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

Abstract

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.