Coupling in quantum dot molecular hetero-assemblies

Abstract

The design of large-scale colloidal quantum dots (QDs) assemblies and the investigation of their interaction with their close environment are of great interest for improving QD-based optoelectronic devices' performances. Understanding the interaction mechanisms taking place when only a few QDs are assembled at a short interparticle distance is relevant to better promote the charge or energy transfer processes. Here, small hetero-assemblies formed of a few CdSe QDs of two different sizes, connected by alkyl dithiols, are fabricated in solution. The interparticle distance is tuned by varying the linear alkyl chain length of the bifunctional spacer from nanometer to sub-nanometer range. The crystallographic analysis highlights that the nearest surfaces involved in the linkage between the QDs are the (101) faces. The thorough spectroscopic investigation enables a sound rationalization of the coupling mechanism between the interacting nanoparticles, ranging from charge transfer/wavefunction delocalization to energy transfer, depending on their separation distance.

Harvesting a Wide Spectral Range of Electronic Coherences with Disordered Quasi‐Homo Dimeric Assemblies at Room Temperature

“…[ 15,38 ] In strongly electronically coupled QD dimers assembled with short sub‐nm ligands, resonances or quasi‐resonances between the excitons of the two constitutive QDs favor the electronic coupling and the delocalization of the electronic states over the two dots. [ 15,36–38 ] In the case of heterodimers, resonances between two excitonic bands can be tuned by adjusting the $$\bar D$$ of the two QDs [ 15,33,38,39 ] so as to ensure an effective electronic coupling. For dimers assembled with QDs of the same $$\bar D,$$ the excitonic bands of each QD are degenerate, which leads intrinsically to a larger number of delocalized dimer states.…”

“…[31] Electronically coupled dimers can also be assembled from small (< 3.5 nm in diameter) CdSe colloidal QD's with narrow size distributions and short ligands to favor interdot coupling. [32][33] However, achieving high levels of monodispersity remains a challenge for such small colloidal CdSe QDs. For such small diameters, intrinsic size dispersions of between 5 and 10% remain unavoidable.…”

Simulating action-2D electronic spectroscopy of quantum dots: insights on the exciton and biexciton interplay from detection-mode and time-gating

“…This journal is © the Owner Societies 2022 been discussed, based on both theoretical and experimental evidences. 50,[75][76][77][78][79] How weak and strong-coupling are associated with specific spectral features in A-2DES maps is a critical issue which is left for future work.…”

Homogeneous Resonant Energy Transfer within Clusters of Monodisperse Colloidal Quantum Dots

“…26−29 Henceforth, the FRET process occurs between two QDs, and we count two possible QD−QD FRET configurations: first, the two QDs come from the same monodisperse colloidal suspension, provided the emission wavelength of the donor exactly coincides with the absorption wavelength of the acceptor; second, the two partners come from two different monodisperse populations, well characterized by two distinct mean emission wavelengths (i.e., two distinct mean sizes) carefully chosen to satisfy the overlap conditions of FRET. 27,30,31 But even in the second case, the probability to observe two same-population QDs interacting through FRET cannot be neglected. Each monodisperse population of QDs may give rise to such a homogeneous resonant energy transfer (homo-FRET).…”

“…Quantum dots (QDs) are luminescent semiconductor nanoparticles whose optical properties of absorption and emission are tunable as functions of the nanoparticle radius and ligand capping. − Benefiting from such a physical and chemical versatility, QDs are often used as fluorescent probes and markers for biosensing and imaging. ,− In particular, these nanocrystals are photobleaching-free and structurally robust, so they are commonly preferred over molecular fluorophores exhibiting a weaker photochemical stability . Numerous biosensors are indeed based on the detection of QD fluorescence. − In many cases, QDs are employed as donors and exchange their energy through Förster resonant energy transfer (FRET) with organic fluorophores tagging the target molecules. − But given the above-mentioned advantages, QDs are also well suited for playing the role of acceptor fluorescent markers, instead of molecular chromophores. − Henceforth, the FRET process occurs between two QDs, and we count two possible QD–QD FRET configurations: first, the two QDs come from the same monodisperse colloidal suspension, provided the emission wavelength of the donor exactly coincides with the absorption wavelength of the acceptor; second, the two partners come from two different monodisperse populations, well characterized by two distinct mean emission wavelengths (i.e., two distinct mean sizes) carefully chosen to satisfy the overlap conditions of FRET. ,, But even in the second case, the probability to observe two same-population QDs interacting through FRET cannot be neglected. Each monodisperse population of QDs may give rise to such a homogeneous resonant energy transfer (homo-FRET) .…”