Comment on "Interfacial pH at an isolated silica-water interface"

Article Abstract:

The pH at the neat water-silica interface is detected and it is described that the tethered chromophore is only sensitive to the pH in the local environment within 1 nm of the surface. Rather than evidencing the formation of a stable surface layer, the experiments probably indicate changes in the chromophore structure at the surface that are known to occur when base or salts are added and hence the original structure can be reproduced after washing with methanol, thereby reversing the aggregation or reintroducing the contaminations.

All Other Basic Inorganic Chemical Manufacturing, Industrial inorganic chemicals, not elsewhere classified, Silica Gel, Water, Adsorption, Hydrogen-ion concentration, pH measurement

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Probing the interfacial structure of aqueous electrolytes with femtosecond second harmonic generation spectroscopy

Article Abstract:

The second harmonic generation (SHG) intensity of surfactant tetrabutylammonium iodide (TBAI) solutions and the surface concentration are measured and evaluated as a proof of principle experiment. The variation in SHG response at intermediate bulk concentrations of sodium and potassium halide solutions that results from changes in the nonresonant water background and the high concentration solutions of sodium and potassium iodide are analyzed.

Molecular dynamics, Optical properties, Electrolyte solutions, Structure, Ammonium compounds, Ammonium chloride, Ammonium paratungstate, Ammonium salts, Harmonic functions

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Evidence for an enhanced hydronium concentration at the liquid water surface

Article Abstract:

A comparative second harmonic generation study of aqueous solutions of hydroiodic acid (HI) and alkali iodides (NaI and KI) is described, which establish lower limits of 55% and 34% larger surface iodide concentrations for HI solutions relative to NaI and KI solutions. The results implies that hydronium ions must exist in much higher densities near the liquid surface than do the alkali ions, in support of theoretical predictions.

Science & research, Research, Iodides, Aqueous solution reactions

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