Detection of volatile organic compounds: From chemical gas sensors to terahertz spectroscopy

Volatile organic compounds are released by different sources causing air pollution. Moreover, some of these carbon-based organic chemicals are considered as biomarkers in the exhaled breath of individuals and can be used to identify various kinds of diseases. Hence, the increasing demand to control air quality and human health has promoted the development of monitoring systems based on high-performance gas sensing structures. This review highlights the achievements in sensing technologies for the detection of volatile organic compounds. Particularly, chemiresistive gas sensors and detection systems based on the terahertz spectroscopy method are outlined. The progress in research studies is discussed and the potential of both techniques is evaluated considering the current challenges. Afterward, a brief summary is also provided along with the advances and issues for future investigations and the manufacturing of highly sensitive and selective monitoring systems.