Time-resolved photoluminescence (PL) and transient absorption (TA) spectroscopy are conducted in order to get knowledge on the excited state of CdSe nanorods (NR), and to assess the impact of Au nanoparticles (NP) on the carrier dynamics of hybrid Au-CdSe NRs. The decay dynamics measured in solution show an increase of non-radiative decay channels in the presence of Au NPs, whose characteristic lifetimes vary from a few ps to tens of ps. The ultrafast electron transfer from CdSe NRs to Au NPs efficiently competes with intraband relaxation dynamics, allowing observation of the hot-electron transfer process. Furthermore, the time-averaged PL decay of CdSe NRs shows a strongly multiexponential feature that was analyzed by single-particle spectroscopy. The PL decay of individual NRs fluctuates in time and is correlated with the PL intensity. We show that the time-averaged decay of bare CdSe NRs is composed of (i) a long lifetime component corresponding to bright CdSe NRs (ON state) and (ii) a short lifetime component corresponding to charged NRs that open additional fast non-radiative channels (OFF state). When Au NPs are attached to CdSe NRs, the ON state PL decays still show a long lifetime component, suggesting that the length of the NRs may hinder electron transfer if the exciton is formed far from the Au NPs. Finally, quantitative analysis of the OFF state decays shows that electron transfer occurs even in the presence of fast non-radiative pathways in charged systems.

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CdTe quantum dots coated with a silica layer containing CdS-like clusters exhibit intense photoluminescence and a spectral red-shift. Biexciton Auger recombination of these particles is examined by transient absorption spectroscopy. A lengthening of the Auger recombination lifetime by a factor of ∼3.5 in the presence of the CdS-like clusters is observed and may contribute to the good PL properties of these nanostructures.

International audienceFluorescent microarrays exploit fluorescent labeled targets bound to immobilized biomolecular probes. Their signal-to-noise ratio is limited by the collection aperture in common confocal geometries. Taking advantage of a very high rejection filter deposited onto a silicon arrayed detector (coupled-charge device or complementary metal-oxide semiconductor), it is demonstrated that a highly compact lens-free assay with photon collection of order unity operates with a 30-fold improvement over a conventional (substrate + free-space optics) scheme. Through analysis of improvements over the present demonstrator, a single molecule per pixel sensitivity is predicted