The effects of the lengths and orientations of single-walled carbon nanotubes on the electrochemistry of nanotube-modified electrodes

Gooding, J. Justin; Chou, Alison; Liu, Jingquan; Lošić, Dušan; Shapter, Joseph G.; Hibbert, David Brynn

doi:10.1016/j.elecom.2007.03.023

Cited by 112 publications

(138 citation statements)

References 52 publications

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“…It has been suggested (24,25,41,49,50) that sidewalls are electrochemically inactive in CNTs and that only edge-plane-like sites and open oxygenated nanotube ends are active. Our work shows this earlier hypothesis is incorrect.…”

Section: Resultsmentioning

confidence: 99%

Quantitative nanoscale visualization of heterogeneous electron transfer rates in 2D carbon nanotube networks

Güell¹,

Ebejer²,

Snowden³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

113

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Carbon nanotubes have attracted considerable interest for electrochemical, electrocatalytic, and sensing applications, yet there remains uncertainty concerning the intrinsic electrochemical (EC) activity. In this study, we use scanning electrochemical cell microscopy (SECCM) to determine local heterogeneous electron transfer (HET) kinetics in a random 2D network of single-walled carbon nanotubes (SWNTs) on an Si∕SiO 2 substrate. The high spatial resolution of SECCM, which employs a mobile nanoscale EC cell as a probe for imaging, enables us to sample the responses of individual portions of a wide range of SWNTs within this complex arrangement. Using two redox processes, the oxidation of ferrocenylmethyl trimethylammonium and the reduction of ruthenium (III) hexaamine, we have obtained conclusive evidence for the high intrinsic EC activity of the sidewalls of the large majority of SWNTs in networks. Moreover, we show that the ends of SWNTs and the points where two SWNTs cross do not show appreciably different HET kinetics relative to the sidewall. Using finite element method modeling, we deduce standard rate constants for the two redox couples and demonstrate that HET based solely on characteristic defects in the SWNT side wall is highly unlikely. This is further confirmed by the analysis of individual line profiles taken as the SECCM probe scans over an SWNT. More generally, the studies herein demonstrate SECCM to be a powerful and versatile method for activity mapping of complex electrode materials under conditions of high mass transport, where kinetic assignments can be made with confidence.W ithin the family of nanostructured materials, carbon nanotubes (CNTs) have attracted particular attention because they are readily synthesised at low cost, have exceptional electronic properties, exhibit chemical and mechanical stability, and are amenable to a wide range of simple chemical functionalization routes (1-3). These characteristics have led to CNTs being considered ideal substrates for electronics (4), sensing systems (5, 6), electrocatalytic supports (7), and batteries (8). Furthermore, the different configurations in which CNTs can be arranged broaden their versatility and allow custom design of devices for specific applications. Individual single-walled carbon nanotubes (SWNTs) (9), 2D networks (10-12), and 3D nanostructures (13) have all been employed successfully.Understanding heterogeneous electron transfer (HET) at CNTs is of considerable importance, due to the wide range of electroanalytical and electrocatalytic systems based on CNTs (14-17), and also because electrochemistry provides an attractive route to functionalize and tailor the properties of . Probing HET in 1D electrode materials is interesting fundamentally, given their inherent electronic structure and properties (21,22). However, as we highlight herein, despite many studies aimed at characterizing HET at CNTs, substantial questions remain unanswered, such as the location and rate of HET.A popular approach for studying electrochemistry at CNT...

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Section: Resultsmentioning

confidence: 99%

Quantitative nanoscale visualization of heterogeneous electron transfer rates in 2D carbon nanotube networks

Güell¹,

Ebejer²,

Snowden³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

113

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“…The higher values of DE p and E fwhm for the SWCNT/FMCA compared to its SWCNT/FDCA counterpart may be related to different factors. First, some workers [13][14][15]33 have attributed this phenomenon to ferrocene species being located in a range of environments with a range of E 1/2 . This should not be totally surprising if one considers the distribution of lengths of the SWCNTs on the gold substrate, and that the ferrocenes studied in this work could possibly be attached to the ends and/or defect sites of the SWCNTs via ester bonds (i.e.…”

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

confidence: 99%

“…Hence, until now, it was not known how CNTs co-assembled with ferroceneterminated thiols could impact on the electrochemistry of ferrocene moiety. The only known reports on CNTs are those where Fcs were covalently attached onto the ends of CNT SAMs via amide 13,14 or ester 15 bonds. This somewhat surprising considering that CNTs could enhance intermolecular electron transfer between ferrocene sites by behaving as electronic bridges.…”

Section: Introductionmentioning

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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“…Redox enzymes Gooding et al (2003); Liu et al (2005); Patolsky et al (2004), electroactive complexes Nkosi & Ozoemena (2008); Ozoemena et al (2007); Yu et al (2008) and ferrocene Flavel et al (2009;; Gooding et al (2007); Yu et al (2007) were rightly attached to vertical aligned SWCNTs. Ferrocene, a molecular redox probe usually used for ET studies because of its ideal Nerstian behavior, was attached by Shapter and coworkers Yu et al (2007) an they found that the presence of nanotubes in samples modified with ferrocene with or without the forest, improve the ET.…”

Section: Redox Species Anchored To Forestsmentioning

confidence: 99%

“…This result is very important because it suggests that vertical alignment of carbon nanotubes can transport electrons. Moreover, other works show that orientation of nanotubes affect ET properties: for randomly dispersed carbon nanotubes the ET is low with respect to vertical alignment due to difficulty of hopping for electrons from one nanotube to an other Gooding et al (2007). The possibility of anchoring enzymes or biomolecules would open the way to making biosensing with carbon nanotubes forests: Gooding works and Willner's are the milestones in this sense Gooding et al (2003); Patolsky et al (2004).…”

Section: Redox Species Anchored To Forestsmentioning

confidence: 99%

Electrochemical Biosensing with Carbon Nanotubes

Lamberti¹,

Giomo²,

Elvassore³

2011

Carbon Nanotubes - Growth and Applications

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The effects of the lengths and orientations of single-walled carbon nanotubes on the electrochemistry of nanotube-modified electrodes

Cited by 112 publications

References 52 publications

Quantitative nanoscale visualization of heterogeneous electron transfer rates in 2D carbon nanotube networks

Quantitative nanoscale visualization of heterogeneous electron transfer rates in 2D carbon nanotube networks

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

Electrochemical Biosensing with Carbon Nanotubes

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