Quaternary Ammonium Bromide Surfactant Adsorption on Low-Index Surfaces of Gold. 2. Au(100) and the Role of Crystallographic-Dependent Adsorption in the Formation of Anisotropic Nanoparticles
Bibliographic record
Abstract
A qualitative and quantitative description of the coadsorption of a quaternary ammonium bromide surfactant on Au(100) has been determined using electrochemical techniques. Cyclic voltammetry reveals that both the cationic surfactant ion and its halide counterion are adsorbed on the surface of unreconstructed Au(100) over a wide range of electrode potentials or charge densities. The relative Gibbs excesses of the cationic and anionic components of octyltrimethylammonium (OTA(+)) bromide have been determined using the thermodynamics of ideally polarized electrodes. Coadsorbed OTA(+) does not strongly affect the behavior of bromide layers on Au(100) with low-coverage films being replaced by commensurate overlayers at positive electrode charge densities. The presence of surface bromide allows for the stabilization of adsorbed OTA(+) at positive polarizations. Furthermore, charge-induced phase changes in the bromide layer lead to subtle but appreciable changes in the surface excesses of OTA(+) ions which is consistent with a hierarchical model of surfactant adsorbed upon a halide-modified Au(100) surface. A comparison of the OTA(+) adsorption isotherms on Au(100) and Au(111) reveals that the presence of coadsorbed bromide does not lead to preferential accumulation of cationic surfactant ions on a particular crystal facet. These results are inconsistent with explanations of anisotropic nanoparticle formation that invoke a thermodynamic argument of preferred surfactant adsorption on different crystal facets of an embryonic nanoparticle seed crystal.
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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".