Electronic coupling between two nanocrystals is a facinating research topic. We focus on the developement of coupled collidal quantum dots (CQDs) by fusing two core/shell architechtures to form a dimer. Depending on the hybridization of wavefunctions based on the semiconductor type (type-I or type-II behavior) and the distance barrier between them,it is possible to achieve and tune the electronic coupling in a fused dimer and thus can be called CQD molecule. Utilizing the "artificial atom" character in CQDs, we have demonstrated a facile colloidal strategy to prepare artificial CQD molecule (CQDM). We explored the generality of the synthetic method and tunability of electronic coupling in model CdSe/CdS core/shell system via experimental and theoretical approaches (Nature Commun 2019 and J. Chem. Phys. 2019).
CQDM as Bowtie Nanoantenna: The tips of a tetrahedral nanocrystals are more reactive than the facets. Utilizing these behavior, we have prepared bowtie CQDM from core/shell CQDs. The CQD bowtie possess an electric field hotspot at the epicenter, which acts as selective photochemical reaction center (Angew. Chem. 2021).
Potential Future Applications of Prepared CQDMs:
The prepared CQDM remains a prospective candidate for numerous applications. Fine tuning of the core properties, shell barrier heights via nanocrystal chemistry, can lead to multitude possibilities towards targeted applications as in dual color emission, sensing, quantum computing etc. We are working on each of the topics, and stay tuned with this page for further update. Read more in our recent perspective in (Acc. Chem. Res. 2021).
New publication on "Neck Barrier Control" for tuning hybridization in CQD Molecules. (J. Am. Chem. Soc. 2021)
Cryogenic single particle spectroscopy maps the "Interacting Charging States" in CQDMs precisely. At 4K, CQD monomers manifest a simple emission spectrum comprising a main emission peak with well-defined phonon sidebands, CQDMs exhibit a complex spectrum with multiple peaks, assigned to various charging states of two neighboring cores of CQDMs. Effects of moving surface charges are identified and verified with COMSOL simulations. (ACS Nano 2022)
Two distinct coupling regimes depending on the "Neck-Barrier" at the Dimer interface are identified at room temperature. Single-particle emission spectroscopy reveals a “connected-but-confined” situation where neighboring CQDs are weakly fused to each other, manifesting a weak-coupling regime, and a “connected-and-delocalized” situation where the neck is filled beyond the facet size, leading to a rod-like architecture manifesting strong coupling. Emitted photons from the CQDMs in the weak-coupling regime highly bunched unlike CQD monomers, while the antibunching is regained at the strong-coupling regime. The handle of the neck girth is found to dictate the many-body interplay in CQDMs and determines the emitted photon purity. (Matter 2022)
Theresearch 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]).