Monolayer/bilayer transition in Langmuir films of derivatized gold nanoparticles at the gas/water interface: An x-ray scattering study
Bibliographic record
Abstract
The microscopic structure of Langmuir films of derivatized gold nanoparticles has been studied as a function of area/particle on the water surface. The molecules (AuSHDA) consist of gold particles of mean core diameter D approximately 22 angstroms that have been stabilized by attachment of carboxylic acid terminated alkylthiols, HS-(CH2)15-COOH. Compression of the film results in a broad plateau of finite pressure in the surface pressure versus area/particle isotherm that is consistent with a first-order monolayer/bilayer transition. X-ray specular reflectivity (XR) and grazing incidence diffraction show that when first spread at large area/particle, AuSHDA particles aggregate two dimensionally to form hexagonally packed monolayer domains at a nearest-neighbor distance of a = 34 angstroms. The lateral positional correlations associated with the two-dimensional (2D) hexagonal order are of short range and extend over only a few interparticle distances; this appears to be a result of the polydispersity in particle size. Subsequent compression of the film increases the surface coverage by the monolayer but has little effect on the interparticle distance in the close-packed domains. The XR and off-specular diffuse scattering (XOSDS) results near the onset of the monolayer/bilayer coexistence plateau are consistent with complete surface coverage by a laterally homogeneous monolayer of AuSHDA particles. On the high-density side of the plateau, the electron-density profile extracted from XR clearly shows the formation of a bilayer in which the newly formed second layer on top is slightly less dense than the first layer. In contrast to the case of the homogeneous monolayer, the XOSDS intensities observed from the bilayer are higher than the prediction based on the capillary wave model and the assumption of homogeneity, indicating the presence of lateral density inhomogeneities in the bilayer. According to the results of Bragg rod measurements, the 2D hexagonal order in the two layers of the bilayer are only partially correlated.
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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".