Abstract
Most trace gas detection methods developed so far largely rely on active sampling procedures, which are known to introduce different kinds of artifacts. Here, we demonstrate sampling-free in situ trace gas detection in millimeter scale volumes with fiber coupled cantilever enhanced photoacoustic spectroscopy. Our 2.4 mm diameter fiber-tip sensor is free from the wavelength modulation induced background signal (a phenomenon that is often overlooked in photoacoustic spectroscopy) and reaches a normalized noise equivalent absorption coefficient of 1.3 × 10-9 W cm-1 Hz-1/2 for acetylene detection. To validate its in situ gas detection capability, we inserted the sensor into a mini fermenter for headspace monitoring of CO2 production during yeast fermentation. Our results show that the sensor can easily follow the different stages of the CO2 production of the fermentation process in great detail.
Highlights
Trace gas detection is important for many scientific and industrial purposes
From this set of data, one can calculate that the fibertip sensor reaches a noise equivalent concentration (NEC) of 24 ppb, which corresponds to a normalized noise equivalent absorption coefficient (NNEA) of 1.3 × 10−9 W cm−1 Hz−1/2
We developed a fiber-tip photoacoustic sensor that is background-free and that achieves a NNEA of 1.3 × 10−9 W cm−1 Hz−1/2
Summary
Majority of the trace gas detection methods developed so far largely depend on active sampling procedures in which the target gases have to be pumped or carried to a measurement cell, where the gas sample is analyzed in optimum settings. Even though these approaches allow one to achieve ultra-high sensitivity, the sampling procedures themselves often introduce some unavoidable limitations. Further difficulties arise when multiple gas sources are present in the sampling flow, as traditional sampling based detection methods are unable to track a specific gas component to its source This limitation appears as one of the major challenges of studies, for instance, on human breath and plant tissue gas analysis.
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