Studies of electron transfer through self-assembled monolayers using impedance spectroscopy

Protsailo, Lesia; Fawcett, W. Ronald

doi:10.1016/s0013-4686(00)00420-5

Cited by 162 publications

(147 citation statements)

References 23 publications

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“…Previous recent studies in the literature using electrochemical impedance have concentrated on monitoring adsorption kinetics [16,18], characterization of defects and possibility of any electron transfer through the monolayer film [29,30]. Our results to be described below show that, under the formation conditions employed, there is no evidence of defects in the monolayer or electron transfer through it.…”

Section: Electrochemical Impedance Spectroscopymentioning

confidence: 54%

“…Figure 8c at 0.6 V shows a much slower decline of frequency after ca. 700 s as most of the monolayer has assembled and high-rate mass increase has turned to a slow transformation process of ordering [30]. It can be seen that the rate of change of crystal resonant frequency due to adsorption at 0.6 V is clearly higher than that at OCP and at 0.0 V applied potential.…”

Section: Electrochemical Quartz Crystal Microbalancementioning

confidence: 96%

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Studies on Self‐Assembled Alkanethiol Monolayers Formed at Applied Potential on Polycrystalline Gold Electrodes

et al. 2003

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1-Dodecanethiol assembly on polycrystalline gold electrodes at fixed positive potentials has been investigated by chronoamperometry and electrochemical quartz crystal microbalance and the films formed characterized by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that 1-dodecanethiol adsorption on gold is enhanced by application of positive potentials to the electrode surface and that adsorption proceeds faster than in the case of open circuit deposition. Compact defect-free monolayers of capacitance values of 1.1 ± 1.6 mF cm À2 are produced in time intervals as short as 100 s, with no roughness, as demonstrated for the first time by electrochemical impedance analysis. Control of surface potential during alkanethiol assembly appears to improve monolayer quality and to allow for shorter assembly periods. Monolayers can be removed by cycling in alkaline solution or in dilute sulfuric acid. These results are important for the fast construction of defect-free bilayers.

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Section: Electrochemical Impedance Spectroscopymentioning

confidence: 54%

Section: Electrochemical Quartz Crystal Microbalancementioning

confidence: 96%

Studies on Self‐Assembled Alkanethiol Monolayers Formed at Applied Potential on Polycrystalline Gold Electrodes

et al. 2003

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“…35,[38][39][40][41] To establish the HET kinetics in this acidic solution, EIS experiments were carried out for each of the modified electrode, as described by Creager and Wooster.…”

Section: Heterogeneous Electron Transfer Dynamics In 05 M H 2 So 4 Smentioning

confidence: 99%

Heterogeneous electron transfer kinetics and electrocatalytic behaviour of mixed self-assembled ferrocenes and SWCNT layers

Nkosi

Pillay

Ozoemena

et al. 2010

Phys. Chem. Chem. Phys.

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The electron transfer dynamics and electrocatalytic behaviour of ferrocene-terminated self-assembled monolayers (SAMs), co-adsorbed with single-walled carbon nanotubes (SWCNTs) on a gold electrode, have been interrogated for the first time. Ferrocene monocarboxylic acid (FMCA) or ferrocene dicarboxylic acid (FDCA) was covalently attached to the cysteamine (Cys) monolayer to form Au-Cys-FMCA and Au-Cys-FDCA, respectively. The same covalent attachment strategy was used to form the mixed SWCNTs and ferrocene-terminated layers (i.e. Au-Cys-SWCNT/FMCA and Au-Cys-SWCNT/FDCA). Using cyclic voltammetry and electrochemical impedance spectroscopy, the impact of neighbouring SWCNTs on the electron transfer dynamics of the ferrocene molecular assemblies in an acidic medium (0.5 M H 2 SO 4 ) and in a solution of an outer-sphere redox probe ([Fe(CN) ) was explored. The electron transfer rate constants in both media essentially decreased as Au-Cys-FMCA 4 Au-Cys-SWCNT/FDCA 4 Au-Cys-FDCA 4 Au-Cys-SWCNT/FMCA. This trend has been interpreted in terms of several factors such as the locations of the ferrocene species in a range of environments with a range of potentials, the proximity/interactions of the ferrocenes with one another, and electrostatic interaction or repulsion existing between the negatively-charged redox probe and the modified electrodes. The thiocyanate ion (SCN À ) was used as a model analyte to examine the influence of the neighbouring SWCNTs on the electrocatalytic ability of the ferrocene assemblies. The Au-Cys-SWCNT/FDCA showed the best catalytic activity (in terms of onset potential and catalytic peak current height) for the oxidation of SCN À , possibly due to the repulsive interactions between the negatively charged SCN À and high number of surface -COOH species at the SWCNT/FDCA. This study has provided some useful insights as to how CNTs co-assembled with ferrocene-terminated thiols could impact on the electron transfer kinetics as well as the electrocatalytic detection of the self-assembled ferrocene layers.

