Fullerene flakes : A diacetylene‐functionalized fullerene derivative self‐organizes into flakelike microparticles (see picture). Both the diacetylene and C60 moieties can be effectively cross‐linked, which leads to supramolecular materials with remarkable resistivity to solvent, heat, and mechanical stress. Moreover, the surface of the cross‐linked flakelike objects is highly durable and water‐repellent.
There is a persistent need for small‐molecule fluorescent labels optimized for single‐molecule imaging in the cellular environment. Application of these labels comes with a set of strict requirements: strong absorption, efficient and stable emission, water solubility and membrane permeability, low background emission, and red‐shifted absorption to avoid cell autofluorescence. We have designed and characterized several fluorophores, termed “DCDHF” fluorophores, for use in live‐cell imaging based on the push–pull design: an amine donor group and a 2‐dicyanomethylene‐3‐cyano‐2,5‐dihydrofuran (DCDHF) acceptor group, separated by a π‐rich conjugated network. In general, the DCDHF fluorophores are comparatively photostable, sensitive to local environment, and their chemistries and photophysics are tunable to optimize absorption wavelength, membrane affinity, and solubility. Especially valuable are fluorophores with sophisticated photophysics for applications requiring additional facets of control, such as photoactivation. For example, we have reengineered a red‐emitting DCDHF fluorophore so that it is dark until photoactivated with a short burst of low‐intensity violet light. This molecule and its relatives provide a new class of bright photoactivatable small‐molecule fluorophores, which are needed for super‐resolution imaging schemes that require active control (here turning‐on) of single‐molecule emission. 相似文献
Thermodynamic and transport properties of the La-diluted Kondo lattice CeNi(2)Ge(2) were studied in a wide temperature range. The Ce-rich alloys Ce(1-x)La(x)Ni(2)Ge(2) were found to exhibit distinct features of the coherent heavy Fermi liquid. At intermediate compositions (0.7≤x≤0.9), non-Fermi liquid properties have been observed, followed by the local Fermi liquid behavior in the dilute limit. The 4f-electron contribution to the specific heat was found to follow the predictions of the Kondo-impurity model in both the local as well as the coherent regimes, with the characteristic Kondo temperature decreasing rapidly from about 30 K for the parent compound CeNi(2)Ge(2) to about 1 K in the most dilute samples. The specific heat does not show any evidence for the emergence of a new characteristic energy scale related to the formation of the coherent Kondo lattice. 相似文献
Honey is a natural product and can be described by its botanical origin, determined by the plants from which the bees collect nectar. It significantly influences the taste of honey and is often used as a quality criterion. Unfortunately, this opens up the possibility of food fraud. Currently, various methods are used to check the authenticity of monofloral honey. The laborious, manual melissopalynology is considered an essential tool in the verification process. In this work, the volatile organic compounds obtained from the headspace of honey are used to prove their authenticity. The headspace of 58 honey samples was analyzed using a commercial easy-to-use gas chromatography-coupled ion mobility spectrometer with a headspace sampler (HS-GCxIMS). The honey samples were successfully differentiated by their six different botanical origins using specific markers with principal component analysis in combination with linear discriminant analysis. In addition, 15 honey-typical compounds were identified using measurements of reference compounds. Taking a previously published strategy, retention times of marker compounds were correlated with GC-coupled mass spectrometry (GC-MS) measurements to assist in the identification process. 相似文献
The dynamic equilibria of organomagnesium reagents are known to be very complex, and the relative reactivity of their components is poorly understood. Herein, a combination of DFT calculations and kinetic experiments is employed to investigate the detailed reaction mechanism of the Pummerer coupling between sulfoxides and turbo-organomagnesium amides. Among the various aggregates studied, unprecedented heterometallic open cubane structures are demonstrated to yield favorable barriers through a concerted anion-anion coupling/ S−O cleavage step. Beyond a structural curiosity, these results introduce open cubane organometallics as key reactive intermediates in turbo-organomagnesium amide mixtures. 相似文献
Understanding the factors that determine the luminescence lifetime of transition metal compounds is key for applications in photocatalysis and photodynamic therapy. Here we show that for (bpy = 2,2’-bipyridine), the generally accepted idea that emission lifetimes can be controlled optimizing the energy barrier from the emissive triplet metal-to-ligand charge-transfer (3MLCT) state to the thermally-activated triplet metal-centered (3MC) state or the energy gap between both states is a misconception. Further, we demonstrate that considering a single relaxation pathway determined from the minimum that is lowest in energy leads to wrong temperature-dependent emission lifetimes predictions. Instead, we obtain excellent agreement with experimental temperature-dependent lifetimes when an extended kinetic model that includes all the pathways related to multiple Jahn–Teller isomers and their effective reaction barriers is employed. These concepts are essential to correctly design other luminescent transition metal complexes with tailored emission lifetimes based on theoretical predictions. 相似文献