Oleylamine as a reducing agent in syntheses of magic-size clusters and monodisperse quantum dots: optical and photoconductivity studies
Bibliographic record
Abstract
Separation of magic size clusters (MSCs) from monodisperse quantum dots (QDs) has generally been a difficult task while employing the commonly used synthesis procedure, where for preparation of PbSe QDs, Se-TOP (TOP = trioctylphosphine) is injected into Pb-oleate in 1-octadecene medium. In this study, we report for the first time a simple method to prepare MSCs, QDs and particles close to the bulk of PbSe using oleylamine (OAM) as the reducing agent, where the individual entities are efficiently separated. The chemical yield is found to be 95%. Studies on optical properties revealed the absorption and emission peaks of MSCs at fixed positions of 600 and 780 nm, respectively, while QDs exhibit significant shift to longer wavelengths for both the cases, depending on the particle size. Shift of the emission peak position for QDs is observed to be larger for initial stages of the waiting time as compared to those for longer waiting times. This can be attributed to two factors: faster growth in particle size is favoured kinetically in the initial stages, while thermodynamic stability occurs in the later stages, and reduction in surface to core contribution with increase of waiting time. QDs were found to emit at only one particular wavelength while they absorbed at two or more wavelengths. The quantum yields (QYs) of particles of sizes 4.1 and 5.1 nm are found to be 80 and 30%, respectively. The lifetime values are found to be 1.0-1.3 μs for QDs having an emission peak in the range of 1300-1500 nm. The hybrid device of PbSe (5 nm size) and MEHPPV (2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) shows increased conductivity both in the dark and in light, due to absorption in the region of NIR photons in the former and additionally in the visible region in the latter.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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".