Innovative UV broadband spectrometer revolutionizes air pollutant analysis
Laser-based technology developed at TU Graz enables continuous real-time analysis of air pollutants as well as their interaction with other gases and sunlight.
Sunlight has a major influence on chemical processes, especially its high-energy UV radiation is strongly absorbed and dissolved by all materials photochemical reactions of the substances present in the air. A well-known example is the formation of ground-level ozone when UV light hits nitrogen oxides. A research team led by Birgitta Schutze-Bernhardt from the Institute for Experimental Physics at Graz University of Technology is now taking advantage of this high reaction potential for a new method of environmental monitoring: They have developed the world's first broadband UV dual-combspectrometer developed, with the Air pollutants continuously measured and their reaction with the environment can be observed in real time. A paper on the development was recently published in the specialist magazine Optica.
Dual comb spectrometers have been around for almost 20 years. A source emits light in a wide wavelength range, which, when shown according to its optical frequencies, is reminiscent of the teeth of a comb. If this light penetrates a gaseous sample of material, the molecules it contains absorb some of the light. The light wavelengths changed in this way allow conclusions to be drawn about the ingredients and optical properties of the gas being examined.
The special thing about the spectrometer developed by Birgitta Schutze-Bernhardt is that a laser system emits double light pulses in the ultraviolet spectrum. When this UV light hits gas molecules, it stimulates the molecules electronically and causes them to rotate and vibrate - so-called rovibronic transitions - which are unique to each gaseous substance. In addition, the broadband UV dual-comb spectrometer combines three properties that conventional spectrometers previously only had to offer in parts: (1) a large bandwidth of the emitted UV light, which provides a lot of information about the optical properties of the gas samples with a single measurement can be collected, (2) a high spectral resolution, which will also enable the investigation of complex gas mixtures such as our Earth's atmosphere in the future, and (3) short measurement times when examining the gas samples. “This makes our spectrometer suitable for sensitive measurements with which changes in gas concentrations and the course of chemical reactions can be observed very precisely,” explains Lukas Fürst, doctoral student in the “Coherent Sensing” working group and first author of the publication.
The researchers developed and tested their spectrometer using formaldehyde. The air pollutant is created when fossil fuels and wood are burned, as well as indoors through fumes from adhesives used in furniture. “With our new spectrometer, formaldehyde emissions in the textile or wood processing industry or in cities with increased smog levels can be monitored in real time, thus improving the protection of personnel and the environment,” explains Birgitta Schultze-Bernhardt. The application of the spectrometer can also be transferred to other air pollutants such as nitrogen oxides and ozone and other climate-relevant trace gases. The research team hopes that this will provide new insights into their effects in the atmosphere. Based on this, new strategies for improving air quality could be derived.
Source: chemie.de