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Nanotechnology to the Rescue: Highly selective sensing of methanol, acetone, NH3 or formaldehyde

Sotiris E. Pratsinis
Particle Technology Laboratory, ETH Zurich, Switzerland

Smartphones offer physical (voice, location and touch) recognition but not yet any molecular (chemical) recognition. Advances in flame-made gas sensors might be able to a address this capitalizing on combustion’s distinct advantages over traditional wet chemistry processes: a) very porous sensing films with metastable phase composition, b) embedded noble metals into chemoresistive metal oxide particles and c) capacity for online monitoring of film deposition and conversion of oxides to bromides for sensing NH3 at room temperature (Adv. Sci. 2020: 7, 1903390).

Gas sensors can be extremely compact, inexpensive and highly sensitive but their success is hindered frequently by limited selectivity (ACS Sens. 2019:4, 268). The latter is enhanced drastically by filters (or concentrators, Mater. Horizons 2021: 8, 661) and the unique nanostructure of flame-deposited sensing films. So the concept is exemplified, first, by assembling an adsorbent with a flame-made sensor to detect methanol down to ppb in the presence of high ethanol concentrations in both liquor and breath mixtures for prevention of methanol poisoning (Nature Comm. 2019: 10, 4220), a plague in the developing world. Such filter – sensors have been assembled into hand-held devices to detect quantitatively methanol in liquors from six continents (Nature Food 2020: 1, 351). Most notably, such devices detect methanol in antiseptics (iScience 2021: 102050) & breath samples of humans that had consumed beer, wine or liquor (Anal. Chem. 2021: 93, 1170). Also this device sensed formaldehyde in real indoor air down to 3 ppb (J. Hazar. Mater. 2020: 399, 123052).
Second, and if time permits, it will be shown how the selectivity is enhanced by continuous catalytic destruction of interferants (ethanol from sanitizers or breath isoprene) on flame-made catalysts before reaching sensors to detect breath acetone (Adv. Sci. 2020: 7, 2001503). Such devices have high selectivity and fast response – recovery times with stable performance over, at least, 145 days, as validated by mass spectrometry and tested with 146 breath samples during excersize and rest of volunteers for lipolysis monitoring (Small Sci. 2021, 1, 2100004).

Sotiris E. Pratsinis (www.ptl.ethz.ch) is professor of Process Engineering & Materials Science at ETH Zurich, Switzerland. He has a chemical engineering diploma from Aristotle University of Thessaloniki, Greece (1977) and a Ph.D. from University of California, Los Angeles (1985). He was in the faculty of University of Cincinnati till joining ETH in 1998. His research on multiscale aerosol particle dynamics facilitated flame synthesis of nanostructured materials with closely controlled characteristics. This scalable process contributed decisively to identifying the origins of nanosilver toxicity, and, for the first time, to flame-made theranostic materials, nutritional supplements and gas sensors. He has graduated 44 PhDs (now at leading positions in industry and academia worldwide), published 400+ refereed articles, filed 20+ patents that are licensed to industry and have contributed to creation of four spinoffs. One of them, HeiQ Materials, was the first ever from ETH Zurich to join the London Stock Exchange in December 2020.