Post‐Deposition Activation of Latent Hydrogen‐Bonding: A New Paradigm for Enhancing the Performances of Bulk Heterojunction Solar Cells

Small conjugated molecules (SM) are gaining momentum as an alternative to semiconducting polymers for the production of solution‐processed bulk heterojunction (BHJ) solar cells. The major issue with SM‐BHJs is the low carrier mobility due to the scarce control on the phase‐segregation process and consequent lack of preferential percolative pathways for electrons and holes to the extraction electrodes. Here, a new paradigm for fine tuning the phase‐segregation in SM‐BHJs, based on the post‐deposition exploitation of latent hydrogen bonding in binary mixtures of PCBM with suitably functionalized electron donor molecules, is demonstrated. The strategy consist in the chemical protection of the H‐bond forming sites of the donor species with a thermo‐labile functionality whose controlled thermal cleavage leads to the formation of stable, crystalline, phase‐separated molecular aggregates. This approach allows the fine tuning of the nanoscale film connectivity and thereby to simultaneously optimize the generation of geminate carriers at the donor–acceptor interfaces and the extraction of free charges via ordered phase‐separated domains. As a result, the PV efficiency undergoes an over twenty‐fold increase with respect to control devices. This strategy, demonstrated here with mixtures of diketopyrrolopyrrole derivatives with PCBM can be extended to other molecular systems for achieving highly efficient SM‐BHJ solar cells.     

Esterolytic and lipolytic activities of lactic acid bacteria isolated from ewe's milk and cheese

In the present work, we report on the esterase and lipase activities of lactic acid bacteria representing the genera Lactococcus, Leuconostoc, Lactobacillus, and Enterococcus isolated from ewe's milk and cheeses. Esterase activity was studied using alpha- and beta-naphthyl derivatives of 2 to 12 carbon atoms and postelectrophoretic detection. The lactic acid bacteria evaluated had intracellular esterase activities, which preferentially degraded the alpha- and beta-naphthyl derivatives of 2 to 6 carbon atoms. By studying postelectrophoretic patterns, it was found that some strains presented more than one esterase. Lactobacillus plantarum O236 showed four enzymes that hydrolyze carboxyl ester linkages with different specificity. Lipase activity was studied in intracellular and extracellular fractions using tributyrin, tricaprylin, triolein, and milk fat as substrates. The intracellular and extracellular fractions of Leuconostoc mesenteroides O257, Lactobacillus plantarum O236, and Lactobacillus acidophilus O177 were able to hydrolyze tributyrin. L. plantarum O186, L. acidophilus O252, Enterococcus faecium O174 and O426, and Enterococcus faecalis Ov409 showed lipase activity associated with the intracellular fraction on tributyrin. Lactococcus lactis O233, L. plantarum O155, and Lactobacillus casei O190 did not hydrolyze triglycerides. Not all strains that showed esterase activity exhibited high activity on triglycerides. Esterase and lipase activities were species- and strain-specific. Wide variations in activity between strains highlight the need for selecting appropriate starters to produce enzyme-modified cheese as well as accelerated ripened cheese.     

Arsenic (V) removal with nanoparticulate zerovalent iron: Effect of UV light and humic acids

Results on As(V) removal in the presence of oxygen using the zerovalent iron technology with commercial iron nanoparticles (NanoFe^®) are presented, showing the effect of (NanoFe^®) mass, UV light and addition of humic acids. The nanosized iron particles (NZVI) were characterized in their particle size, surface area and constituent phases. As(V) removal was rapid and increased with NZVI mass (0.005–0.1 g L⁻¹) attaining more than 90% after 150 min of time contact with the optimal NanoFe^® concentration. The removal followed a biexponential kinetic decay, with rate constants increasing with NZVI mass. (NanoFe^®) presented an outstanding ability to remove As due to not only a high surface area and low particle size but also to a high intrinsic activity. Humic acids (HA) decreased around 50% the removal efficiency in the dark, indicating competition with As(V) for active surface sites. In contrast, UV light doubled removal rates, the process being even more enhanced in the presence of HA, with an almost total arsenic removal within 4 h. In all cases, adsorption on iron corrosion phases was found the main mechanism of As(V) removal, promoted by formation of Reactive Oxygen Species and enhanced under UV irradiation by the formation of multiple active species. Preliminary results with As-polluted groundwater of the Chacopampean Plain of Argentina (Tucumán Province) are also reported. Addition of NanoFe^® under UV irradiation for 3 h resulted in As contents well in agreement with the regulations (<10 μg L⁻¹).     

Buckwheat honeys: Screening of composition and properties

The quality of 10 buckwheat honeys, collected from Italian and est European beekeepers declaring to produce monofloral honey, were evaluated by means of their pollen, physicochemical, phenolic and volatile composition data. The results of the traditional analyses and in particular electrical conductivity, optical rotation, pH and sugar composition revealed some poorly pure samples that could not fit in the buckwheat tipology. Honey volatiles, analysed by solid phase microextraction (SPME) and gas chromatography–mass-spectrometry (GC/MS), showed more than 100 volatile compounds, most of them present in all honey samples but with quantitative variation. Besides many furfural derivates, 3-methylbutanoic acid was the main volatile compound found in most of honeys. Also the presence of 2- and 3-methylbutanal and pheynalcetaldehyde confirmed the typical buckwheat aroma of some studied samples, corroborating physicochemical data. The HPLC phenolic profile was similar across the samples and p-hydroxybenzoic and p-coumaric acids proved to be the main components.     

