Bimodal Photoluminescence during the Growth of PbS Quantum Dots
Bibliographic record
Abstract
We examine the effect of reaction time, temperature, molar ratio of precursors, capping ligands, and aging on the growth of PbS quantum dots in a “nonviscous”, solventless, mild-constant-temperature system with PbCl 2 and S as precursors. It is found in our system that Ostwald ripening leads to bimodal photoluminescence corresponding to the bimodal size distribution of PbS quantum dots, as evidenced by transmission electron microscopy, in contrast to commonly reported single-peak broadening due to Ostwald ripening. The evolution of photoluminescence spectra mediated by Ostwald ripening is strongly affected by reaction parameters. Under certain conditions, the photoluminescence band exhibits some initial broadening upon the action of Ostwald ripening and then gradually transforms into a bimodal structure. In other cases, bimodal peaks rapidly appear as early as 1 min after the reaction starts. Moreover, it is found that the addition of an additional ligand trioctylphosphine immediately initiates the bimodal photoluminescence, which, however, on the basis of photoluminescence spectra characteristics is not thought to be associated with Ostwald ripening. For the bimodal emission structure, aging can greatly enhance the emission peak at shorter wavelength, but it does not affect the emission peak at longer wavelength. Using our simple system, we are able to synthesize PbS quantum dots with a narrow size distribution evidenced by a full width at half-maximum of the photoluminescence peak as low as 58 meV.
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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 | 0.000 |
| 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 | 0.001 | 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".