In this work we report on the eco-friendly processing of PBDTTPD:PC71BM organic solar cells using water-based nanoparticle (NP) dispersions. The polymer:fullerene NPs are prepared using the miniemulsion-solvent evaporation method, despite employing high-boiling solvents. Polymer solar cells are fabricated from these blend NPs and the device characteristics are studied in function of annealing time and temperature. The photoactive layer formation is carefully analyzed using atomic force microscopy (AFM). Annealing for longer times significantly increases the power conversion efficiency (PCE), up to 3.8%, the highest value reported for surfactant based NP solar cells. Our work shows that the low bandgap polymer PBDTTPD has the ability to afford reasonable efficiencies in NP solar cells in combination with PC71BM and paves the way to a truly eco-friendly processing of organic photovoltaics (OPVs). (C) 2016 Elsevier B.V. All rights reserved. ; The authors acknowledge financial support by Hasselt University (BOF), the Research Foundation Flanders (FWO) (project G.0415.14N), and IAP 7/05 project FS2 (Functional Supramolecular systems), granted by the Science Policy Office of the Belgian Federal Government (BELSPO).
Lead (Pb) and cadmium (Cd) are major environmental pollutants, and the accumulation of these elements in soils and plants is of great concern in agricultural production due to their toxic effects on crop growth. Also, these elements can enter into the food chain and severely affect human and animal health. Bioaugmentation with plant growth-promoting bacteria (PGPB) can contribute to an environmentally friendly and effective remediation approach by improving plant survival and promoting element phytostabilization or extraction under such harsh conditions. We isolated and characterised Pb and Cd-tolerant root-associated bacteria from Helianthus petiolaris growing on a Pb/Cd polluted soil in order to compose inoculants that can promote plant growth and also ameliorate the phytostabilization or phytoextraction efficiency. One hundred and five trace element-tolerant rhizospheric and endophytic bacterial strains belonging to eight different genera were isolated from the aromatic plant species Helianthus petiolaris. Most of the strains showed multiple PGP-capabilities, ability to immobilise trace elements on their cell wall, and promotion of seed germination. Bacillus paramycoides ST9, Bacillus wiedmannii ST29, Bacillus proteolyticus ST89, Brevibacterium frigoritolerans ST30, Cellulosimicrobium cellulans ST54 and Methylobacterium sp. ST85 were selected to perform bioaugmentation assays in greenhouse microcosms. After 2 months, seedlings of sunflower (H. annuus) grown on polluted soil and inoculated with B. proteolyticus ST89 produced 40% more biomass compared to the non-inoculated control plants and accumulated 20 % less Pb and 40% less Cd in the aboveground plant parts. In contrast, B. paramycoides ST9 increased the bioaccumulation factor (BAF) of Pb three times and of Cd six times without inhibiting plant growth. Our results indicate that, depending on the strain, bioaugmentation with specific beneficial bacteria can improve plant growth and either reduce trace element mobility or enhance plant trace element uptake. ; This research was funded by the UHasselt-Methusalem project 08M03VGRJ, as got an UHasselt BOF-BILA grant in the frame of collaboration between Hasselt University, Belgium and the University of Buenos Aires, and Ibero-American Development Bank under FONTAGRO project ATN/RF-16110-RG. ; Thijs, S (reprint author), Hasselt Univ, Ctr Environm Sci, Environm Biol, Agoralaan Bldg D, B-3590 Diepenbeek, Belgium. saran.anabel@inta.gob.ar; valeria.imperato@uhasselt.be; fernandez.lucia@inta.gob.ar; panos.gkorezis@uhasselt.be; jan.d'haen@uhasselt.be; merini.luciano@inta.gob.ar; jaco.vangronsveld@uhasselt.be; sofie.thijs@uhasselt.be
Hybrid materials are being developed to add organic functionalities to inorganic materials. Here, titanium dioxide is modified with organophosphonic acids (PAs). In several applications, the surface properties of the material play a key role in their performance (e.g. separation, sorption, catalysis). Hence, the surface properties of these materials need to be specifically adjusted to meet the requirements of each application (e.g. in membrane separation or chromatography). As the synthesis conditions have an important influence on the obtained surface properties, it is necessary to understand the impact and differences introduced by altering synthesis conditions. Different solvents are being applied for modification, but a comparative study of the impact of this change in environments is missing in literature. Therefore, our aim is to study the impact of concentration, temperature and pH in water and toluene on the properties of TiO2 modified with propylphosphonic acid (3PA). By combining complementary techniques (DRIFT, TGA and P-31/CP MAS NMR), clear differences induced by the solvent can be found. Moreover, in toluene a lower concentration of 3PA is required to obtain closed packed monolayers than in water. Furthermore, both solvent and concentration are influencing the modification degree and binding type formed on the surface. Moreover, only in water, next to the concentration, also the temperature and pH have a strong impact on the binding type of 3PA. A clear difference in thermal stability of 70 degrees C was found between both binding types. (C) 2016 The Authors. Published by Elsevier B.V. ; The FWO (Fonds Wetenschappelijk Onderzoek) is gratefully acknowledged for the financial support granted in project GO12712N. Thanks a lot to Walter Dorinee and Gert Nuyts for the SEM EDX measurements. The Quanta 250 FEG microscope at the University of Antwerp was funded by the Hercules foundation of the Flemish Government.
