Abstract-Thermal Terahertz Analysis for the Detection of Trace Organic Matter

 

Fankai Qin, Ru Chen, Yicen Li, Zhaohui Meng, Sitong Chen, Kun Zhao, Xinyang Miao, Wenfeng Xiang, Wenzheng Yue, Honglei Zhan, 

https://pubs.acs.org/doi/10.1021/acs.energyfuels.0c04354

The technology of trace organic matter (OM) detection offers researchers numerous intriguing possibilities, ranging from fundamental science to applications in many fields. This study proposes a thermal terahertz (THz) analysis (TTA) method that is suitable for detecting trace OM in the field of oil–gas resource and can analyze the differences in the content and type of trace OM. In this research, THz time-domain spectroscopy (THz-TDS) technology combined with pyrolysis technology were used to detect the pyrolysis characteristics of trace OM in sand collected from a desert oilfield. According to thermogravimetric analysis, the main pyrolysis temperature range of the OM was 300–600 °C. Further analysis of the spectra indicated that when the pyrolysis temperature was 300 °C, the OM content in the sand was the highest and the THz waves were the most attenuated due to the strong interaction between OM and THz waves. As the pyrolysis temperature increased, the OM was gradually pyrolyzed into gas and escaped and the peak amplitude (Ep) of the THz-TDS clearly increased. When the pyrolysis temperature reached 600 °C, the OM was completely pyrolyzed while the Ep of the THz-TDS changed very little. Consequently, the trace OM detection method based on THz spectroscopy combined with pyrolysis technology is expected to become a new complementary means for the detection of trace OM information.

Abstract-Determining the Humidity-Dependent Ortho-to-Para Ratio of Water Vapor at Room Temperature Using Terahertz Spectroscopy

Xinyang Miao, Jing Zhu, Kun Zhao, Honglei Zhan, Wenzheng Yue,

https://www.osapublishing.org/as/abstract.cfm?uri=as-72-7-1040&origin=search

The origin of the water spin isomers observed under various physico-chemical conditions is of great interest, including that of H2O molecules in the gas phase. Here, terahertz time-domain spectroscopy (THz-TDS) was used to study the humidity-dependent ortho-to-para (O/P) ratio of water vapor at room temperature. The relative contents of para and ortho molecules were obtained by fitting the absorption lines of water vapor showing the relationship between the spin isomer contents and humidity. Larger O/P ratios with values of 3.2 were observed at lower humidity (<20%) due to the stronger attractive forces of para molecules. The concentration of the ortho isomers then began to decrease at higher humidity (>20%) due to the preferential formation of dimers and clusters at increasing concentrations. Thus, the ratio gradually decreased with increasing humidity.

© 2018 The Author(s)