Langmuir and Langmuir−Blodgett Films of Perylene Tetracarboxylic Derivatives with Varying Alkyl Chain Length: Film Packing and Surface-Enhanced Fluorescence Studies
Bibliographic record
Abstract
The synthesis, film-packing properties in Langmuir and Langmuir−Blodgett (LB) films, and surface-enhanced fluorescence (SEF) of a new family of perylene tetracarboxylic derivatives (PTCD) are reported. The molecular organization on water subphase is extracted from surface pressure−area (π− A ) isotherms recorded under varying compression speeds and subphase temperatures. It was found that the π− A isotherms are temperature dependent and the area per molecule decreases with increasing temperature of the subphase. The effect is more pronounced for molecules with longer lateral chains. The isotherm for these molecules can reach high pressures, indicating strong packing on the water surface. The presence of hysteresis with and without collapsing of the film indicates the formation of aggregates on the water surface. Further, the shift to smaller areas per molecule for successive compressions shows that the aggregates are stable. The π− A isotherms were found to be independent of the compression speed. The area values for Langmuir films show that PTCD derivative molecules have similar arrangements on the water surface. From the extrapolated area per molecule values, it is concluded that the perylene moiety in these molecules is preferentially organized with the molecular axis perpendicular to the surface. Bis( n -pentylimido)perylene (5C-PTCD), a molecule with a shorter alkyl chain, presents a lower degree of molecular packing and vertical alignment. The Langmuir monolayers were transferred onto glass substrates with a transfer ratio of 1. The UV−visible spectra using polarized light show that the packing of PTCD molecules is maintained in Langmuir−Blodgett (LB) films. The distance dependence of SEF provides indirect evidence that the molecular alignment observed in Langmuir films is also kept in LB films. It was found that the SEF enhancement factor for a bis( n -pentadecylimido)perylene (15-PTCD) monolayer on silver islands is larger than that of 5C-PTCD molecules, a finding that further supports the head-on organization in LB films.
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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) | 0.001 | 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".