Abstract
Catalytic packed bed filters ahead of gas sensors can drastically improve their selectivity, a key challenge in medical, food and environmental applications. Yet, such filters require high operation temperatures (usually some hundreds °C) impeding their integration into low-power (e.g., battery-driven) devices. Here, we reveal room-temperature catalytic filters that facilitate highly selective acetone sensing, a breath marker for body fat burn monitoring. Varying the Pt content between 0–10 mol% during flame spray pyrolysis resulted in Al2O3 nanoparticles decorated with Pt/PtOx clusters with predominantly 5–6 nm size, as revealed by X-ray diffraction and electron microscopy. Most importantly, Pt contents above 3 mol% removed up to 100 ppm methanol, isoprene and ethanol completely already at 40 °C and high relative humidity, while acetone was mostly preserved, as confirmed by mass spectrometry. When combined with an inexpensive, chemo-resistive sensor of flame-made Si/WO3, acetone was detected with high selectivity (≥225) over these interferants next to H2, CO, form-/acetaldehyde and 2-propanol. Such catalytic filters do not require additional heating anymore, and thus are attractive for integration into mobile health care devices to monitor, for instance, lifestyle changes in gyms, hospitals or at home.
Highlights
Chemical gas sensors are promising for the generation of handheld devices for air [1] or food quality monitoring [2], medical breath analysis [3] and human detection
Al-ZnO [18] and Si-containing WO3 (Si/WO3) [19] are interfered by isoprene that spikes during physical activity [17]
Room-temperature catalytic filters are introduced that remove alcohols, aldehydes and inorganics (e.g., H2 and CO) selectively over acetone. This is achieved by flame spray pyrolysis (FSP) yielding highly dispersed Pt/PtOx clusters (0–10 mol%) on Al2O3 nanoparticles at controlled composition [38]
Summary
Chemical gas sensors are promising for the generation of handheld devices for air [1] or food quality monitoring [2], medical breath analysis [3] and human detection (e.g., in search and rescue [4] or translational crime control [5]). A packed bed catalytic filter of flame-made ZnO nanoparticles at 260 ◦C was introduced that removed ethanol selectively (i.e., up to 185 ppm) over acetone [23] by exploiting the ZnO’s distinct surface basicity [24]. This filter did not remove critical methanol, isoprene and H2. Room-temperature catalytic filters are introduced that remove alcohols, aldehydes and inorganics (e.g., H2 and CO) selectively over acetone This is achieved by flame spray pyrolysis (FSP) yielding highly dispersed Pt/PtOx clusters (0–10 mol%) on Al2O3 nanoparticles at controlled composition [38]. To demonstrate the filters’ immediate practical impact, it was connected to a flame-made, chemoresistive Si/WO3 sensor [39] and tested for selective acetone sensing
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