Abstract
A fast and reliable photoacoustic (PA) sensor for trace gas detection is reported. The sensor is based on a 3D-printed resonant cell in combination with a continuous wave mode-hop-free external cavity quantum cascade laser to rapidly acquire gas absorption data in the midinfrared range. The cell is designed so as to minimize the window PA background at a selected acoustic resonance. The goal is a resonant PA cell capable of detecting the traces of gases using wavelength modulation of the laser source and second harmonic detection. The versatility and enhancement of the limit of detection at sub-ppm levels are investigated by monitoring specific lines of hydrogen sulfide (H2S). The noise-equivalent absorption normalized to laser-beam power and detection bandwidth is 1.07×10-8 W cm-1 Hz-1/2 for H2S targeting the absorption line at 1247.2 cm−1. These properties make the sensor suitable for various practical sensors for water quality applications.
Highlights
Hydrogen sulfide (H2S) is a very flammable, toxic, and corrosive gas
A photoacoustic sensor was presented that was based on the fast, low cost, compact, and reliable design of a resonant gas cell that can be fabricated using 3D-printing techniques
The use of plastic gas cells manufactured in materials such as high-impact polystyrene (HIPS) would allow the work in corrosive environments, such as in the presence of H2S, due to its chemical resistance, machinability, and low cost
Summary
Hydrogen sulfide (H2S) is a very flammable, toxic, and corrosive gas. It is commonly found in the oil and gas industries, volcanic gases, thermal waters, and as a result of the microbial breakdown of organic matter. It is a water pollutant in groundwater supplies [1], wastewater, and sewer systems [2] relevant to prevent due to health and corrosion problems. The presence of H2S is a cost-effective option for assessing the vulnerability of water supplies to microbial contamination in developing settings [3]. A number of different methods for H2S detection have been developed and validated [4], including photoacoustic spectroscopy (PAS) [5]
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