Depolarized Rayleigh scattering (DRS) spectra of glucose aqueous solutions measured from 0.01 to 1000 cm−1 reveal the presence of two distinct relaxation processes, in addition to the intermolecular Raman modes of the water network. The slow relaxation process with a characteristic time of tens of picoseconds is due to the glucose rotational diffusion and is spectrally separated from the fast relaxation process at picosecond time scales commonly attributed to the hydrogen-bond lifetime; this latter time clearly increases with increase in glucose concentration. This suggests the formation of stable sugar hydration shells where the water dynamics is slower than the bulk. The destructuring effect on the tetrahedral hydrogen bonding of water induced by the sugar is also clearly evidenced when comparing the intermolecular Raman spectra at different molar ratios.
Structural and dynamical properties of glucose aqueous solutions by depolarized Rayleigh scattering
PAOLANTONI, Marco;FIORETTO, Daniele;MORRESI, Assunta;SASSI, Paola;
2008
Abstract
Depolarized Rayleigh scattering (DRS) spectra of glucose aqueous solutions measured from 0.01 to 1000 cm−1 reveal the presence of two distinct relaxation processes, in addition to the intermolecular Raman modes of the water network. The slow relaxation process with a characteristic time of tens of picoseconds is due to the glucose rotational diffusion and is spectrally separated from the fast relaxation process at picosecond time scales commonly attributed to the hydrogen-bond lifetime; this latter time clearly increases with increase in glucose concentration. This suggests the formation of stable sugar hydration shells where the water dynamics is slower than the bulk. The destructuring effect on the tetrahedral hydrogen bonding of water induced by the sugar is also clearly evidenced when comparing the intermolecular Raman spectra at different molar ratios.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
