Application of THz Vibrational Spectroscopy to Molecular Characterization and the Theoretical Fundamentals: An Illustration Using Saccharide Molecules

Abstract

This work illustrates several theoretical fundamentals for the application of THz vibrational spectroscopy to molecular characterization in the solid state using two different types of saccharide systems as examples. Four subjects have been specifically addressed: (1) the qualitative differences in the molecular vibrational signatures monitored by THz and mid-IR vibrational spectroscopy; (2) the selection rules for THz vibrational spectroscopy as applied to crystalline and amorphous systems; (3) a normal mode simulation, using α-l-xylose as an example; and (4) a rigorous mode analysis to quantify the percentage contributions of the intermolecular and intramolecular vibrations to the normal mode of interest.

State-of-the-art in terahertz sensing for food and water security – A comprehensive review

“…Baek et al [118]investigated the feasibility of detecting melamine in foodstuffs and found the characteristic absorption peaks of melamine at 2, 2.26, and 2.6 TH. Zhang et al [143] quantified the percentage contributions of the intermolecular and intramolecular vibrations to the normal mode by using THz vibrational spectroscopy to molecular characterization of saccharide molecules. Cheon et al [144] presented THz molecular resonance fingerprints of DNA methylation in cancer DNA, which could be quantified to identify the types of cancer cells.…”

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“…Quantum chemical calculations have been found to be an effective way to understand and interpret the experimental THz absorption properties. 28,29 Considering the experimental sample is a crystal powder, intermolecular interactions should be considered in the THz spectral analysis. Calculations based on the crystal cell have been suggested to be more reliable than those based on the isolated molecule.…”

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“…The calibration curve of melamine showed a regression coefficient was higher than 0.913, and the detection limit was lower than 13%. Zhang et al [27] illustrated the theory for the application of THz vibrational spectroscopy to molecular characterization of saccharide molecules. In addition, the percentage contributions of the intermolecular and intramolecular vibrations to the normal mode was quantified.…”