Highly sensitive room-temperature surface acoustic wave (SAW) ammonia sensors based on Co3O4/SiO2 composite films

•An ammonia gas sensor based on Co3O4/SiO2 composite films on a SAW device.•The Co3O4/SiO2 composite films inherit the porous structure of SiO2 film.•The existence of SiO2 enhances the sensor sensitivity to ammonia significantly.•The frequency shift of sensor is derived from the change of film condu...

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Bibliographic Details
Published in:Journal of hazardous materials 2014-09, Vol.280, p.127-133
Main Authors: Tang, Yong-Liang, Li, Zhi-Jie, Ma, Jin-Yi, Su, Hai-Qiao, Guo, Yuan-Jun, Wang, Lu, Du, Bo, Chen, Jia-Jun, Zhou, Weilie, Yu, Qing-Kai, Zu, Xiao-Tao
Format: Article
Language:English
Subjects:
Air Pollutants - analysis
Ammonia
Ammonia - analysis
Applied sciences
Co3O4
Cobalt - chemistry
Composite film
Environmental Monitoring - instrumentation
Exact sciences and technology
Oxides - chemistry
Pollution
SAW sensor
Silicon Dioxide - chemistry
SiO2
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Summary:•An ammonia gas sensor based on Co3O4/SiO2 composite films on a SAW device.•The Co3O4/SiO2 composite films inherit the porous structure of SiO2 film.•The existence of SiO2 enhances the sensor sensitivity to ammonia significantly.•The frequency shift of sensor is derived from the change of film conductance.•The sensor can detect ammonia gas in a concentration as low as 1ppm. Surface acoustic wave (SAW) sensors based on Co3O4/SiO2 composite sensing films for ammonia detection were investigated at room temperature. The Co3O4/SiO2 composite films were deposited onto ST-cut quartz SAW resonators by a sol–gel method. SEM and AFM characterizations showed that the films had porous structures. The existence of SiO2 was found to enhance the ammonia sensing property of the sensor significantly. The sensor based on a Co3O4/SiO2 composite film, with 50% Co3O4 loading, which had the highest RMS value (3.72), showed the best sensing property. It exhibited a positive frequency shift of 3500Hz to 1ppm ammonia as well as excellent selectivity, stability and reproducibility at room temperature. Moreover, a 37% decrease in the conductance of the composite film as well as a positive frequency shift of 12,500Hz were observed when the sensor was exposed to 20ppm ammonia, indicating the positive frequency shift was derived from the decrease in film conductance.
ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2014.08.001