This thesis presented the study of carbon-based materials for ultra-sensitive molecular sensing. Reduced Graphene Oxide (rGO), a 2-dimensional one-atomic layer thick carbon material, had the advantage of low-cost, aqueous and industrial-scalable production route. Using rGO as the transducer platform could potentially lower the cost of sensors down to a few dollars per chip. However, there were still limitations in rGO that prevented its widespread usage as a biosensor transducer or in electronics: its low electrical conductivity and large electrical deviations. This thesis was structured to understand and solve these problems for transducer application. The thesis could be broken down into 3 parts: The first part of the thesis presented the critical review of the background and limitations of graphene research, followed by the background and importance of biosensor developments for the detection of sweat sodium ions and circulatory Interleukin-6 proteins. The second part of the thesis tested the hypothesis that the rGO limitations could be eliminated to create a highly sensitive biosensor transducer via (A) improving rGO synthesis (B) pristine Carbon Nanotubes-rGO hybrid film and (C) growth of rGO. The mechanism of ultra-large graphene oxide synthesis and graphene oxide growth was also elucidated in this section. The third part of the thesis then presented the fabrication and test of the practical and homogenous carbon-based biosensor using the transducer synthesized earlier. The thesis showed that through proving the hypothesis correct, it enabled the synthesis of an all organic sodium ion sensor with integrated pump and an ultra-sensitive interleukin-6 bio-sensor. Both of these novel sensors were able to detect the respective molecules in their physiological ranges.

Orientador: Ana Flávia Nogueira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T15:49:22Z (GMT). No. of bitstreams: 1 SakerNeto_Nicolau_M.pdf: 15094468 bytes, checksum: d3c20b6e7dbd840a984fe7d8b1b365a8 (MD5) Previous issue date: 2014 / Resumo: Entre as alternativas promissoras para a produção de energia elétrica de modo econômico e ambientalmente sustentável está o aproveitamento da energia luminosa do Sol pelo efeito fotovoltaico. Células fotovoltaicas orgânicas fazem parte da mais nova geração de células solares, e prometem ser produzidas em larga escala a custo reduzido. Entretanto, células orgânicas atualmente estão limitadas por eficiências comparativamente baixas. O objetivo deste trabalho é introduzir derivados de grafeno em células solares orgânicas poliméricas como aceitador de elétrons e transportadores de cargas na camada absorvedora de luz, em substituição parcial ou total aos atuais materiais mais empregados, derivados de fulerenos C60 e C70. Óxido de grafeno (GO) foi obtido a partir da oxidação de grafite mineral utilizando-se o método de Hummers com modificações. Amostras de grafenos quimicamente modificados (CMGs) foram sintetizadas pela reação direta de dispersões de óxido de grafeno com ácido 2-tiofenoacético (TAA) por uma esterificação de Steglich, ou após um tratamento de óxido de grafeno em meio básico com hidróxido de tetrabutilamônio (TBAH). Os CMGs apresentaram funcionalização bastante limitada, tendo ocorrido principalmente uma desoxigenação dos derivados de grafeno. Ainda assim, os CMGs puderam ser dispersos no solvente usado para a preparação da camada absorvedora de luz, 1,2-diclorobenzeno. Os materiais sintetizados foram aplicados em células poliméricas baseadas no polímero poli(3-hexiltiofeno) (P3HT) e no derivado de fulereno [6,6]-fenil-C71-butanoato de metila (PC71BM), e os parâmetros fotovoltaicos resultantes foram obtidos. As eficiências de conversão fotovoltaicas em células contendo CMGs foram potencialmente limitadas pelo processo de desoxigenação / Abstract: Among the promising alternatives for the economically and environmentally sustainable production of electrical energy is the harnessing of the Sun's luminous energy by the photovoltaic effect. Organic photovoltaic cells are part of the newest generation of solar cells, promising large-scale production at reduced costs. However, organic cells are currently limited by comparatively low efficiencies. The objective of this work is to introduce graphene derivatives in polymer organic solar cells as electron acceptors and charge transporters in the light-absorbing layer, partially or fully replacing the currently most used materials, derivatives of C60 and C70 fullerenes. Graphene oxide (GO) was obtained by the oxidation of mineral graphite using a modified Hummers' method. Samples of chemically modified graphenes (CMGs) were synthesized by the direct reaction of graphene oxide dispersions with 2-thiopheneacetic acid (TAA) via Steglich esterification, or after treatment of graphene oxide in basic medium with tetrabutylammonium hydroxide (TBAH). The CMGs showed very limited functionalization and the main occurrence was a deoxygenation of the graphene derivatives. Still, the CMGs were dispersible in the solvent used for the preparation of the light-absorbing layer, 1,2-dichlorobenzene. The synthesized materials were applied in polymer cells based on the polymer poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C71-butyl methyl ester (PC71BM) and the resulting photovoltaic parameters were obtained. The photovoltaic conversion efficiencies for cells containing CMGs were potentially limited by the deoxygenation process / Mestrado / Quimica Organica / Mestre em Química