Non-Injection and Low-Temperature Approach to Colloidal Photoluminescent PbS Nanocrystals with Narrow Bandwidth
Notice bibliographique
Résumé
Colloidal photoluminescent (PL) PbS nanocrystals have attracted a lot of attention in various applications such as bioimaging and optical telecommunications due to their tunable bandgap in the near-infrared region of the electromagnetic spectrum. Hot-injection processes seem to be the best to engineer high-quality PbS nanocrystals. However, there is a limited body of literature documented on the syntheses, with little information on synthetic parameters affecting the optical properties of the product. Moreover, small PbS nanocrystals with large bandgap greater than 1.38 eV (ca. 900 nm) and narrow bandwidth are rarely reported, due to the fact that high-temperature growth in hot-injection processes leads to large nanocrystals rapidly. This manuscript deals with our noninjection and low temperature approach to small PbS nanocrystal ensembles with bandgap in wavelength shorter than 900 nm and with narrow bandwidth; the growth temperature can be as low as room temperature. For our noninjection approach, systematic study was performed on synthetic parameters affecting the growth, with the growth temperature in the range of 30−120 °C and octadecene (ODE) as a reaction medium. Different acids including oleic aicd (OA) were explored as surface ligands, while two lead source compounds, which are lead oxide (PbO) and lead acetate, and three S source compounds, which are bis(trimethylsilyl)sulfide ((TMS) 2 S), thioacetamide (TAA), and elemental sulfur (S), were investigated. Generally, a solution of a lead precursor in ODE was first prepared via a reaction of a Pb-source compound and an acid; afterward, this solution was mixed with a S-source solution in ODE at room temperature. The use of (TMS) 2 S and OA bestows high-quality PbS nanocrystals, regarding narrow bandwidth of bandgap absorption and photoemission, without storage in dark for digestive and Ostwald ripening leading to self-focusing; in addition to the various acids and Pb and S source compounds explored, feed molar ratios of acid-to-Pb and Pb-to-S, as well as reactant concentrations were thoroughly investigated. Low acid-to-Pb and high Pb-to-S feed molar ratios together with high-reactant concentrations favor the formation of small PbS nanocrystals; meanwhile, from one synthetic batch, the growth of PbS nanocrystals in size is tunable mainly via temperature in addition to growth periods. The PbS nanocrystals exhibit bandwidth (full width at half-maximum) as narrow as ca. 100 nm with growth temperature of 70 °C. Thus, our noninjection approach features easy handling with high reproducibility and high-quality PbS nanocrystals with large bandgap but narrow bandwidth. Finally, bandgap engineering of our as-synthesized PbS nanocrystals was performed straightforwardly at room temperature via the mixing of a solution of Cd oleate in ODE; significant blueshift of bandgap absorption and photoemission with enhanced PL efficiency was accomplished.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
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