Mapping Emission from Clusters of CdSe/ZnS Nanoparticles

Abstract

We have carried out correlated super-resolution and SEM imaging studies of clusters of CdSe/ZnS nanoparticles containing up to ten particles to explore how the fluorescence behavior of these clusters depends on the number of particles, the specific cluster geometry, the shell thickness, and the technique used to produce the clusters. The total emission yield was less than proportional to the number of particles in the clusters for both thick and thin shells. With super-resolution imaging, the emission center of the cluster could be spatially resolved at distance scales on the order of the cluster size. The intrinsic fluorescence intermittency of the nanoparticles altered the emission distribution across the cluster, which enabled the identification of relative emission intensities of individual particles or small groups of particles within the cluster. For clusters undergoing interparticle energy transfer, donor/acceptor pairs and regions where energy was funneled could be identified.

Long Range Energy Transfer in Self-Assembled Stacks of Semiconducting Nanoplatelets

“…Within a chain of NPLs, we thus expect fast transfer between NPLs to modify the luminescence as compared to isolated NPLs. For instance, collective blinking of clusters of 2 to 10 quantum dots has already been reported due to fast energy transfer between the emitters 33 (whereas antibunching of clusters of 4-5 quantum dots was attributed to inter-particle Auger interaction 34 ). The search for even stronger and longer-range FRET-mediated collective photophysical effects between self-assembled chains of nanoplatelets is the topic of our ongoing work.…”

Role of Solid-State Miscibility during Anion Exchange in Cesium Lead Halide Nanocrystals Probed by Single-Particle Fluorescence

“…While anion exchange exhibits similarities to other chemical transformations in colloidal semiconductor nanocrystals, a unique feature of this reaction is the complete solid-state miscibility exhibited between CsPbCl 3 and CsPbBr 3 . , In this study, we aimed to determine how this high miscibility affects the reaction trajectories of individual nanocrystals undergoing anion exchange. Single-nanocrystal fluorescence microscopy has been used to understand how heterogeneity among a population of particles leads to the observed ensemble behavior. ,,− ,− Thus, we used changes in the emission wavelength and intensity as a signature for when individual NCs undergo this transformation. We observed distinct differences for this system compared to related solid-state transformations in which the initial and final crystals lack solid solubility. − On the basis of our observations and previous ensemble kinetic studies, we develop a model in which the decrease in the activation barrier for successive anion exchange events is more gradual than systems that require a phase transformation.…”

A Gain-series Method for Accurate EMCCD Calibration

“…In microscopy applications, EMCCD cameras can detect emission from single fluorophores where emission may be weak. These devices have enabled numerous imaging modalities, and have helped enhance the spatial resolving power of microscopy methods in the biological and material sciences [2][3][4][5][6][7] . EMCCDs have also found use in quantum imaging and sensing where spatially-resolved single-photon detection 8 is used in pair-correlation experiments 9 .…”