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Chloride-induced thickness control in CdSe nanoplatelets

(2018) NANO LETTERS. 18(10). p.6248-6254
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Abstract
Current colloidal synthesis methods for CdSe nanoplatelets (NPLs) routinely yield samples that emit, in discrete steps, from 460 to 550 nm. A significant challenge lies with obtaining thicker NPLs, to further widen the emission range. This is at present typically achieved via colloidal atomic layer deposition onto CdSe cores, or by synthesizing NPL core/shell structures. Here, we demonstrate a novel reaction scheme, where we start from 4.5 monolayer (ML) NPLs and increase the thickness in a two-step reaction that switches from 2D to 3D growth. The key feature is the enhancement of the growth rate of basal facets by the addition of CdCl2, resulting in a series of nearly monodisperse CdSe NPLs with thicknesses between 5.5 and 8.5 ML. Optical characterization yielded emission peaks from 554 nm up to 625 nm with a line width (fwhm) of 9-13 nm, making them one of the narrowest colloidal nanocrystal emitters currently available in this spectral range. The NPLs maintained a short emission lifetime of 5-11 ns. Finally, due to the increased red shift of the NPL band edge photoluminescence excitation spectra revealed several high-energy peaks. Calculation of the NPL band structure allowed us to identify these excited-state transitions, and spectral shifts are consistent with a significant mixing of light and split-off hole states. Clearly, chloride ions can add a new degree of freedom to the growth of 2D colloidal nanocrystals, yielding new insights into both the NPL synthesis as well as their optoelectronic properties.
Keywords
COLLOIDAL QUANTUM-WELLS, SEMICONDUCTOR NANOPLATELETS, AUGER, RECOMBINATION, NANOCRYSTALS, EMISSION, SIZE, GROWTH, HETERONANOPLATELETS, HETEROSTRUCTURES, ABSORPTION, Colloidal synthesis, 2D nanocrystals, halides, photoluminescence, k.p calculations

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Citation

Please use this url to cite or link to this publication:

MLA
Christodoulou, Sotirios et al. “Chloride-induced Thickness Control in CdSe Nanoplatelets.” NANO LETTERS 18.10 (2018): 6248–6254. Print.
APA
Christodoulou, S., Climente, J. I., Planelles, J., Brescia, R., Prato, M., Martin-Garcia, B., Khan, A., et al. (2018). Chloride-induced thickness control in CdSe nanoplatelets. NANO LETTERS, 18(10), 6248–6254.
Chicago author-date
Christodoulou, Sotirios, Juan I Climente, Josep Planelles, Rosaria Brescia, Mirko Prato, Beatriz Martin-Garcia, Ali Khan, and Iwan Moreels. 2018. “Chloride-induced Thickness Control in CdSe Nanoplatelets.” Nano Letters 18 (10): 6248–6254.
Chicago author-date (all authors)
Christodoulou, Sotirios, Juan I Climente, Josep Planelles, Rosaria Brescia, Mirko Prato, Beatriz Martin-Garcia, Ali Khan, and Iwan Moreels. 2018. “Chloride-induced Thickness Control in CdSe Nanoplatelets.” Nano Letters 18 (10): 6248–6254.
Vancouver
1.
Christodoulou S, Climente JI, Planelles J, Brescia R, Prato M, Martin-Garcia B, et al. Chloride-induced thickness control in CdSe nanoplatelets. NANO LETTERS. 2018;18(10):6248–54.
IEEE
[1]
S. Christodoulou et al., “Chloride-induced thickness control in CdSe nanoplatelets,” NANO LETTERS, vol. 18, no. 10, pp. 6248–6254, 2018.
@article{8589967,
  abstract     = {Current colloidal synthesis methods for CdSe nanoplatelets (NPLs) routinely yield samples that emit, in discrete steps, from 460 to 550 nm. A significant challenge lies with obtaining thicker NPLs, to further widen the emission range. This is at present typically achieved via colloidal atomic layer deposition onto CdSe cores, or by synthesizing NPL core/shell structures. Here, we demonstrate a novel reaction scheme, where we start from 4.5 monolayer (ML) NPLs and increase the thickness in a two-step reaction that switches from 2D to 3D growth. The key feature is the enhancement of the growth rate of basal facets by the addition of CdCl2, resulting in a series of nearly monodisperse CdSe NPLs with thicknesses between 5.5 and 8.5 ML. Optical characterization yielded emission peaks from 554 nm up to 625 nm with a line width (fwhm) of 9-13 nm, making them one of the narrowest colloidal nanocrystal emitters currently available in this spectral range. The NPLs maintained a short emission lifetime of 5-11 ns. Finally, due to the increased red shift of the NPL band edge photoluminescence excitation spectra revealed several high-energy peaks. Calculation of the NPL band structure allowed us to identify these excited-state transitions, and spectral shifts are consistent with a significant mixing of light and split-off hole states. Clearly, chloride ions can add a new degree of freedom to the growth of 2D colloidal nanocrystals, yielding new insights into both the NPL synthesis as well as their optoelectronic properties.},
  author       = {Christodoulou, Sotirios and Climente, Juan I and Planelles, Josep and Brescia, Rosaria and Prato, Mirko and Martin-Garcia, Beatriz and Khan, Ali and Moreels, Iwan},
  issn         = {1530-6984},
  journal      = {NANO LETTERS},
  keywords     = {COLLOIDAL QUANTUM-WELLS,SEMICONDUCTOR NANOPLATELETS,AUGER,RECOMBINATION,NANOCRYSTALS,EMISSION,SIZE,GROWTH,HETERONANOPLATELETS,HETEROSTRUCTURES,ABSORPTION,Colloidal synthesis,2D nanocrystals,halides,photoluminescence,k.p calculations},
  language     = {eng},
  number       = {10},
  pages        = {6248--6254},
  title        = {Chloride-induced thickness control in CdSe nanoplatelets},
  url          = {http://dx.doi.org/10.1021/acs.nanolett.8b02361},
  volume       = {18},
  year         = {2018},
}

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