Molecular dynamics of glycerol and glycerol-trehalose bioprotectant solutions nanoconfined in porous silicon

TL;DR

This study investigates how nanoconfinement and trehalose addition influence the molecular dynamics of glycerol and glycerol-trehalose solutions, revealing slowed relaxation and complex non-Debye behavior relevant for bioprotection.

Contribution

It provides new insights into the combined effects of nanoconfinement and trehalose on the molecular dynamics of bioprotectant solutions using neutron scattering.

Findings

Confinement accelerates and inhomogenizes relaxation dynamics.

Glass transition temperatures shift lower under confinement.

Trehalose slows down dynamics and enhances non-exponential relaxation.

Abstract

Glycerol and trehalose-glycerol binary solutions are glass-forming liquids with remarkable bioprotectant properties. Incoherent quasielastic neutron scattering (QENS) is used to reveal the different effects of nanoconfinement and addition of trehalose on the molecular dynamics in the normal liquid and supercooled liquid phases, on a nanosecond timescale. Confinement has been realized in straight channels of diameter D=8 nm formed by porous silicon. It leads to a faster and more inhomogeneous relaxation dynamics deep in the liquid phase. This confinement effect remains at lower temperature where it affects the glassy dynamics. The glass transitions of the confined systems are shifted to low temperature with respect to the bulk ones. Adding trehalose tends to slow down the overall glassy dynamics and increases the non-exponential character of the structural relaxation. Unprecedented results are obtained for the binary bioprotectant solution, which exhibits an extremely non-Debye relaxation dynamics as a result of the combination of the effects of confinement and mixing of two constituents.