Ion-Specific Effects on Hydrogen Bond Network at a Submicropore Confined Liquid-Vacuum Interface: An in Situ Liquid ToF-SIMS Study

Abstract

The hydrogen bond (HB), one of the essential properties of water, tends to link water molecules to form dynamic water clusters. Extrinsic ions could change the size distribution of water clusters by influencing HBs. But the mechanism, especially the influence range of ions on HBs, is still in dispute due to limitation of analytical methods. Herein, we use in situ liquid ToF-SIMS analysis combined with density functional theory calculation to study the influence of different halide anions on HBs at a submicropore confined liquid–vacuum interface. Our experimental results demonstrated that anions show synchronous local and long-range effects on HBs. Specifically, the larger the anion is, the greater degree the long-range HB network and the local hydration number of anions are influenced. More importantly, we found that the long-range effect on the HB network is influenced by nuclear quantum effects, whereas the local effect on water molecules in the first hydration shell is not.

A Facile Strategy to Prepare Small Water Clusters via Interacting with Functional Molecules

“…The presence of SF and SDS makes the amount of SWCs increase, indicating that these two functional molecules can destroy big water clusters and facilitate the formation of SWCs, supporting the conclusion from the 17 O NMR results that they can turn big water clusters into small and uniform water clusters. By contrast, halide anions were introduced to pure water, but the total content of SWCs was not significantly increased in comparison with that of pure water [ 24 ].…”

“…Physical methods, such as the methods of magnetic field, electric field [ 20 ], temperature [ 21 ], and microwave radiation, can reduce the size of water clusters to some extent, but it is still a challenge without external physical fields. Therefore, the effect of chemical additive imposing on the structure of SWCs has attracted tremendous attention [ 22 , 23 , 24 , 25 , 26 ]. For example, cations could increase the median water cluster size in common electrolyte aqueous solution systems and anions decrease it, as revealed by the half-width of 17 O nuclear magnetic resonance (NMR).…”

pH-Dependent Water Clusters in Photoacid Solution: Real-Time Observation by ToF-SIMS at a Submicropore Confined Liquid-Vacuum Interface

“…Fabrication of the microfluidic reactor was described in our previous paper (Liu et al, 2019). Briefly, a micro-chamber was made by pouring PDMS on a silicon mode fabricated by soft lithography.…”

“…Here hydrochloride acid (HCl) was chosen since it was known that Cl − has negligible effects on HB networks and water clusters (Näslund et al, 2005;Liu et al, 2019). In-situ liquid ToF-SIMS measurement of the size distributions of protonated water clusters in HCl solutions under different pH were shown in Figure 3.…”

“…Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a highly surface sensitive technique with high spatial and time resolutions. In combination with a microfluidic reactor, in-situ liquid ToF-SIMS analysis could be conducted to overcome the limitation of liquid sample analysis in high vacuum environment of ToF-SIMS and thus provide important spatial and temporal chemical information at the poreconfined liquid-vacuum interface (Yang et al, 2011;Liu et al, 2018Liu et al, , 2019.…”