Recently, Prof. GAO Xiaoming’s team from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, developed a novel photoacoustic spectroscopy (PAS)-based sensor that enabled simultaneous, high-sensitive detection of CO₂, CH₄, and N₂O, with improved long-term measurement accuracy. 

Related research result was published in Analytical Chemistry.

Global warming caused by greenhouse gases is now leading to phenomena such as melting glaciers, rising sea levels, and more intense storms, affecting the balance of the global ecosystem. PAS enables gas detection by detecting acoustic waves generated by the absorption of modulated optical radiation by the gas. It has the advantages of zero background, large dynamic range and unlimited detection bands.

The novel PAS greenhouse gas sensor developed in this research successfully achieved simultaneous detection of three kinds of greenhouse gases by coupling three acoustic resonators into a photoacoustic cell.

Researchers integrated a sine-wave-driven speaker into a special photoacoustic cell with multiple resonators. By using a mathematical method called fast Fourier transform, they converted the noise signals from the time domain to the frequency domain. This helped them quickly find the main frequencies of the acoustic resonators.

The researchers further improved the system's performance by making laser beams reflect back and forth four times inside the resonators. For gases like CO₂, N₂O, and NO, which took a long time to complete the relaxation process, researchers added water vapor to accelerate the relaxation rate. This increased the sensor's sensitivity.

The system was then validated through continuously measuring these gases from different sources for up to 10 hours.

“Our sensor offers an effective solution for environmental monitoring," said Dr. CAO Yuan, a member of the team.