Thesis (Ph. D.)--Ohio State University, 2002. / Title from first page of PDF file. Document formatted into pages; contains xxv, 213 p.: ill. Includes abstract and vita. Advisor: Richard T. Sayre, Dept. of Plant Biology. Includes bibliographical references (p. 1887-213).

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Made available in DSpace on 2018-06-27T18:56:13Z (GMT). No. of bitstreams: 3 Rochele Cristine Aymay Bevilaqua.pdf: 4584354 bytes, checksum: 395258de907af3f78f22cdd57483ea53 (MD5) Rochele Cristine Aymay Bevilaqua.pdf.txt: 183116 bytes, checksum: 85dded0e1a86682707a6ccf16e494abd (MD5) Rochele Cristine Aymay Bevilaqua.pdf.jpg: 3219 bytes, checksum: b175371ca0df47f8e821438052396b10 (MD5) Previous issue date: 2010-08-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work, we study nanostructures through first principles calculations based on the Density Functional Theory to use as gas sensors. At first, the proposal is based on the study of carbon nanotubes filled with iron oxides, particularly hematite and magnetite, for interaction with O2, N2 and CO2. Based on the analysis of electronic properties of semiconductors tubes with different diameters SWNT (8,0), (10,0) e (13,0) is verified that gases cause changes in al cases, making them as potential candidates to detect gases on the environment. In addition to these carbon-based nanostructures to serve as nanosensores, a second proposal was raised: the use of biomolecules as gas sensor. We chose the chlorophyll a and pheophytin a (a derivative without a magnesium atom in its structure) as an economically favorable alternative due to its low cost and easy to obtain. In fact, these pigments proved to be good sensor devices because the modest binding energy (-0.20 eV to -0.13 eV chlorophyll a to pheophytin a) that indicate a physical interaction with the gases O2, N2 and CO2. So it s possible to say that we can use both of systems carbon nanotubos filled iron oxides and chlorophyll a and its derivative as filters or gas sensors since the removal of gases from these nanostructures can occur easily making them reusable. / Nesta dissertação, estudaram-se nanoestruturas para sensoriamento de gases por meio de cálculos de primeiros princípios baseados na Teoria do Funcional da Densidade. Primeiramente, a proposta se baseia no estudo de nanotubos de carbono preenchidos com óxidos de ferro, em particular a hematita e a magnetita, para interação com O2, N2 e CO2. Em todos os sistemas estudados utilizaram-se tubos semicondutores de diferentes diâmetros. Através da análise de propriedades eletrônicas, verificou-se que os gases ocasionam alterações nos nanotubos de carbono, tornado-os potenciais candidatos para detecção de gases no meio ambiente. Além dessas nanoestruturas baseadas em carbono para servir como nanosensores, uma segunda proposta foi levantada: a utilização de biomoléculas. Optou-se, então, pelo uso de porfirinas, em especial pela clorofila a e a feofitina a, como uma alternativa economicamente favorável devido ao seu baixo custo e fácil obtenção. De fato, esses pigmentos apresentaram-se como bons dispositivos sensores em razão das energias de ligação (-0,20 eV para a clorofila a e -0,13 eV para a feofitina a) que indicam uma interação física com os gases O2, N2 e CO2. Portanto, os resultados obtidos sugerem que essas nanoestruturas nanotubos de carbono preenchidos com óxidos de ferro e a clorofila a e seu derivado podem ser utilizadas como nanosensores efetivos de gases uma vez que a detecção dessas moléculas pode ser facilmente efetuada sem prejudicar a reutilização desses sistemas.

Nutritional factors with antioxidant properties, such as those contained in edible algae or green plants, might be implicated in protection against cancer development. Chlorophyll and other tetrapyrrolic compounds, structurally related to heme and antioxidant bile pigment bilirubin, belong to important candidate molecules, which might be responsible for these effects. Based on our studies demonstrating antiproliferative effects of S. platensis edible alga extract on experimental model of human pancreatic adenocarcinoma we investigated in detail the effect of chlorophyll occurring abundantly in this alga. Since only scarce data exist on the antiproliferative effects of chlorophylls, the aim of our study was to assess these effects. The study was performed on experimental models of human pancreatic and prostate cancer. The inhibitory effects of chlorophylls (chlorophyll a, chlorophyll b, chlorophyllin and pheophytin a) on cell proliferation and cell viability were investigated in in vitro studies. Chlorophylls reduced the mRNA expression as well as activity of hemeoxygenase in tested pancreatic cancer cells. Simultaneously, chlorophylls played an important role in redox environment of studied cancer cell lines including modulation of mitochondrial membrane potential, reactive oxygen species (ROS)...

A new rising star in the carbon nanomaterial family is carbon dots. Carbon dots have received great attention due to their excellent luminescence and low toxicity. In this project, a new carbon dot derived from birch leaves is studied and characterized. The birch leaf carbon dot (BL-CD) exhibits narrow red photoluminescence (peak = 670 nm, full width at half maximum = 23 nm) with a photoluminescence quantum yield of 26% in dilute methanol solution.  The presence of the characteristic peaks of the pigment pheophytin-a in the absorption spectrum and the photoluminescence spectrum of the BL-CD and the absence of a crystal structure together with the narrow and excitation-independent photoluminescence indicate a carbon dot with a non-emissive amorphous structure with emissive molecular sites consisting of the pigment. The photoluminescence quenching of the BL-CDs in solid-state is reduced by the introduction of a hostmaterial. The use of a host enabled the employment of BL-CDs as the emitter in a light-emitting electrochemical cell (LEC). This project paves the way for further development of the environmentally friendly and sustainable BL-CD LEC.