Tuning the electrocrystallization parameters of semiconducting Co[TCNQ]2-based materials to yield either single nanowires or crystalline thin films

Nafady, A, Bond, A, Bilyk, A, Harris, A, Bhatt, A, O'Mullane, A and De Marco, R 2007, 'Tuning the electrocrystallization parameters of semiconducting Co[TCNQ]2-based materials to yield either single nanowires or crystalline thin films', Journal of the American Chemical Society, vol. 129, no. 8, pp. 2369-2382.


Document type: Journal Article
Collection: Journal Articles

Title Tuning the electrocrystallization parameters of semiconducting Co[TCNQ]2-based materials to yield either single nanowires or crystalline thin films
Author(s) Nafady, A
Bond, A
Bilyk, A
Harris, A
Bhatt, A
O'Mullane, A
De Marco, R
Year 2007
Journal name Journal of the American Chemical Society
Volume number 129
Issue number 8
Start page 2369
End page 2382
Total pages 14
Publisher American Chemical Society
Abstract Electrocrystallization of single nanowires and/or crystalline thin films of the semiconducting and magnetic Co[TCNQ]2(H2O)2 (TCNQ = tetracyanoquinodimethane) charge-transfer complex onto glassy carbon, indium tin oxide, or metallic electrodes occurs when TCNQ is reduced in acetonitrile (0.1 M [NBu4][ClO4]) in the presence of hydrated cobalt(II) salts. The morphology of the deposited solid is potential dependent. Other factors influencing the electrocrystallization process include deposition time, concentration, and identity of the Co2+(MeCN) counteranion. Mechanistic details have been elucidated by use of cyclic voltammetry, chronoamperometry, electrochemical quartz crystal microbalance, and galvanostatic methods together with spectroscopic and microscopic techniques. The results provide direct evidence that electrocrystallization takes place through two distinctly different, potential-dependent mechanisms, with progressive nucleation and 3-D growth being controlled by the generation of [TCNQ]•- at the electrode and the diffusion of Co2+(MeCN) from the bulk solution. Images obtained by scanning electron microscopy reveal that electrocrystallization of Co[TCNQ]2(H2O)2 at potentials in the range of 0.1−0 V vs Ag/AgCl, corresponding to the [TCNQ]0/•- diffusion-controlled regime, gives rise to arrays of well-separated, needle-shaped nanowires via the overall reaction 2[TCNQ]•-(MeCN) + Co2+(MeCN) + 2H2O {Co[TCNQ]2(H2O)2}(s). In this potential region, nucleation and growth occur at randomly separated defect sites on the electrode surface. In contrast, at more negative potentials, a compact film of densely packed, uniformly oriented, hexagonal-shaped nanorods is formed. This is achieved at a substantially increased number of nucleation sites created by direct reduction of a thin film of what is proposed to be cobalt-stabilized {(Co2+)([TCNQ2]•-)2} dimeric anion. Despite the potential-dependent morphology of the electrocrystallized Co[TCNQ]2(H2O)2 and the markedly different nucleation−growth mechanisms, IR, Raman, elemental, and thermogravimetric analyses, together with X-ray diffraction, all confirmed the formation of a highly pure and crystalline phase of Co[TCNQ]2(H2O)2 on the electrode surface. Thus, differences in the electrodeposited material are confined to morphology and not to phase or composition differences. This study highlights the importance of the electrocrystallization approach in constructing and precisely controlling the morphology and stoichiometry of Co[TCNQ]2-based materials.
Subject Electrochemistry
DOI - identifier 10.1021/ja067219j
ISSN 0002-7863
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