Ellipsometry measurements and impedance spectroscopy on Langmuir-Blodgett membranes on Si/SiO2 for ion sensitive sensor

LB films containing butyrylcholinestrase (BuChE) are fabricated to realize an ion-sensitive field-effect transistor (ISFET) for the detection of organ ophosphorus pesticides in water. A common pesticide known as trichlorfon is examined in our work. Adsorbing the enzyme molecules onto stearylamine mon olayer using the electrostatic force forms the BuChE-immobilised Langmuir-B lodgett (LB) films. Enzyme/stearylamine mixed LB films are immobilized onto ISFET and treated by glutaraldehyde vapor to improve the LB film's stabili ty. Two techniques, the ellipsomerty and spectroscopy methods, have been us ed to investigate the homogeneity and stability of these films. In ellipsom etry the refractive index and thickness of Si/SiO2/LB films are measured. B y utilizing the spectroscopy technique the impedance spectrum of Si/SiO2 an d Si/SiO2/LB films are obtained and compared to ellipsometry results. (C) 2 001 Elsevier Science B.V. All rights reserved.