Call number: LD2668 .T4 1955 E44 / Master of Science

Esta dissertação teve como objetivo o desenvolvimento de um dispositivo microfluídico para a determinação de nutrientes em solo. A motivação para o desenvolvimento de uma plataforma microfluídica dedicada à agricultura vem do crescimento populacional, que chegará em 2030 a 8,5 bilhões de pessoas, ante 7,3 bilhões atuais. Com um crescimento tão expressivo da população mundial o fornecimento de alimentos torna-se vital. A agricultura desempenha um papel notável no fornecimento de alimentos e na economia brasileira. O monitoramento de nutrientes no solo para uma boa produção é indispensável. O desenvolvimento de dispositivos microfluídicos vêm tomando destaque na área industrial, alimentar, ambiental e criminal, devido a sua portabilidade, baixo peso, custo de fabricação e consumo de reagentes. Com uma aplicação de amostra de 50 µL no centro do dispositivo microfluídico, o líquido percola o interior do dispositivo por capilaridade até as zonas reacionais, onde estão depositados pequenos volumes de reagente. Após a amostra reagir na zona reacional, uma alteração visual da cor é observada e esta pode ser utilizada para quantificar a espécie de interesse. Dentre os extratores utilizados, a água não é um bom extrator para os analitos aqui trabalhados. A curva analítica de borato e cobalto apresentaram resultados promissores tanto em solução aquosa quanto em ácido cítrico 2%. O emprego de solução de ácido cítrico 2% para construção da curva analítica e extração de ferro e cobre do solo é um reagente eficiente se comparado a água e citrato neutro de amônio. Para o fosfato, o emprego de soluções de água ou citrato neutro de amônio podem ser empregados. A construção de testes para quantificação de nitrito, nitrato e zinco apresentaram problemas de reprodutibilidade. As reações colorimétricas apresentaram resultados promissores para aplicação em dispositivos microfluídicos a base papel. A associação entre reações colorimétricas simples e dispositivos microfluídicos possibilitou o desenvolvimento de testes químicos para serem empregados na agricultura. Os dados gerados podem ser utilizados na modelação da distribuição de nutrientes no terreno em estudo e posterior correção visando benefícios à agricultura. / This dissertation aimed at the development of a microfluidic device for the determination of nutrients in soil. The motivation for the development of a microfluidic platform dedicated to agriculture comes from population growth, which in 2030 will reach 8.5 billion people, compared to 7.3 billion today. With such a significant growth of the world population, food supply becomes vital. Agriculture plays a notable role in food supply and in the Brazilian economy. The monitoring of nutrients in the soil for good production is indispensable. The development of microfluidic devices has been highlighted in the industrial, food, environmental and criminal areas, due to their portability, low weight, manufacturing cost and reagent consumption. With a 50 ?L sample application in the center of the microfluidic device, the liquid percolates the interior of the device by capillarity to the reaction zones where small volumes of reagent are deposited. After the sample reacts in the reaction zone, a visual color change is observed and this can be used to quantify the species of interest. Among the extractors used, water is not a good extractor for the analytes used here. The analytical curve of borate and cobalt presented promising results in both aqueous solution and 2% citric acid. The use of 2% citric acid solution for the construction of the analytical curve and extraction of iron and copper from the soil is an efficient reagent when compared to water and neutral ammonium citrate. For phosphate, the use of water solutions or neutral ammonium citrate may be employed. The construction of tests for quantification of nitrite, nitrate and zinc presented problems of reproducibility. The colorimetric reactions presented promising results for application in paper - based microfluidic devices. The association between simple colorimetric reactions and microfluidic devices allowed the development of chemical tests to be used in agriculture. The data generated can be used in the modeling of nutrient distribution in the field under study and later correction aiming at benefits to agriculture.

Esta dissertação teve como objetivo o desenvolvimento de um dispositivo microfluídico para a determinação de nutrientes em solo. A motivação para o desenvolvimento de uma plataforma microfluídica dedicada à agricultura vem do crescimento populacional, que chegará em 2030 a 8,5 bilhões de pessoas, ante 7,3 bilhões atuais. Com um crescimento tão expressivo da população mundial o fornecimento de alimentos torna-se vital. A agricultura desempenha um papel notável no fornecimento de alimentos e na economia brasileira. O monitoramento de nutrientes no solo para uma boa produção é indispensável. O desenvolvimento de dispositivos microfluídicos vêm tomando destaque na área industrial, alimentar, ambiental e criminal, devido a sua portabilidade, baixo peso, custo de fabricação e consumo de reagentes. Com uma aplicação de amostra de 50 µL no centro do dispositivo microfluídico, o líquido percola o interior do dispositivo por capilaridade até as zonas reacionais, onde estão depositados pequenos volumes de reagente. Após a amostra reagir na zona reacional, uma alteração visual da cor é observada e esta pode ser utilizada para quantificar a espécie de interesse. Dentre os extratores utilizados, a água não é um bom extrator para os analitos aqui trabalhados. A curva analítica de borato e cobalto apresentaram resultados promissores tanto em solução aquosa quanto em ácido cítrico 2%. O emprego de solução de ácido cítrico 2% para construção da curva analítica e extração de ferro e cobre do solo é um reagente eficiente se comparado a água e citrato neutro de amônio. Para o fosfato, o emprego de soluções de água ou citrato neutro de amônio podem ser empregados. A construção de testes para quantificação de nitrito, nitrato e zinco apresentaram problemas de reprodutibilidade. As reações colorimétricas apresentaram resultados promissores para aplicação em dispositivos microfluídicos a base papel. A associação entre reações colorimétricas simples e dispositivos microfluídicos possibilitou o desenvolvimento de testes químicos para serem empregados na agricultura. Os dados gerados podem ser utilizados na modelação da distribuição de nutrientes no terreno em estudo e posterior correção visando benefícios à agricultura. / This dissertation aimed at the development of a microfluidic device for the determination of nutrients in soil. The motivation for the development of a microfluidic platform dedicated to agriculture comes from population growth, which in 2030 will reach 8.5 billion people, compared to 7.3 billion today. With such a significant growth of the world population, food supply becomes vital. Agriculture plays a notable role in food supply and in the Brazilian economy. The monitoring of nutrients in the soil for good production is indispensable. The development of microfluidic devices has been highlighted in the industrial, food, environmental and criminal areas, due to their portability, low weight, manufacturing cost and reagent consumption. With a 50 ?L sample application in the center of the microfluidic device, the liquid percolates the interior of the device by capillarity to the reaction zones where small volumes of reagent are deposited. After the sample reacts in the reaction zone, a visual color change is observed and this can be used to quantify the species of interest. Among the extractors used, water is not a good extractor for the analytes used here. The analytical curve of borate and cobalt presented promising results in both aqueous solution and 2% citric acid. The use of 2% citric acid solution for the construction of the analytical curve and extraction of iron and copper from the soil is an efficient reagent when compared to water and neutral ammonium citrate. For phosphate, the use of water solutions or neutral ammonium citrate may be employed. The construction of tests for quantification of nitrite, nitrate and zinc presented problems of reproducibility. The colorimetric reactions presented promising results for application in paper - based microfluidic devices. The association between simple colorimetric reactions and microfluidic devices allowed the development of chemical tests to be used in agriculture. The data generated can be used in the modeling of nutrient distribution in the field under study and later correction aiming at benefits to agriculture.

