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Doctoral Thesis
DOI
https://doi.org/10.11606/T.88.2010.tde-23032010-105054
Document
Author
Full name
José Roberto Siqueira Junior
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2010
Supervisor
Committee
Oliveira Junior, Osvaldo Novais de (President)
Bianchi, Rodrigo Fernando
Fonseca, Fernando Josepetti
Graeff, Carlos Frederico de Oliveira
Scalvi, Luis Vicente de Andrade
Title in Portuguese
Filmes automontados de nanotubos de carbono aplicados em sensores
Keywords in Portuguese
Dispositivos de efeito de campo
Filmes automontados
Nanotubos de carbono
Sensores
Abstract in Portuguese
Nanotubos de carbono (CNTs) têm se mostrado versáteis para melhorar propriedades de outros materiais. A integração de CNTs com materiais biológicos, por exemplo, permite obter biossensores com propriedades e sensibilidade otimizadas. Com a manipulação de CNTs em filmes nanoestruturados, pode-se formar nanocompósitos híbridos, cuja interação sinérgica requer métodos experimentais com controle da arquitetura molecular. Neste estudo, utilizamos a técnica de automontagem para obter dois tipos de sensores incorporando CNTs. No primeiro, filmes automontados de CNTs de parede múltiplas (MWNTs) dispersos em poliamidoamina (PAMAM) e alternados com ftalocianina tetrassulfonada de níquel (NiTsPc) foram usados como sensores amperométricos para detectar o neurotransmissor dopamina. As propriedades eletroquímicas obtidas com voltametria cíclica indicaram que a incorporação de MWNTs no filme PAMAM-NT/NiTsPc eleva a corrente de pico redox em três vezes e diminui em 50 mV o potencial de oxidação da dopamina. Isso permitiu detectar dopamina na presença de um interferente típico, o ácido ascórbico. Os sensores apresentaram limite de detecção de 0,5 mol L-1 e alta estabilidade. No segundo, filmes nanoestruturados de PAMAM com nanotubos de carbono de parede única (SWNTs), funcionalizados com grupos carboxílicos, foram fabricados sobre dispositivos de efeito de campo do tipo electrolyte-insulator-semiconductor (EIS) e light-addressable potentiometric sensors (LAPS). Estes dispositivos modificados foram usados em biossensores de penicilina G, após imobilização da enzima penicilinase. A morfologia do filme PAMAM/SWNT era típica de uma estrutura porosa, com grande área superficial, apropriada para adsorção da enzima e facilitar a penetração de íons H+ no filme. Esses biossensores exibiram alta sensibilidade ao pH de 55-58 mV/pH e propriedades melhoradas para a detecção de penicilina G, com sensibilidade de 100 mV/década e melhor desempenho com menor tempo de resposta e sinal mais estável.
Title in English
Layer-by-Layer assembly of carbon nanotubes applied in sensing
Keywords in English
Carbon nanotubes
Field-effect devices
Layer-by-Layer films
Sensors
Abstract in English
Carbon nanotubes (CNTs) are versatile in enhancing the properties of other materials. They can be integrated with biological materials, for instance, in the fabrication of biosensors with optimized sensitivity and performance. With manipulation of CNTs in nanostructured films, one may form hybrid nanocomposites whose synergistic interaction requires experimental methods with control of molecular architecture. In this study, we used the layer-by-layer (LbL) technique to obtain two types of sensors incorporating CNTs. In the first, LbL films of multi-walled carbon nanotubes (MWNTs) dispersed in polyamidoamine (PAMAM) dendrimers and alternated with nickel phthalocyanine (NiTsPc) layers were used in the amperometric detection of the neutransmitter dopamine. The electrochemical properties obtained with cyclic voltammetry indicated that the incorporation of MWNTs in the PAMAM-NT/NiTsPc led to a 3-fold increase in the peak current, in addition to a decrease of 50 mV in the oxidation potential of dopamine. The latter permitted the detection of dopamine even in the presence of a typical interferent, the ascorbic acid. These sensors exhibited a limit of detection of ca. 0.5 mol L-1 and high stability. In the second type, LbL films of PAMAM and single-walled carbon nanotubes (SWNTs), functionalized with carboxylic groups, were deposited on field-effect devices, using electrolyte-insulator-semiconductor (EIS) and light-addressable potentiometric sensors (LAPS). These modified devices were employed as biosensors to detect penicillin G, after immobilizing the enzyme penicillinase. The PAMAM/SWNT film exhibited a highly porous morphology with large surface area, being suitable for enzyme adsorption, in addition to facilitating the penetration of H+ ions through the film. Such biosensors had a high pH sensitivity of ca. 55-58 mV/pH and improved properties toward penicillin G, with sensitivity of 100 mV/decade and enhanced performance, with faster response time and higher stability.
 
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Publishing Date
2010-03-24
 
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