Field-effect sensors for monitoring the layer-by-layer adsorption of charged macromolecules

Capacitive EIS (electrolyte-insulator-semiconductor) sensors and ISFETs (ion-sensitive field-effect transistor) have been utilised for the detection of the layer-by-layer adsorption of charged macromolecules. The field-effect-based sensors with the adsorbed multilayers have been characterised by capacitance-voltage, constant-capacitance and constant-voltage-mode methods. The effect of the number and polarity of the polyelectrolyte layers on the shift of the capacitance-voltage curves along the capacitance and voltage axis has been investigated. Alternating potential shifts of about 30-50 mV have been observed after the adsorption of each polyanion and polycation layer, respectively. The possible mechanisms for the sensor response are discussed. (c) 2006 Elsevier B.V. All rights reserved.