Vibrational Raman Spectroscopy of the Hydration Shell of Ions

Ionic perturbation of water has important implications in various chemical, biological and environmental processes. Previous studies revealed the structural dynamical presence ions, mainly with concentrated electrolyte solutions having significant interionic interactions. These investigations highlighted need selective extraction hydration shell from a dilute solution that is largely free Double-difference infrared (DDIR) Raman multivariate curve resolution (Raman-MCR), as well MD simulation, provided valuable insight this direction, suggesting perturbed resides immediate vicinity ion, called shell. Recently, we have introduced difference spectroscopy simultaneous fitting (Raman-DS-SCF) analysis can quantitatively extract vibrational response pertaining to fully hydrated ions/solute. The DS-SCF novel hydrogen-bond (H-bond) features water, such existence extremely weakly interacting water–OH (νmax ~ 3600 cm−1) high-charge-density metal ions (Mg2+, Dy3+). In addition, Raman-DS-SCF retrieves shared water–shared-ion pair (WSIP), which different either cation anion. Herein, discuss H-bonding cation, anion, zwitterion hydrophobes also inter-ionic interactions, focus on recent results our laboratory using spectroscopy.