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Colloidal nanoplatelets with two-dimensional electronic structure

Nature Materials volume 10, pages 936–941 (2011)Cite this article

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Abstract

The syntheses of strongly anisotropic nanocrystals with one dimension much smaller than the two others, such as nanoplatelets, are still greatly underdeveloped. Here, we demonstrate the formation of atomically flat quasi-two-dimensional colloidal CdSe, CdS and CdTe nanoplatelets with well-defined thicknesses ranging from 4 to 11 monolayers. These nanoplatelets have the electronic properties of two-dimensional quantum wells formed by molecular beam epitaxy, and their thickness-dependent absorption and emissionspectra are described very well within an eight-band Pidgeon–Brown model. They present an extremely narrow emission spectrum with full-width at half-maximum less than 40 meV at room temperature. The radiative fluorescent lifetime measured in CdSe nanoplatelets decreases with temperature, reaching 1 ns at 6 K, two orders of magnitude less than for spherical CdSe nanoparticles. This makes the nanoplatelets the fastest colloidal fluorescent emitters and strongly suggests that they show a giant oscillator strength transition.

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Figure 1: TEM images of nanoplatelets.
Figure 2: Emission and absorption spectra of II–VI compound nanoplatelets.
Figure 3: The model and the experimental data.
Figure 4: Lifetime and fluorescent emission intensity of 7-ML-thick CdSe NPLs versus temperature.

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Acknowledgements

B.D. acknowledges funding from the Agence Nationale pour la Recherche, the city of Paris, and the Région Ile-de-France. B.D. is grateful for discussions with P. Senellart. We thank N. Lequeux for help with the powder X-ray diffraction measurements and X. Xu for advice with TEM measurements. Al.L.E acknowledges the financial support of the Office of Naval Research and of the Saint-Gobain-ESPCI programme.

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Authors and Affiliations

  1. Laboratoire de Physique et d’Etude des Matériaux, UMR8213 du CNRS, ESPCI, 10 rue Vauquelin 75231 Paris, France

    S. Ithurria, M. D. Tessier, B. Mahler, R. P. S. M. Lobo & B. Dubertret

  2. Naval Research Laboratory, Washington, DC 20375, USA

    Al. L. Efros

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  1. S. Ithurria
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  6. Al. L. Efros
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Contributions

S.I. led the work related to the NPL synthesis and characterization, and initiated the low-temperature measurements. M.D.T. carried out the experiments at low temperature. R.P.S.M.L. helped with the low-temperature measurements and set-up. B.M. carried out the CdTe NPL synthesis. B.D. guided the work. Al.L.E. provided the theoretical description of the NPLs. B.D. and Al.L.E. wrote the manuscript.

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Correspondence to B. Dubertret or Al. L. Efros.

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The authors declare no competing financial interests.

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Ithurria, S., Tessier, M., Mahler, B. et al. Colloidal nanoplatelets with two-dimensional electronic structure. Nature Mater 10, 936–941 (2011). https://doi.org/10.1038/nmat3145

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