Insights
into energy flow dynamics at ice surfaces are essential
for understanding chemical dynamics relevant to atmospheric and geographical
sciences. Here, employing ultrafast surface-specific spectroscopy,
we report the interfacial vibrational dynamics of ice I
h
. A comparison to liquid water surfaces reveals accelerated vibrational
energy relaxation and dissipation at the ice surface for hydrogen-bonded
OH groups. In contrast, free-OH groups sticking into the vapor phase
exhibit substantially slower vibrational dynamics on ice. The acceleration
and deceleration of vibrational dynamics of these different OH groups
at the ice surface are attributed to enhanced intermolecular coupling
and reduced rotational mobility, respectively. Our results highlight
the unique properties of free-OH groups on ice, putatively linked
to the high catalytic activities of ice surfaces.
Ice-nucleating proteins (INPs) from Pseudomonas syringae are among the most active ice nucleators known, enabling ice formation at temperatures close to the melting point of water. The working mechanisms of INPs remain elusive, but their ice nucleation activity has been proposed to depend on the ability to form large INP aggregates. Here, we provide experimental evidence that INPs alone are not sufficient to achieve maximum freezing efficiency and that intact membranes are critical. Ice nucleation measurements of phospholipids and lipopolysaccharides show that these membrane components are not part of the active nucleation site but rather enable INP assembly. Substantially improved ice nucleation by INP assemblies is observed for deuterated water, indicating stabilization of assemblies by the stronger hydrogen bonds of D 2 O. Together, these results show that the degree of order/disorder and the assembly size are critically important in determining the extent to which bacterial INPs can facilitate ice nucleation.
Background: Inspired by structural hierarchies and the related excellent mechanical properties of biological materials, we created a smoothly graded micro-to nanoporous structure from a thermoplastic polymer.
The freezing of water into ice is a key process that is still not fully understood. It generally requires an impurity of some description to initiate the heterogeneous nucleation of...
We study the molecular-level properties of the singlecrystal ice I h surface using interface-specific sum frequency generation spectroscopy. We probe the water vibrational bend region around 1650 cm −1 of the basal plane of hexagonal ice to understand the interfacial structure from vibrational properties. As opposed to the stretch mode of ice, the bending mode response depends very weakly on temperature. The large line width of the bending mode response, relative to the response on water, is inconsistent with inhomogeneous broadening and points to ultrafast pure dephasing. The bending mode of ice provides an excellent means to study adsorbate−ice interactions and understand differences in ice and water reactivity.
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