Ultrasensitive gas sensor based on hollow tungsten trioxide-nickel oxide (WO3-NiO) nanoflowers for fast and selective xylene detection.

In this work, 5-20 at% gas-accessible WO3-NiO hollow nanoflowers were synthesized through a one-step hydrothermal route and used to fabricate metal oxide semiconductor (MOS) based gas sensor. The gas-accessible WO3-NiO hollow nanostructures showed much larger BET surface areas (168.0-203.8 m2 g-1) than that of the pure NiO (45.9 m2 g-1). In the comprehensive gas sensing test, the gas device based on 10 at% WO3-NiO hollow microspheres exhibited the best xylene sensing performance, showing ultrahigh xylene sensitivity (354.7-50 ppm) with short response-recovery times within 1 min. (51 and 57 s respectively) and ultralow detection limit (1.5-50 ppb xylene). Additionally, the 10 at% WO3-NiO based sensor also showed superior xylene selectivity against other interfering gases in a wide temperature range (250-350 °C). Especially at the optimal 300 °C, the 50-ppm xylene sensitivity was 8.1 and 10.3 times higher than that of 50-ppm representative acetone (Sxylene/Sacetone = 8.1) and ethanol (Sxylene/Sethanol = 10.3) gases, respectively. The mechanisms for the excellent xylene sensing performance were also discussed.