Surface Chemical Properties of Eutectic and Frozen NaCl Solutions Probed by XPS and NEXAFS

Křepelová, Adéla; Huthwelker, Thomas; Bluhm, Hendrik; Ammann, Markus

doi:10.1002/cphc.201000461

Cited by 46 publications

(45 citation statements)

References 31 publications

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“…These results represent the starting point for an improved understanding of the structure of eutectic and sub-eutectic frozen salt solutions in presence of ice (high relative humidity), and in the hydrate stability domain of the phase diagram (low relative humidity). Moreover, the Cl K-edge measurements complement and extend previously reported measurements at the O K-edge NEXAFS for the same system [52], which is sensitive to the hydrogen bonding environment of the water molecules. However, compared to the oxygen K-edge, the higher kinetic energy of the chlorine K-edge Auger electron corresponds to an increased probing depth of about 2-8 nm, and, therefore, to a much more bulk-sensitive measurement.…”

Section: Phase Changes Of Nacl-water Binary Systemssupporting

confidence: 83%

“…In the following, we show how NEXAFS spectroscopy at the Cl K-edge can be highly informative on the nature of the NaCl structure in NaCl-water binary systems. Using XPS and NEXAFS spectroscopies of the O 1s core level and O K-edge, respectively, we previously showed that these systems follow the phase rules at the airice interface [52]. This finding contrasts some earlier observations, where the presence of liquid-like Cl below the eutectic point of bulk solutions [53] was postulated (see Ref.…”

Section: Phase Changes Of Nacl-water Binary Systemsmentioning

confidence: 61%

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The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

et al. 2016

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Recent years have witnessed fast advancements in near ambient pressure X-ray photoelectron (NAPP) spectroscopy, which is emerging as a powerful tool for the investigation of surfaces in presence of vapors and liquids. In this paper we present a new chamber for the investigation of solid/vapor interfaces relevant to environmental and atmospheric chemistry that fits to the NAPP endstation at the Swiss Light Source. The new chamber allows for performing X-ray photoelectron spectroscopy (XPS) and electron yield near-edge X-ray absorption fine structure spectroscopy (NEXAFS) using soft, tender and hard X-ray in vacuum and in near-ambient pressures up to 20 mbar at environmentally relevant conditions of temperature and relative humidity. In addition, the flow tube design of the chamber enables the dosing of sticky reactive gases with short pressure equilibration time. The accessible photoelectron kinetic energy ranges from 2 to 7000 eV. This range allows the determination of surface and bulk electronic properties of ice and other environmental materials, such as metal oxides and frozen solutions, which are relevant to understanding atmospheric chemistry. The design of this instrument and first results on systems of great interest to the environmental and atmospheric chemistry community are presented. In particular, nearambient pressure XPS and NEXAFS, coupled to a UV-laser setup, were used to study the adsorption of water on a TiO 2 powder sample. The results are in line with previously proposed adsorption models of water on TiO 2 , and, furthermore, indicate that the concentration of water molecules tends to increase upon UV irradiation. In a second example we illustrate how NEXAFS spectroscopy measurements at the chlorine K-edge can provide new insight on the structures of eutectic and sub-eutectic frozen NaCl solutions at high and low relative humidity, respectively, indicating the formation of solution and solid NaCl phases, respectively. Finally, we demonstrate the assets of this new chamber for the dosing of sticky acidic gases and, in particular, for the investigation of formic acid uptake on ice surfaces.Keywords Metal oxides Á Ice Á Halogens Á X-ray photoelectron spectroscopy (XPS) Á Near-edge X-ray absorption fine structure (NEXAFS) Á Near ambient pressure photoemission (NAPP)

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Section: Phase Changes Of Nacl-water Binary Systemssupporting

confidence: 83%

Section: Phase Changes Of Nacl-water Binary Systemsmentioning

confidence: 61%

The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

et al. 2016

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“…Wren and Donaldson (2011) reported only a minor increase in nitrate concentration at the ice surface and suggested that nitrate might be favourably incorporated into pockets or grain boundaries inside bulk ice at 258-268 K. A similar tendency of nitrite to be captured in liquid reservoirs inside growing ice was suggested earlier (Takenaka et al, 1996). Using surfacesensitive spectroscopy Křepelová et al (2010a) showed that frozen solutions of NaCl above the eutectic exhibited a composition on the ice surface consistent with the phase diagram of the bulk solution. This is in agreement with earlier work by Döppenschmidt and Butt (2000) where solid NaCl crystals were identified at the ice surface at temperatures below the eutectic using AFM.…”

