Soluble phthalocyanines as suitable coatings for highly sensitive gas phase VOC-detection

The interaction of modified phthalocyanines (PCs) was studied with benzene, toluene, m-xylene and a-octane by using thickness shear mode resonators (T SMRs). The n-octane showed linear sorption isotherms, whereas the aromatic compounds revealed extremely nonlinear adsorption isotherms with high inten sities at low concentrations. The nonlinear isotherms are described in a th eoretical model by assuming selective and unselective sorption and by combi ning Langmuir- and Henry-type of sorption isotherms. The sorption of all ar omatics takes place in the bull; as it is deduced from the proportionality of the sensor signals with coating thickness. To indicate the high sensitiv ity, the calculated limit of detection for a phthalocyaninatoplatin(II)coat ing was 0.5 ppm for benzene and 0.2 ppm for toluene. (C) 2000 Elsevier Scie nce S.A. All rights reserved.