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With New Technology, You Can Find Hazardous Gases in Seconds
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Posted by Okachinepa on 01/12/2025 @


Courtesy of SynEvol
Credit: Florian Sterl
A novel technique for quickly and accurately detecting and identifying tiny levels of gases has been revealed by researchers. This novel technique, called coherently regulated quartz-enhanced photoacoustic spectroscopy, may open the door for extremely sensitive, real-time sensors that are employed in fields such as chemical process control, medical breath analysis, and environmental monitoring.
According to Simon Angstenberger, the research team leader from the University of Stuttgart in Germany, "since most gases are present in small amounts, detecting gases at low concentrations is important in a wide variety of industries and applications." "Our method is not restricted to any particular gas and does not require prior knowledge of the gas that might be present, in contrast to other trace gas detection techniques that rely on photoacoustics."
In just three seconds, the researchers showcased their approach by recording the entire methane spectrum (3050 to 3450 nanometers), which normally takes about half an hour.
"By identifying greenhouse gases like methane, which is a powerful contributor to climate change, this new technology could be used for climate monitoring," Angstenberger added. "It also has potential applications in chemical production plants for process control and the detection of toxic or flammable gas leaks, as well as in early cancer detection through breath analysis."
By examining each gas's distinct light absorption properties, spectroscopy may identify compounds, including gases, by creating a "fingerprint" for each one. Nevertheless, rapid detection of low gas concentrations necessitates not only a fast-tuning laser but also a very sensitive detection mechanism and accurate electrical control of the laser timing.
The researchers employed a laser with a very fast controllable wavelength in the new study that was created recently by partners at Stuttgart Instruments GmbH, a university spin-off. Additionally, they used QEPAS, or quartz-enhanced photoacoustic spectroscopy, as the sensitive detection method. By electronically detecting the vibrations of a quartz tuning fork at a resonance frequency of 12,420 Hz, which is caused by a laser pulsed at the same frequency, this spectroscopy method detects gas absorption. The fork's prongs move as a result of the laser's quick pulses heating the gas between them, producing a detectable piezoelectric voltage.
Although the tuning fork's high quality factor, which causes it to ring for a long time, enables us to detect tiny concentrations using what scientists refer to as resonant improvement, it restricts the rate of acquisition," Angstenberger clarified. This is because the fork continues to move when we switch wavelengths to get the molecule's fingerprint. We must somehow halt the movement in order to measure the next feature.
The researchers came up with a method known as coherent control to get around this issue. This required keeping the laser output power constant while adjusting the pulse time by precisely half a fork oscillation cycle. As a result, when the prongs of the fork move inward, the laser pulse reaches the gas between them. By acting against the prongs' movement as the gas heats up and expands, this method reduces the fork oscillation. The fork stops shaking after a few hundred microseconds of laser light flashing, at which point the subsequent measurement can be taken.
Angstenberger stated, "Ultra-fast identification of gases using their vibrational and rotational fingerprints is made possible by adding coherent control to QEPAS." "We can achieve real-time monitoring with a broad laser tuning range of 1.3 to 18 µm, making it capable of detecting virtually any trace gas, unlike traditional setups limited to specific gases or single absorption peaks."
Using a commercially available QEPAS gas cell and a laser created by Stuttgart Instruments, the researchers tested the new technique by analyzing a pre-calibrated methane mixture that had 100 parts per million of methane in the gas cell. They demonstrated that while the spectral fingerprint is blurred by scanning too quickly with standard QEPAS, it remains distinct and unaltered when using the coherent control approach.
In order to ascertain the new technology's maximum speed and lowest sensing concentration, the researchers intend to investigate its limitations in the future. Additionally, they hope to utilize it to sense several gasses simultaneously.
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