Sol gel derived composites as novel materials for electrochemical sensor technology

Advances in chemical sensors and biosensors are highly desired due to their numerous applications in medical diagnostics, environmental monitoring and process control. The development of new materials can greatly improve existing sensor technologies or can create new generation technologies for a better future. Sol-gel technology, known for several years in material science, is gaining popularity in the sensor community for the stable encapsulation of recognition elements and hence for the development of chemical sensors or biosensors. Several sensing schemes have been developed based on sol-gel derived materials and thin films. Most of the sol-gel based sensing schemes were directed towards photometric sensing. In contrast, electrochemical devices have received little attention.; We have investigated the use of new sol-gel carbon composites for the fabrication of thick-film and disk-type amperometric biosensors. Coupling of the sol-gel and thick film technologies offers one step fabrication process by obviating the need for thermal curing and the associated enzyme deactivation problems, commonly encountered with electrodes prepared from conventional inks. The glucose sensors fabricated using glucose oxidase doped sol-gel carbon inks were chemically or physically modified to improve the sensitivity, stability, linearity and selectivity. Immunosensing capabilities of antibody doped thick film carbon sensors towards the amperometric sensing of IgG are illustrated. Sol-gel carbon composites were also used to fabricate surface renewable disk type electrodes. Chemically modified and unmodified sol-gel carbon composite disk electrodes were used in electrochemical flow detection, electrocatalysis, HPLC detection and trace metal sensing. The intrinsic catalytic activity of sol-gel based materials was also investigated in connection with the low potential and stable oxidation of NADH and hydrogen peroxide. By dispersing gold powder within the sol-gel matrix, polishable or disposable gold ceramic electrodes were obtained. Similar to sol-gel carbon electrodes, gold ceramic electrodes also possess bulk modification or surface renewable characteristics. These gold ceramic electrodes were bulk modified with glucose oxidase for fabricating surface renewable or screen printed metal biosensor. Surface modification of gold electrodes was also illustrated using self assembled thiolated sol-gel networks. Sol-gels thus provide simple and versatile materials or surfaces for the fabrication of novel electrochemical sensors.