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Hou S, Liu Q, Deng H, He J, Zhao W, Wu Z, Zhang Q, Shang L. Identification and low-frequency vibrational analysis of three free anthraquinones via terahertz spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 293:122439. [PMID: 36773425 DOI: 10.1016/j.saa.2023.122439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/11/2023] [Accepted: 02/01/2023] [Indexed: 06/18/2023]
Abstract
In this study, terahertz time-domain spectroscopy (THz-TDS) was used to obtain the terahertz absorption spectra of three free anthraquinones (Chrysophanol, Emodin, Physcion) in the frequency range of 0.2-4.3 THz. The results show that terahertz spectroscopy is an effective detecting such compounds. Meanwhile, the theoretical spectrum using density functional theory calculations agrees well with the experimental spectrum. A modal decoupling method was used to identify each low-frequency vibrational mode and determine the average contribution of different atoms and groups. Modal decoupling provides a better understanding of molecules' mixed vibrational modes and enables quantifying the atoms' vibrational contributions. Results show that the substituent group facilitates the transition between the fundamental vibrational modes; subsequently, the substituent group shifts the vibrational centre of gravity of the three molecules and affects the vibrational contribution of hydrogen bonds. Furthermore, insignificant Emodin absorption is related to the nearly symmetrical structure formed by the substituents. The feasibility of terahertz analysis of differential molecular structures has also been confirmed.
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Affiliation(s)
- Senlin Hou
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Quancheng Liu
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China.
| | - Hu Deng
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China; Tianfu Institute of Research and Innovation, Southwest University of Science and Technology, ChengDu 610299, China
| | - Jun He
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Wei Zhao
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Zhixiang Wu
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Qi Zhang
- Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, China
| | - Liping Shang
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China; Tianfu Institute of Research and Innovation, Southwest University of Science and Technology, ChengDu 610299, China.
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Zhu Z, Bian Y, Zhang X, Zeng R, Yang B. Study on the crystallization behavior and conformation adjustment scale of poly(lactic acid) in the terahertz frequency range. Phys Chem Chem Phys 2023; 25:8472-8481. [PMID: 36883295 DOI: 10.1039/d3cp00208j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The observed properties of crystalline polymers are determined by their internal structure, which in turn is the result of their different crystallization behaviors. Here, we investigate the crystallization behavior of poly(lactic acid) (PLA) by terahertz time-domain spectroscopy (THz-TDS) at varied temperatures. We find that the changes in the chain packing and conformation of PLA are characterized by THz spectroscopy. Combining X-ray diffraction (XRD) and infrared spectroscopy (IR), we attributed the blue-shift of the THz peak to the tightness of the chain packing, while its absorption enhancement is caused by the conformation transition. The effects of chain packing and chain conformation on the characteristic peak are phased. Furthermore, absorption discontinuities of the characteristic peaks of PLA crystallized at different temperatures are observed, which originated from differences in the degree of conformational transition caused by different thermal energies. We find that the crystallization temperature at which the absorption mutation of PLA occurs corresponds to the temperature at which the motion of the segment and molecular chain is excited, respectively. At these two temperatures, PLA exhibits different scales of conformational transitions leading to stronger absorption and larger absorption changes at higher crystallization temperatures. The results demonstrate that the driving force of PLA crystallization is indeed from changes in chain packing and chain conformation, and the molecular motion scale can also be characterized by THz spectroscopy.
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Affiliation(s)
- Zhenqi Zhu
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China.
| | - Yujing Bian
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China.
| | - Xun Zhang
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China.
| | - Ruonan Zeng
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China.
| | - Bin Yang
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China.
- Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China
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Quancheng L, Hu D, Hongzhen L, Minchang W, Qi Z, Ying K, Liping S. Terahertz spectral identification and low-frequency vibrational analysis of dinitrotoluene isomers. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 283:121722. [PMID: 35952591 DOI: 10.1016/j.saa.2022.121722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 06/15/2023]
Abstract
Identifying dinitrotoluene (DNT) isomers has always been a challenging problem. In this study, five DNT isomers were investigated using terahertz time-domain spectroscopy (THz-TDS), which demonstrated significant spectral differences including variations in absorption positions and intensities. This suggests that THz-TDS is ideal for rapid identification of DNT isomers. We also employed density functional theory to further discuss the origin of these spectral differences. The results indicate that steric effects between substitute groups, rather than inter-molecular hydrogen bonding, lead to differences in low-frequency vibrations.
