Preferential sorption of polar compounds by fluoroalkyloxy substituted phthalocyanines for the use in sorption based gas sensors

The gas sensing properties of purpose-made phthalocyanines (Pcs) having fluoroalkyloxy, fluoroaryloxy, or non-fluorinated alkyloxy substituents are described. Fourteen Pcs with Ni and Zn metal centers were synthesized systematically changing substituents and substitution pattern. A high sensitivity for polar volatile organic compounds (VOCs) is intended, which is a group of chemicals that is usually less accessible for Pcs as sensing material. Especially, octa fluoroalkyloxy substituted Pcs are very sensitive to polar compounds such as ethyl acetate or acetonitrile. Partition coefficients as high as 5000 are a proof of a high enrichment of these compounds in the sensitive layer. The concept is demonstrated using quartz crystal microbalance (QCM) sensors and twelve VOCs as analytes representing common chemical classes and covering a wide range of chemical properties. Besides, through combination of conventional alkyloxy substituted Pcs with ones having the new fluoroalkyloxy substituents a sensor array with very diverging responses can be created. As the described Pcs are readily available via standard synthesis procedures this is a simple, but effective approach to extend the sensing capabilities of Pcs making them even more attractive as sensitive materials in the use of sorption based chemical sensors, not only the QCM, but also other acoustic transducers.