Room-Temperature Catalyst Enables Selective Acetone Sensing

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.

Acetone Sensing and Catalytic Conversion by Pd-Loaded SnO2

“…Already, the addition of small amounts of Pd strongly decreases the oxidation temperature that practically levels off at about 150 • C at 1% Pd. Similar behavior has been observed recently [50] in catalytic oxidation of acetone over Pt/Al 2 O 3 . However, a stronger temperature shift from 325 to almost 50 • C was observed, and leveling off started with a Pt loading of 3%.…”

A Strategy to Enhance Humidity Robustness of p‐Type CuO Sensors for Breath Acetone Quantification

“…In addition, it is worth noting that CeO 2 –CuO sensor can also be used for the detection of ethanol (Figure S4a, Supporting Information). In cases where ethanol detection is undesired (e.g., for acetone detection in breath analysis), it can however be removed using an upstream room‐temperature catalytic 3 mol% Pt‐Al 2 O 3 filter [ 37 ] (see Supporting Information on material preparation and filter assembly). This filter combusts interfering ethanol to sensor‐inert species, while maintaining most of the acetone (i.e., 15% reduction).…”

“…This filter combusts interfering ethanol to sensor‐inert species, while maintaining most of the acetone (i.e., 15% reduction). The high reactivity at room temperature is attributed to the presence of well‐dispersed Pt clusters, [ 37 ] while the selective combustion of interferants over acetone may come from the Al 2 O 3 support [ 38 ] that converts alcohols preferentially over acetone. [ 39 ] This way, the acetone selectivity toward ethanol could be improved by >95% (Figure S6, Supporting Information).…”

“…While in our controlled setting, the ethanol varied only slightly, it could reach higher concentrations in some cases (e.g., during hand disinfection), affecting the sensor precision. In this case, a catalytic packed bed Pt/Al 2 O 3 filter [ 37 ] can be used to mitigate the ethanol problem (as shown in Figure S6, Supporting Information). It is worth noting that the sensor was also robust to abrupt changes in RH before and during the exhalations, as is illustrated in Figure 4d.…”

Handheld Device for Selective Benzene Sensing over Toluene and Xylene

“…The benzene response hardly changed (i.e., 2 ± 0.1, squares in Figure 1c ) between 10% and 80% RH. Moreover, the benzene selectivity over toluene (triangles) and m ‐xylene (circles) is preserved consistently, as both compounds are not picked up by the detector over the entire RH range, similar to heated [ 39 ] and room temperature [ 40 ] catalytic filters preceding sensors for selective acetone detection in human breath. [ 41 ] This is a distinct advantage for environmental benzene monitoring over other sensors susceptible to humidity changes: For instance, Au/MWCNT suffered from a large loss in benzene response (i.e., 80%) when increasing the RH from 10 to 60%.…”