Colloidal CdSe Nanocrystals from Tri-n-Octylphosphine: Part I: Growth and Optical Properties from Polar and Non-Polar Solvents
Bibliographic record
Abstract
This manuscript reports the ready synthesis of high-quality colloidal CdSe nanocrystals from tri-n-octylphosphine (TOP) and reports the optical properties of the resulting CdSe dispersed in nonpolar and polar environments. With cadmium oxide (CdO) as the Cd precursor and TOPSe as the Se source, the CdSe nanocrystals were synthesized in a reaction medium consisting of TOP. The synthetic approach is as simple as: the swift injection of a TOPSe/TOP solution into a CdO/TOP solution at one particular (high) temperature, with subsequent growth at a lower temperature. The temporal evolution of the optical properties, including absorption and luminescence, were monitored in detail. The photoluminescence (PL) properties of the TOP-capped CdSe investigated comprise the intensity, emission peak wavelength, full width at half maximum of the PL spectra, and stability; these PL properties are sensitive to the history of growth as well as the environment of dispersion. An appropriate parameter, termed "Sensitivity Index (SI)," is proposed to define the percent difference in the PL intensity that arises when the dots are dispersed in non-polar hexane (Hex) as compared to polar tetrahydrofuran (THF). The decrease in the PL efficiency on going from Hex to THF is attributed to changes in surface states rather than in the internal core as more ligands are removed in THF. Dilution experiments further confirm the suggestion of the ligand removal mechanism and provide a conceptual estimate of surface quality via the SI parameter. Due to a slow growth in size (the size of the nanocrystals is almost constant during early 20 min) and good PL stability (tested as PL changes after storage for days both in dispersed or solid states, as well as after UV-irradiation), we suggest that our synthetic approach is likely to be practical for large-scale CdSe nanocrystals with good PL stability.
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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".