Specific Cation Effects\non the Bimodal Acid–Base\nBehavior of the Silica/Water Interface
Bibliographic record
Abstract
Using nonresonant second harmonic generation spectroscopy,\nwe have\nmonitored the change in surface charge density of the silica/water\ninterface over a broad pH range in the presence of different alkali\nchlorides. Planar silica is known to possess two types of surface\nsites with pKa values of ∼4 and\n∼9, which are attributed to different solvation environments\nof the silanols. We report that varying the alkali chloride electrolyte\nsignificantly changes the effective acid dissociation constant (pKaeff) for the less acidic silanol\ngroups, with the silica/NaClaq and silica/CsClaq interfaces exhibiting the lowest and highest pKaeff values of 8.3(1) and 10.8(1), respectively.\nAdditionally, the relative populations of the two silanol groups are\nalso very sensitive to the electrolyte identity. The greatest percentage\nof acidic silanol groups was 60(2)% for the silica/LiClaq interface in contrast to the lowest value of 20(2)% for the silica/NaClaq interface. We attribute these changes in the bimodal behavior\nto the influence of alkali ions on the interfacial water structure\nand its corresponding effect on surface acidity.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".