Long‐Range Visible Fluorescence Tunability Using Component‐Modulated Coupled Quantum Dots

Abstract

Coupled quantum semiconductor dots are often referred to as artifi cial molecules because their electronic properties are dictated by the mutual interaction of two constituent blocks. [ 1 , 2 ] Unlike the electronic property tuning by varying the size or shape of a single nanomaterial, coupled quantum dots rely on controlling energy states via band-offset engineering at the material interface. [ 3 , 4 ] The possibility of obtaining long-range optical tunability from coupled quantum dots demonstrates a route for going far beyond the limits imposed by individual nanomaterials by the spatial separation of the charge carriers, which provides yet another important way to tailor nanomaterial properties. Coupled semiconductor heterostructures are typically classifi ed as type-I or type-II depending on the relative alignment of the conduction and valence bands of the constituent materials forming the heterointerface. [5][6][7] For a type-II coupled structure, the relative alignment of the conduction and valence bands of the constituent materials offers a spatially indirect bandgap resulting in a transition energy gap smaller than the bandgaps of either of the constituting semiconductors. Thus, such coupled structures offer engineering of the energy gap by variation of component sizes or extent of diffusion at the interface. Recent interest in component-modulated coupled materials include core/shell nanostructures, heterojunctions, and superlattices, which offer diverse functionalities due to the spatial charge distribution across the material junctions. [ 8 -13 ] Synthesis of facet selective multicomponent heterostructures, such as hetero-nanorods, [14][15][16][17] tetrapods, [ 18 ] and dumbbells have drawn signifi cant scientifi c importance because of their capability for exciton separation within a single coupled material. [ 19 , 20 ] However, these structures often lead to a disappearance of emission owing to the spatially separated nanoradiative intermediate states and lack in-plane conformation variation capability due to one and multidimensional morphologies. [ 21 ] The promise of in-plane conformation variation is of practical importance because a fi xed biasing across a close-packed monolayer of asymmetric coupled dots may provide a route to control electronic properties for different conformations that may lead in realizing the q-bits for quantum information processing, [ 22 , 23 ] in addition to application in optoelectronic devices. [24][25][26] In principle, control over coupled junction provides a means for controlling quantum coupling interactions, the extent of which can be controlled by tuning synthetic conditions. The intermixing between constituent nanomaterials may result in new intermediate transition states depending on the size of the constituents, which could be useful in tailoring long-range emissions in the visible or IR range. Here, we report a simple route for tailoring emission over the entire visible range by chemically designing type-II asymmetric coupled quantum dots composed of di...

Nanostructure formation via post growth of particles

“…78 The fusion process is achieved simply via redispersing pre-synthesized ZnSe and CdS prolate nanodots in octadecene, while the reaction annealing time can control the extent of fusion of the interfaces. The NP fusion between CdS and ZnSe not only permits the tuning of their emission spectra but also optimizes the excited state lifetimes.…”

Influence of Ga coverage on the sizes of GaAs quantum dash pairs grown by high temperature droplet epitaxy

“…Among these nanostructures, QD molecules (QDMs) have received much attention due to their potential applications in quantum computing 5. The simplest and most investigated QDM is coupled QDs 6. QD pairs can be conveniently fabricated by stacking vertical QD pairs 7.…”

In situ synthesis of binary cobalt–ruthenium nanofiber alloy counter electrode for electrolyte-free cadmium sulfide quantum dot solar cells

“…The intensity of the emission peaks gradually increases with the increase of the loading of S precursor in QDs from 0.5 to 2.0 mmol. However, after further increasing the loading amounts, the intensity of the emission peaks falls off, and the broad emission spectra gradually reduce, which we attribute to the expectation that the Ostwald ripening accompanied by gradual decrease of the QDs concentration and the introduction of unpredictable defect states during the growth of QDs, thus leading to the quenching of PL intensity [40]. Furthermore, the photograph of various phials containing CdS QDs (in deionized water) from left to right by increasing amount of precursors under 365 nm UV illumination can be seen in Fig.…”