Gradiently Alloyed Zn<i><sub>x</sub></i>Cd<sub>1-</sub><i><sub>x</sub></i>S Colloidal Photoluminescent Quantum Dots Synthesized via a Noninjection One-Pot Approach
Bibliographic record
Abstract
High-quality colloidal photoluminescent (PL) ZnCdS quantum dots (QDs) with gradient distribution of components, consisting of Cd-rich inner cores and Zn-rich outer shells, were synthesized via a noninjection one-pot approach. This newly developed synthetic approach uses zinc stearate (Zn(St) 2 ), cadmium acetate dihydrate (Cd(OAc) 2 ·2H 2 O), and elemental sulfur as Zn, Cd, and S source compounds, respectively. The growth of the cubic-structured QDs was carried out at 240 °C in a reaction flask consisting of the source compounds, together with stearic acid (SA), 2,2‘-dithiobisbenzothiazole (MBTS), and 1-octadecene (ODE); all of these chemicals were loaded at room temperature. The temporal evolution of the optical properties of the growing QDs, including absorption and photoemission, was monitored in detail; the evolution monitored indicates that the growth kinetics, the composition, and the distribution of the Zn and Cd in the resulting ternary Zn x Cd 1- x S QDs are sensitive to feed Zn−Cd−S molar ratios. Detailed investigation on the feed Zn−Cd−S molar ratio affecting the QD growth and optical property was performed, together with detailed structural characterization by solid-state NMR including cross polarization (CP) and dipolar dephased cross polarization (DDCP); also, the resulting QDs were characterized by XPS, TEM, and XRD. Accordingly, the synthesis-structure−property relationship was explored systematically. Tuning the feed Zn−Cd−S stoichiometry, high-quality Zn x Cd 1- x S QDs exhibiting sharp excitonic absorptions, narrow PL emissions with full width at half-maximum (fwhm) on the order of 19−21 nm, and high PL quantum yield (QY, up to 23%), could be fabricated with relatively low Zn and S feed amount, such as 1Zn−1Cd−1S feed molar ratio. In general, our noninjection approach features great synthetic reproducibility and is easy to scale up, with a plausible alloying mechanism of the formation of a Cd-rich core in the early growth stage, followed by a gradual formation of Zn-rich outer layers with increasing zinc content toward the surface.
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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".