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Please use this identifier to cite or link to this item: http://hdl.handle.net/10204/4935

Title: Heterogeneous electron transfer kinetics and electrocatalytic behaviour of mixed self-assembled ferrocenes and SWCNT layers
Authors: Nkosi, D
Pillay, J
Ozoemena, KI
Nouneh, K
Oyama, M
Keywords: Transfer kinetics
Electron transfer kinetics
Self-assembled monolayers
Single walled carbon nanotubes
Electrocatalytic behaviour
Self-assembled ferrocenes
Chemistry chemical
Chemistry chemical physics,
Issue Date: Jan-2010
Publisher: The Royal Society of Chemistry
Citation: Nkosi, D, Pillay, J, Ozoemena, KI et al. 2010. Heterogeneous electron transfer kinetics and electrocatalytic behaviour of mixed self-assembled ferrocenes and SWCNT layers. Physical Chemistry Chemical Physics, Vol. 129(3), pp 604-613
Series/Report no.: Workflow request;6125
Abstract: 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)(6)](4-)/[Fe(CN)(6)](3-)) was explored. The electron transfer rate constants in both media essentially decreased as Au-Cys-FMCA > Au-Cys-SWCNT/FDCA > Au-Cys-FDCA > 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(-)) 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(-), possibly due to the repulsive interactions between the negatively charged SCN(-) 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.
Description: Copyright: 2010 the Owner Societies
URI: http://www.ncbi.nlm.nih.gov/pubmed/20066346
ISSN: 1463-9076
Appears in Collections:National Centre for nano-structured materials
General science, engineering & technology

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