Ligand-induced symmetry breaking, size and morphology in colloidal lead sulfide QDs: from classic to thiourea precursors
Bibliographic record
Abstract
Colloidal lead chalcogenide quantum dots (CQDs) exhibit promising optoelectronic properties for applications in solar cell devices and as thermoelectrics.Herein, we report and discuss a ferroelectric structural distortion, at the picometer scale resolution, in PbS CQDs prepared using both classic and new synthetic pathways.The investigation was performed using synchrotron X-ray total scattering data and advanced methods of analysis that rely on a homo-core-shell model and evaluate the atomic arrangement, stoichiometry, size and morphology of nanocrystals.The CQDs show comparable size-dependent relative elongation, up to 0.7 % of one body diagonal of the cubic rock-salt structure, which corresponds to a rhombohedral lattice deformation.The findings suggest a joint role for the oleate ligands (which induce surface tensile strain) and the Pb(II) lone pair as the driving forces of the deformation.Pb displacements along the [111] direction, which provoke a ferrolectric distortion related to the lattice change, fall in the 0.0 -0.1 Å range.Overall, the findings suggest the local nature of the metal off-centering, leading to different average displacements which depend on the synthetic conditions.
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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".