High Morphological Stability Research Articles

A conjugated donor-acceptor block copolymer enables over 11% efficiency for single-component polymer solar cells

<h2>Summary</h2> Covalently linking donor (D) and acceptor (A) moieties into single material can be an effective strategy to enable efficient exciton dissociation and charge generation. Herein, we synthesized a conjugated D-A block copolymer (PBDB-T-<i>b</i>-PYT), in which a donor block (PBDB-T) was connected to an acceptor block (PYT). Compared with the bulk heterojunction (BHJ) blend mixture containing PBDB-T and PYT with high molecular weights, more efficient exciton dissociation and charge transfer (CT) were observed in the single-component PBDB-T-<i>b</i>-PYT films. Impressively, a single-material organic solar cell (SMOSC) fabricated from PBDB-T-<i>b</i>-PYT alone exhibited a power conversion efficiency (PCE) of 11.32% and a certificated PCE of 10.8%. In addition, higher morphological stability and lower energy loss were also observed in the PBDB-T-<i>b</i>-PYT SMOSC compared with the control PBDB-T:PYT BHJ devices. The results manifest that our newly designed PBDB-T-<i>b</i>-PYT provides a promising design strategy for D-A block copolymers for highly efficient and stable SMOSCs.

One-Pot Synthesis of Copper Iodide-Polypyrrole Nanocomposites

A novel one-pot chemical synthesis of functional copper iodide-polypyrrole composites, CuI-PPy, has been proposed. The fabrication process allows the formation of nanodimensional metal salt/polymer hybrid structures in a fully controlled time- and concentration-dependent manner. The impact of certain experimental conditions, viz., duration of synthesis, sequence of component addition and concentrations of the intact reagents on the structure, dimensionality and yield of the end-product was evaluated in detail. More specifically, the amount of marshite CuI within the hybrid composite can be ranged from 60 to 90 wt.%, depending on synthetic conditions (type and concentration of components, process duration). In addition, the conditions allowing the synthesis of nano-sized CuI distributed inside the polypyrrole matrix were found. A high morphological stability and reproducibility of the synthesized nanodimensional metal-polymer hybrid materials were approved. Finally, the electrochemical activity of the formed composites was verified by cyclic voltammetry studies. The stability of CuI-PPy composite deposited on the electrodes was strongly affected by the applied anodic limit. The proposed one-pot synthesis of the hybrid nanodimensional copper iodide-polypyrrole composites is highly innovative, meets the requirements of Green Chemistry and is potentially useful for future biosensor development. In addition, this study is expected to generally contribute to the knowledge on the hybrid nano-based composites with tailored properties.

Comparative study of fungal stability between Metarhizium strains after successive subculture

BackgroundMetarhizium species are considered one of the most outstanding powerful biological control agents that have been commercialized as biopesticides against various agricultural pests. Fungal stability with successive in vitro cultivation is a desirable trait for a large-scale production of fungal biopesticide.Main bodyThe new Egyptian strain Metarhizium anisopliae AUMC 3262 exhibited auspicious results when compared to Metarhizium brunneum ARSEF 4556 and M. brunneum V275 based on the variations of fungal characteristics, and essential quality control parameters (radial growth rate, conidial yield, viability, and virulence) after repeated in vitro subculturing. Changes in morphological characteristics were noted at both AUMC 3262 and ARSEF 4556. Following the 5th subculture, decreased conidial yield was noted, though radial growth remained stable, confirming that there is a non-positive correlation between conidial yield and radial growth rate for these species. In contrast, V275 showed a high morphological stability, conidial yield, and radial growth rate after repeated subculture. The three tested strains manifested high viability up to 100% and displayed the same pattern of Pr1 production. A slight variation was recorded in the median lethal time (LT50) values against the great wax moth, Galleria mellonella (L.), larvae between different subcultures of the tested Metarhizium strains.ConclusionThe new Egyptian strain AUMC 3262 showed a high stability with a slight difference in some parameters after the successive subculture compared to both ARSEF4556 and V275.

The oldest representative of the extant barklice genus Psyllipsocus (Psocodea: Trogiomorpha: Psyllipsocidae) from the Cenomanian amber of Myanmar

We describe Psyllipsocus yoshizawai sp. nov., the oldest and first Cretaceous species of the extant genus Psyllipsocus (Psocodea: Trogiomorpha: Psyllipsocidae). This is the fifth genus and sixth species to be identified within the family Psyllipsocidae from the Cretaceous and the third genus and fourth species of psyllipsocids from the Cenomanian amber of Myanmar (Burmese amber, in Tanai). Its taxonomic affinities with the other fossil and living psyllipsocid genera are discussed. The attribution to the extant genus Psyllipsocus is based on the absence of any significant differences with this genus that could not correspond to a specific level. This situation is rare but not exceptional, as some other extant insect genera have already been recorded from the Burmese amber. It suggests a high morphological stability of the genus over time. A checklist of the known Cretaceous psocodean species from amber is given.

