Abstract
In this contribution, a new surface acoustic wave (SAW)-based sensor was proposed for sensing hydrogen sulfide (H2S) at room temperature (30 °C), which was composed of a phase discrimination circuit, a SAW-sensing device patterned with delay line, and a triethanolamine (TEA) coating along the SAW propagation path of the sensing device. The TEA was chosen as the sensitive interface for H2S sensing, owing to the high adsorption efficiency by van der Waals’ interactions and hydrogen bonds with H2S molecules at room temperature. The adsorption in TEA towards H2S modulates the SAW propagation, and the change in the corresponding phase was converted into voltage signal proportional to H2S concentration was collected as the sensor signal. A SAW delay line patterned on Y-cut quartz substrate with Al metallization was developed photographically, and lower insertion and excellent temperature stability were achieved thanks to the single-phase unidirectional transducers (SPUDTs) and lower cross-sensitivity of the piezoelectric substrate. The synthesized TEA by the reaction of ethylene oxide and ammonia was dropped into the SAW propagation path of the developed SAW device to build the H2S sensor. The developed SAW sensor was characterized by being collecting into the phase discrimination circuit. The gas experimental results appear that fast response (7 s at 4 ppm H2S), high sensitivity (0.152 mV/ppm) and lower detection limit (0.15 ppm) were achieved at room temperature. It means the proposed SAW sensor will be promising for H2S sensing.
Highlights
As a toxic combustible gas with peculiar odor, hydrogen sulfide (H2 S) may cause acute poisoning and chronic, which will damage the central nervous and respiratory system and stimulate the mucous membrane, and even cause death [1]
The surface acoustic wave (SAW) delay line pattern was used for the proposed SAW H2 S sensor, which was consists of two photo-lithographically defined Aluminum (Al) interdigital transducers (IDTs) separated by a path length of 2 mm fabricated on Y-cut quartz substrate with excellent temperature stability
The gas bag with H2 S mixed with N2 at various concentrations is connected to one branch of the Y-shaped shunt tube through a plastic tube, and the other branches of the Y-shaped shunt are connected to the gas bag with N2 acted as the carrier gas and the air pump, and connected to the SAW sensor
Summary
As a toxic combustible gas with peculiar odor, hydrogen sulfide (H2 S) may cause acute poisoning and chronic, which will damage the central nervous and respiratory system and stimulate the mucous membrane, and even cause death [1]. The metal oxide sensor realizes the detection of H2 S physically or chemically by the gas adsorption on the surface of the metal semiconductor, changing the resistance of the semiconductor. Such a sensor appears to have a fast response and high sensitivity, but still suffers from high working temperature to play the catalytic role, which induces more power and a weak working life. H2 S gas sensing technology, surface acoustic wave (SAW)-based gas sensors have attracted more attention because of its high sensitivity, fast response, and small volume. The proposed SAW sensor was exposed to various concentration of H2 S at room temperature (30 ◦ C), and the resulting performance, measured in terms of sensitivity, temperature stability, detection limit, and repeatability was characterized experimentally
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