Abstract
Modification of gold electrode by self-assembled
trans-Fe(cyclam)(NCS)(2)(+) complex ion to produce an
electrochemical sensor for nitric oxide detection was investigated.
Dopamine, serotonin and nitrite were examined as interferents. The
synthesized complex was characterized by X-ray diffraction and by
infrared spectroscopy. The modified electrode was characterized by
cyclic voltammetry and by surface enhanced Raman spectroscopy,
analytical curves were obtained by square wave voltammetry and Monte
Carlo calculations were made to model the interaction of NO molecules
with the unmodified and modified surfaces. The complex has distorted
octahedron geometry with the thiocyanate groups bonded to the iron ion
by the nitrogen atom and in the trans orientation. SERS spectrum and
Monte Carlo calculations supported that the complex ion is adsorbed on
Au surface from the Au-S bond. The electrochemical current for NO
oxidation on the modified electrode was higher than that presented by
the bare Au electrode and a good correlation was presented by the
experimental analytical curve and the calculated Monte Carlo interaction
energy versus amount NO molecules plot. The Monte Carlo calculations
indicated that the higher current response for NO oxidation on the
Au/trans-Fe(cyclam)(NCS)(2)(+) surface was due to the stronger
interaction of the NO molecules with complex adsorbed on the Au surface
than the interaction of NO with the bare Au surface. The theoretical
analyses also revealed that NO molecules cluster on Au surface.
Dopamine, serotonin and nitrite were interferents for the detection of
NO with dopamine and serotonin was less significant interferents than
the nitrite. The proposed modified electrode presented good
electrochemical stability, detection limit and quantification limit of
5.15 x 10(-8) mol L-1 and 1.72 x 10(-7), respectively, which were about
one order of magnitude lesser than the corresponding values obtained for
the bare Au electrode. The results indicated that the proposed electrode
has potential to be applied as a sensor for NO detection. (C) 2012
Elsevier Ltd. All rights reserved.
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