MESOPOROUS MATERIALS IN ELECTROCHEMICAL DEVICES

G. A. GONZÁLEZ , A. S. PEINETTI , F. BATTAGLINI

Gijón, España

Congreso; ESEAC 2010 - 13th International Conference on Electroanalysis; 2010

ESEAC

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 Fick’s 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 Fick’s diffusion model. Eventually, molecular displacements are even found to follow the Fick´s law of diffusion. 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. This work is one of the first attempts to describe the mass transport in membranes with potential application in electrochemical sensors.