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

Low-cost metal oxide sensors are highly attractive for emerging applications such as breath analysis. Particularly promising are p-type sensors that can operate at low temperatures, a key requirement for compact and low-power devices. To date, however, these sensors lack sufficient sensitivity, selectivity, and humidity robustness to fulfil stringent requirements faced in real applications. Herein, a flame-made and low-power sensor (operated at 150 °C) that consists of CeO₂-decorated CuO nanoparticles is introduced, as determined by X-ray diffraction and X-ray photoelectron spectroscopy analysis. Most remarkably, this sensor features excellent robustness to 10-90% relative humidity. This is attributed to the presence of CeO₂ nanoclusters, which may act by scavenging OH^- and allow the readsorption of oxygen onto the CuO surface. To demonstrate its immediate impact, this sensor is investigated for the detection of acetone, a biomarker for fat burning. It detects acetone with high sensitivity (i.e., 50 ppb) and features excellent acetone selectivity (>9.8) toward key inorganic interferants (i.e., NH₃, H₂, and CO). Most importantly, the CeO₂-CuO sensor accurately quantifies acetone concentrations in the exhaled breath of 16 volunteers (bias and precision of 90 and 457 ppb). As a result, it is attractive for low-power and humidity robust detection of volatiles in breath analysis.