The dephasing of particle plasmons is investigated using light-scattering spectroscopy on individual gold nanoparticles. We find a drastic reduction of the plasmon dephasing rate in nanorods as compared to small nanospheres due to a suppression of interband damping. The rods studied here also show very little radiation damping, due to their small volumes. These findings imply large local-field enhancement factors and relatively high light-scattering efficiencies, making metal nanorods extremely interesting for optical applications. Comparison with theory shows that pure dephasing and interface damping give negligible contributions to the total plasmon dephasing rate.

We report on the state-of-the art synthesis and improved luminescence properties of thiol-capped CdTe nanocrystals (NCs) synthesized in water. The optimized pH (12) and molar ratio of thiol to Cd ions (1.3:1) increases the room-temperature photoluminescence quantum efficiency of as-synthesized CdTe NCs capped by thioglycolic acid (TGA) to values of 40−60%. By employing mercaptopropionic acid (MPA) as a stabilizer, we have synthesized large (up to 6.0 nm in diameter) NCs so that the spectral range of the NCs' emission currently available within this synthetic route extends from 500 to 800 nm. Sizing curve for thiol-capped CdTe NCs is provided. In contrast to CdTe NCs capped by TGA, MPA-capped CdTe NCs show up to 1 order of magnitude longer (up to 145 ns) emission decay times, which become monoexponential for larger particles. This phenomenon is explained by considering the energetics of the Te-related traps in respect to the valence-band position of CdTe NCs. The correlation between luminescence quantum efficiencies, luminescence lifetimes, and Stokes shifts of CdTe NC fractions is demonstrated, being in agreement with a model proposed previously that connects the emission properties of NCs with their surface quality determined by the Oswald ripening conditions during growth. imaging, and plasmonics.

A method for biomolecular recognition is reported using light scattering of a single gold nanoparticle functionalized with biotin. Addition of streptavidin and subsequent specific binding events alter the dielectric environment of the nanoparticle, resulting in a spectral shift of the particle plasmon resonance. As we use single nanoparticles showing a homogeneous scattering spectrum, spectral shifts as small as 2 meV can be detected.

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We propose a cascaded energy transfer structure made of semiconductor nanocrystals. Funnel-like band gap profiles are realized applying layer-by-layer assembly to CdTe nanocrystals of distinct sizes. Optical excitations efficiently transfer along the band gap gradient and are finally captured by the largest nanocrystals. The photoluminescence yield from the center layer is surprisingly high. The stepwise passing on of excitation energy avoids hot carriers, and the funnel structure recycles otherwise trapped and lost electron−hole pairs.

We report on efficient resonant energy transfer in bilayers of water-soluble CdTe quantum dots. The bilayers of CdTe nanocrystals of two different sizes capped by short-chain thiols were formed by layer-by-layer assembly. Temporally and spectrally resolved fluorescence spectroscopy reveals spectral diffusion of the fluorescence signal for quantum dots within one layer as well as rapid (254 ps) energy transfer from layers of small dots to layers of larger dots, which is fast for nanocrystal pairs. Subspecies within the inhomogeneous distribution of donor nanocrystals even show energy transfer rates of (134 ps)−1 due to a large spectral overlap with acceptor nanocrystals.

The commercial availability of stand-alone setups for the determination of absolute photoluminescence quantum yields (Phi(f)) in conjunction with the increasing use of integrating sphere accessories for spectrofluorometers is expected to have a considerable influence not only on the characterization of chromophore systems for use in optical and opto-electronic devices, but also on the determination of this key parameter for (bio)analytically relevant dyes and functional luminophores. Despite the huge potential of systems measuring absolute Phi(f) values and the renewed interest in dependable data, evaluated protocols for even the most elementary case, the determination of the fluorescence quantum yield of transparent dilute solutions of small organic dyes with integrating sphere methods, are still missing. This encouraged us to evaluate the performance and sources of uncertainty of a simple commercial integrating sphere setup with dilute solutions of two of the best characterized fluorescence quantum yield standards, quinine sulfate dihydrate and rhodamine 101, strongly differing in spectral overlap between absorption and emission. Special attention is dedicated to illustrate common pitfalls of this approach, thereby deriving simple procedures to minimize measurement uncertainties and improve the comparability of data for the broad community of users of fluorescence techniques.

In semiconductor nanocrystals the electronic energy gap is determined not only by the material but also by the size of the nanocrystals. This allows the construction of an energy‐gap gradient normal to multiple layers of nanocrystals where the diameters of the nanocrystals are monotonically increasing or decreasing in subsequent layers. In such devices we observe a highly efficient funneling of excitation energy from layers comprising smaller nanocrystals towards the layer with the largest nanocrystals in the center of the funnel. Most importantly, not only are excitons in radiative states transferred, but also excitons from trapped states, usually lost for luminescence, can be effectively recycled, hence increasing the overall luminescence yield.