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Appl. Sci. 2018, 8(3), 420; https://doi.org/10.3390/app8030420

Molecular Characterization and Theoretical Calculation of Plant Growth Regulators Based on Terahertz Time-Domain Spectroscopy

1,2
,
1,2
,
1,2
,
1,2
,
1,2
and
1,2,3,*
1
College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
2
Key Laboratory of Sensors Sensing, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, China
3
State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058, China
*
Author to whom correspondence should be addressed.
Received: 21 January 2018 / Revised: 15 February 2018 / Accepted: 4 March 2018 / Published: 12 March 2018
(This article belongs to the Special Issue Laser Processing for Bioengineering Applications)
View Full-Text   |   Download PDF [1116 KB, uploaded 12 March 2018]   |  

Abstract

Terahertz (THz), as an advanced spectral technology, has unique absorption characteristics for most biological macromolecules. In this work, the theoretical fundamentals for the application of THz time-domain spectroscopy (THz-TDS) to molecular characterization and fingerprint peak detection of three plant growth regulators (PGRs), including 2,4-Dichlorophenoxyacetic acid (2,4-D), forchlorfenuron (CPPU) and indole-3-acetic acid (IAA) were researched. Meanwhile, the effects of eight types of window functions on THz spectra were studied when converting time-domain spectra into frequency-domain spectra by Fourier transform. Based on the optimal window function, the THz absorption coefficient and refractive index of PGRs in frequencies of 0.2–3 THz were extracted. The molecule structure and vibration mode of three PGR samples were simulated by using density functional theory (DFT). The results showed that the three PGRs had different fingerprint peaks. Characteristic absorption and anomalous dispersion of 2,4-D were found at 1.35, 1.57 and 2.67 THz, those of CPPU were found at 1.77 and 2.44 THz, and the absorption peak of IAA was located at 2.5 THz. The absorption peaks obtained from THz spectra were identified according to the theoretical calculation results of DFT. These fingerprint peaks in THz spectra were generated by the interior stretching vibration and external deformation vibration of molecular groups. The experimental results revealed the feasibility of identifying PGRs species and detecting residues using THz-TDS. View Full-Text
Keywords: terahertz time-domain spectroscopy; window function; plant growth regulators; absorption coefficient; refractive index; density functional theory terahertz time-domain spectroscopy; window function; plant growth regulators; absorption coefficient; refractive index; density functional theory
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Qu, F.; Lin, L.; Cai, C.; Dong, T.; He, Y.; Nie, P. Molecular Characterization and Theoretical Calculation of Plant Growth Regulators Based on Terahertz Time-Domain Spectroscopy. Appl. Sci. 2018, 8, 420.

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