Section: Solutes During the Freezing Processmentioning

confidence: 61%

“…Freezing of emulsions that resemble water droplets in the atmosphere can be kinetically hindered so that a meta-stable liquid phase exists well below the eutectic temperature (Koop et al, 2000;Bogdan, 2010). Using surface-sensitive, synchrotron-based X-ray spectroscopy, Křepelová et al (2010a) found no evidence for liquid on the surface of frozen solutions of NaCl below the eutectic. This technique probes the local, chemical environment of the chloride anions and does not rely on assumptions based on bulk properties to derive conclusions about the physical state of the probe.…”

Section: Below the Eutectic Compositionmentioning

confidence: 99%

“…This technique probes the local, chemical environment of the chloride anions and does not rely on assumptions based on bulk properties to derive conclusions about the physical state of the probe. One difference between the two studies is that Křepelová et al (2010a) exclusively probed the upper surface, while Cho et al (2002) also probed the bulk ice. We propose here that geometric constraints to the liquid volume kept in the micro-pockets might explain the observed freezing point depression (Sect.…”

Section: Below the Eutectic Compositionmentioning

confidence: 99%

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A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

et al. 2014

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Abstract. Snow in the environment acts as a host to rich chemistry and provides a matrix for physical exchange of contaminants within the ecosystem. The goal of this review is to summarise the current state of knowledge of physical processes and chemical reactivity in surface snow with relevance to polar regions. It focuses on a description of impurities in distinct compartments present in surface snow, such as snow crystals, grain boundaries, crystal surfaces, and liquid parts. It emphasises the microscopic description of the ice surface and its link with the environment. Distinct differences between the disordered air–ice interface, often termed quasi-liquid layer, and a liquid phase are highlighted. The reactivity in these different compartments of surface snow is discussed using many experimental studies, simulations, and selected snow models from the molecular to the macro-scale. Although new experimental techniques have extended our knowledge of the surface properties of ice and their impact on some single reactions and processes, others occurring on, at or within snow grains remain unquantified. The presence of liquid or liquid-like compartments either due to the formation of brine or disorder at surfaces of snow crystals below the freezing point may strongly modify reaction rates. Therefore, future experiments should include a detailed characterisation of the surface properties of the ice matrices. A further point that remains largely unresolved is the distribution of impurities between the different domains of the condensed phase inside the snowpack, i.e. in the bulk solid, in liquid at the surface or trapped in confined pockets within or between grains, or at the surface. While surface-sensitive laboratory techniques may in the future help to resolve this point for equilibrium conditions, additional uncertainty for the environmental snowpack may be caused by the highly dynamic nature of the snowpack due to the fast metamorphism occurring under certain environmental conditions. Due to these gaps in knowledge the first snow chemistry models have attempted to reproduce certain processes like the long-term incorporation of volatile compounds in snow and firn or the release of reactive species from the snowpack. Although so far none of the models offers a coupled approach of physical and chemical processes or a detailed representation of the different compartments, they have successfully been used to reproduce some field experiments. A fully coupled snow chemistry and physics model remains to be developed.

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Effects of discharge mode and gas composition for plasma‐hydrophilized titanium surface on hydrophilic sustainability

Hirano

Yamane

Ohtsu

2020

Surface & Interface Analysis

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Plasma hydrophilization under various conditions was carried out on Ti substrates to investigate the effect of the applied parameters on the hydrophilic sustainability. The plasma was discharged from gases comprising Ar and/or O2 at various ratios using DC and RF modes. Notable differences in the surface morphology by the plasma conditions was hardly found, while the ratio of hydroxide on the surface was influenced by the discharge mode. The hydrophilicity was significantly improved regardless of the treatment conditions, that is, the gas composition and discharge mode. The deterioration of the hydrophilicity was occurred by storing in the ambient atmosphere or distilled water, wherein the deterioration in distilled water was suppressed when using DC as a discharge mode. The hydrophilicity was preserved when the specimens was stored in a physiological solution such as phosphate buffered saline solution due to the adsorption of Na+ and Cl− in the solution; its effect was far superior to that contributed by the parameter settings. In conclusion, plasma discharge mode enabled to improve the deterioration of hydrophilicity only slightly.

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Surface Chemical Properties of Eutectic and Frozen NaCl Solutions Probed by XPS and NEXAFS

Cited by 46 publications

References 31 publications

The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

Effects of discharge mode and gas composition for plasma‐hydrophilized titanium surface on hydrophilic sustainability

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