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Affiliation(s)
- Liu Quancheng
- School of Information Engineering, Southwest University of Science and Technology, Mianyang, China.
| | - Deng Hu
- School of Information Engineering, Southwest University of Science and Technology, Mianyang, China
| | - Li Hongzhen
- Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, China
| | - Wang Minchang
- State Key Laboratory of Fluorine&Nitrogen Chemicals, Xi'an Modern Chemistry Research Institute, Xi'an, China
| | - Zhang Qi
- Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, China
| | - Kang Ying
- State Key Laboratory of Fluorine&Nitrogen Chemicals, Xi'an Modern Chemistry Research Institute, Xi'an, China
| | - Shang Liping
- School of Information Engineering, Southwest University of Science and Technology, Mianyang, China
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Zeng R, Bian Y, Zhang X, Zhu Z, Yang B. Terahertz Spectroscopy Study of the Stereoisomers of Threonine. APPLIED SPECTROSCOPY 2022; 76:1132-1141. [PMID: 35469427 DOI: 10.1177/00037028221099958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The terahertz (THz) band contains a wealth of information about vibration and rotational energy levels, most of the vibration modes between amino acid molecules are in the THz band, so it reflects many unique absorption characteristics in the THz band. The use of terahertz time-domain spectroscopy can not only effectively identify different kinds of amino acids but also distinguish various isomers of the same amino acid due to the varied vibration modes. The absorption spectra of four stereoisomers of threonine were investigated by terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infrared spectroscopy. The results show that the isomers show similarity in the infrared band, while manifest evidently the similarity between enantiomers L-threonine and D-threonine, and between L-allo-threonine and D-allo-threonine, and the difference between diastereoisomer L-threonine/D-threonine and L-allo-threonine/D-allo-threonine in the terahertz band. In order to fully understand the origin of the terahertz absorption characteristics of isomer molecules, simulation calculations were carried out in combination with density functional theory to connect the vibrational modes and molecular structures, Furthermore, the unit cell configurations of L-thr and L-allo-thr and the differences between various low-frequency vibrational modes are analyzed from the perspective of hydrogen bond configuration. By further extracting terahertz optical parameters such as refractive index and imaginary part of the dielectric constant of threonine isomers, the results show that the refractive index spectrum and dielectric loss spectrum can clearly show the response characteristics of the orientation polarization of dipole inside threonine isomers in terahertz band.
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Affiliation(s)
- Ruonan Zeng
- College of Textile Science and Engineering (International College of Silk), 12646Zhejiang Sci-Tech University, Hangzhou, China
| | - Yujing Bian
- College of Textile Science and Engineering (International College of Silk), 12646Zhejiang Sci-Tech University, Hangzhou, China
| | - Xun Zhang
- College of Textile Science and Engineering (International College of Silk), 12646Zhejiang Sci-Tech University, Hangzhou, China
| | - Zhenqi Zhu
- College of Textile Science and Engineering (International College of Silk), 12646Zhejiang Sci-Tech University, Hangzhou, China
| | - Bin Yang
- College of Textile Science and Engineering (International College of Silk), 12646Zhejiang Sci-Tech University, Hangzhou, China
- Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Ministry of Education, 12646Zhejiang Sci-Tech University, Hangzhou, China
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Zhu Z, Bian Y, Zhang X, Zeng R, Yang B. Study of Crystallinity and Conformation of Poly(lactic acid) by Terahertz Spectroscopy. Anal Chem 2022; 94:11104-11111. [PMID: 35881498 DOI: 10.1021/acs.analchem.2c02652] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
During crystallization, conformational changes are often accompanied by the formation of interactions. Terahertz (THz) spectroscopy exhibits strong responses to the crystalline poly(lactic acid) (PLA). Therefore, we estimate the relative crystallinity and investigate the effect of conformational transition on the vibration of PLA by THz spectroscopy. By comparing with the results of X-ray diffraction (XRD) and differential scanning calorimetry (DSC), the validity of THz spectroscopy to calculate crystallinity is verified. Furthermore, the peak intensity of PLA at 2.01 THz increases with crystallinity. Combined with Fourier transform infrared spectroscopy (FTIR), the vibrational intensity of PLA at 2.01 THz is highly correlated with the contribution of gt conformation, showing a linear relationship. In addition, the vibrational peak of PLA also reflects the interchain interactions. We believe that the increase in peak intensity with increasing crystallinity originates from the effect of the dipole-dipole interactions between the carbonyl groups. Our study demonstrates the ability of THz spectroscopy to estimate the crystallinity of PLA, and the peak at 2.01 THz shows conformational and interaction sensitivities.
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Affiliation(s)
- Zhenqi Zhu
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
| | - Yujing Bian
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
| | - Xun Zhang
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
| | - Ruonan Zeng
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
| | - Bin Yang
- College of Textile Science and Engineering (International Institute of Silk), Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China.,Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
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