Ann Iron Oxide-Based Semiconductor Gars Sensor for Dimethyldisulfide

Abstract

Iron oxide-based semiconductor gas sensors were exploited for detecting dimethyldisulfide (DMDS) gas, an important flavor component of consomme soup. Among the various metals and metal oxides tested, Pr₆O₁₁ was the most effective additive to Fe₂O₃ for promoting the sensitivity to DMDS vapor (20 ppm) in air at 300°C, giving the highest sensitivity at a Pr₆o₁₁ content of 5wt%. The sensor using 5wt%Pr₆O₁₁-added Fe₂O₃ was also fairly good in selectivity to DMDS among various flavor components of consomme soup. As characterized by XRD, 5wt%Pr₆O₁₁-added Fe₂O₃ system contained no crystalline phases other than Fe₂O₃, while PrFeO₃ was observed at Pr₆O₁₁ contents of 1Owt% and above. The Pr⁴⁺/Pr³⁺ ratio as revealed from XPS analysis remained far higher for Pr₆O₁₁-added systems than that for pure Pr₆O₁₁, though it tended to decrease with increasing Pr₆O₁₁ content. These results suggest that, at low Pr₆O₁₁ contents, a major part of Pr components added exist as finely dispersed Pr⁴⁺ species on the surface of Fe₂O₃ particles and that such surface Pr⁴⁺ species are responsible for the observed enhancement of gas sensitivity to DMDS.