Enhancing the fluorescence of individual thick shell CdSe/CdS nanocrystals by coupling to gold structures

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.