Development of a piezoelectric chemical sensor using metalloporphyrins compounds as a coating material

The piezoelectric quartz crystal chemical sensor was developed for volatile organic compounds (VOCs) detection. The sensing sensitivity of the devices was measured based on the small change in mass of quartz crystal. The addition of mass causes changes its natural frequency when exposing the thin film towards vapor molecules. The system sensor was used with metalloporphyrin thin films as a sensing element. Seven types of metalloporphyrin compounds have been used for deposition of the thin films. They were: 2-nitro-5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrin copper (III) (CuTPPnitro), 5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrin ruthinium (II) carbonyl (RuTPP), 5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrin iron (III) cloride (FeTPP), 5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrin manganese (III) cloride (MnTPP), 5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrin cobalt (II) (CoTPP), 5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrin nickel (II) (NiTPP) and 5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrin zinc (ZnTPP). The LB technique has been used to form metalloporphyrin organic compounds as a thin films onto quartz crystal surface. The sensing sensitivity was studied by exposing saturated vapor of o-xylene towards LB thin films. From the result it was observed that the various responses were shown for each of the thin films towards o-xylene vapor. The physical and chemical interaction between thin films and the vapor molecule are the factors influencing the sensing sensitivity of the sensor system.