NiO/NiWO4 Composite Yolk–Shell Spheres with Nanoscale NiO Outer Layer for Ultrasensitive and Selective Detection of Subppm-level p‑Xylene

• Published in: ACS applied materials & interfaces Vol. 9; no. 37; pp. 32034 - 32043
• Main Authors: Kim, Tae-Hyung, Kwak, Chang-Hoon, Lee, Jong-Heun
• Format: Journal Article
• Language: English
• Published: American Chemical Society 20.09.2017
• Subjects: gas sensor; p-xylene; mesopore; heterostructure; NiO/NiWO4
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.7b10294

NiO/NiWO4 composite yolk–shell spheres with a nanoscale NiO outer layer were prepared using one-pot ultrasonic spray pyrolysis and their gas sensing characteristics were studied. The NiO/NiWO4 yolk–shell spheres exhibited an extremely high response to 5 ppm p-xylene (ratio of resistance to gas and air = 343.5) and negligible cross-responses to 5 ppm ethanol, ammonia, carbon monoxide, hydrogen, and benzene, whereas pure NiO yolk–shell spheres showed very low responses and selectivity to all the analyte gases. The detection limit for p-xylene was as low as 22.7 ppb. This ultrasensitive and selective detection of p-xylene is attributed to a synergistic catalytic effect between NiO and NiWO4, high gas accessibility with large specific surface area, and increased chemiresistive variation due to the formation of a heterojunction. The NiO/NiWO4 yolk–shell spheres with a thin NiO outer layer can be used to detect subppm-level p-xylene in a highly sensitive and selective manner for monitoring indoor air pollution.