浓度微扰下硝酸水溶液中氢键作用的二维相关拉曼光谱研究

doi:10.3964/j.issn.1000-0593(2025)04-0958-06

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Abstract Nitric acid is known as the “mother of the national defense industry”, and the dilution concentration of its aqueous solution is crucial for producing explosives. This paper improves the Raman excitation and collection efficiency by constructing a cavity-enhanced Raman spectrometer. It achieves the measurement of aqueous nitric acid solutions with fine concentration differences ranging from 35.49% to 88.98% in nitric acid mass fraction (ω). Analyzing the Raman spectra of nitric acid within the range of 900～1 400 cm^-1, it was found that the N—OH stretching vibration mode at 965 cm^-1 showed a significant frequency shift with changes in nitric acid concentration. When 35.49%≤ω≤55.10%, an increase in nitric acid concentration induces a rapid red shift in the N—OH stretching vibration mode, attributed to the formation of HNO₃—nH₂O (n=1, 2, …) cluster structures. When ω>55.10%, the degree of redshift in the N—OH stretching vibration mode gradually decreases, which may be because the hydrogen bonds (H-bonds) formed between nitric acid and water molecules decrease. When ω>68.78%, the degree of redshift in the N—OH stretching vibration mode expands again due to increased H-bonds within nitric acid molecules. In addition, the intensity of the N—O fully symmetric stretching vibration mode at 1 050 cm^-1 and the N—OH asymmetric stretching vibration mode at 1 300 cm^-1 as a function of nitric acid concentration were also studied. When 35.49%≤ω≤55.10%, the area ratio of Raman peaks at 1 050 and 1 300 cm^-1 decreases rapidly as the nitric acid concentration increases. However, the decrease in the area ratio at 1 050 and 1 300 cm^-1 slows down atω>55.10%. The area ratio tends to stabilize at ω>68.78%, which is attributed to NO^-₃ gradually decreases and undissociated HNO₃ increases. The above Raman shift and peak intensity indicate that within the available sample range in this paper, the HNO₃—nH₂O cluster structure will transform when ω reaches 55.10% and 68.78%, respectively. Further, explain the mechanism of peak intensity and frequency shift changes by combining density functional theory (DFT). The HNO₃—3H₂O and HNO₃—2H₂O cluster structures are the main forms in aqueous nitric acid solutions at 35.49%≤ω≤55.10%, and these cluster structures gradually transform into HNO₃—H₂O at ω>55.10%, and the undissociated HNO₃ gradually dominates in aqueous nitric acid solution at ω>68.78%. Finally, a two-dimensional correlation analysis was performed on the one-dimensional Raman spectrum to reveal the peak sources of HNO₃/NO^-₃. The results confirmed that the Raman peak at 1 051 cm^-1 represents NO^-₃, while the Raman peaks at 1 308 and 958 cm^-1 belong to the undissociated HNO₃ molecule. These results contribute to understanding intermolecular interactions in aqueous nitric acid solutions with different concentrations and provide a reference for the application of nitric acid in chemical engineering, material chemistry, and the national defense industry.

Key words：Raman spectroscopy; Aqueous nitric acid solution; Hydrogen bonding; Two-dimensional correlation spectroscopy; DFT calculations

Received: 2024-05-20 Accepted: 2024-09-05

ZTFLH:

O561.3

Corresponding Authors: WANG Xiao-zhuo E-mail: xiaozhuowang77@163.com

Cite this article:

YANG Bo,ZHANG Ya-ru,CHENG Bi-yao, et al. Investigation of Hydrogen Bonding in Aqueous Nitric Acid Solution Under Concentration Perturbation by Two-Dimensional Correlated Raman Spectroscopy[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(04): 958-963.

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2025)04-0958-06 OR https://www.gpxygpfx.com/EN/Y2025/V45/I04/958