INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Mesoporous materials en electrochemical devices
Autor/es:
GRACIELA A. GONZALEZ; ANA SOL PEINETTI; FERNANDO BATTAGLINI
Lugar:
Gijon, España
Reunión:
Congreso; 13th International Conference on Electroanalysis; 2010
Institución organizadora:
International Society of Electroanalytical Chemistry
Resumen:
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The design of an electrochemical sensor based on the effect of
mesoscopic domains on the amperometric response of an electroactive probe by
applying cyclic or square wave voltammetry is reported. We present the numerical
simulation of a system compromising a mesoporous material placed at a close
distance of a working electrode. The concentration of the reactant close to a
working electrode is responsible of the electrochemical response of the system,
and the concentration profiles are the results of mass transport process through
the membrane. The digital simulation allows comparing the responses for three
different situations: one consisting in blocking mechanically the surface with
an insulating varnish, other in which the membrane is chemically blocked by
adsorption of proteins, and other in which the membrane is only the frontier
between the reagents and a catalyst (an enzyme) involved in a reaction, being
the catalyst the species diffusing through the membrane. The digital simulation
allows comparing the responses for the different situations regarding the way
in which the mass transport occurs. The
developed model is compared with experimental results. The effect of the ratio
between the size of the pore and the analyte on the system response is
evaluated. When the probe´s molecular diameter is close to the size of the
pore, the mass transport cannot be described by the Ficks law. The single-file
diffusion model can give a better description for these systems. In particular,
systems with open ends following the single-file model lead to an enhancement
of the mean square displacement respect to those following the Ficks diffusion
model. Eventually, molecular displacements are even found to follow the Fick´s law of diffusion [1]. The numerical
model developed presented in this work permits to evaluate the way in which the
probe mass transport occurs, depending on the ratio between the pore diameter and
the probe´s molecular size. We report an
experimental enhancement in the amperometric response of the system when the probe´s
molecular size is close to the pore diameter respect to the predictions
obtained using the Fick´s law of diffusion. This change in behavior was also
observed in other system involving pores and pipes in the nanometer scale
[2,3]. This work is one of the first attempts to describe the mass transport in
membranes with potential application in electrochemical sensors.