Synthesis and DMMP sensing properties of fluoroalkyloxy and fluoroaryloxy substituted phthalocyanines in acoustic sensors

Ni(II) and Zn(II) phthalocyanines (Pcs) having fluorinated and non-fluorinated alkyl and aryl oxy substituents were synthesized and characterized as sensitive coatings for chemical gas sensors, namely quartz crystal microbalance (QCM) and surface acoustic wave sensors. The materials are highly suitable for the detection of the organophosphate class of chemicals like dimethyl methyl phosphonate (DMMP). DMMP is not only used as a simulant for nerve agents such as sarin, but also constitutes an interesting target analyte in many other application fields. The fluorinated substituents attached to the Pc core increase the affinity for polar compounds of the Pc molecule resulting in the observed high sensitivity for organophosphates being polar molecules. The octakis(2,2,3,3-tetrafluoropropyloxy) substituted ZnPc shows the highest sensitivity towards DMMP among the tested materials with detection limits below 100 ppb. At the same time the influence of background humidity on the sensor signal is very low and the cross-sensitivity values to possible interferents contained in ambient air are 1000 times lower. The presented results demonstrate the viability of the new phthalocyanine compounds as highly sensitive and selective materials for detection of DMMP.