Study of spatial inhomogeneity in inverted all‐polymer solar cells: Effect of solvent and annealing

The efficiency optimization of bulk heterojunction solar cells requires the control of the local active materials arrangement in order to obtain the best compromise between efficient charge generation and charge collection. Here, we investigate the large scale (10–100 μm) inhomogeneity of the photoluminescence (PL) and the external quantum efficiency (EQE) in inverted all‐polymer solar cells (APSC) with regioregular poly(3‐hexylthiophene) (P3HT):poly(9,9‐dioctylfluorene‐co‐benzothiadiazole) (F8BT) active blends. The morphology and the local active polymer mixing are changed by depositing the active layer from four different solvents and by thermal annealing. The simultaneous PL and EQE mapping allowed us to inspect the effects of local irregularities of active layer thickness, polymer mixing, polymer aggregation on the charge generation and collection efficiencies. In particular, we show that the increase of the solvent boiling point affects the EQE non‐uniformity due to thickness fluctuations, the density non‐uniformity of rrP3HT aggregate phase, and the blend components clustering. The thermal annealing leads to a general improvement of EQE and to an F8BT clustering in all the samples with locally decrease of the EQE. We estimate that the film uniformity optimization can lead to a total EQE improvement between 2.7 and 6.3 times. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 804–813     

Development of a Neutral Diketopyrrolopyrrole Phosphine Oxide for the Selective Bioimaging of Mitochondria at the Nanomolar Level

Development of novel bioimaging materials that exhibit organelle specific accumulation continues to be at the forefront of research interests and efforts. Among the various subcellular organelles, mitochondria, which are found in the cytoplasm of eukaryotic cells, are of particular interest in relation to their vital function. To date, most molecular probes that target mitochondria utilise delocalised lipophilic cations such as triphenylphosphonium and pyridinium. However, the use of such charged motifs is known to be detrimental to the working function of the mitochondrial transmembrane potential and there remains a strong case for development of neutral mitochondrial fluorescent probes. Herein, we demonstrate for the first time the exploitation of diketopyrrolopyrrole-based chemistries for the realisation of a neutral fluorescent probe that exhibits organelle specific accumulation within the mitochondria at the nanomolar level. The synthesised probe, which bears a neutral triphenylphosphine oxide moiety, exhibits a large Stokes shift and high fluorescence quantum yield in water, both highly sought-after properties in the development of bioimaging agents. In vitro studies reveal no interference with cell metabolism when tested for the human MCF7 breast cancer cell and nanomolar subcellular organelle colocalisation with commercially available mitochondrial staining agent Mitotracker Red. In light of its novelty, neutral structure and the preferential accumulation at nanomolar concentrations we anticipate this work to be of significant interest for the increasingly larger community devoted to the realisation of neutral mitochondrial selective systems and more widely to those engaged in the rational development of superior organic architectures in the biological field.     

A Multifunctional Subphthalocyanine Nanosphere for Targeting,Labeling, and Killing of Antibiotic‐Resistant Bacteria

Developing a material that can combat antibiotic‐resistant bacteria, a major global health threat, is an urgent requirement. To tackle this challenge, we synthesized a multifunctional subphthalocyanine (SubPc) polymer nanosphere that has the ability to target, label, and photoinactivate antibiotic‐resistant bacteria in a single treatment with more than 99 % efficiency, even with a dose as low as 4.2 J cm⁻² and a loading concentration of 10 nM . The positively charged nanosphere shell composed of covalently linked SubPc units can increase the local concentration of photosensitizers at therapeutic sites. The nanosphere shows superior performance compared to corresponding monomers presumably because of their enhanced water dispersibility, higher efficiency of singlet‐oxygen generation, and phototoxicity. In addition, this material is useful in fluorescence labeling of living cells and shows promise in photoacoustic imaging of bacteria in vivo.     

