Improved Spectral Coverage and Fluorescence Quenching in Donor–acceptor Systems Involving Indolo[3‐2‐b]carbazole and Boron‐dipyrromethene or Diketopyrrolopyrrole

A novel π‐conjugated triad and a polymer incorporating indolo[3,2‐b]‐carbazole (ICZ) and 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) were synthesized via a Sonogashira coupling. Compared to the parent BODIPY the absorption and fluorescence spectrum were for both compounds broader and redshifted. The redshift of the fluorescence and the decrease of the fluorescence quantum yield and decay time upon increasing solvent polarity were attributed to the formation of a partial charge‐transfer state. Upon excitation in the ICZ absorption band the ICZ fluorescence was quenched in both compounds mainly due to energy transfer to the BODIPY moiety. In a similar ICZ–π–DPP polymer (where DPP is diketopyrrolopyrrole), a smaller redshift of the absorption and fluorescence spectra compared to the parent DPP was observed. A less efficient quenching of the ICZ fluorescence in the ICZ–π–DPP polymer could be related to the unfavorable orientation of the transition dipoles of ICZ and DPP. The rate constant for energy transfer was for all compounds an order of magnitude smaller than predicted by Förster theory. While in a solid film of the triad a further redshift of the absorption maximum of nearly 100 nm was observed, no such shift was observed for the ICZ–π–BODIPY polymer.     

C3 or C4 macrophytes: a specific carbon source for the development of semi-aquatic and terrestrial arthropods in central Amazonian river-floodplains according to delta13C values

C4 plant species were proposed to generally represent inferior food sources compared to C3 plants thus are avoided by herbivores, particularly insects. This was tested in semi-aquatic and terrestrial arthropods from Amazonian river-floodplains by carbon isotope discrimination (delta13C). Two semi-aquatic grasshopper species (Stenacris f. fissicauda, Tucavaca gracilis-Acrididae) obtain their carbon during development from specific C4 macrophytes and two semi-aquatic species (Cornops aquaticum-Acrididae, Paulinia acuminata-Pauliniidae) from specific C3 macrophytes. The terrestrial millipede Mestosoma hylaeicum (Paradoxosomatidae) obtains about 45% of its carbon from roots of one C4 macrophyte during the development of immatures whereas adults use other food sources, including C3 trees. Results suggest, that (1) both C4 and C3 plants represent distinct hosts for terrestrial arthropods in Amazonia; (2) immatures may use plant species with a different photosynthetic pathway than adults.     

C3 or C4 Macrophytes: A Specific Carbon Source for the Development of Semi-Aquatic and Terrestrial Arthropods in Central Amazonian River-Floodplains According to δ13C Values

Abstract

C₄ plant species were proposed to generally represent inferior food sources compared to C₃ plants thus are avoided by herbivores, particularly insects. This was tested in semi-aquatic and terrestrial arthropods from Amazonian river-floodplains by carbon isotope discrimination (δ¹³C). Two semi-aquatic grasshopper species (Stenacris f. fissicauda, Tucayaca gracilis—Acrididae) obtain their carbon during development from specific C₄ macrophytes and two semi-aquatic species (Cornops aquaticum—Acrididae, Paulinia acuminata—Pauliniidae) from specific C₃ macrophytes. The terrestrial millipede Mestosoma hylaeicum (Paradoxosomatidae) obtains about 45% of its carbon from roots of one C₄ macrophyte during the development of immatures whereas adults use other food sources, including C₃ trees. Results suggest, that (1) both C₄ and C₃ plants represent distinct hosts for terrestrial arthropods in Amazonia; (2) immatures may use plant species with a different photosynthetic pathway than adults.     

Triplet harvesting in poly(9‐vinylcarbazole) and poly(9‐(2,3‐epoxypropyl)carbazole) doped with CdSe/ZnS quantum dots encapsulated with 16‐(N‐carbazolyl) hexadecanoic acid ligands

Semiconductor quantum dots (QDs) can be used as alternative for transition metal complexes to harvest the nonemissive triplet excitons in organic light‐emitting diodes (OLEDs). In search for a QD‐based OLED material generating blue emission, poly(9‐vinylcarbazole) (PVK) and poly(9‐(2,3‐epoxypropyl) carbazole) (PEPK) are chosen as host for blue‐emitting CdSe/ZnS core/shell QDs. The QDs are encapsulated with 16‐(N‐carbazolyl) hexadecanoic acid (C16), a ligand terminated by a carbazole moiety. As alternative for PVK, PEPK, where the lower molecular weight and less extensive excimer formation could promise a better film formation and more extensive exciton hopping, is explored. The efficiencies of singlet ( ) and triplet ( ) energy transfer to the C16 capped QDs are estimated by combining stationary photoluminescence spectra and fluorescence decays of pristine polymer films with those of polymer films doped with the QDs. At a loading of 30 wt % of the QDs, increases from 12 ± 1% in PVK to 41 ± 2% in PEPK while increases from 37 ± 22% in PVK to 72 ± 48% in PEPK. The investigation of the film morphology by atomic force microscopy confirms that the main factor limiting the triplet transfer efficiency in the PVK matrix is the clustering of the C16 capped QDs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 539–551