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
Sensors and Actuators B Chemical (Impact Factor: 4.1). 10/2006; 118:163-170. DOI: 10.1016/j.snb.2006.04.013


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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Available from: Arshak Poghossian, Aug 07, 2014
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    • "In development of solid state sensor, recent approaches are ISFET (ion-sensitive field effect transistor), LAPS (light addressable potentiometric sensor), and capacitance-based electrolyte insulator semiconductor (EIS) [1-4]. Among these developments, EIS has shown potential in terms of its simple structure, label-free detection, easy fabrication procedure, and cost effectiveness [5,6]. In addition, nanoparticles have generated considerable interest as diagnostic tool because of their small sizes and comparatively higher surface area that leads to more interaction with ions in solution [7-10]. "
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    • "The sensitive layer consists of a Ta O film deposited on top of an extended gate, and corresponds to the part of the device that is actually submersed in the electrolyte solutions. Ta O has a high surface buffer capacity which is ideal for achieving maximum sensitivity [1] being one of the more stable materials used as sensitive layer for pH, enzymes, and DNA [7], [20]–[22]. "
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    • "Consequently, the direction of the potential change after adsorption of negatively charged SWNTs corresponds to the case as if the Ta O surface would have been additionally negatively charged. Similar effects were reported for a polyelectrolyte multilayer formation onto a p-Si-SO [30], [31] and a p-Si-SO -diamond [32] capacitive EIS sensor. Before the noise experiments, the gate-leakage current and the pH sensitivity of bare and functionalized p-Si-SiO -Ta O sensors have been examined. "
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