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“…Um emparelhamento perfeito entre os alcanotióis (geralmente com uma inclinação de 20 a 30 graus em relação à normal da superfície) e o retículo do ouro resulta numa estrutura altamente ordenada (Figura 2) e tem feito deste sistema objeto de um grande número de estudos por meios espectroscópicos, microscópicos e eletroquímicos 12 . Vári-os trabalhos têm sido dedicados ao entendimento da estrutura e do ordenamento das monocamadas, que são caracterizadas pelo alto grau de organização e têm sido empregadas em estudos de transferência de elétrons [34][35][36][37][38][39] , adsorção de proteínas 38,[40][41][42][43] e, principalmente, em vários campos da eletroanalítica 12,[19][20][21][22][44][45][46][47][48][49][50][51][52][53] . A preparação da monocamada possui um papel fundamental no desempenho eletroanalítico do eletrodo modificado.…”

Section: Introductionunclassified

Emprego de monocamadas auto-organizadas no desenvolvimento de sensores eletroquímicos

Freire¹,

Pessôa²,

Kubota³

2003

Quím. Nova

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Recebido em 18/7/02; aceito 9/10/02 SELF-ASSEMBLED MONOLAYERS APPLICATIONS FOR THE DEVELOPMENT OF ELECTROCHEMICAL SENSORS. Selfassembled monolayers (SAMs) modified electrodes exhibit unique behavior that can greatly benefit electrochemical sensing. This brief review highlights the applications of SAM modified electrodes in electroanalytical chemistry. After a general introduction, which includes the approaches for SAM development, different electrochemical systems for detecting inorganic and organic species are described and discussed. Special attention to the coupling of biological sensing element to the SAM is given, which can selectively recognize the analyte. Future prospects are also evaluated.Keywords: chemically modified electrodes; self-assembled monolayers; electrochemical sensors. INTRODUÇÃOO desenvolvimento de sensores eletroquímicos é uma das áreas de maior e mais rápido crescimento dentro da Química Analítica, principalmente devido aos novos desafios impostos por amostras de interesse industrial, clínico e ambiental, que têm levado a uma crescente busca por sensores com melhores características, tais como alta sensibilidade, seletividade e estabilidade [1][2][3][4][5][6][7][8] . Apesar da grande versatilidade e perspectivas apresentadas pelos sensores eletroquímicos, a utilidade de um eletrodo é muitas vezes limitada devido a uma passivação gradual de sua superfície, que é conseqüência principalmente da adsorção dos produtos da própria reação de óxido-redução utilizada na detecção, ou ainda, dos sub-produtos destas reações que podem se polimerizar e se depositar sobre a superfície dos eletrodos 6 . Além disso, a sensibilidade de muitos analitos importantes pode ser prejudicada em função da cinética de transferência de elétrons entre estes compostos e os materiais dos eletrodos ser excessivamente lenta 9 . Uma outra limitação é a dificuldade de discriminar entre compostos alvos que possuam características redox similares 9 . Uma área que oferece grande potencial para minimizar os problemas acima descritos, e conseqüentemente para aumentar a aplicabilidade e eficiência dos sensores eletroquímicos, é a que compreende os chamados eletrodos quimicamente modificados (EQM) 9,10 . A habilidade para controlar e manipular deliberadamente as propriedades das superfícies dos eletrodos pode proporcionar uma variedade de efeitos atrativos, levando a superfícies com características que podem contornar efetivamente muitos dos problemas apresentados pelos sensores eletroquímicos tradicionais.Estudos experimentais, suportados pela teoria, têm mostrado que a velocidade de transferência de elétrons pode ser sensivelmente afetada em função da modificação da superfície dos eletrodos 11. A classificação das reações do eletrodo pode ser feita com base no grau de interação entre os reagentes e a superfície do eletrodo, ocorrida durante o estado de transição da transferência de elétrons 12 . Os processos de transferência de elétrons onde as interações entre as espécies reagentes e a superfície do eletrodo são fracas e não es...

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Studies of electron transfer through self-assembled monolayers using impedance spectroscopy

Cited by 162 publications

References 23 publications

Studies on Self‐Assembled Alkanethiol Monolayers Formed at Applied Potential on Polycrystalline Gold Electrodes

Studies on Self‐Assembled Alkanethiol Monolayers Formed at Applied Potential on Polycrystalline Gold Electrodes

Heterogeneous electron transfer kinetics and electrocatalytic behaviour of mixed self-assembled ferrocenes and SWCNT layers

Emprego de monocamadas auto-organizadas no desenvolvimento de sensores eletroquímicos

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