Get turned on: Fluorescent photochromic organic nanoparticles (FPONs) of 1 (see picture) show a strongly enhanced fluorescence emission with increasing concentration and bistable photochromism. High‐contrast on/off fluorescence switching has been successfully implemented in size‐tuned FPONs of 1 and also in a photo‐rewritable polymer film highly loaded with 1.

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The fluorescence emission properties of 2-(2'-hydroxy-4'-R-phenyl)benzothiazole (HBT-R) nanoparticles with different substituents (R = -COOH, -H, -CH(3), -OH, and -OCH(3)) were investigated using spectroscopic and theoretical methods. HBT-Rs displayed dual enol and keto (excited-state intramolecular proton transfer (ESIPT)) emissions in nonpolar solvents. The spectral change of their ESIPT emissions was affected differently by the electron donating (or withdrawing) power of the substituents; a bathochromic shift for the electron donating group and a hypsochromic shift in electron withdrawing group. In addition, the changes in energy levels calculated by the ab initio method were consistent with the spectral shifts of HBT-R in solution. We prepared aggregated HBT-R nanoparticles using a simple reprecipitation process in tetrahydrofuran-water solvents. The ESIPT emission of aggregated HBT-R nanoparticles was strongly enhanced (over 45 times) compared to those of monomer HBT-Rs in toluene, as markedly shifted ESIPT emissions are observed at longer wavelength without any quenching by self-absorption. Aggregated HBT-R nanoparticles showed longer lifetimes than those of monomer molecules. The temperature effect on the aqueous dispersion of the aggregated HBT-R nanoparticles was also explored. It shows a fluorescent ratiometric change in a range of temperature from 7 to 65 degrees C. A mechanism of a temperature-dependent equilibrium between the nanoparticles and the solvated enols is proposed for the emission color change.

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Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

The complexation of pyrene into the cavity of -cyclodextrin ( -CD) has been studied in aqueous solutions of pure -CD and -CD substituted poly(allylamine) by using fluorescence spectroscopy. Two different approaches to obtain the association constant, both already described in the literature, are compared. It is shown that the evaluation of the fluorescence intensities of the first and third vibronic band of the pyrene fluorescence spectrum gives the correct result because the different quantum yields of free and complexed pyrene are considered correctly. The sole analysis of the Ham effect of pyrene leads to too high values of the association constant. A subsequent formation of 1:1 and 2:1 complexes between -CD and pyrene was confirmed. The synthesized -CD polymers exhibit a significant change in the complexation behavior depending on the degree of substitution (DS). At high DS (up to 23%) only 2:1 complex formation was observed, an evidence for intramolecular, chelate-like complexes due to the high local -CD concentration. At low DS (below 5%) 2:1 complexes are formed only intermolecularly. Compared with pure -CD, the overall complexation constant of the -CD polymers increases by more than 2 orders of magnitude with increasing DS and is independent of the polymer molecular weight. The supramolecular structure of the complex is not changed due to the linkage of the cyclic oligosaccharide to the polymer chain.

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Mehr hilft mehr: Fluoreszierende photochrome organische Nanopartikel (FPONs) aus 1 (siehe Bild) zeigen eine mit zunehmender Konzentration stark ansteigende Fluoreszenzemission sowie eine bistabile Photochromie. Ein kontrastreiches Ein/Aus‐Schalten der Fluoreszenz wurde in größenabgestimmten FPONs aus 1 und in einem wiederbeschreibbaren Polymerfilm mit hoher Beladung an 1 verwirklicht.