Sn Doped Co3O4 Nanosheet Based Isoprene Sensor for Dynamic Metabolic Monitoring.

Sensitive and selective analysis of ppb-level breath isoprene (C5H8) by a smart chemiresistive gas sensor has attracted increasing attention for real-time metabolic monitoring. However, it remains a challenge due to its relatively weak reducibility. Herein, we report a high-performance isoprene sensor based on Sn-doped Co3O4 nanosheets. Abundant asymmetric oxygen vacancies (Co3+-OV-Sn4+) via 1 at % Sn doping, as well as preferential (400) exposed facets, noticeably improve the partial oxidation capability of isoprene at low temperature, contributing to a drastic enhancement of isoprene response. The present sensor exhibits a tiny response to diverse interference gas molecules in breath (acetone, ethanol, CO, etc.), an exceptional isoprene response (Rg/Ra = 115.2 to 10 ppm) at a low operation temperature of 100 °C, and an ultralow detection limit (LoD) of 0.13 ppb. Quantitative tracking of ppb-level breath isoprene variations during exercise could be achieved, as verified by the high linear correlation (R2 > 0.98) with proton transfer reaction-mass spectrometry (PTR‑MS) analysis, highlighting its potential for noninvasive metabolic monitoring.