SIQUEIRA JUNIOR, J.R. Layer-by-Layer assembly of carbon nanotubes applied in sensing. 2009. 113 p. Tese (Doutorado) -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

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... ol 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 µmol 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. AA Ácido ascórbico AFM Microscopia de força atômica CC Fotocorrente constante CHEMFET Chemical field-effect transistor CNT Nanotubos de carbono ConCap Capacitância constante C/V Capacitância-voltagem DA Neurotransmissor dopamina EIS Electrolyte-insulator-semiconductor EIS-PE EIS modificado com filme LbL de PAMAM/PSS EIS-NT EIS modificado com filme LbL de PAMAM/SWNT EnFET Enzimatic field-effect transistor LbL Layer-by-layer MIS Metal-insulator-semiconductor capacitance MWNT Multi-walled carbon nanotubes NiTsPc Metaloftalocianina tetrassulfonada de níquel NTFET Nanotube-based field-effect transistor PAMAM Dendrímero poliamidoamina PAMAM-NT Complexo de MWNT disperso em solução de PAMAM PEN Enzima penicilinase PEx Técnicas de projeção multi-dimensional PSS Poliestireno sulfonado SWNT Single-walled carbon nanotubes UV-vis Espectroscopia de ultravioleta visível