PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS

Detalhes bibliográficos
Autor(a) principal: Mossanha, Rosana
Data de Publicação: 2011
Tipo de documento: Dissertação
Idioma: por
Título da fonte: Biblioteca Digital de Teses e Dissertações da UEPG
Texto Completo: http://tede2.uepg.br/jspui/handle/prefix/2093
Resumo: In this work were studied investigated different types of modifiers for the formation of self-assembled monolayers on the gold surface. The monolayers used were formed by different structural arrangements, alkyl chains and functional groups. The thiols groups used were: 3-mercaptopropionic acid (MPA), thiolactic acid (TLA), cystamine (CYS) and 11-mercaptoundecanoic acid. The electroactivity of films of different thiols was assessed by the probe molecule, Fe(CN)63-/4-. It was possible to observe through the cyclic voltammetry technique, the formation and organization of the films, monitoring the behavior of the redox couple. The voltammograms showed a decrease in the faradaic current response with the increase of immersion time of the gold substrate in ethanolic solution of thiols, suggesting that the process of electron transfer occurs through the pinholes of the electrodes surface and tunneling. The monolayers of 3-mercaptopropionic acid (MPA) and thiolactic acid (TLA) had a better coating of the surface in immersion time of 3 hours. While the 11-mercaptopropionic acid (MUA) and cystamine (CYS) needed more time to organize the monolayer, 24 hours, because the MUA is a long chain molecule and CYS because the cleavage of S-S. The size of thiol chain influenced the surface organization, short-chain thiols tend to form monolayers with a considerable amount of defects, leading to a lower coating on the electrode surface. Indeed, the MUA that contains a high number of carbons in the chain showed a higher surface coverage, which caused loss of voltammetric response. The electrode surface roughness and the active area, calculated by the voltammetric data, showed a decrease with the formation of the monolayers on gold surface. Aiming to estimate the amount of molecules immobilized on the surface, it was calculated the superficial excess ) by voltammetric charge obtained from the reductive desorption. The obtained values were of 1.88x10-10 for Au-CYS, 5.03x10-10 to Au-MPA, 1.06x10-8 for Au-MUA and 1.35x10-10 mol.cm-2 for the Au-TLA, demonstrating an almost complete coverage of active sites on the surface. By the electrochemical impedance spectroscopy technique, it was possible to determine the kinetic parameters of the SAMs, which were consistent with those obtained by cyclic voltammetry. Analyzing the performance of sensors for dopamine determination through the VC, it was found that the SAM formed by TLA presented the most satisfactory results regarding the sensitivity and selectivity compared to the analyte DA. Studies at different scan rates for the electrodes, Au-MPA, Au-TLA and Au-CYS in the presence of the analite showed that the anodic peak current linearly increases with the square root of scan rate, indicating that the electron transfer process is controlled by diffusion of species to the electrode surface. Dopamine was quantified by CV and SWV technique, in the linear range from 1.1 to 6.6x10-7 mol L-1 with detection limits of 1,42x10-7 mol L-1 and 4,77x10-8 mol L-1, respectively. Using the technique of VOQ, TLA-Au electrode was able to distinguish between AA and DA, when present in the same solution, with a potential difference of approximately 340 mV.
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spelling Pessoa, Christiana AndradeCPF:02089192445http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4792376U2Rodrigues, Paulo Rogério PintoCPF:49965905991http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4701775U3Galli, AndressaCPF:03215352940http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4772370Y8CPF:03918322980http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4425001Z8Mossanha, Rosana2017-07-24T19:38:05Z2011-06-032017-07-24T19:38:05Z2011-03-03MOSSANHA, Rosana. PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS. 2011. 