Search

Raman phonon differential spectrometrics (DPS) and contact angle measurements resolved that solvation of the NaX (X = HSO 4 , NO 3 , ClO 4 , SCN) complex salts stiffens the H O stretching phonon from 3200 to ~ 3500 cm − 1 and softens the O:H nonbond phonon from 180 to ~ 70 cm − 1 with rising of solution surface stress. The solute capability of bond transition in terms of the fraction coefficient, follows the relation, f NaX (C) ∝ 1-exp(− C/C 0 ) towards saturation, with C being the solute concentration and C 0 the decay constant. Observations evidence that: (i) the solute ionic field electrification aligns, stretches, and polarizes its neighboring H 2 O molecules, which shortens the H O bond but lengthens the O:H nonbond via O O Coulomb repulsion; (ii) the effect of X − electrification on the O:H O bond relaxation varies with solute type and solute concentration. Exercises not only verify the essentiality of solvent O:H O bond cooperative relaxation and polarization but also demonstrate the power of DPS that resolves processes occurred upon solvation. [ABSTRACT FROM AUTHOR]

A combination of the differential Raman spectrometrics and contact-angle measurements has enabled resolution of the hydrogen bond (HB, O:H O) relaxation and molecular dynamics in the NaX hydration shells. Observations suggest that the aqueous ions create each an electric field to form the hydration shells through O:H O bond elongation and polarization. The ionic polarization shares the same, and even stronger, effect of molecular undercoordination that shortens the H O bond and stiffen its phonon, and meanwhile, the O O Coulomb repulsivity lengthen and soften the O:H nonbond with an association of polarization. O:H O bond electrification raises not only the structure order of molecules and the viscosity in the hydration shells but also the skin stress and thermal stability of the solution. Exercises not only deepen our insight into the salt solute-solvent interaction involved in the Hofmeister series in terms of O:H O bond electrification but also provide a powerful means quantifying the dynamic, local, molecular-site-resolved information regarding the O:H O bond cooperativity in aqueous solutions. [ABSTRACT FROM AUTHOR]