Abstract
The fluorescence properties of individual CdSe/CdS nanocrystals (NCs) with a very thick shell and deposited on metallic structures are analyzed in detail. The results obtained for two metallic structures consisting of a continuous or a semi-continuous gold film are compared. Under low pulsed excitation, a strong acceleration of radiative processes is observed. The probability of electron–hole pair recombinations through Auger processes dramatically decreases, resulting in a suppression of blinking and the appearance of biexcitonic cascades. An original method of photons postselection also enables us to determine the decay rate corresponding to biexcitonic recombinations. Finally, a detailed analysis of the excitation process and the photon collection efficiency enables us to discriminate the effect of the gold structure in terms of excitation and fluorescence acceleration. It is found that high collection percentages can be achieved through the modification of NC emission with plasmonic structures.
Highlights
Very broad bandwidth that increases the accordability of the cavity with the emission of the fluorophore [15]
The duration of low emitting periods never exceeds 50 ms, in sharp contrast with standard CdSe/ZnS NCs [23]. These periods are not completely dark as for CdSe/ZnS NCs but correspond to a gray state with a quantum efficiency (QE) at least of the order of 20% [24]. When they are coupled to metallic structures, the following results show that the thick shell provides an intrinsic spacer between the emitter and the metal that avoids the quenching of the fluorescence
The relative positions of the A and B bumps in figure 1(b) correspond, respectively, to the mean intensity of X∗ and X states. They are proportional to the radiative QE of each state
Summary
Very broad bandwidth that increases the accordability of the cavity with the emission of the fluorophore [15]. The duration of low emitting periods never exceeds 50 ms, in sharp contrast with standard CdSe/ZnS NCs [23] These periods are not completely dark as for CdSe/ZnS NCs but correspond to a gray state with a quantum efficiency (QE) at least of the order of 20% [24]. When they are coupled to metallic structures, the following results show that the thick shell provides an intrinsic spacer between the emitter and the metal that avoids the quenching of the fluorescence. It is shown that a high efficiency of the photon collection and a strong reduction of the excited state lifetime can be simultaneously achieved
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