Article

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

University of Applied Sciences Aachen, Division Jülich, Laboratory for Chemical Sensors and Biosensors, Ginsterweg 1, 52428 Jülich, Germany; Institute of Thin Films and Interfaces (ISG 2), Research Centre Jülich GmbH, 52425 Jülich, Germany
Sensors and Actuators B: Chemical 01/2006; DOI:10.1016/j.snb.2006.04.013

ABSTRACT 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.

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Keywords

Alternating potential shifts
 
capacitance
 
capacitance–voltage
 
capacitance–voltage curves
 
Capacitive EIS
 
constant-capacitance
 
constant-voltage-mode methods
 
field-effect-based sensors
 
ion-sensitive field-effect transistor
 
macromolecules
 
polyelectrolyte layers
 
sensor response
 
voltage axis