We have made a series of Quasi-Elastic Neutron Scattering (QENS) studies of supercooled water confined in 3-D and 1-D geometries, specifically, interstitial water in aged cement paste (3-D) and water confined in MCM-41-S and Double Wall Nano Tube DWNT (l-D). In addition, we also include the cases of hydration water on protein surface and other biopolymer surfaces (pseudo 2-D). By analyzing the QENS spectra using Relaxing Cage Model (RCM), we are able to extract accurately the self-intermediate scattering function of hydrogen atoms FH(Q,t), at low-Q as a function of temperature T, showing an α-relaxation process at long time. We can then construct the Dynamic Response Function χT(Q,t) = -dFH(Q,t)/dT. χT(Q,t) as a function of t at constant Q shows a single peak at the characteristic α-relaxation time (τ), the amplitude of which grows as we approach the dynamic crossover temperature TL observed before in each of these geometries. However, the peak height of χT(Q,t) decreases after passing the crossover temperature TL. We make an argument to relate the occurrence of the extremum of the peak height in χT to the existence of the dynamic crossover temperature in each of these cases.
- Confined supercooled water
- Dynamic crossover phenomenon
- Dynamic response function
ASJC Scopus subject areas
- Physical and Theoretical Chemistry