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Trends in reactivity of unsubstituted and
substitutedcobalt-phthalocyanines for the electrocatalysis of
glucose oxidation
Cristian Barrera a, Igor Zhukov b, Evelyn Villagra a, Fethi
Bedioui c, Maritza A. Paez a,Juan Costamagna a, Jose H. Zagal
a,*
a Facultad de Qumica y Biologa, Departamento de Qumica de los
Materiales, Universidad de Santiago de Chile (USACH),
Casilla 40, Correo 33, Santiago, Chileb On leave from Department
of Chemistry, Moscow State University, Moscow, Russian
Federation
c Laboratoire de Pharmacologie Chimique et Genetique, UMR CNRS
8151/U INSERM 640, Ecole Nationale Superieure de Chimie de
Paris,
11 rue Pierre et Marie Curie, 75231 Paris cedex 05, France
Received 7 December 2005; received in revised form 18 January
2006; accepted 10 February 2006Available online 23 March 2006
Abstract
This study shows that cobalt macrocyclics, namely
Co-phthalocyanine (CoPc), Co-hexadecafluorophthalocyanine
(CoF16Pc), Co-octaethylhexyloxyphthalocyanine (CoOEHPc),
Co-tetraaminophthalocyanine (CoTAPc) and
Co-tetrasulfophthalocyanine (CoTSPc),strongly adsorbed on a
graphite electrode surface, exhibit true electrocatalytic activity
for the oxidation of glucose in alkaline solution.The Tafel
analysis of the electrochemical process occurring at these
chemically modified electrodes, that become molecular
phthalocy-anine electrodes, suggests that a first-one electron step
is rate controlling with the symmetry of the energy barrier
depending on the typeof substituents grafted on the macrocycle. The
effect of substituents on the phthalocyanine ring on the catalytic
activity was analyzed anda non-linear correlation is found. The
volcano-shaped plot obtained when comparing catalytic activities
versus the Co(II)/(I) formalpotential indicates that a narrow
window of Co(II)/(I) formal potentials exists for achieving maximum
activity. In the particular caseof the present work, we find that
the most active phthalocyanine is the unsubstituted CoPc. 2006
Elsevier B.V. All rights reserved.
Keywords: Cobalt phthalocyanine; Glucose oxidation;
Electrocatalysis; Modified electrode
1. Introduction
The oxidation of most carbohydrates, specially thereducing
sugars is rather favorable from the thermody-
namic point of view, so it can be expected that they canbe
easily detected electrochemically following liquid chro-matography
(LCEC). However, their electrochemical oxi-dation is not easy, as
it requires a large overpotential onconventional electrodes that
are commonly used in LCEC.Besides glucose oxidase-based biosensors
that work only invery specific conditions and do not apply for
LCEC, the
electrodes generally used consist of carbon paste, glassycarbon,
platinum, gold or nickel materials [17]. Also,one of the main
drawbacks linked to these materials comesfrom the need for multiple
pulsed potential steps to achieve
cleaning and activating sequences within the detection pro-cess.
It is then interesting to find alternative electrode mate-rials
that present higher catalytic activity and morepractical operating
procedures. The most promisingapproach for doing so is the use of
chemically modifiedelectrodes (CMEs) containing selected redox
species. Vari-ous attempts have been made during the last recent
years,and CMEs made from nickel oxide [8,9], ruthenium oxideor
other metal oxide [10,11], copper oxide [1215] andmixed valent
Prussian blue [16] have been examined forthe oxidation of
glucose.
0022-0728/$ - see front matter 2006 Elsevier B.V. All rights
reserved.
doi:10.1016/j.jelechem.2006.02.009
* Corresponding author.E-mail address: [email protected]
(J.H. Zagal).
www.elsevier.com/locate/jelechem
Journal of Electroanalytical Chemistry 589 (2006) 212218
Journal of
ElectroanalyticalChemistry
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