Effects of Au Addition on the Performance of Thermal Electronic Noses Based on Porous Cu₂O-SnO₂ Nanospheres

The electronic nose is an increasingly useful tool in many fields and applications. Our thermal electronic nose approach, based on nanostructured metal oxide chemiresistors in a thermal gradient, has the advantage of being tiny and therefore integrable in portable and wearable devices. Obviously, a wise choice of the nanomaterial is crucial for the device's performance and should therefore be carefully considered. Here we show how the addition of different amounts of Au (between 1 and 5 wt%) on Cu₂O-SnO₂ nanospheres affects the thermal electronic nose performance. Interestingly, the best performance is not achieved with the material offering the highest intrinsic selectivity. This confirms the importance of specific studies, since the performance of chemoresistive gas sensors does not linearly affect the performance of the electronic nose. By optimizing the amount of Au, the device achieved a perfect classification of the tested gases (acetone, ethanol, and toluene) and a good concentration estimation (with a mean absolute percentage error around 16%). These performances, combined with potentially smaller dimensions of less than 0.5 mm², make this thermal electronic nose an ideal candidate for numerous applications, such as in the agri-food, environmental, and biomedical sectors.