(The) adsorption-desorption characteristics of odorants on phospholipids LB film-coated QCM as an olfactory sensor model

Abstract

The adsorption-desorption characteristics of some gases on different lipid LB film-coated QCM were examined in addition to the monolayer behaviors and LB film transfer of some phospholipids. From those results the basic olfactory sensing system using a pattern recognition method has been proposed. The multilayers of lipid LB films were deposited on 9 MHz QCMby using $Ba^{2+}$ salt at high pH condition in case of DPPA or by mixing the lipids with film deposition promoter such as Octadecylamin or DPPA. The adsorption-desorption characteristics of gases on lipid films on QCM were defined by some working parameters from the sensor response curves. The standard gas was generated by bubbling the liquid with $N_2$ gas. Because of the nonspecific physisorption of chemical vapors on lipids film, the adsorption and desorption responses of gases were highly reproducible. It was also observed that the output signals of QCM were varied with the number of LB film layers. To identify the odorants, a multi(four or six)-channel sensor in which the channels were coated with different mixed lipid films was constructed. With these data we constructed circular profile patterns and two channel plots and some materials are clustered. In the two channel plot, the proper coating material could be selected by observing the clustering within confidence level. Using the SOFM neural network system, nine kinds of different chemical vapors and three different mixtures of methanol-butanol were identified within 90-95% accuracy.