160 f. Dissertação (Mestrado em Química) - UNIVERSIDADE ESTADUAL DE PONTA GROSSA, Ponta Grossa, 2011.http://tede2.uepg.br/jspui/handle/prefix/2093In this work were studied investigated different types of modifiers for the formation of self-assembled monolayers on the gold surface. The monolayers used were formed by different structural arrangements, alkyl chains and functional groups. The thiols groups used were: 3-mercaptopropionic acid (MPA), thiolactic acid (TLA), cystamine (CYS) and 11-mercaptoundecanoic acid. The electroactivity of films of different thiols was assessed by the probe molecule, Fe(CN)63-/4-. It was possible to observe through the cyclic voltammetry technique, the formation and organization of the films, monitoring the behavior of the redox couple. The voltammograms showed a decrease in the faradaic current response with the increase of immersion time of the gold substrate in ethanolic solution of thiols, suggesting that the process of electron transfer occurs through the pinholes of the electrodes surface and tunneling. The monolayers of 3-mercaptopropionic acid (MPA) and thiolactic acid (TLA) had a better coating of the surface in immersion time of 3 hours. While the 11-mercaptopropionic acid (MUA) and cystamine (CYS) needed more time to organize the monolayer, 24 hours, because the MUA is a long chain molecule and CYS because the cleavage of S-S. The size of thiol chain influenced the surface organization, short-chain thiols tend to form monolayers with a considerable amount of defects, leading to a lower coating on the electrode surface. Indeed, the MUA that contains a high number of carbons in the chain showed a higher surface coverage, which caused loss of voltammetric response. The electrode surface roughness and the active area, calculated by the voltammetric data, showed a decrease with the formation of the monolayers on gold surface. Aiming to estimate the amount of molecules immobilized on the surface, it was calculated the superficial excess ) by voltammetric charge obtained from the reductive desorption. The obtained values were of 1.88x10-10 for Au-CYS, 5.03x10-10 to Au-MPA, 1.06x10-8 for Au-MUA and 1.35x10-10 mol.cm-2 for the Au-TLA, demonstrating an almost complete coverage of active sites on the surface. By the electrochemical impedance spectroscopy technique, it was possible to determine the kinetic parameters of the SAMs, which were consistent with those obtained by cyclic voltammetry. Analyzing the performance of sensors for dopamine determination through the VC, it was found that the SAM formed by TLA presented the most satisfactory results regarding the sensitivity and selectivity compared to the analyte DA. Studies at different scan rates for the electrodes, Au-MPA, Au-TLA and Au-CYS in the presence of the analite showed that the anodic peak current linearly increases with the square root of scan rate, indicating that the electron transfer process is controlled by diffusion of species to the electrode surface. Dopamine was quantified by CV and SWV technique, in the linear range from 1.1 to 6.6x10-7 mol L-1 with detection limits of 1,42x10-7 mol L-1 and 4,77x10-8 mol L-1, respectively. Using the technique of VOQ, TLA-Au electrode was able to distinguish between AA and DA, when present in the same solution, with a potential difference of approximately 340 mV.Neste trabalho foram investigados diferentes tipos de modificadores para a formação de monocamadas auto-organizadas sobre a superfície do ouro. As monocamadas utilizadas foram formadas por diferentes arranjos estruturais, tamanho da cadeia carbônica e grupos funcionais. Os tióis utilizados foram: ácido 3- mercaptopropiônico (MPA), ácido tioláctico (TLA), cistamina (CYS) e o ácido 11-mercaptoundecanóico. A eletroatividade dos filmes dos diferentes tióis foi avaliada pela molécula sonda, Fe(CN)6]3-/4-. Foi possível constatar através da técnica de voltametria cíclica, a formação e a organização dos filmes, monitorando o comportamento do par redox. Os voltamogramas mostraram um decréscimo nas respostas da corrente faradaica com o aumento do tempo de imersão do substrato ouro na solução etanólica dos tióis, sugerindo que o processo de transferência de elétrons ocorre através dos pinholes da superfície e por tunelamento. Os eletrodos com as monocamadas de ácido 3-mercaptopropiônico (MPA) e o ácido tioláctico (TLA) obtiveram melhor recobrimento da superfície no tempo de imersão de 3 horas. Enquanto que o ácido 11-mercaptopropiônico (MUA) e a cistamina (CYS) necessitaram de maior tempo de imersão para organização da monocamada, de 24 horas, devido o MUA ser uma molécula de cadeia longa e a CYS devido a quebra da ligação S-S. O tamanho da cadeia do tiol influenciou no empacotamento da superfície, tióis de cadeia curtas tendem a formar monocamadas com uma quantidade de defeitos considerável, levando ao um menor recobrimento na superfície eletródica. O MUA que contém um número elevado de carbonos na cadeia apresentou um maior recobrimento da superfície, o que ocasionou perda da resposta voltamétrica. A rugosidade e a área ativa dos diferentes eletrodos, calculadas a partir dos voltamogramas, diminuíram com a formação das monocamadas sobre a superfície do ouro. Com o objetivo de estimar a quantidade de moléculas imobilizadas sobre