NH3-Sensing Mechanism Using Surface Acoustic Wave Sensor with AlO(OH) Film

Abstract

In this study, AlO(OH) (boehmite) film was deposited onto a surface acoustic wave (SAW) resonator using a combined sol-gel and spin-coating technology, and prepared and used as a sensitive layer for a high-performance ammonia sensor. The prepared AlO(OH) film has a mesoporous structure and a good affinity to NH3 (ammonia gas) molecules, and thus can selectively adsorb and react with NH3. When exposed to ammonia gases, the SAW sensor shows an initial positive response of the frequency shift, and then a slight decrease of the frequency responses. The sensing mechanism of the NH3 sensor is based on the competition between mass-loading and elastic-loading effects. The sensor operated at room temperature shows a positive response of 1540 Hz to 10 ppm NH3, with excellent sensitivity, selectivity and stability.

Investigation of Ammonia-sensing Mechanism on Polypyrrole Gas Sensor Based on Experimental and Theoretical Evidence

“…Ammonia is a harmful gas and environmental pollutant, (1,2) and the atmospheric concentration of ammonia is gradually increasing due to a wide range of human activities, which include agriculture and the manufacturing of electronics and chemicals. (3,4) The lower limit of human olfactory perception of ammonia is about 50 ppm, and the respiratory system, eyes, and skin are damaged when the ammonia concentration is over 500 ppm.…”

Preparation of MoS2 Nanospheres using a Hydrothermal Method and Their Application as Ammonia Gas Sensors Based on Delay Line Surface Acoustic Wave Devices

“…The frequency variation for 5–50 ppm NH 3 gas is shown in Table 2 for sensor−3, from which the sensitivity was calculated to be 4878 Hz/ppm. Compared with other works in the literature, this study showed an excellent sensitivity performance [ 34 , 35 , 36 , 37 , 38 ], as shown in Table 3 .…”

Development of Dual-Selective Chemiresistive Sensor for NH3 and NOx at Room Temperature Using MoS2/MoO2 Heterostructures

“…The presence of the hydroxyl group was further confirmed in the FTIR and XPS results. Moreover, the physically adsorbed hydroxyl group amplifies the adsorption of gas molecules . However, beyond 78% relative humidity, the sensor’s response decreases, indicating that the continuous moisture layer completely occupies the active sites of the MoS 2 surface, resulting in a water-poisoning effect …”