Terahertz continuous wave spectroscopy: a portable advanced method for atmospheric gas sensing

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Environmental Science

Background:

• Air quality monitoring is crucial due to increasing environmental concerns.
• Volatile organic compounds (VOCs) and greenhouse gases (GHGs) are significant air pollutants.
• Existing detection methods may lack portability or high resolution.

Purpose of the Study:

• To prove the feasibility of a compact, portable Terahertz (THz) spectroscopy system for air contaminant detection.
• To characterize the THz absorption spectra of five specific VOCs (methanol, ethanol, isopropanol, 1-butanol, 2-butanol).
• To investigate the detection of VOCs in mixtures with ambient air and ethanol.

Main Methods:

• Utilized Terahertz (THz) continuous wave high-resolution spectroscopy.
• Determined the molar absorption coefficients of five VOCs in the 0.06-1.2 THz spectral region.
• Analyzed the spectral response of VOC mixtures.

Main Results:

• Successfully characterized the THz optical response of methanol, ethanol, isopropanol, 1-butanol, and 2-butanol.
• Reported the THz spectral characterization of 1-butanol and 2-butanol for the first time.
• Demonstrated that spectral absorption of mixtures can be described as a linear combination of pure compounds, enabling component differentiation.

Conclusions:

• The developed THz spectroscopy system is feasible for detecting and differentiating VOCs in air.
• This proof-of-concept study validates the use of THz spectroscopy for environmental air pollutant tracking.
• The compact and portable nature of the system offers potential for widespread air quality monitoring applications.