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Temperature Dependence of Proton Coverage and the Total Potential at Fused Silica:Water Interfaces from
Amani O Alghamdi1, Nicole M Gonzalez1, Franz M Geiger1
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60202, United States.
Journal of the American Chemical Society
|April 15, 2025
Summary
Increasing temperature makes the silica-water interface more negative, impacting interfacial potential and proton coverage. This study details a new method for measuring these temperature-dependent interfacial properties.
Area of Science:
- Physical Chemistry
- Surface Science
- Electrochemistry
Background:
- The amphoteric nature of the silica:water interface is crucial for understanding various chemical and physical processes.
- Temperature and ionic strength significantly influence interfacial properties, but their combined effects on interfacial amphoterism require further investigation.
Purpose of the Study:
- To investigate the temperature and ionic strength dependence of interfacial amphoterism at the fused silica:water interface.
- To develop and present a blueprint for phase- and amplitude-resolved second harmonic generation (SHG) measurements at buried aqueous interfaces.
- To quantify changes in interfacial potential and proton surface coverage with varying temperature and ionic strength.
Main Methods:
- Utilized phase- and amplitude-resolved second harmonic generation (SHG) spectroscopy.
- Employed a Y-crystal-based oscillator and a Galilean beam expander for SHG measurements.
- Calibrated nonlinear susceptibility measurements to determine interfacial structure.
- Investigated the fused silica:water interface across a temperature range of 20–60 °C and varying ionic strengths.
Main Results:
- The total interfacial potential becomes increasingly negative with rising temperature (20–60 °C).
- Interfacial structure, indicated by second-order nonlinear susceptibility, remained largely temperature invariant.
- Voltage increases with temperature showed a near-linear trend, rising faster at low ionic strength.
- Proton surface coverage increased with temperature, leading to a more negatively charged surface.
Conclusions:
- Findings are consistent with temperature-dependent equilibrium constants governing the amphoteric silica:water interface.
- The developed SHG methodology provides a robust approach for studying buried aqueous interfaces.
- Results contribute to interfacial model development, atomistic simulations, Hofmeister effect studies, and interfacial electrocatalysis research.
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