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Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/2257

Title: Scanning tunneling microscopy, fourier transform infrared spectroscopy, and electrochemical characterization of 2-naphthalenethiol self-assembled monolayers on the Au surface: A study of bridge-mediated electron transfer in ruthenium complex
Authors: Ganesh, V.
Lakshminarayanan, V.
Issue Date: 2005
Publisher: American Chemical Society
Citation: Journal of Physical Chemistry B, 2005, Vol.109, p16372-16381.
Abstract: We have studied the structure, adsorption kinetics, and barrier properties of self-assembled monolayers of 2-naphthalenethiol on Au using electrochemical techniques, grazing-angle Fourier transform infrared (FTIR) spectroscopy, and scanning tunneling microscopy (STM). The results of cyclic voltammetric and impedance measurements using redox probes show that 2-naphthalenethiol on Au forms a stable and reproducible, but moderately blocking, monolayer. Annealing of the self-assembled monolayer (SAM)-modified surface at 72 ± 2 C remarkably improves the blocking property of the monolayer of 2-naphthalenethiol on Au. From the study of kinetics of SAM formation, we find that the self-assembly follows Langmuir adsorption isotherm. Our STM and FTIR results show that the molecules are adsorbed with the naphthalene ring tilted from the surface normal by forming a 3 × 3 R30 overlayer structure. From our studies, we conclude that the electron-transfer reaction of ferro/ferricyanide in the freshly formed monolayer occurs predominantly through the pinholes and defects present in the monolayer. However, in the case of thermally annealed specimen, although the ferro/ferricyanide reaction is almost completely blocked, the electron-transfer reaction of hexaammineruthenium(III) chloride is not significantly inhibited. It is proposed that the electron-transfer reaction in the case of the ruthenium redox couple takes place by a tunneling mechanism through the high-electron-density aromatic naphthalene ring acting as a bridge between the monolayer-modified electrode and the ruthenium complex.
Description: Restricted Access.
URI: http://hdl.handle.net/2289/2257
ISSN: 1520-6106
1520-5215 (Online)
Alternative Location: http://dx.doi.org/10.1021/jp052489u
Copyright: 2005 American Chemical Society
Appears in Collections:Research Papers (SCM)

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