Influence of Molecular Structure on the Aggregating Properties of Thiacarbocyanine Dyes Adsorbed to Langmuir Films at the Air−Water Interface
Bibliographic record
Abstract
The influence of substituents on the adsorption and aggregation of the anionic 3,3‘-disulfopropyl-5,5‘-dichloro-9-ethylthiacarbocyanine (THIATS) and its cationic analogue 3,3‘-diethyl-5,5‘-dichloro-9-ethylthiacarbocyanine (TDC) was investigated in Langmuir films at the air−water interface. Dioctadecyldimethylammonium bromide (DODAB) and octadecylammonium chloride (ODACl) were used to adsorb THIATS. Arachidic acid (AA) and dihexadecyl phosphate (DHP) were used to adsorb TDC. J-aggregate formation has been observed for the four different combinations of dyes and surfactants. The absorption and emission spectra of THIATS at the air−water interface revealed one narrow intense J-band which was not influenced by the chemical structure of the amphiphiles or by the concentration of THIATS in the subphase. Fluorescence microscopy experiments suggest that, depending on the subphase dye concentration, aggregation of dye molecules leads either to a layer of J-aggregates distributed homogeneously on the scale of a few micrometers or to the observation of individual domains of J-aggregates. For TDC adsorbed to an AA film, the absorption and emission spectra revealed the formation of two J-bands that coexist at the interface. The absorption spectra of TDC adsorbed onto a DHP film showed only one J-band, whose maximum gradually shifted from an initial value of 646 nm to 637 nm and then to 652 nm. The flexible alkyl spacer chain between the localized negative charges of the sulfate groups and the nitrogen atoms of the benzthiazole units allows a packing of the THIATS molecules that is less dependent on the charge distribution in the oppositely charged lipid film than for TDC. Fluorescence micrographs of THIATS/DODAB and TDC/AA films reveal different spatial features. They confirm the predominant influence of the lipid on the TDC/AA film morphology, as concluded from the spectral data. The presented study offers substantial information that was still lacking in this field of research: the time-dependence adsorption of the dyes onto charged monolayers as well as an investigation of the influence of the substitution pattern and the role of the packing of the amphiphiles on the formation of a specific type of aggregate.
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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 | 0.001 |
| 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 | 0.001 | 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".