Odor identification using a SnO2-based sensor array

The effect of grain size of SnO2 was examined on the sensitivities of SnO2 thick films to odoriferous and odorless gases. The sensitivity to odors and the odor selectivity to odorless gases depended strongly on the grain size, and the optimum mean grain size of SnO2 for odor sensing was about 176 nm observed by SEM. The odor selectivity to odorless gases was further improved by adding PbOx to the SnO2 thick films. By coating the original PbOx-added SnO2 thick films with various metal oxide catalytic layers, the sensing elements became characterized by the peculiar odor selectivities. An odor identification system has been developed utilizing the SnO2-based sensor array composed of the original thick film and seven sensing elements with different metal oxide catalytic layers, and pattern recognition technique. Odors of a similar nature from citrus fruit oils of grapefruit, sweet orange, lemon, bergamot and petit grain, and aromas of ground coffee beans produced in different countries were identified by principal component analysis (PCA).