Optical electronic nose based on porphyrin and phthalocyanine thin films

The classification of product quality based on an optical electronic nose is becoming an instrument of much interest in beverage industry. The optical electronic nose is composed of a molecular sensing layer, UV-Vis spectrophotometer and a data analysis unit. The sensing layer was fabricated from 3 types of organic compounds, namely Zinc-2,9,16,23- tetra- tert- butyl- 29H,31H- phthalocyanine (ZnTTBPc), Zinc-5,10,15,20-tetraphenyl- 21H,23H-porphyrin (ZnTPP) and manganese(III)-5,10,15,20-tetraphenyl-21H,23H-porphyrin chloride (MnTPPCl) by using the spin-coating technique. The UV-Vis Spectrophotometer set up was used to detect gases and chemical vapors by measuring changes in the absorption spectrum of the spin-coated thin film upon gas exposure. The sensitivity of the organic film was tested by using volatile organic compounds (VOCs) vapor, for instance, methanol, ethanol, isopropanol, acetone (5% eq.), acetic acid (5% eq.) and methyl benzoate (5% eq.), which are common VOCs in food and beverages. The Principal Components Analysis (PCA) was then applied to the absorption spectral data to classify the type of the tested chemical vapors. The results indicate that this sensing film with the three organic compounds produced a good separation of data groups according to the chemical type.