Tracking water dimers in ambient nanocapsules by vibrational spectroscopy.
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Proceedings of the National Academy of Sciences
Department of Physics
https://doi.org/10.1073/pnas.2212497119
Department of Physics
https://doi.org/10.1073/pnas.2212497119
Abstract
Description
Nanoconfined few-molecule water clusters are invaluable systems to study fundamental aspects of hydrogen bonding. Unfortunately, most experiments on water clusters must be performed at cryogenic temperatures. Probing water clusters in noncryogenic systems is however crucial to understand the behavior of confined water in atmospheric or biological settings, but such systems usually require either complex synthesis and/or introduce many confounding external bonds to the clusters. Here, we show that combining Raman spectroscopy with the molecular nanocapsule cucurbituril is a powerful technique to sequester and analyze water clusters in ambient conditions. We observe sharp peaks in vibrational spectra arising from a single rigid confined water dimer. The high resolution and rich information in these vibrational spectra allow us to track specific isotopic exchanges inside the water dimer, verified with density-functional theory and kinetic population modeling. We showcase the versatility of such molecular nanocapsules by tracking water cluster vibrations through systematic changes in confinement size, in temperatures up to 120° C, and in their chemical environment.
AH acknowledges funding from the Churchill Scholarship. BdN acknowledges support from the Royal Society (URF\R1\211162). JJB acknowledges funding support from ERC PICOFORCE (No. 883703), EPSRC EP/L027151/1 and EP/R020965/1.
AH acknowledges funding from the Churchill Scholarship. BdN acknowledges support from the Royal Society (URF\R1\211162). JJB acknowledges funding support from ERC PICOFORCE (No. 883703), EPSRC EP/L027151/1 and EP/R020965/1.