Towards non-blinking colloidal quantum dots

Abstract

At a single-molecule level, fluorophore emission intensity fluctuates between bright and dark states. These fluctuations, known as blinking, limit the use of fluorophores in single-molecule experiments. The dark-state duration shows a universal heavy-tailed power-law distribution characterized by the occurrence of long non-emissive periods. Here we have synthesized novel CdSe-CdS core-shell quantum dots with thick crystalline shells, 68% of which do not blink when observed individually at 33 Hz for 5 min. We have established a direct correlation between shell thickness and blinking occurrences. Importantly, the statistics of dark periods that appear at high acquisition rates (1 kHz) are not heavy tailed, in striking contrast with previous observations. Blinking statistics are thus not as universal as thought so far. We anticipate that our results will help to better understand the physico-chemistry of single-fluorophore emission and rationalize the design of other fluorophores that do not blink.

Blinking suppression and biexcitonic emission in thick-shell CdSe/CdS nanocrystals at cryogenic temperature

“…For higher values of T , Q(T ) increases more slowly due to the decrease of g (2) (τ ) at high values of τ . This behavior corresponds to the absence of long periods of low emission.…”

“…All these properties were related to the power-law statistics followed by the duration of the extinction periods 34 that is not observed for CdSe/CdS NCs. 2,35 Even if the ACF remains close to 1, the slight deviation from unity has a strong impact in terms of intensity fluctuations. This can be illustrated through the Mandel factor Q(T ).…”

“…From T = 10 μs to 10 ms, Q(T ) increases linearly. This can be understood through the equation directly linking Q(T ) to the ACF g (2) (τ ): 36,38 …”

Slow Auger Recombination of Charged Excitons in Nonblinking Perovskite Nanocrystals without Spectral Diffusion

“…So far, effective suppressions of both Auger recombination and PL blinking has been realized only in several specific heterostructures such as "giant" CdSe/CdS core/shell NCs [14,15].…”

Excited-State Dynamics in Colloidal Semiconductor Nanocrystals

“…Methods to reduce blinking of NCs (i.e., to make random switches to a dark state less frequent) include surface protection using organic ligands [281] or an inorganic shell material [195,282,283], and also plasmonic enhancement of radiative decay [284]. This indicates that blinking involves slow changes on the surface of the QD that introduce non-radiative decay pathways.…”