Protons at Ice Surfaces

Abstract

Lieber obenauf: Untersuchungen zum Protonentransfer und H/D‐Austausch in Eisfilmen zeigen, dass sich das Proton vorrangig auf deren Oberfläche befindet. Es kann kurze Strecken mithilfe eines Staffel‐Hopping‐Mechanismus zurücklegen (siehe Bild), selbst wenn die Molekülbewegung weitgehend eingefroren ist. Diese Eigenschaften legen die Möglichkeit für protonenkatalysierte Reaktionen an kalten Eisoberflächen, z. B. auf interstellaren Staubpartikeln, nahe.

Autoionization at the surface of neat water: is the top layer pH neutral, basic, or acidic?

“…The inability to use ion scattering to qualitatively check for interior proton mobility was partially overcome in a later study showing that protons released by HCl buried in ice are able to move to the ice surface. 73 The conclusion based on that new approach is also consistent with the isotopic exchange data for ice nanocrystals, which clearly show interior proton mobility in crystalline ice. 21,70 However, the response to adsorbates of the interior proton activity of nanocrystals as described above demonstrates that protons can move from the surface of ice to the interior at low temperatures, contradictory to interpretations of both the RIS 71,73 and the soft-landedproton data.…”

“…73 The conclusion based on that new approach is also consistent with the isotopic exchange data for ice nanocrystals, which clearly show interior proton mobility in crystalline ice. 21,70 However, the response to adsorbates of the interior proton activity of nanocrystals as described above demonstrates that protons can move from the surface of ice to the interior at low temperatures, contradictory to interpretations of both the RIS 71,73 and the soft-landedproton data. 69 Computational results discussed above suggest that the activation barrier of the exchange process inside pure ice nanoparticles originates mostly from a combination of surface autoionization, and proton injection from the surface to the crystal interior.…”

“…71,72 This section focuses on the nature, results and interpretation of the study of proton activity (a product of concentration and average mobility) within and on the surface of ice using molecular probes: FTIR monitoring of exchange by D 2 O isolated in H 2 O nanocrystals, reflective ion scattering from H 2 O-D 2 O films, and surface soft-landing of protons. Particular emphasis is given to two most recent studies; the RIS thinfilm work of Kang et al 73 and our current results for ice nanocrystals. 21 Both of these studies offer additional strong evidence of the ability of protons to move within ice, while also indicating at least an order-of-magnitude greater proton activity at the ice surface relative to the interior.…”

Biophysical properties of the voltage‐gated proton channel HV1

“…Finally Kang and co-workers 117 concluded that “the proton mobility issue is considered yet unresolved”. They report that vertical movement of protons in an ice film is possible below and above 140 K and the differences between lateral and vertical transport in ice might be explained through the thermodynamic affinity from protons to the ice surface 118, 119 . To summarize, there is no consensus value for the mobility of protons and deuterium in ice.…”