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The electromagnetic properties of ordered hole nanostructures in very thin metal films are characterized using CdSe/CdS nanocrystals (NCs) as nanoprobes. The characterization of the local density of optical states (LDOS) on the nanostructure is possible by the measurement of their photoluminescence decay rate. Statistical measurements are performed in the far field to show the average increase of optical modes. A determinist approach using an active single NC nanoprobe in the near field gives access to a more precise characterization of the LDOS. The optical properties of the structure come from the coupling between localized surface plasmons created by the holes and surface plasmon polaritons. A strong concentration of optical modes is observed around the holes thanks to the active near-field nanoprobe. With different NC orientations, the strong influence of the component perpendicular to the surface in the very near field of the LDOS is observed. Finite differential time domain simulations of the different components of the electric field in the very near field of the structure confirm that the localization of the electric field around the holes is only due to the normal component as observed with the nanoprobe.

We first report the synthesis of supraparticles with a mean diameter of 130 nm consisting in a compact self-assembly of colloidal CdSe/CdS/ZnS nanocrystals encapsulated in a silica shell. This provides a system with robust optical properties such as a high quantum efficiency, a stable and Poissonian emission at room temperature. Additionally, enhancement of the photoluminescence decay rate through Förster resonance energy transfer is observed. [ABSTRACT FROM AUTHOR]

The excitation energy dependency of single colloidal CdSe-CdS core-shell nanocrystals is investigated at ambient conditions. It was demonstrated that the photoluminescence blinking effect is totally suppressed by optically exciting nanocrystals with a laser wavelength located at a very low absorption spectrum range. The mechanism of this effect is theoretically attributed to excitation of only the core instead of both the core and the shell. The signal to noise ratio and the photon count are also significantly improved and better purity in terms of single photon generation is achieved. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We demonstrate a spatially uniform enhancement of individual quantum dot (QD) fluorescence emission using plasmonic grating decouplers on thin gold or silver films. Individual QDs are deposited within the grating in a controlled way to investigate the position dependency on both the radiation pattern and emission enhancement. We also describe the optimization of the grating decoupler. We achieve a fluorescence enhancement ~3 times higher than using flat plasmon film, for any QD position in the grating. [ABSTRACT FROM AUTHOR]

Colloidal semiconductor quantum dots (QDs) are promising candidates for various applications in electronics and quantum optics. However, they are sensitive and vulnerable to the chemical environment due to their highly dynamic surface with a large portion of exposed atoms. Hence, oxidation and detrimental defects on the nanocrystal (NC) interface dramatically deteriorate their optical as well as electrical properties. In this study, a simple strategy is proposed not only to obtain good preservation of colloidal semiconductor QDs by using a protective polymer matrix but also to provide excellent accessibility to micro-fabrication by optical lithography. A high-quality QD-polymer nanocomposite with mono-dispersion of the NCs is synthesized by incorporating the colloidal CdSe/CdS NCs into an SU-8 photoresist. Our approach shows that the oxidation of the core/shell QDs embedded in the SU-8 resist is completely avoidable. The deterministic insertion of multiple QDs or a single QD into photonic structures is demonstrated. Single photon generation is obtained and well-preserved in the nanocomposite and the polymeric structures., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We demonstrate a spatially uniform enhancement of individual quantum dot (QD) fluorescence emission using plasmonic grating decouplers on thin gold or silver films. Individual QDs are deposited within the grating in a controlled way to investigate the position dependency on both the radiation pattern and emission enhancement. We also describe the optimization of the grating decoupler. We achieve a fluorescence enhancement ~3 times higher than using flat plasmon film, for any QD position in the grating.

A parallelized 3D FDTD (Finite-Difference Time-Domain) solver has been used to study the near-field electromagnetic intensity upon plasmonics nanostructures. The studied structures are obtained from AFM (Atomic Force Microscopy) topography measured on real disordered gold layers deposited by thermal evaporation under ultra-high vacuum. The simulation results obtained with these 3D metallic nanostructures are in good agreement with previous experimental results: the localization of the electromagnetic intensity in subwavelength areas ("hot spots") is demonstrated; the spectral and polarization dependences of the position of these "hot spots" are also satisfactory; the enhancement factors obtained are realistic compared to the experimental ones. These results could be useful to further our understanding of the electromagnetic behavior of random metal layers.