Coupled Colloidal Quantum Dot Molecules

Uri Banin^a

^aThe Institute of Chemistry and Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, Israel

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Spring Meeting 2022 (NSM22)

#SNI22. Semiconductor Nanocrystals I: Basic Science (synthesis, spectroscopy, electronic structure, device and application)

Online, Spain, 2022 March 7th - 11th

Organizers: Emmanuel Lhuillier, Sandrine Ithurria and Angshuman Nag

Invited Speaker, Uri Banin, presentation 175
DOI: https://doi.org/10.29363/nanoge.nsm.2022.175
Publication date: 7th February 2022

Colloidal semiconductor Quantum Dots (CQDs) that contain hundreds to thousands of atoms manifest size dependent tunable properties and have reached an exquisite level of control, leading to their technological applications in optoelectronics and bioimaging. Considering them as artificial atoms, CQD molecules connected with molecular linkers such as DNA strands were studied. Yet, in these structures the presence of a high potential barrier limits coupling between the quantum states of neighboring CQDs limiting their full potential as coupled systems. Although coupled quantum dots were prepared by means of molecular beam epitaxy (MBE), their typical dimensions limit coupling to small energy scales suitable to low temperature operation. Furthermore, while MBE grown structures are inherently buried within a host semiconductor, CQDs are free in solution and accessible for wet-chemical manipulations.

Herein, we introduce a facile and powerful strategy for programmed synthesis of coupled CQDs molecules with precise control over the composition and size of the barrier in between the artificial atoms to allow for tuning the electronic coupling characteristics and their optical properties.¹ Our approach entails fusing two CdSe/CdS core/shell CQDs via constrained oriented attachment.² This yields a dimer with a tailored barrier dictated by the shell composition, thickness and fusion reaction conditions. The fusion reaction also enables tuning the neck barrier width.³ The possible nanocrystal facets in which such fusion takes place are analysed with atomic resolution revealing the distribution of possible crystal fusion scenarios. Coherent coupling is revealed by ensemble and single particle spectroscopic signatures, in agreement with quantum mechanical simulations.⁴ Cryogenic single nanocrystal spectroscopy accompanied by the simulations, unravels the complete tracking of fluorescence and charging events in such coupled colloidal quantum dot molecules.

This sets the stage for nanocrystals chemistry to yield a diverse selection of coupled CQD molecules utilizing the rich collection of ubiquitous artificial atom core/shell CQD building blocks. Such CQD molecules are of direct relevance for numerous applications including in displays, sensing, biological tagging and emerging quantum technologies.

References:

[1] [1] Koley, S.; Cui, J.; Panfil, Y.E.; Banin, U. Coupled Colloidal Quantum Dot Molecules. Acc. Chem. Res. 2021, 54, 5, 1178–1188.

[2] [2] Cui, J.; Panfil, Y.E.; Koley, S.; Shamalia, D.; Waiskopf, N.; Remennik, S.; Popov, I.; Oded, M.; Banin, U. Colloidal quantum dot molecules manifesting quantum coupling at room temperature. Nature Comm. 2019, 10, 5401.

[3] [3] Cui. J.; Koley, S.; Panfil, Y.E.; Levi, A.; Ossia, Y.; Waiskopf, N.; Remennik, S.; Oded, M.; Banin, U. Neck Barrier Engineering in Quantum Dot Dimer Molecules via Intraparticle Ripening. J. Am. Chem. Soc., 2021.

[4] Panfil, Y.E>; Shamalia, D.; Cui. J.; Koley, S.; Banin U. Electronic coupling in colloidal quantum dot molecules; the case of CdSe/CdS core/shell homodimers,” J. Chem. Phys. 2019, 151, 224501.

Acknowledgements:

The research leading to these results has received financial support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. [741767], CoupledNC).

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