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in der Helmholtz-Gemeinschaft
Capacitive SensorsA capacitive silicon-based enzyme sensor has been developed for the detection of penicillin in aqueous solutions. It consists of a pH-sensitive EIS (electrolyte-insulator-semiconductor) structure on which a layer of the enzyme penicillinase is immobilized. The immobilization is performed by means of heterobifunctional cross-linking molecules that allow a covalent binding of the enzyme molecules to the sensor surface and prevent the enzyme from polymerizing.
Scheme of the penicillin sensor. The penicillinase converts penicillin to penicilloic acid which releases H+ ions in the surrounding solution. These H+ ions are detected by the pH-sensitive layer on top of the EIS structure, for instance Si3N4, and the resulting sensor signal is a measure of the penicillin concentration in the solution.
The sensitivity as well as the detection limits of the
sensor can be varied by adjusting the pH and the buffer capacity of the
penicillin solution. Hence, depending on the measuring parameters, a lower
detection limit of around 50 ng/ml and an upper limit of more than
The structuring of the sensor by means of an anodic etching
process of the silicon substrate results in an enlarged porous
surface. This allows the immobilization of a greater amount of enzyme
and a miniaturization of the whole sensor.
Main features:
Low-cost production and the possibility of miniaturization using silicon planar technology. Easy storage and handling when replacing the sensor chip.
Porous silicon can be prepared by an anodic etching process in aqueous HF/ethanol solution. The pore size is adjustable from several nm up to µm dimensions.
Scanning electron micrograph of a n-type porous silicon surface
For references click here!
For further information please contact: Prof. Dr. Michael J. Schöning
URL: <http://www.fz-juelich.de/isg/sensorik/bcs-pen-e.html> |
