Taking air pollutant analysis to the next level
Researchers supported by the EU-funded ELFIS project have developed a novel laser-based device that makes it possible to continually measure in real time air pollutants and how they react with other gases and sunlight. The technology is believed to be the world’s first broadband ultraviolet (UV) dual-comb spectrometer, and is described in a paper published in the journal ‘Optica’. Dual-comb spectroscopy entails the use of two laser sources with discrete, regularly spaced frequency lines. Laser sources with this type of spectrum are called frequency combs since, when arranged according to its optical frequencies, the emitted light resembles the teeth of a comb. When the light penetrates a gaseous material, the gas’ molecules absorb some of the light, which changes the light’s wavelengths. These altered wavelengths provide scientists with valuable information about the ingredients and optical properties of the gas being analysed.
A unique feature
As explained in a news item posted on the website of ELFIS project coordinator Graz University of Technology (TU Graz), Austria, the ELFIS spectrometer’s special feature is that its laser system emits double light pulses in the UV spectrum. When the UV light penetrates the gas molecules, it excites them electronically and also makes them rotate and vibrate in ways that are unique to each gas. The broadband UV dual-comb spectrometer has three advantages over conventional spectrometers. First, the large bandwidth of the emitted UV light makes it possible to collect a lot of information on the gas sample’s optical properties with a single measurement. Its second advantage is the high spectral resolution achieved, and third, the short measurement times involved in gas sample analysis. “This makes our spectrometer suitable for sensitive measurements by which changes in gas concentrations and the course of chemical reactions can be observed very precisely,” remarks study lead author TU Graz PhD student Lukas Fürst. The research team used an air pollutant called formaldehyde to test their spectrometer. Formaldehyde is a strong-smelling, colourless, flammable chemical that is produced industrially and mainly used in the production of industrial resins for particleboard and coatings. “With our new spectrometer, formaldehyde emissions in the textile or wood processing industries as well as in cities with increased smog levels can be monitored in real time, thus improving the protection of personnel and the environment,” explains study senior author Prof. Birgitta Schultze-Bernhardt, also of TU Graz. However, formaldehyde is not the only pollutant on which the spectrometer can be used. Its application also extends to air pollutants such as nitrogen oxides and ozone, as well as other climate-relevant trace gases. The researchers supported by ELFIS (Electronic Fingerprint Spectroscopy) hope that this new information on how these gases affect the atmosphere could pave the way for new strategies to improve air quality. For more information, please see: ELFIS project
Keywords
ELFIS, spectrometer, dual-comb spectrometer, ultraviolet, UV, gas, laser, light, formaldehyde, air quality