Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/199316

Title

Grafting of thin organic films by electrooxidation of arylhydrazines

Author(s)

Malmos, Kristoffer;  Iruthayaraj, Joseph;  Ogaki, Ryosuke;  Kingshott, Peter;  Besenbacher, Flemming;  Pedersen, Steen U.;  Daasbjerg, Kim

Abstract

Anodic oxidation of arylhydrazines in aqueous solution leads to formation of a chemisorbed monolayer on the electrode surface of both glassy carbon and gold. The grafting process occurs in a three-electron process, in which the arylhydrazine is oxidized to the actual grafting agent, that is, the corresponding aryl radical, via the formation of the aryldiazene as intermediate. Analysis of the modified surface by X-ray photoelectron spectroscopy and polarization modulation infrared reflection absorption spectroscopy shows conclusively that the bonding to the surface does not occur through the hydrazine group but rather through the aryl group after expulsion of nitrogen. In general, the method is found to be tolerant toward variations in the experimental conditions, but at high pH (>7), the grafting rate increases considerably and multilayers may be formed. The more efficient grafting at high pH can be attributed to an increase of the rate of the deprotonation steps in the oxidation mechanism, the result of which will be that the aryl radical formation takes place close to the surface to be modified. In general, the monolayer exhibits a low susceptibility toward further grafting due to a lowering of the electron transfer rate and the occurrence of physisorption. In particular, at high concentrations of the arylhydrazine, physisorbed products formed during the grafting process are layered on top of the chemisorbed film, hence enhancing the blocking effect and precluding further growth.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Engineering and Industrial Sciences. Industrial Research Institute Swinburne

Source

Journal of Physical Chemistry C, Vol. 115, no. 27 (Jul 2011), pp. 13343-13352

Publication year

2011

FOR Code(s)

0303 Macromolecular and Materials Chemistry;  0306 Physical Chemistry (Incl. Structural);  0904 Chemical Engineering

Keyword(s)

Aryl;  Arylhydrazines;  Covalent modification;  Diazonium salts;  Electrochemical oxidation;  Electrodes;  Electrooxidation;  Glassy carbon;  Monolayers;  Phenylhydrazine;  Reduction

Publisher

American Chemical Society

ISSN

1932-7447

Publisher URL

http://dx.doi.org/10.1021/jp202911d

Copyright

Copyright © 2011 American Chemical Society.

Peer reviewed