Role of Hydrogen Bonding in the pH-Dependent Aggregation of Colloidal Gold Particles Bearing Solution-Facing Carboxylic Acid Groups
Bibliographic record
Abstract
The kinetic stability of aqueous gold colloids containing particles of 11 nm diameter and bearing solution-facing carboxylic acid groups has been analyzed by experiment and theory. Three different types of particles were made whose surfaces were modified by three different thiolate-tethered acids of varying chain-length and p K a: 6-mercaptohexanoic and 12-mercaptododecanoic acids (p K a 4.80 in H 2 O/EtOH, 80:20 by volume), and N -(2-( S )-methylacetic acid)-6-mercaptohexamide (p K a 3.85). As measured by a combination of UV−visible absorption spectroscopy and dynamic light scattering, the particles were reversibly aggregated and dispersed by cycling the pH of solution between low (<p K a of the surface-bound acid) and high values (>p K a ), or the ionic strength between high and low values, respectively. Conditions of aggregation were satisfactorily and quantitatively explained using a model incorporating a superposition of a repulsive electric double layer and van der Waals attraction. That is, colloidal kinetic stability was predicted accurately using the classical theory of Deraguin, Landau, Verwey, and Overbeek (DLVO), without resorting to the addition of ad hoc forces such as hydrogen bonding.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.000 | 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 teacher head, 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".