A research team led by Professor Zhang Weijun at the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has developed a new detection technology that enables rapid and sensitive detection of nitrogen dioxide (NO₂).

As NO₂ is a major pollutant affecting air quality, highly sensitive and accurate measurement of NO₂ is of great significance to atmospheric chemistry research and air pollution prevention and control.

Source: Zhou Jiacheng

In this research, an amplitude modulation technique was applied to a multimode diode laser for the first time, and an amplitude modulated multimode-diode-laser-based Cavity Enhanced Absorption Spectroscopy (AM-CEAS) system was developed for extremely sensitive NO₂ detection.

The new instrument uses phase-sensitive detection for ultra-sensitive absorption measurement. The accuracy of it is over four times lower than that of the Cavity Ring-down Spectroscopy (CRDS) method using the same instrument during one second and 30 seconds of data acquisition time.

Combined with ring-down time measurement, the AM-CEAS method eliminates the calibration process of mirror reflectivity and achieves the measurement of absolute concentration of NO₂. It also has the advantages of high injection efficiency, low cavity-mode noise and phase-sensitive detection of modulation spectroscopy.

The AM-CEAS instrument is a simple, reliable, low-cost, self-calibration tool suitable for long-term stability and low maintenance requirements, with good prospects for scientific research and business applications.

The technology is detailed in the article, Amplitude-Modulated Cavity-Enhanced Absorption Spectroscopy with Phase-Sensitive Detection: A New Approach Applied to the Fast and Sensitive Detection of NO₂, which was published in the journal Analytical Chemistry.