Ishikawa D, He A, Xu Y, Fujii T, Ozaki Y. Evidence for two kinds of hydrogen-bonding networks in ionic solutions by 2D infrared correlation spectroscopy.
Sci Rep 2025;
15:16991. [PMID:
40379684 PMCID:
PMC12084574 DOI:
10.1038/s41598-025-00774-0]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2025] [Accepted: 04/30/2025] [Indexed: 05/19/2025] Open
Abstract
IR spectra from 4000 to 100 cm-1 were measured for four kinds of alkali chloride solutions (LiCl, NaCl, KCl, CsCl solutions) with different concentrations. Their second derivative spectra revealed two bands around 3400 and 3160 cm-1 attributed to the OH stretching mode of weakly hydrogen-bonded (WHB) and strongly hydrogen-bonded (SHB) water species, respectively. Two-dimensional correlation spectroscopy (2D-COS) was applied to analyze the IR spectra. Two autopeaks in a 2D synchronous spectrum correspond to the WHB and SHB bands, respectively. Moreover, 2D-COS confirmed the existence of two bands around 700 and 350 cm-1 in the 1000 -100 cm-1 region. The bands at 700 and 350 cm-1 are assignable to liberational L2 modes and correlated with SHB (~ 3160 cm-1) and WHB band (~ 3400 cm-1), respectively, revealed by the hetero 2D-COS spectrum. These results suggest the two kinds of hydrogen-bonding networks are constructed by SHB or WHB water species in the alkali chloride solutions.
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