PORE MORPHOLOGY INFLUENCE ON CATALYTIC TURN-OVER FOR ENZYME-ACTIVATEDPOROUS SILICON MATRICES

The enzyme glucose oxidase (GOx) was coupled to porous silicon of diff erent morphologies and the catalytic turn-over of glucose was recorded for the samples. The recorded catalytic turn-over of the samples clea rly indicated the influence of morphology, with respect to dopant conc entration and current density, of the porous silicon carrier matrix. T he highest rise in catalytic turn-over (350 times), when compared to a non-porous surface, was recorded for a sample with an n-type epilayer on an n(+)-type substrate anodised at 100 mA/cm(2). A storage and ope rational stability measurement was performed on the sample showing the highest catalytic efficiency. After 5 months of refrigerated storage a 2% loss of activity was noted, and after 4 days of constant glucose load (0.5 mM) a 56% loss of activity was recorded. A BET (Brunauer, Em met, and Teller) nitrogen adsorption analysis was performed on one of the substrate types, p(+)-type (0.001-0.025 Omega cm). In spite of the fine porous morphology with a high surface area the recorded enzyme a ctivities were moderate. The pore morphology achieved on this substrat e most likely comprised too small pores in a too dense porous matrix g iving poor diffusion conditions to give efficient access for the enzym e during the coupling procedure and for the reactant transport during operation to fully utilise the surface enlargement of the porous layer . (C) 1998 Elsevier Science S.A. All rights reserved.