a superfície, foram calculados os excessos superficiais por meio da carga voltamétrica obtida da dessorção redutiva. Os valores obtidos foram de = 1,88x10-10 para Au-CYS, 5,03x10-10 para Au-MPA, 1,06x10-8 para Au-MUA e 1,35x10-10 mol.cm-2 para o Au-TLA, demonstrando uma cobertura quase completa dos sítios ativos da superfície. Pela técnica de espectroscopia de impedância eletroquímica foi possível determinar os parâmetros cinéticos das SAMs, os quais foram consistentes com os obtidos pelos voltamogramas cíclicos. Analisando o desempenho dos sensores para a determinação de dopamina (DA) através da VC, verificou que a SAM formada pelo TLA foi a que apresentou resultados mais satisfatórios quanto a sensibilidade e seletividade em relação a este analito. Estudos em diferentes velocidades de varredura para os eletrodos Au-MPA, Au-TLA e Au-CYS na presença do analito mostraram que a corrente de pico anódica aumenta linearmente com a raiz quadrada da velocidade de varredura, indicando que o processo de transferência de elétrons é controlado pela difusão das espécies à superfície do eletrodo. A dopamina foi quantificada pela técnica de VC e VOQ, na faixa linear de 1,1 a 6,6x10-7 mol L-1 com limites de detecção de 1,42x10-7 mol L-1e 4,77x10-8 mol L-1, respectivamente. Utilizando-se a técnica de VOQ, o eletrodo Au-TLA foi capaz de distinguir o ácido ascórbico (AA) e DA quando presentes na mesma solução, com uma diferença de potencial de aproximadamente 340 mV.Made available in DSpace on 2017-07-24T19:38:05Z (GMT). No. of bitstreams: 1 Rosana Mossanha.pdf: 1591695 bytes, checksum: aac2e3d256b391dd0e8f113bb72eb620 (MD5) Previous issue date: 2011-03-03application/pdfporUNIVERSIDADE ESTADUAL DE PONTA GROSSAPrograma de Pós-Graduação em Química AplicadaUEPGBRQuímicamonocamadas auto-organizadaseletrodo de ourotióisdopaminaself-assembled monolayersgold electrodethiolsdopamineCNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICAPREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADASinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisinfo:eu-repo/semantics/openAccessreponame:Biblioteca Digital de Teses e Dissertações da UEPGinstname:Universidade Estadual de Ponta Grossa (UEPG)instacron:UEPGORIGINALRosana Mossanha.pdfapplication/pdf1591695http://tede2.uepg.br/jspui/bitstream/prefix/2093/1/Rosana%20Mossanha.pdfaac2e3d256b391dd0e8f113bb72eb620MD51prefix/20932017-07-24 16:38:05.241oai:tede2.uepg.br:prefix/2093Biblioteca Digital de Teses e Dissertaçõeshttps://tede2.uepg.br/jspui/PUBhttp://tede2.uepg.br/oai/requestbicen@uepg.br||mv_fidelis@yahoo.com.bropendoar:2017-07-24T19:38:05Biblioteca Digital de Teses e Dissertações da UEPG - Universidade Estadual de Ponta Grossa (UEPG)false
dc.title.por.fl_str_mv PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
title PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
spellingShingle PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
Mossanha, Rosana
monocamadas auto-organizadas
eletrodo de ouro
tióis
dopamina
self-assembled monolayers
gold electrode
thiols
dopamine
CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
title_short PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
title_full PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
title_fullStr PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
title_full_unstemmed PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
title_sort PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS
author Mossanha, Rosana
author_facet Mossanha, Rosana
author_role author
dc.contributor.advisor1.fl_str_mv Pessoa, Christiana Andrade
dc.contributor.advisor1ID.fl_str_mv CPF:02089192445
dc.contributor.advisor1Lattes.fl_str_mv http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4792376U2
dc.contributor.referee1.fl_str_mv Rodrigues, Paulo Rogério Pinto
dc.contributor.referee1ID.fl_str_mv CPF:49965905991
dc.contributor.referee1Lattes.fl_str_mv http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4701775U3
dc.contributor.referee2.fl_str_mv Galli, Andressa
dc.contributor.referee2ID.fl_str_mv CPF:03215352940
dc.contributor.referee2Lattes.fl_str_mv http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4772370Y8
dc.contributor.authorID.fl_str_mv CPF:03918322980
dc.contributor.authorLattes.fl_str_mv http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4425001Z8
dc.contributor.author.fl_str_mv Mossanha, Rosana
contributor_str_mv Pessoa, Christiana Andrade
Rodrigues, Paulo Rogério Pinto
Galli, Andressa
dc.subject.por.fl_str_mv monocamadas auto-organizadas
eletrodo de ouro
tióis
dopamina
topic monocamadas auto-organizadas
eletrodo de ouro
tióis
dopamina
self-assembled monolayers
gold electrode
thiols
dopamine
CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
