Recent advances in quartz enhanced photoacoustic sensing

Abstract

This review aims to discuss the latest advancements in quartz-enhanced photoacoustic spectroscopy (QEPAS) based trace-gas sensing. Starting from the QEPAS basic physical principles, the most used QEPAS configurations will be described. This is followed by a detailed theoretical analysis and experimental study regarding the influence of quartz tuning forks (QTFs) geometry on their optoacoustic transducer performance. Furthermore, an overview of the latest developments in QEPAS trace-gas sensor technology employing custom QTFs will be reported. Results obtained by exploiting novel micro-resonator configurations, capable of increasing the QEPAS signal-to-noise ratio by more than two orders of magnitude and the utilization of QTF overtone flexural modes for QEPAS based sensing will be presented. A comparison of the QEPAS performance of different spectrophone configurations is reported based upon signal-to-noise ratio. Finally, a novel QEPAS approach allowing simultaneous dual-gas detection will be described.

Quartz-Enhanced Photoacoustic Detection of Ethane in the Near-IR Exploiting a Highly Performant Spectrophone

“…The spectrophone SP1 employs a standard 32.7 kHz quartz tuning fork (QTF) coupled with two 4.4 mm long tubes having inner diameters of 0.6 mm and positioned 50 µm distant from the QTF surface. This resonator tubes configuration has represented the reference spectrophone structure for QEPAS experiments until 2013, allowing a signal-to-noise ratio (SNR) enhancement up to a factor of 30 compared to a bare QTF [19]. Spectrophone SP2 is composed of a QTF with T-shape prongs coupled with two 12.4 mm long resonator tubes having inner diameters of 1.59 mm and positioned 200 µm distant from the QTF.…”

“…For instance, a non-dispersive infrared (NDIR) sensor was mounted on a UAV for environmental monitoring and proved to be able to detect CO 2 concentrations of 0.5% in air with a 10 s warm-up time [8]. Similarly, a tunable diode laser absorption spectroscopy (TDLAS) sensor was mounted on a UAV for remote detection of CH 4 clouds and sources localization [18].Among the laser-based techniques, quartz-enhanced photoacoustic spectroscopy (QEPAS) offers unique advantages, such as the possibility to avoid the use of optical detectors, wavelength-independent detection, compact and robust sensor architectures [19]. The core element of a QEPAS sensor is the spectrophone composed of a quartz tuning fork (QTF) and a pair of micro-resonator tubes.…”

“…Among the laser-based techniques, quartz-enhanced photoacoustic spectroscopy (QEPAS) offers unique advantages, such as the possibility to avoid the use of optical detectors, wavelength-independent detection, compact and robust sensor architectures [19]. The core element of a QEPAS sensor is the spectrophone composed of a quartz tuning fork (QTF) and a pair of micro-resonator tubes.…”

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

“…Continued efforts are taken to exploit the advantages of PAS while, at the same time, achieving or exceeding the sensitivity of TLAS, e.g. by improving acoustic transducers [10] or by investigating novel approaches to PAS and other techniques of indirect spectroscopy [11,12].…”

Damping Mechanisms of Piezoelectric Quartz Tuning Forks Employed in Photoacoustic Spectroscopy for Trace Gas Sensing

“…Exploiting the piezoelectric effect occurring in quartz, a charge displacement occurs on prong surface as the prongs bend, leading to the generation of a piezoelectric current proportional to the amplitude of the exciting voltage . Recently, the use of QTFs has been extended to other applications, such as atomic force microscopy, photoacoustic gas sensing, rheology, and high‐resolution accelerometer and gyroscopes measurements . In quartz‐enhanced photoacoustic spectroscopy (QEPAS) the QTF is immersed in a low‐pressure gas and a laser beam is focused between the two prongs.…”