated by ultrasound could increase extraction of valuable components from fruit peels by damaging cell membranes of samples and accelerating heat and mass transfer by disrupted cell walls of samples. Meanwhile, the gas water solvents could enhance the extraction efficiency of polyphenols and antioxidant activity from apple peels by enhancing cavitation phenomenon generated by ultrasound. The efficiency of polyphenols purification from apple peel extracts with adsorption/desorption process by ultrasound treatment with the polyaromatic amberlite adsorbent XAD-16 and with membrane electro-filtration were studied. The obtained data demonstrated that the sonication significantly facilitated adsorption kinetics and increased activation energy of polyphenols adsorption. In addition, the desorption ratio was positively affected by the sonication during the adsorption step. On the other hand, the results demonstrated that the membrane electro-filtration allowed the purification of polyphenols in the anode (+) space and obtaining larger volume of filtrates.

The previously described 2-aryl-4-chloro-3-iodoquinolines were prepared following literature procedure and in turn converted to the corresponding hitherto unknown 2-aryl-3-iodo-4-(phenylamino)quinoline derivatives using aniline in refluxing ethanol. These 2-aryl-3-iodo-4-(phenylamino)quinolines were reacted with allybromide in ethanol at room temperature to afford 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives. The 2-aryl-3-iodo-4-(phenylamino)quinoline and 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were subjected to metal-catalysed carbon-carbon bond formations. Palladium(0)-copper iodide catalysed Sonogashira cross-coupling of 2-aryl-3-iodo-4-(phenylamino)quinoline with terminal alkynes afforded series of 1,2,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines in a single step operation. On the other hand, the 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were found to undergo palladium-catalysed intramolecular Heck reaction to yield the corresponding 1,3,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines. All new compounds were characterized by using a combination of NMR (1H and 13C), IR, mass spectroscopic techniques as well as elemental analysis. / Chemistry / MSc. (Chemistry)

The previously described 2-aryl-4-chloro-3-iodoquinolines were prepared following literature procedure and in turn converted to the corresponding hitherto unknown 2-aryl-3-iodo-4-(phenylamino)quinoline derivatives using aniline in refluxing ethanol. These 2-aryl-3-iodo-4-(phenylamino)quinolines were reacted with allybromide in ethanol at room temperature to afford 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives. The 2-aryl-3-iodo-4-(phenylamino)quinoline and 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were subjected to metal-catalysed carbon-carbon bond formations. Palladium(0)-copper iodide catalysed Sonogashira cross-coupling of 2-aryl-3-iodo-4-(phenylamino)quinoline with terminal alkynes afforded series of 1,2,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines in a single step operation. On the other hand, the 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were found to undergo palladium-catalysed intramolecular Heck reaction to yield the corresponding 1,3,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines. All new compounds were characterized by using a combination of NMR (1H and 13C), IR, mass spectroscopic techniques as well as elemental analysis. / Chemistry / MSc. (Chemistry)

No description available.