Maximization of Fructooligosaccharides and β-Fructofuranosidase Production by Aspergillus japonicus under Solid-State Fermentation Conditions

The conditions of temperature, moisture content, and inoculum rate able to maximize the production of fructooligosaccharides (FOS) and β-fructofuranosidase (FFase) enzyme by solid-state fermentation were established. Fermentation assays were performed using the support material (coffee silverskin) moistened to 60, 70, or 80 % with a 240-g/l sucrose solution and inoculated with a spore suspension of Aspergillus japonicus to obtain 2?×?10⁵, 2?×?10⁶, or 2?×?10⁷ spores/gram dry material. The fermentation runs were maintained under static conditions at 26, 30, or 34 °C during 20 h. The moisture content did not influence the FOS and FFase production; however, temperature between 26 and 30 °C and inoculum rate of approximately 2?×?10⁷ spores/gram dry material maximized the results (FOS?=?208.8 g/l with productivity of 10.44 g/l h; FFase?=?64.12 units U/ml with productivity of 4.0 U/ml h). These results are considerably higher than those obtained under no optimized fermentation conditions and represent an important contribution for the establishment of a new industrial process for FOS and FFase production.     

Hybrid Self-Assembling Nanoparticles Encapsulating Zoledronic Acid: A Strategy for Fostering Their Clinical Use

Self-assembling nanoparticles (SANPs) promise an effective delivery of bisphosphonates or microRNAs in the treatment of glioblastoma (GBM) and are obtained through the sequential mixing of four components immediately before use. The self-assembling approach facilitates technology transfer, but the complexity of the SANP preparation protocol raises significant concerns in the clinical setting due to the high risk of human errors during the procedure. In this work, it was hypothesized that the SANP preparation protocol could be simplified by using freeze-dried formulations. An in-depth thermodynamic study was conducted on solutions of different cryoprotectants, namely sucrose, mannitol and trehalose, to test their ability to stabilize the produced SANPs. In addition, the ability of SANPs to deliver drugs after lyophilization was assessed on selected formulations encapsulating zoledronic acid in vitro in the T98G GBM cell line and in vivo in an orthotopic mouse model. Results showed that, after lyophilization optimization, freeze-dried SANPs encapsulating zoledronic acid could retain their delivery ability, showing a significant inhibition of T98G cell growth both in vitro and in vivo. Overall, these results suggest that freeze-drying may help boost the industrial development of SANPs for the delivery of drugs to the brain.     

Use of weak cation exchange resin Lewatit S 8528 as alternative to strong ion exchange resins for calcium salt removal

Softening of beet sugar juices using the weak cation exchange resin Lewatit® S 8528, both in hydrogen and sodium form has been studied. After analyzing the influence of the main operating parameters on decalcification efficiencies through a Taguchi approach, experimental runs were carried out at 40 BV/h and 80 °C to determine operation time, breakthrough point and resin capacity. The performance of the Lewatit S 8528 resin was compared with that of the industrially used Amberlite SR1L Na, a strong cation exchange resin. The experimental results showed that the use of Lewatit S 8528 in the acidic form is a feasible alternative to the classical strong cation exchange resins, providing calcium removal efficiencies higher than 80%. The mean calcium concentration in the softened thin juice was lower than 18 mg CaO/L. The breakthrough point corresponding to weak resin Lewatit S 8528 in H⁺ form, 700 bed volume, was considerable higher than that obtained for the strong resin Amberlite (300 BV). No considerably increase in the concentration of reducing sugars in the softened juice was observed. The consumption of chemical reagents in the regeneration stage was 3.2 ± 0.5 kg H₂SO₄/m³, considerably lower than the consumption of sodium chloride, 44 ± 1 kg NaCl/m³ when the strong Amberlite resin was used.     

Alternaria toxins in Argentinean wheat,bran, and flour

Alternaria species have been reported to infect a wide variety of vegetables, fruits, and cereal crops. Wheat is one of the most consumed cereal worldwide. A sensitive HPLC-DAD methodology was applied to quantify alternariol (AOH), alternariol methyl ether (AME) and tenuazonic acid (TeA) in 65 samples of whole wheat, bran, and flour. The extraction methodology allowed extracting the three toxins simultaneously. Limits of detection in wheat were 3.4, 4.5, and 0.5 µg kg^?1 for AOH, AME and TeA, respectively. For bran, these data were 3.1, 4.5, and 12 µg kg^?1 and for flour 50, 70, and 14 µg kg^?1, respectively. The studied recoveries were higher than 70% and RSD was below 10%. Wheat and bran samples showed low AOH and AME contamination compared to TeA. The averages levels found for TeA in wheat, bran and flour were 19,190, 16,760, and 7360 µg kg^?1, respectively.     

Coarse-grained kinetic modelling of bilayer heterojunction organic solar cells

The on-lattice kinetic Monte Carlo (KMC) method provides a powerful tool to simulate the J–V properties of organic solar cells. However, the computational cost associated with charge injection may limits its applicability. In the attempt to overcome this limitation, we describe in this paper a coarse-grained numerical approach to photocurrent generation in bilayer heterojunction solar cells. Starting from the KMC algorithm, a self-consistent numerical procedure is proposed to find the steady-state solutions of the kinetic equations describing particle dynamics in one dimension across the layer thickness. Our model incorporates the generation, transport and recombinations of charge carriers, excitons, and electron/hole pairs, whose introduction is required to correctly describe interfacial phenomena at the coarse-grained level. A continuum model of the electrostatic interactions among charge carriers is proposed and used to compute their hopping rates during the simulation. The model is used to investigate the J–V properties of Cathode/PCBM/P3HT/PEDOT:PSS/ITO bilayer devices, showing that Fermi level pinning at the Cathode/PCBM interface must be invoked to accurately model the experimental behavior. From the fitting to the experimental J–V data, we conclude the short-circuit current density to be mainly associated with a high exciton diffusion length. The analogies and differences between our model and existing KMC and drift–diffusion approaches are also discussed.