PM FTIRRAS Studies of Potential-Controlled Transformations of a Monolayer and a Bilayer of 4-Pentadecylpyridine, a Model Surfactant, Adsorbed on a Au(111) Electrode Surface
Bibliographic record
Abstract
Polarization modulation Fourier transform infrared reflection−absorption spectroscopy (PM FTIRRAS) has been combined with electrochemistry to monitor the potential-induced transformations of a monolayer and a bilayer formed by 4-pentadecylpyridine (C15−4Py), a model amphiphilic compound, at a Au(111) electrode surface. The optical constants for a solution of randomly oriented C15−4Py molecules have been determined and used to calculate the integrated band intensities for a monolayer and bilayer of randomly oriented molecules. The orientation of the hydrophobic and hydrophilic parts of the molecule with respect to the surface normal was determined from the ratio of the intensity of experimental to calculated bands. The CH stretch region of the spectra was used to determine the tilt angle between hydrocarbon chains and the surface normal. The tilt angle varied with potential. The minimum value of the tilt angle was 16° for the monolayer and 27° for the bilayer. In the monolayer, the headgroup of the C15−4Py molecule lies almost flat on the Au(111) surface. At negative potentials, the angle between the plane of the pyridine ring and the surface normal is 68°. As applied potential becomes more positive, the pyridine group stands up gradually and the tilt angle decreases to 63°. In the bilayer, the C 2 axis of the pyridine group in the leaflet turned to the electrolyte solution is tilted at ∼70° with respect to the normal and this tilt angle changes little with potential. In the leaflet turned to the electrode, the angle between the C 2 axis of the headgroup and the surface normal changes from 64° to 54° by moving from negative to positive potentials. The PM IRRAS data also show that in the bilayer, the plane of the pyridine group rotates with respect to the C 2 axis when the electrode potential changes. In the monolayer, the tilt angle of the C 2 axis changes but the plane of the pyridine moiety does not rotate with potential.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".