Inkjet-printed sol-gel films containing metal phthalocyanines/porphyrins for opto-electronic nose applications

In this work, five metal porphyrins and phthalocyanines embedded in transparent sol-gel films were deposited by piezoelectric inkjet printing, characterized and used as gas sensors. Explored compounds include magnesium/manganese(III) chloride/zinc 5,10,15,20-tetraphenyl-21H,23H-porphyrin, magnesium 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine, and zinc 2,9,16,23-tetratertbutyl-29H,31H-phthalocyanine. Porphyrin/Phthalocyanine was blended with sol-gel solution to produce inks that were printed on glass substrates. The printed films were used as sensing layers for discrimination of volatile organic compounds (VOCs). Printed films were characterized by UV/vis spectroscopy, FTIR spectroscopy, and scanning electron microscopy. The employed sensing compounds are promising materials for optical gas sensors due to selective spectral alterations when exposed to oxidizing and reducing gases as well as VOCs. These alterations were observed by UV/vis spectroscopy and used to distinguish between several VOCs. To do so, a single printed sensing layer was exposed to methanol, ethanol, acetone and isopropanol vapor, respectively. During exposure the absorbance spectrum was continually measured and split into several wavelength intervals. By calculating the area integral of each interval and considering these as separate sensors it is possible to use a single sensing film to emulate sensor arrays. The results showed that the fabricated layers exhibit reversible optical modulations in the UV/vis spectra when exposed to various VOCs. The data have been analyzed by principal component analysis (PCA) and cluster analysis (CA). Results demonstrate the analytes to be distinguishable as isolated clusters in the PCA domains. The best results were obtained from ZnTPP and MgTPP containing films, whereas layers doped with Mn(III) ClTPP give unusable response. (C) 2012 Elsevier B.V. All rights reserved.