A VERSATILE MATRIX FOR THE CONSTRUCTION OF SENSORS

G. A. GONZÁLEZ A , M. L.CORTEZ A,B, F. BATTAGLINI A

Gijón

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

ESEAC

The modification of electrode surfaces with carbon nanotubes and surfactants has widely been explored in the last years . An important characteristic of these materials is the capacity to facilitate the electron transfer process when interactions with the electrode surface are involved in the redox reaction. In this work we present the construction of a stable and versatile matrix using a polyelectrolyte (polyalylamine, PAA) and a tensioactive (sodium dodecyl sulfate, DS). This combination is easily handled and chemically modifiable. In this matrix a redox mediator can be assembled for its use as an amperometric sensor. The amino group present in PAA  was modified with a polypyridyl osmium complex (OsPAA) that, in the presence of DS precipitates, generating a product that is soluble in organic solvent (DMF or methanol). This organic solution is applied on graphite surfaces. The evaporation of these solutions generates an extremely stable and resistant film showing a quasi-reversible electrochemical behavior. Onto this film, glucose oxidase was efficiently adsorbed, where a catalytic current of 250 mA cm-2 can be obtained in saturated conditions. This system, compared to others built by self-assembled, present the following advantages, it can be applied on any conducting surface (graphite, gold, etc) without the need of an anchor molecule (thiols, diazonium salts), it presents excellent electron transfer properties through the film and with other molecules, it is able to be modified covalently through the amino groups or by self-assembled interactions and it is highly stable in time. Simultaneously the amperometric response was modeled using finite-element software to obtain the cyclic voltammetric responses and the concentration profiles. The space dimension was set to 2D and the boundary condition was as an infinite plane electrode; the generated current is calculated by Butler-Volmer equation. Kinetic constants referred to catalysis and enzyme regeneration from were used. Kinetic constant referred to the enzyme saturation in this environment and wired enzyme concentration arise from adjustment of the model to experimental cyclic voltammetries. The agreement between experimental and numerical results from several experiments presents three outcomes. First, the wired enzyme concentration is related to the film thickness. Second, in this system the enzyme is saturated at a substrate concentration higher than in self-assembles without DS or in solution. Finally, the relevance of numerical model to analysis this kind of system is shown.