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Title: Monovalent and Divalent Cations at the a-Al2O3(0001)/Water Interface: How Cation Identity Affects Interfacial Ordering and Vibrational Dynamics

Abstract

Mineral oxide-water interfaces are important for a wide range of industrial, geochemical, and biological processes. The reactivity of these interfaces is strongly impacted by the presence of ions. Thus, it is critical to understand how ions alter the interfacial environment. This can be achieved by measuring the changes in the structure and vibrational dynamics of interfacial water induced by the presence of ions in close vicinity to the mineral surface. The a-Al2O3(0001) surface represents a flexible platform to study the effect of ions on interfacial aqueous environments at positive, neutral and negative surface charge. Using vibrational sum frequency generation (vSFG) in the frequency and time domain, we investigate how monovalent and divalent cations affect the hydrogen bonding environment of the first few layers of interfacial water next to a-Al2O3(0001). Our results indicate that monovalent cations, such as Li+, Na+, K+, and Cs+, appear to have lower binding affinities for the interface compared to Ca2+, Sr2+, and Ba2+. This leads to an interfacial region that is structured in a cation valence dependent manner. Addition of divalent cations at the negatively charged interface (pH 10) increases the spectral intensity in the 3400 cm-1 region compared to neat pH 10 H2O, in contrastmore » to monovalent cations that only attenuate the vSFG signal. Time resolved vSFG measurements reveal that the O-H vibrational lifetime (T1) of interfacial species at pH 10 in the presence of NaCl and BaCl2 remains similar, but restructuring of the surface seen in steady state vSFG is manifested in the degree to which strongly hydrogen bonded species recover to their original populations post excitation. By tracking the accumulation of ions at the interface via the vSFG response, we can characterize the unique surface arrangements of interfacial water molecules induced by a range of monovalent and divalent cations at the a-Al2O3(0001)/water interface.« less

Authors:
 [1]; ORCiD logo [2];  [1];  [1]
  1. Temple University
  2. BATTELLE (PACIFIC NW LAB)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1572496
Report Number(s):
PNNL-SA-143148
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry C
Additional Journal Information:
Journal Volume: 123; Journal Issue: 30
Country of Publication:
United States
Language:
English

Citation Formats

Piontek, Stefan, Tuladhar, Aashish, Marshall, Tim, and Borguet, Eric. Monovalent and Divalent Cations at the a-Al2O3(0001)/Water Interface: How Cation Identity Affects Interfacial Ordering and Vibrational Dynamics. United States: N. p., 2019. Web. doi:10.1021/acs.jpcc.9b01618.
Piontek, Stefan, Tuladhar, Aashish, Marshall, Tim, & Borguet, Eric. Monovalent and Divalent Cations at the a-Al2O3(0001)/Water Interface: How Cation Identity Affects Interfacial Ordering and Vibrational Dynamics. United States. doi:10.1021/acs.jpcc.9b01618.
Piontek, Stefan, Tuladhar, Aashish, Marshall, Tim, and Borguet, Eric. Thu . "Monovalent and Divalent Cations at the a-Al2O3(0001)/Water Interface: How Cation Identity Affects Interfacial Ordering and Vibrational Dynamics". United States. doi:10.1021/acs.jpcc.9b01618.
@article{osti_1572496,
title = {Monovalent and Divalent Cations at the a-Al2O3(0001)/Water Interface: How Cation Identity Affects Interfacial Ordering and Vibrational Dynamics},
author = {Piontek, Stefan and Tuladhar, Aashish and Marshall, Tim and Borguet, Eric},
abstractNote = {Mineral oxide-water interfaces are important for a wide range of industrial, geochemical, and biological processes. The reactivity of these interfaces is strongly impacted by the presence of ions. Thus, it is critical to understand how ions alter the interfacial environment. This can be achieved by measuring the changes in the structure and vibrational dynamics of interfacial water induced by the presence of ions in close vicinity to the mineral surface. The a-Al2O3(0001) surface represents a flexible platform to study the effect of ions on interfacial aqueous environments at positive, neutral and negative surface charge. Using vibrational sum frequency generation (vSFG) in the frequency and time domain, we investigate how monovalent and divalent cations affect the hydrogen bonding environment of the first few layers of interfacial water next to a-Al2O3(0001). Our results indicate that monovalent cations, such as Li+, Na+, K+, and Cs+, appear to have lower binding affinities for the interface compared to Ca2+, Sr2+, and Ba2+. This leads to an interfacial region that is structured in a cation valence dependent manner. Addition of divalent cations at the negatively charged interface (pH 10) increases the spectral intensity in the 3400 cm-1 region compared to neat pH 10 H2O, in contrast to monovalent cations that only attenuate the vSFG signal. Time resolved vSFG measurements reveal that the O-H vibrational lifetime (T1) of interfacial species at pH 10 in the presence of NaCl and BaCl2 remains similar, but restructuring of the surface seen in steady state vSFG is manifested in the degree to which strongly hydrogen bonded species recover to their original populations post excitation. By tracking the accumulation of ions at the interface via the vSFG response, we can characterize the unique surface arrangements of interfacial water molecules induced by a range of monovalent and divalent cations at the a-Al2O3(0001)/water interface.},
doi = {10.1021/acs.jpcc.9b01618},
journal = {Journal of Physical Chemistry C},
number = 30,
volume = 123,
place = {United States},
year = {2019},
month = {8}
}