dc.subject.eng.fl_str_mv self-assembled monolayers
gold electrode
thiols
dopamine
dc.subject.cnpq.fl_str_mv CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
description In this work were studied investigated different types of modifiers for the formation of self-assembled monolayers on the gold surface. The monolayers used were formed by different structural arrangements, alkyl chains and functional groups. The thiols groups used were: 3-mercaptopropionic acid (MPA), thiolactic acid (TLA), cystamine (CYS) and 11-mercaptoundecanoic acid. The electroactivity of films of different thiols was assessed by the probe molecule, Fe(CN)63-/4-. It was possible to observe through the cyclic voltammetry technique, the formation and organization of the films, monitoring the behavior of the redox couple. The voltammograms showed a decrease in the faradaic current response with the increase of immersion time of the gold substrate in ethanolic solution of thiols, suggesting that the process of electron transfer occurs through the pinholes of the electrodes surface and tunneling. The monolayers of 3-mercaptopropionic acid (MPA) and thiolactic acid (TLA) had a better coating of the surface in immersion time of 3 hours. While the 11-mercaptopropionic acid (MUA) and cystamine (CYS) needed more time to organize the monolayer, 24 hours, because the MUA is a long chain molecule and CYS because the cleavage of S-S. The size of thiol chain influenced the surface organization, short-chain thiols tend to form monolayers with a considerable amount of defects, leading to a lower coating on the electrode surface. Indeed, the MUA that contains a high number of carbons in the chain showed a higher surface coverage, which caused loss of voltammetric response. The electrode surface roughness and the active area, calculated by the voltammetric data, showed a decrease with the formation of the monolayers on gold surface. Aiming to estimate the amount of molecules immobilized on the surface, it was calculated the superficial excess ) by voltammetric charge obtained from the reductive desorption. The obtained values were of 1.88x10-10 for Au-CYS, 5.03x10-10 to Au-MPA, 1.06x10-8 for Au-MUA and 1.35x10-10 mol.cm-2 for the Au-TLA, demonstrating an almost complete coverage of active sites on the surface. By the electrochemical impedance spectroscopy technique, it was possible to determine the kinetic parameters of the SAMs, which were consistent with those obtained by cyclic voltammetry. Analyzing the performance of sensors for dopamine determination through the VC, it was found that the SAM formed by TLA presented the most satisfactory results regarding the sensitivity and selectivity compared to the analyte DA. Studies at different scan rates for the electrodes, Au-MPA, Au-TLA and Au-CYS in the presence of the analite showed that the anodic peak current linearly increases with the square root of scan rate, indicating that the electron transfer process is controlled by diffusion of species to the electrode surface. Dopamine was quantified by CV and SWV technique, in the linear range from 1.1 to 6.6x10-7 mol L-1 with detection limits of 1,42x10-7 mol L-1 and 4,77x10-8 mol L-1, respectively. Using the technique of VOQ, TLA-Au electrode was able to distinguish between AA and DA, when present in the same solution, with a potential difference of approximately 340 mV.
publishDate 2011
dc.date.available.fl_str_mv 2011-06-03
2017-07-24T19:38:05Z
dc.date.issued.fl_str_mv 2011-03-03
dc.date.accessioned.fl_str_mv 2017-07-24T19:38:05Z
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/masterThesis
format masterThesis
status_str publishedVersion
dc.identifier.citation.fl_str_mv MOSSANHA, Rosana. PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS. 2011. 160 f. Dissertação (Mestrado em Química) - UNIVERSIDADE ESTADUAL DE PONTA GROSSA, Ponta Grossa, 2011.
dc.identifier.uri.fl_str_mv http://tede2.uepg.br/jspui/handle/prefix/2093
identifier_str_mv MOSSANHA, Rosana. PREPARAÇÃO, CARACTERIZAÇÃO E ESTUDOS ELETROQUÍMICOS DE ELETRODOS MODIFICADOS COM DIFERENTES MONOCAMADAS AUTOORGANIZADAS. 2011. 160 f. Dissertação (Mestrado em Química) - UNIVERSIDADE ESTADUAL DE PONTA GROSSA, Ponta Grossa, 2011.
url http://tede2.uepg.br/jspui/handle/prefix/2093
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dc.publisher.none.fl_str_mv UNIVERSIDADE ESTADUAL DE PONTA GROSSA
dc.publisher.program.fl_str_mv Programa de Pós-Graduação em Química Aplicada
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dc.publisher.country.fl_str_mv BR
dc.publisher.department.fl_str_mv Química
publisher.none.fl_str_mv UNIVERSIDADE ESTADUAL DE PONTA GROSSA
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