Chem. J. Chinese Universities ›› 2020, Vol. 41 ›› Issue (9): 1968.doi: 10.7503/cjcu20200401

• Article • Previous Articles     Next Articles

Near Infrared Spectroscopy for Low-temperature Water Structure Analysis

ZHAO Hongtao, SUN Yan, GUO Yichang, CAI Wensheng, SHAO Xueguang()   

  1. Research Center for Analytical Sciences, College of Chemistry, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China
  • Received:2020-06-30 Online:2020-09-10 Published:2020-09-02
  • Contact: SHAO Xueguang E-mail:xshao@nankai.edu.cn
  • Supported by:
    Supported by the National Natural Science Foundation of China(21775076)

Abstract:

The structure of water and its flexibility have been widely studied due to the mysterious behavior in biological and chemical process. Under supercooled conditions, water may have special properties, such as the thermodynamic response and phase transformation. In this study, water structure in dimethyl sulfoxide(DMSO)-water mixture at low temperature was studied by near infrared spectroscopy combined with Raman spectroscopy and molecular dynamics simulation for understanding the mechanism of DMSO in reducing the freezing point of water. Through the analysis of the near-infrared and Raman spectra of the mixtures with diffe- rent DMSO contents, the spectral feature reflecting the interaction of DMSO and water was found, and two hydrogen-bonded DMSO-water structures(DW2 and D2W) were determined in the mixture of different DMSO/ water ratio. Analyzing the spectra obtained by temperature-dependent near-infrared spectroscopy for a 30%DMSO-water mixture over the temperature range from 20 oC to -70 oC, it was found that DW2 structure inhibits the formation of tetrahedral water structure at low temperature and this founding can be used to explain the reason for DMSO reducing the freezing point of the mixture. The result of molecular dynamics simulation also gave a proof for the reliability of the conclusion.

Key words: Near infrared spectroscopy, Water structure, Dimethyl sulfoxide(DMSO)-water mixture, Freezing point

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