Nuclear quantum effects (NQEs), including zero-point energy, tunneling and nuclear delocalization, affect the properties of molecules, such as water, containing light elements like hydrogen. Numerous characteristics of water and aqueous solutions, including proton transfer, hydrogen bonding networks, can change due to the nuclear delocalization. For example, previous bulk studies suggest slower dynamics in D2O than H2O, due to stronger hydrogen bonds resulting from reduced delocalization of deuterium. The presence of an interface alters the properties of the aqueous phase, such as structural characteristics of the hydrogen bonding network and vibrational energy transfer. The hydrogen bonding heterogeneity of water at an interface can be revealed by time-resolved sum-frequency generation spectroscopy of the O-H and the O-D stretch vibrational modes. We observed a slower vibrational lifetime for the α-Al2O3(0001)/D2O versus the α-Al2O3(0001)/H2O interface. Simulations indicate that nuclear quantum effects lead to a significant increase in proton transfer rates at interfaces, and so we hypothesize that relaxation via proton transfer is the cause of the discrepancy in the vibrational relaxation rates between H2O and D2O at the alumina surface. The comparison of the isotope effect allowed us to determine the nuclear quantum effect’s impact on vibrational lifetime as a probe of hydrogen bonding heterogeneity of interfacial water.

Impact of nuclear quantum effects on interfacial hydrogen bonding networks

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.