Immobilization and Stabilization of Beta-Xylosidases from Penicillium janczewskii

β-Xylosidases are critical for complete degradation of xylan, the second main constituent of plant cell walls. A minor β-xylosidase (BXYL II) from Penicillium janczewskii was purified by ammonium sulfate precipitation (30% saturation) followed by DEAE-Sephadex chromatography in pH 6.5 and elution with KCl. The enzyme presented molecular weight (MW) of 301 kDa estimated by size exclusion chromatography. Optimal activity was observed in pH 3.0 and 70–75 °C, with higher stability in pH 3.0–4.5 and half-lives of 11, 5, and 2 min at 65, 70, and 75 °C, respectively. Inhibition was moderate with Pb⁺² and citrate and total with Cu⁺², Hg⁺², and Co⁺². Partially purified BXYL II and BXYL I (the main β-xylosidase from this fungus) were individually immobilized and stabilized in glyoxyl agarose gels. At 65 °C, immobilized BXYL I and BXYL II presented half-lives of 4.9 and 23.1 h, respectively, therefore being 12.3-fold and 33-fold more stable than their unipuntual CNBr derivatives (reference mimicking soluble enzyme behaviors). During long-term incubation in pH 5.0 at 50 °C, BXYL I and BXYL II glyoxyl derivatives preserved 85 and 35% activity after 25 and 7 days, respectively. Immobilized BXYL I retained 70% activity after 10 reuse cycles of p-nitrophenyl-β-D-xylopyranoside hydrolysis.

     

Effect of grinding method on the analysis of essential oil from <Emphasis Type="Italic">Baccharis articulata</Emphasis> (Lam.) Pers.

Grinding methods were evaluated aiming to determine yield and composition of essential oils (EOs) from Baccharis articulata (Lam) Pers., called as carqueja, a native plant from South Brazil. Cryogenic, knife (with and without cooling) and ball mills were used. The major constituents found in EOs were β-pinene, caryophyllene, spathulenol and caryophyllene oxide, but differences in 21 compounds were observed. All grinding processes reduced monoterpenes and oxygenated sesquiterpenes with concentration of hydrocarbon sesquiterpenes. The sesquiterpenes (hydrocarbons and oxygenated) were found from 63.55 to 86.02% while the monoterpene hydrocarbons’ concentration ranged from 13.98 to 36.45%. Plants milled with knife mill provided EOs with profile similar to those not grinded. Despite the lower working temperature, cryogenic milling resulted in smaller EO yield (0.40 ± 0.03%) in comparison to other grinding methods (yields from 0.50 ± 0.02 to 0.56 ± 0.03%) and different chromatographic profile. Microscopic analysis showed the smaller particle size provided by cryogenic grinding, which leads to glandular trichome rupture and consequently to loss of EOs. This study showed that grinding should be carefully evaluated to provide reproducible results in essential oil analysis.     

Chemical Composition and Antioxidant Activity of Essential Oils from Eugenia patrisii Vahl,E. punicifolia (Kunth) DC., and Myrcia tomentosa (Aubl.) DC., Leaf of Family Myrtaceae

Essential oils (EOs) were extracted from Eugenia patrisii, E. punicifolia, and Myrcia tomentosa, specimens A and B, using hydrodistillation. Gas chromatography coupled with mass spectrometry (GC/MS) was used to identify the volatile constituents present, and the antioxidant capacity of EOs was determined using diphenylpicryl-hydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays. For E. patrisii, germacrene D (20.03%), bicyclogermacrene (11.82%), and (E)-caryophyllene (11.04%) were identified as the major constituents of the EOs extracted from specimen A, whereas specimen B primarily comprised γ-elemene (25.89%), germacrene B (8.11%), and (E)-caryophyllene (10.76%). The EOs of E. punicifolia specimen A contained β-Elemene (25.12%), (E)-caryophyllene (13.11%), and bicyclogermacrene (9.88%), while specimen B was composed of (E)-caryophyllene (11.47%), bicyclogermacrene (5.86%), β-pinene (5.86%), and γ-muurolene (5.55%). The specimen A of M. tomentosa was characterized by γ-elemene (12.52%), germacrene D (11.45%), and (E)-caryophyllene (10.22%), while specimen B contained spathulenol (40.70%), α-zingiberene (9.58%), and γ-elemene (6.89%). Additionally, the chemical composition of the EOs was qualitatively and quantitatively affected by the collection period. Furthermore, the EOs of the studied specimens, especially specimen A of E. punicifolia, showed a greater antioxidant activity in DPPH rather than TEAC, as represented by a significantly high inhibition percentage (408.0%).