Bimetallic PdAg Nanocrystals Assembled on ZnO Nanorods: A Selective ppb-Level Triethylamine Sensor

Bimetallic nanocrystals typically exhibit excellent catalytic properties, surpassing the combination of two single metal properties, due to the synergistic effect of bimetal. This study aims to improve the response and selectivity and reduce power consumption of the ZnO sensor simultaneously through bimetallic nanocrystal modification. Pd, Ag, and PdAg nanocrystals with a size of 3 nm were successfully prepared and then uniformly assembled on the surface of ZnO nanorods to prepare Pd/ZnO, Ag/ZnO, and PdAg/ZnO composites, respectively. The PdAg/ZnO sensor exhibits ultrahigh response (10212) and selectivity, short response time (3 s), excellent long-term stability to 20 ppm of TEA at 250 °C, and actual detection limit as low as 10 ppb. Compared to ZnO, the PdAg/ZnO sensor not only reduces the operating temperature by 50 °C but also significantly improves response and selectivity. The ultrahigh response of the PdAg/ZnO sensor should be attributed to the strong dissociation effect of PdAg nanocrystals on oxygen and the formation of the Schottky barrier between PdAg and ZnO. The ultrahigh selectivity of the PdAg/ZnO sensor may be ascribed to the synergistic catalytic effect of PdAg nanocrystals for the oxidation of TEA. This study provides an effective strategy to comprehensively improve the response and selectivity and reduce operating temperature of MOS-based sensors.