Dual emission and optical gain in PbS/CdS nanocrystals: Role of shell volume and of core/shell interface
Bibliographic record
Abstract
Colloidal semiconductor nanocrystals (NCs) emitting simultaneously at two distinct wavelengths are of great interest for multiple applications ranging from ultrasensitive self-calibrating nanoscale sensing to light-emitting diodes and white-light emission. The physical mechanism governing dual emission in core/shell NCs composed of two materials is still under investigation; in particular, the roles of the volume of the shell and of the core/shell interface are not well understood. Here we compare three different PbS/CdS NCs with identical cores, but shells of different thicknesses and different core/shell interfaces. We study photoluminescence (PL) characteristics and ultrafast exciton dynamics with subpicosecond time resolution. We find that dual emission is possible for both thick and thin quantum-confined shells, and for different core/shell interfaces. We show that very thick shells allow the decoupling of shell excitons from core ones and we fully describe the dynamic exciton barrier, connected to efficient shell PL. We discuss the efficiency of shell PL in relation to the properties of the NCs and show that it can give rise to optical gain. Our results provide a comprehensive understanding of the physical phenomena governing dual-emission mechanisms in NCs.
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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) | 0.000 | 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 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".