The monolayer behavior at the air/water interface, transfer characteristics of substituted metallo-phthalocyanices (MPcs) on QCM, and its application to $NO_2$ sensing system were examined. Alkyl-substituted MPcs have a symmetric 2-ethylhexyloxy side chain, and complex central metal atoms were dihydrogen, copper, cobalt, lead, platinum and tin. Sensing membranes were prepared by a constant-perimeter type Langmuir trough with a vertical dipping unit and KSV-3000. MPcs membranes were deposited onto a gold coated Quartz Crystal Microbalance(QCM). The adsorption-desorption amount of $NO_2$ gas was measured by frequency change of QCM.
T he pretreated membrane with $NO_2$ at room temperature was purged with $N_2$, and the initial frequency was perfectly recovered. From the NMR and FTIR spectroscopy, the adsorption sites of $NO_2$ on MPcs were both core metal and side chain (ether group). $NO_2$ would be physically adsorbed on the metal core but desorbed easily by purging with pure $N_2$ gas, while in the case of the hydrocarbon chain $NO_2$ be adsorbed irreversibly.
