Abstract
A new room temperature supra-molecular cryptophane A (CrypA)-coated surface acoustic wave (SAW) sensor for sensing methane gas is presented. The sensor is composed of differential resonator-oscillators, a supra-molecular CrypA coated along the acoustic propagation path, and a frequency signal acquisition module (FSAM). A two-port SAW resonator configuration with low insertion loss, single resonation mode, and high quality factor was designed on a temperature-compensated ST-X quartz substrate, and as the feedback of the differntial oscillators. Prior to development, the coupling of modes (COM) simulation was conducted to predict the device performance. The supramolecular CrypA was synthesized from vanillyl alcohol using a double trimerisation method and deposited onto the SAW propagation path of the sensing resonators via different film deposition methods. Experiential results indicate the CrypA-coated sensor made using a dropping method exhibits higher sensor response compared to the unit prepared by the spinning approach because of the obviously larger surface roughness. Fast response and excellent repeatability were observed in gas sensing experiments, and the estimated detection limit and measured sensitivity are ~0.05% and ~204 Hz/%, respectively.
Highlights
Mining accidents with heavy casualties caused by methane gas explosions occur frequently, leading to huge economic losses
The surface acoustic wave (SAW) sensor was exposed to N2 and to characterize the sensor responses towards methane gas at room temperature
(Zurich, Switzerland), the detection the International Union of Pure and Applied Chemistry (IUPAC) (Zurich, Switzerland), the detection limit of of the the developed developed sensor sensor can can be be estimated estimated to to less less than than 0.05%, 0.05%, the the same same rank rank to to the the reported reported limit sensor but the dynamic range is larger more
Summary
Mining accidents with heavy casualties caused by methane gas explosions occur frequently, leading to huge economic losses. The most effective way to respond to such an issue is the early detection and monitoring of methane accumulation in mines or landfills. The current approaches for sensing methane gas include gas chromatography, electrochemical, optical, and semiconductor technologies. These techniques differ substantially in their approaches, and each have their own advantages and disadvantages [1,2,3,4]. Gas chromatography can perform an accurate quantitative analysis on methane gas, but, it is expensive and unsuitable for in situ monitoring which is essential in most cases [1]. The main challenge for optical methane sensors is that it is hard to find a suitable light source in the infrared range, and Sensors 2016, 16, 73; doi:10.3390/s16010073 www.mdpi.com/journal/sensors
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