Abstract
A highly sensitive quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a custom quartz tuning fork (QTF) with a small-gap of 200 μm was demonstrated. With the help of the finite element modeling (FEM) simulation software COMSOL, the change tendency of the QEPAS signal under the influence of the laser beam vertical position and the length of the micro-resonator (mR) were calculated theoretically. Water vapor (H2O) was selected as the target analyte. The experimental results agreed well with those of the simulation, which verified the correctness of the theoretical model. An 11-fold signal enhancement was achieved with the addition of an mR with an optimal length of 5 mm in comparison to the bare QTF. Finally, the H2O-QEPAS sensor, which was based on a small-gap QTF, achieved a minimum detection limit (MDL) of 1.3 ppm, indicating an improvement of the sensor performance when compared to the standard QTF that has a gap of 300 μm.
Highlights
Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a sensitive gas sensing technique that was invented in 2002 [1]
As an innovation based on traditional photoacoustic spectroscopy (PAS), QEPAS utilizes a millimeter-sized quartz tuning fork (QTF) as an acoustic transducer instead of a wide-band microphone employed in PAS
The performance of a QEPAS sensor system is correlated with the measured signal value
Summary
Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a sensitive gas sensing technique that was invented in 2002 [1]. An optimization of the dimensions of the QTF and the structure of the acoustic detection module could improve QEPAS sensor performance [13–17]. ~400–500 μm,μm, thisthis results in blockage of laser beam radiation the of times of a commercial [18]. Thespherical sphericalwave wavepropagation propagationdecreases decreaseswith withthe thecube cubeof of the the distance, distance, which suggests that the energy of the sound wave will diminish rapidly as the distance from which suggests that the energy of the sound wave will diminish rapidly as the distance from the the generation generation source source point point of of the the sound sound wave wave increases From this this perspective, perspective, employing employing aa small‐gap small-gap sensor. The improvement of a QEPAS sensor detection sensitivity using a QTF with a small‐gap of 200 μm was demonstrated for the first time.
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