Charge Separation and Recombination in CdTe/CdSe Core/Shell Nanocrystals as a Function of Shell Coverage: Probing the Onset of the Quasi Type-II Regime
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Bibliographic record
Abstract
Femtosecond transient absorption (TA) is used to investigate population dynamics of electronic states in CdTe/CdSe core/shell nanocrystals (NCs) with varying CdSe shell coverage. Upon CdSe shell growth, the CdTe/CdSe NCs show a gradual evolution of surface passivation toward a quasi-type-II charge separation regime. Our results indicate that ultrafast electron transfer (ET) through the interface of CdTe/CdSe NCs becomes measurable as the CdSe shell approaches the quasi-type-II regime which we experimentally determined to be at 0.4 nm (shell) for a 3.4 nm CdTe core. This work reports the first measurement using femtosecond TA to study the electronic states in CdTe/CdSe NCs and spectroscopically observe the evolution of an ultrafast charge transfer (CT) in such a core/shell system. Time-resolved photoluminescence (PL) spectroscopy is used to study the radiative lifetimes of the CdTe/CdSe NCs. One monolayer CdSe coverage leads to longer-lived PL, which is red-shifted by 140 nm compared to the CdTe core PL. It is concluded that this is due to greater electron−hole separation providing a longer-lived CT state.
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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 | 0.001 | 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 it