Light refreshments will be served “Observation of Dynamic Crossover Phenomena in Nanoconfined Supercooled Water and Its Relation to the Existence of the Second (Liquid-Liquid) Critical Point in Water”

We have observed fragile-to-strong dynamic crossover phenomena of alpha relaxation time and self diffusion constant in 1-d and 2-d confined supercooled water. The alpha relaxation time is measured by Quasi-Elastic Neutron Scattering (QENS) experiments and the self diffusion constant by Nuclear Magnetic Resonance (NMR) experiments. Water is confined in 1-d geometry in cylindrical pores of nanoscale silica materials, MCM-41 and in Single-wall and Double-wall Carbon Nanotubes. It is in 2-d geometry as the hydration water on surfaces of biopolymers, protein, DNA, and RNA. The crossover phenomena can also be observed by measuring the Mean Square Hydrogen Atom Displacement derived from Incoherent Elastic Neutron Scattering experiments and from appearance of a Boson peak in Incoherent Inelastic Neutron Scattering experiments. We observe a pronounced violation of the Stokes-Einstein relation at and below the crossover temperature at ambient pressure. Upon applying pressure to the confined water, the crossover temperature is shown to track closely the Widom line emanating from the existence of a liquidliquid critical point in an unattainable deeply supercooled state of bulk water. Relations of the dynamic crossover phenomena to the existence of a density minimum in supercooled confined water and to conformational flexibility of the hydrated biopolymers will be discussed [see 1, 2