Anisotropic deposition profiles of TiO2 in Zeotile-4 ordered mesoporous silica material are obtained using Atomic Layer Deposition (ALD) involving alternating pulses of tetrakis(dimethylamino) titanium (TDMAT) and water. TiO2 concentration profiles visualized by transmission electron microscopy (TEM) on particle cross sections reveal the systematic deeper penetration of the deposition front along the main channels and the more limited penetration in the perpendicular direction through the narrower slit-like mesopores. In ordered mesoporous material with one-dimensional pore system ALD leads to pore plugging. Diffusion limited ALD is shown to be useful for TiO2 deposition in anisotropic mesoporous support materials. ; This work was supported by the Flemish IWT in the frame of the strategic basic research (SBO) project and by the Flemish FWO. JAM. acknowledges the Flemish government for long term structural funding. C.D. acknowledges the European Research Council for an ERG Starting Grant (Grant 239865), and J.D. acknowledges the Flemish FWO for a Ph.D. research grant.
The stability of polymer solar cells (PSCs) can be influenced by the introduction of particular moieties on the conjugated polymer side chains. In this study, two series of donor-acceptor copolymers, based on bis(thienyl)dialkoxybenzene donor and benzo[c][1,2,5]thiadiazole (BT) or thiazolo[5,4-d]thiazole (TzTz) acceptor units, were selected toward effective device scalability by roll-coating. The influence of the partial exchange (5% or 10%) of the solubilizing 2-hexyldecyloxy by alternative 2-phenylethoxy groups on efficiency and stability was investigated. With an increasing 2-phenylethoxy ratio, a decrease in solar cell efficiency was observed for the BT-based series, whereas the efficiencies for the devices based on the TzTz polymers remained approximately the same. The photochemical degradation rate for PSCs based on the TzTz polymers decreased with an increasing 2-phenylethoxy ratio. Lifetime studies under constant sun irradiance showed a diminishing initial degradation rate for the BT-based devices upon including the alternative side chains, whereas the (more stable) TzTz-based devices degraded at a faster rate from the start of the experiment upon partly exchanging the side chains. No clear trends in the degradation behavior, linked to the copolymer structural changes, could be established at this point, evidencing the complex interplay of events determining PSCs' lifetime. ; This work has been supported by the Villum Foundation's Young Investigator Program (second round; project: Materials for Energy Production). The work was partly done during an external research stay of Ilona Heckler at Hasselt University in the group of Wouter Maes. The Hasselt University co-authors acknowledge the support by the IAP (Interuniversity Attraction Poles) 7/05 project FS2 (Functional Supramolecular Systems), granted by the Science Policy Office of the Belgian Federal Government (BELSPO), and the Research Foundation-Flanders (Fonds voor Wetenschappelijk Onderzoek-Vlaanderen) (Projects G.0415.14N, G.0B67.15N and M.ERA-NET Project RADESOL).
Cable bacteria are long, multicellular micro-organisms that are capable of transporting electrons from cell to cell along the longitudinal axis of their centimeter-long filaments. The conductive structures that mediate this long-distance electron transport are thought to be located in the cell envelope. Therefore, this study examines in detail the architecture of the cell envelope of cable bacterium filaments by combining different sample preparation methods (chemical fixation, resin-embedding, and cryo-fixation) with a portfolio of imaging techniques (scanning electron microscopy, transmission electron microscopy and tomography, focused ion beam scanning electron microscopy, and atomic force microscopy). We systematically imaged intact filaments with varying diameters. In addition, we investigated the periplasmic fiber sheath that remains after the cytoplasm and membranes were removed by chemical extraction. Based on these investigations, we present a quantitative structural model of a cable bacterium. Cable bacteria build their cell envelope by a parallel concatenation of ridge compartments that have a standard size. Larger diameter filaments simply incorporate more parallel ridge compartments. Each ridge compartment contains a ∼50 nm diameter fiber in the periplasmic space. These fibers are continuous across cell-to-cell junctions, which display a conspicuous cartwheel structure that is likely made by invaginations of the outer cell membrane around the periplasmic fibers. The continuity of the periplasmic fibers across cells makes them a prime candidate for the sought-after electron conducting structure in cable bacteria. ; This research was financially supported by the European Research Council under the European Union's Seventh Framework Program (FP/2007-2013) through ERC Grant 306933 (FM), the Research Foundation Flanders (FWO project grant G031416N to FM and JM), and the Netherlands Organization for Scientific Research (VICI grant 016.VICI.170.072 to FM). RB is supported by an aspirant grant from Research Foundation Flanders. LN, AB, LD, and TB were supported by the Danish Council for Independent Research, Technology and Production Sciences—project on Microcable-based Nanoelectronics and the Danish National Research Foundation Center of Excellence CEM—Center for Electromicrobiology.
