Density fluctuations of water–glucose mixtures studied by inelastic ultra-violet scattering

Abstract

The dynamics of density fluctuations of aqueous glucose solutions were studied in the water-rich region by means of Brillouin ultra-violet scattering. The temperature dependence of the position and line-width of inelastic peaks gives evidence of a strong relaxation process located in the picosecond timescale. In the approximation of a single exponential process, the relaxation time, τ, was obtained for different glucose concentrations; its temperature dependence is well described by an Arrhenius law characterized by an activation energy comparable to that of pure water. This result supports the hypothesis that the microscopic mechanism responsible for the main relaxation process in sugar–water solutions is the continuum rearrangement of the hydrogen-bond network. A comparison is also reported with previous results on aqueous trehalose solutions, showing the acoustic absorption scales with the number of glucoside units for both glucose and trehalose aqueous solutions.