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A dual functional chromogenic calix[4]arene, which contains both hydroxy azophenols and triazoles for colorimetric sensing and cationic recognition, respectively, has been synthesized. This system was further functionalized with dimethallylsilane to permit grafting to a glass surface. This grafting may be used to produce a surface modified glass slides that act as reusable ion-selective colorimetric sensors. UV/Vis spectral studies revealed that this compound is capable of binding the calcium cation in aqueous media and producing an easily detectable color change. The same is true for the modified surface setup. For the free receptor in acetonitrile solution, the absorption maximum undergoes a red shift from 390 nm to 496 nm upon exposure to calcium cations. In the case of the modified surface, exposure to acetonitrile solution of calcium perchlorate leads to a change in color from orange to red. Washing with acetone serves to remove the metal cations from the calix[4]arene-functionalized glass and restore the original orange color. The system is then ready for reuse. Specifically, following treatment with acetone, the glass may be submerged in a metal solution once again. In the case of exposure to calcium salts, this re-exposure results in a color change analogous to what was seen for a pristine system. In accord with design expectations, this process may be repeated several times. On the basis of this reproducibility, we think this system meets the reusability requirements necessary for the development of a practical sensor device. / text

Thesis (M.S.)--Rochester Institute of Technology, 1993. / Typescript. Includes bibliographical references (leaves 69-71).

Thesis (M.S.)--Rochester Institute of Technology, 1992. / Typescript. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 50-62). Also available on the World Wide Web.

The thesis presents the development of polymer based electrospun nanofibers as diagnostic probes for the selective detection of toxic metal ions in water. Through modification of the chemical characteristics of nanofibers by pre- and post-electrospinning treatments, three different diagnostic probes were successfully developed. These were the fluorescent pyridylazo-2-naphthol-poly(acrylic acid) nanofiber probe, the colorimetric probe based on glutathione-stabilized silver/copper alloy nanoparticles and the colorimetric probe based on 2-(2’-Pyridyl)-imidazole functionalized nanofibers. The probes were characterized by Fourier transform infrared spectroscopy (FTIR), Energy dispersive x-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The fluorescent nanofiber probe was developed towards the determination of Ni²⁺. Covalently functionalized pyridylazo-2-naphthol-poly(acrylic acid) polymeric nanofibers were employed. The solid state Ni²⁺ probe exhibited a good correlation between the fluorescence intensity and nickel concentration up to 1.0 mg/mL based on the Stern-Volmer mechanism. The detection limit of the nanofiber probe was found to be 0.07 ng/mL. The versatility of the fluorescent probe was demonstrated by affording a simple, rapid and selective detection of Ni²⁺ in the presence of other competing metal ions by direct analysis without employing any sample handling steps. For the second part of the study, a simple strategy based on the in-situ synthesis of the glutathione stabilized silver/copper alloy nanoparticles (Ag/Cu alloy NPs) in nylon 6 provided a fast procedure for fabricating a colorimetric probe for the detection of Ni²⁺ in water samples. The electrospun nanofiber composites responded to Ni²⁺ ions but did not suffer any interference from the other metal ions. The effect of Ni²⁺ concentration on the nanocomposite fibers was considered and the “eye-ball” limit of detection was found to be 5.8 μg/mL. Lastly, the third probe was developed by covalently linking an imidazole derivative; 2-(2′-Pyridyl)-imidazole (PIMH) to Poly(vinylbenzyl chloride) (PVBC) and nylon 6 nanofibers by post-electrospinning treatments using a wet chemical method and graft copolymerization technique, respectively. The post-electrospinning modifications of the nanofibers were achieved without altering their fibrous morphology. The color change to red-orange in the presence of Fe²⁺ for both the grafted nylon 6 (white) and the chemically modified PVBC (yellow) nanofibers was instantaneous. The developed diagnostic probes exhibited the desired selectivity towards the targeted metal ions.

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