Volatile organic compound sensor arrays based on zinc phthalocyanine and zinc porphyrin thin films

In this paper, organic thin films based on two types of metal-macromolecules, i.e., zinc-2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (ZnTTBPc) and zinc-5,10,15,20-tetra-phenyl-21H,23H-porphyrin (ZnTPP), were demonstrated to discriminate among diverse volatile organic compounds (VOCs) even if they have very similar functional group. The ZnTTBPc and the ZnTPP thin films have been prepared by spin coating technique and then were tested for their optical response to VOCs, which share a similar carbonyl (C=0) group, namely acetone, formaldehyde (in a mixture form with methanol) and acetic acid, based on UV-Vis absorption. The transduction employs the optical response of selected spectral ranges arranged in an array configuration, which is then subjected to the principal component analysis (PCA). The PCA results have shown successful discrimination of these VOCs. Density functional theory (DFT) calculation was employed to study the interactions between these VOCs and the sensing materials. The calculation yields different degrees of interactions for each VOC, in compliment with the experimental results. This work supports the prospects of this organic sensor for beverage industry where VOCs are abundant in their products.