ABSTRACT: Abstract Acetone is a toxic air pollutant and a key breath marker for non?invasively monitoring fat metabolism. Its routine detection in realistic gas mixtures (i.e., human breath and indoor air), however, is challenging, as low?cost acetone sensors suffer from insufficient selectivity. Here, a compact detector for acetone sensing is introduced, having unprecedented selectivity (>250) over the most challenging interferants (e.g., alcohols, aldehydes, aromatics, isoprene, ammonia, H2, and CO). That way, acetone is quantified with fast response (<1 min) down to, at least, 50 parts per billion (ppb) in gas mixtures with such interferants having up to two orders of magnitude higher concentration than acetone at realistic relative humidities (RH = 30–90%). The detector consists of a catalytic packed bed (30 mg) of flame?made Al2O3 nanoparticles (120 m2 g?1) decorated with Pt nanoclusters (average size 9 nm) and a highly sensitive chemo?resistive sensor made by flame aerosol deposition and in situ annealing of nanostructured Si?doped ??WO3 (Si/WO3). Most importantly, the catalytic packed bed converts interferants continuously enabling highly selective acetone sensing even in the exhaled breath of a volunteer. The detector exhibits stable performance over, at least, 145 days at 90% RH, as validated by mass spectrometry. A solid?state detector is presented that quantifies acetone down to 50 parts per billion (ppb) with unmet selectivity in gas mixtures having two orders of magnitude higher interferant concentrations and in exhaled human breath. It is low?cost, combining a nanostructured Pt/Al2O3 catalyst with a Si/WO3 chemoresistive sensor in a compact design, and is promising for hand?held breath analyzers or wearable air quality monitors.
