Feature difference of interaction between various organic solvent vapors and metal phthalocyanines coated on quartz crystal

Interaction between organic solvent vapors, zinc phthalocyanine (ZnPc) and copper phthalocyanine (CuPc) coated on quartz crystal resonators were investigated for various types of organic solvent vapors including acetone, propanol, ethanol, tetrahydrofuran, methanol, nail lacquer remover, 100 Pipers and Masterblend whiskies. The major different features of the resonance frequency shift as a function of time were extracted in order to employ in gas sensor. The sensor consists of ZnPc or CuPc thin film with the thickness of ∼300 nm coated on quartz crystal with resonance frequency of 2 MHz. It used as a transducer by convert the surface adsorption into the frequency shift. When the odor interacts with ZnPc or CuPc layer, the quartz frequency normally decreases from the fundamental frequency due to the additional mass on quartz surface. The different types of organic solvent have different sensitivity to the thin film and these changing lead to the different frequency shift characteristics. The frequency shift were collected and the selected data points at the time of 5, 10, 15, 20, 70, 75, and 80 minutes after dropping alcohol were used to extract the feature by using the principal component analysis (PCA) in order to classify the type of alcohol. The PCA can be used to identify the major characteristic difference of various organic solvent interactions. The main features can be identified by the amount of the frequency shift and the decay characteristics.