High quality CdS nanocrystals: surface effects

Zezza, Fulvio; Comparelli, Roberto; Striccoli, Marinella; Curri, M. Lucia; Tommasi, R.; Agostiano, Angela; Monica, M. Della

doi:10.1016/s0379-6779(03)00320-5

Cited by 43 publications

(37 citation statements)

References 10 publications

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“…47 For example, a signature of these localized states is the increase of direct CdS exciton recombination in tetrapods of increasing arm length. 42 In addition, it has been suggested that an interfacial barrier can be formed in the conduction band between the CdSe and the CdS due to the strain arising from the lattice mismatch and the associated internal electric field.…”

Section: B the Role Of Localized Trap Statesmentioning

confidence: 99%

Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

et al. 2012

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CdSe/CdS nanocrystal tetrapods are interesting building blocks for excitonic circuits, where the flow of excitation energy is gated by an external stimulus. The physical morphology of the nanoparticle, along with the electronic structure, which favors electron delocalization between the two semiconductors, suggests that all orientations of a particle relative to an external electric field will allow for excitons to be dissociated, stored, and released at a later time. While this approach, in principle, works, and fluorescence quenching of over 95% can be achieved electrically, we find that discrete trap states within the CdS are required to dissociate and store the exciton. These states are rapidly filled up with increasing excitation density, leading to a dramatic reduction in quenching efficiency. Charge separation is not instantaneous on the CdS excitonic antennae in which light absorption occurs, but arises from the relaxed exciton following hole localization in the core. Consequently, whereas strong electromodulation of the core exciton is observed, the core multiexciton and the CdS arm exciton are not affected by an external electric field.

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Section: B the Role Of Localized Trap Statesmentioning

confidence: 99%

Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

et al. 2012

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“…This systematic energy level shift also suggests presence of specific energy levels related to Ag dopants. A Gaussian deconvolution (not shown here) of our data suggests presence of two luminescence centers related to (a) sulfur related surface states and (b) Ag/Cl related levels [3][4][5][6][7]16]. There is a variation in their relative intensities and a systematic peak shift to longer wavelengths with Cd concentration variation.…”

Section: Methodsmentioning

confidence: 69%

Photoluminescence shifts in silver-doped nanocrystalline Cd1−xZnxS

Karar

Jayaswal

Halder

et al. 2007

Journal of Alloys and Compounds

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“…Las muestras de QDs se lavaron según el método descrito por ZEZZA et al [12] con la diferencia que en este trabajó se aplicó a QDs envejecidos o degradados. Se añadió etanol en exceso, se agitó y centrifugó la solución resultante y se procedió a separar el sobrenadante.…”

Section: Método De Lavadounclassified

“…4, La disminución en intensidad de la banda atribuible a defectos respecto a la banda excitónica después de haber agregado ODE y dejar reposar por un tiempo ya ha sido reportado por ZEZZA et al [12] y se asocia al reacomodo superficial de los surfactantes que se da posterior al lavado.…”

Section: En Launclassified

“…Esto podría atribuirse a la remoción de los residuos de la reacción que pudieron formar defectos y un reacomodo de los surfactantes como se describió en el párrafo anterior, mostrando de esta manera una forma de pasivación de defectos superficiales en QDs envejecidos. Es de hacer notar que el método de lavado empleado en este trabajo, en contraste con el descrito por ZEZZA et al [12], el cual es aplicado a muestras "recién" sintetizadas, es aplicado para QDs envejecidos. Los resultados obtenidos mediante este método muestran una mayor pasivación para muestras con una mayor relación área/volumen, es decir, QDs de menor tamaño.…”

Section: En Launclassified

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Caracterización óptica de defectos superficialesen puntos cuánticos coloidales de Seleniuro de Cadmio (CdSe)

Elias

Flores

2015

Matéria (Rio J.)

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RESUMENEn el presente estudio se han caracterizado ópticamente defectos superficiales ("non-stoichiometric" y "dangling bonds") en puntos cuánticos (QDs) coloidales de CdSe sintetizados por el método de descomposición térmica. En especial, se estudió la presencia de defectos vinculados con una alta relación área/volumen de los QDs. Los espectros de fotoluminiscencia (PL) de estos QDs presentan dos bandas, atribuibles a la recombinación excitónica y a la recombinación excitónica vía defectos superficiales. Luego de la síntesis las muestras permanecieron durante un tiempo sin ningún tratamiento adicional. Durante este tiempo se observó mediante el monitoreo de la evolución de las bandas de PL, un incremento en la intensidad de la banda atribuible a defectos respecto a la de emisión excitónica. Posteriormente, las muestras se lavaron utilizando abundante etanol y fueron disueltas en 1-octadeceno. Con este tratamiento se ha observado una recuperación gradual de la PL de la banda excitónica. Esto podría atribuirse a la remoción de los residuos de la reacción que pudieron formar defectos y a un reacomodo de los surfactantes, mostrando de esta manera una forma de pasivación de defectos superficiales. Para todas las muestras estudiadas en este trabajo, se observó mayor presencia de defectos superficiales para QDs con mayor relación área/volumen.Palabras clave: Fotoluminiscencia, puntos cuánticos coloidales, CdSe, defectos superficiales, surfactantes. ABSTRACTIn this work, non-stoichiometric defects and dangling bond defects were optically characterized for CdSe colloidal quantum dots (QDs), which were prepared by the thermal decomposition method. Particularly, the presence of defects linked to a high QD surface to volume ratio was studied. The photoluminescence (PL) spectra of the samples show two bands, which could be associated to excitonic recombination and excitonic recombination via surface defects. The samples remained untreated for a period of time after preparation. During this time a gradual deterioration of the QDs was observed by monitoring the evolution of PL spectra. An increase in intensity of the band associated to recombination via defects, with respect to the excitonic emission band, was observed. Subsequently, the samples were washed using abundant ethanol and dissolved in 1-octadecene. After this treatment a gradual recovery of the excitonic PL band was observed. This could be attributed to the removal of reaction residues that could give rise to defects, and to a rearrangement of the surfactants, thus showing a form of surface defects passivation. For all the samples, investigated in this work, a greater presence of surface defects for QDs of higher surface to volume ratio was observed.

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High quality CdS nanocrystals: surface effects

Cited by 43 publications

References 10 publications

Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

Photoluminescence shifts in silver-doped nanocrystalline Cd1−xZnxS

Caracterización óptica de defectos superficialesen puntos cuánticos coloidales de Seleniuro de Cadmio (CdSe)

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