Exclusive Detection of Dimethyl Sulfide by a Pd–WO3 Sensor with the CuO/Al2O3 Filtering Overlayer

Selective detection of trace (weakly reducing) dimethyl sulfide (DMS) in highly humid exhaled breath using metal oxide semiconductor (MOS) sensors, with the presence of strong reducing H2S interference gas, is essential for the early diagnosis of hepatic diseases. However, it remains a big challenge in principle. Herein, a bilayer MOS sensor with a Pd–WO3 sensing film and a CuO/Al2O3 filtering overlayer was proposed. The temperature-dependent H2S catalytic oxidation experiment suggests that CuO could effectively filter H2S even under room temperature. Dispersing the CuO particles into insulative Al2O3 carrier could not only selectively remove H2S without significant consumption of DMS but also isolate the underlying Pd–WO3 sensing layer’s response signal from interference caused by that of CuO. By adding the CuO/Al2O3 1:9 filtering overlayer, the response ratio of DMS to H2S was significantly enhanced from 3.3 to 50.4, furthermore, an ultrahigh response (701.3) to 10 ppm DMS, and a low limit of detection of 10 ppb under 90% RH were achieved, which promises the future breath disease diagnosis.