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Gold nanoclusters prepared with a controlled amount of Ag exhibit intense fluorescence with a quantum yield of ~16% and a "quasi-monoexponential" long lifetime of >200 ns. Characterization of the luminescent probes indicates high photostability and easy detection in cells. Additionally, fluorescence enhancement in the presence of proteins was found.

New types of fluorescent platinum nanoclusters (λ max. = 570 nm) have been synthesized using glutathione for ligand etching. These nanoclusters are mainly in the oxidation state Pt I (90%) exhibiting an intense fluorescence signal (QY∼17%) in the yellow region and lead to the formation of blue-emitting species for a long etching time process.

The asymmetric substituted BODIPY dye 4,4-difluoro-1,3-dimethyl-4-bora-3a,4a-diaza-s-indacene crystallizes in three different crystal habits, that is, as needles (I), leaves (II), or microcrystalline sublimed crystals (III). All crystals share the same crystal structure but exhibit varying solid-state fluorescence from yellow-orange to deep red. The crystal structure mainly consists of one-dimensional chains of J-aggregates which leads to excitonic luminescence at λ = 600 nm. The point-dipole approximation is used to calculate the excitonic splitting to a value of 3300 cm–1, which is in good agreement with the experimental observations. The influence of the macroscopic appearance on the luminescence properties is discussed in terms of reflectivity of the surface and reabsorption within the material. It turns out that the long-range order modulates the solid-state luminescence due to the small Stokes shift of the dye.

Fluorescence-detected circular dichroism (FDCD) spectroscopy is applied for the first time to supramolecular host-guest and host-protein systems and compared to the more known electronic circular dichroism (ECD). We find that...

The phenomenon of photoacidity, i.e., an increase in acidity by several orders of magnitude upon electronic excitation, is frequently encountered in aromatic alcohols capable of transferring a proton to a suitable acceptor. A promising new class of neutral super-photoacids based on pyranine derivatives has been shown to exhibit pronounced solvatochromic effects. To disclose the underlying mechanisms contributing to excited-state proton transfer (ESPT) and the temporal characteristics of solvation and ESPT, we scrutinize the associated ultrafast dynamics of the strongest photoacid of this class, namely tris(1,1,1,3,3,3-hexafluoropropan-2-yl)8-hydroxypyrene-1,3,6-trisulfonate, in acetoneous environment, thereby finding experimental evidence for ESPT even under these adverse conditions for proton transfer. Juxtaposing results from time-correlated single-photon counting and femtosecond transient absorption measurements combined with a complete decomposition of all signal components, i.e., absorption of ground and excited states as well as stimulated emission, we disclose dynamics of solvation, rotational diffusion, and radiative relaxation processes in acetone and identify the relevant steps of ESPT along with the associated time scales. Graphical abstract

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