Bicomponent Random Approach for the Synthesis of Donor Polymers for Efficient All-Polymer Solar Cells Processed from A Green Solvent.

All-polymer solar cells (all-PSCs) can offer unique merits of high morphological stability to thermal and mechanical stress. To realize their full potential as flexible or wearable devices, it is highly desirable that the all-PSCs can be fabricated from a green solvent with simple post-treatment to avoid thermal annealing on the flexible substrate. This posed a severe challenge on material design to tune their properties with suitable solubility, aggregation, and morphology. To address this challenge, here, a simple bicomponent random approach on a D-A-type polymer donor was developed by just varying the D-A molar ratio. Under this approach, a series of new random polymers PBDTa-TPDb with different molar ratios of the D component of 2D-benzo[1,2-b:4,5-b']dithiophene (BDT) and A component of thieno[3,4-c]pyrrole-4,6-dione (TPD) were designed and synthesized. The energy levels, light absorption, solubility, and packing structure of random donors PBDTa-TPDb were found to vary substantially with the various D-A molar ratios. The devices based on PBDTa-TPDb/P(NDI2HD-T) were fabricated to explore the synergistic effects of the processing solvent and composition of D-A-type random polymers. The results show that nanoscale morphology, balanced miscibility/crystallinity of blend, and photovoltaic properties could be rationally optimized by tuning the composition of random donors. As a result, as-cast all-PSC-based optimal donor PBDT5-TPD4 achieves the best power conversion efficiency (PCE) of 8.20% processed from a green solvent, which performs better than that the reference polymer (PCE: 6.41%). This efficiency is the highest value for all-PSCs from BDT-TPD-based donors. Moreover, the optimized devices were relatively insensitive to the thickness of the active layer and exhibited good stability.

Fabrication and In Situ Cross-Linking of Carboxylic-Acid-Functionalized Poly(Ester Amide) Scaffolds for Tissue Engineering

Three-dimensional (3D) scaffolds are important tools for tissue engineering and should ideally provide both biochemical cues and biomechanical support for cells. Poly(ester amide)s (PEAs) have emerged as promising materials for the preparation of tissue engineering scaffolds, and the pendant side chains of residues, such as l-lysine and l-aspartic acid, can provide sites for the conjugation of biochemical signals. However, it has been challenging to combine scaffold morphological stability with the presentation of reactive groups on PEA scaffolds. We describe here a new approach involving the functionalization of a l-lysine-containing PEA with maleic anhydride to simultaneously introduce cross-linkable alkenes and carboxylic acid conjugation sites. Maleic-acid-functionalized PEA was processed to form 3D scaffolds using a salt leaching method and the scaffolds were cross-linked in situ using a poly(ethylene glycol) dimethacrylate cross-linking agent by thermal free radical curing. Microcomputed tomography analysis indicated that the cross-linked scaffolds had higher polymer volume fraction, lower porosity, and smaller pore size than the non-cross-linked scaffolds, but both scaffolds exhibited high morphological stability and negligible mass loss upon incubation in phosphate-buffered saline for 5 days. The Young’s moduli of the cross-linked and non-cross-linked scaffolds were 28 and 9 kPa, respectively. Fluorescein-labeled bovine serum albumin was successfully conjugated to the scaffolds using a carbodiimide-based coupling. Finally, it was shown that the scaffolds supported the attachment and proliferation of mouse embryonic mesenchymal multipotent cells, showing their promise as platforms for tissue engineering applications.

Morphogenetic stability of variegated Vanilla planifolia Jacks. plants micropropagated in a temporary immersion system (TIB®)

ISSR markers are useful to identify molecular changes in variegated vanilla (Vanilla planifolia Jacks.) plants derived from a temporary immersion system. Clonal propagation through in vitro cultures produces individuals that are identical to the parent plant from which they were subcultured. However, there is evidence of phenotypic variations between propagated clones. The most common phenotypic variations are changes in leaf pigmentation, i.e., variegated individuals. Many such phenotypic variations are exploited by the ornamental industry. In a previous study by our group on indirect organogenesis in vanilla (Ramirez-Mosqueda and Iglesias-Andreu in In Vitro Cell Dev Biol Plant 52:154–160, 2015), variegated Vanilla planifolia Jacks. plants were generated in vitro. A temporary immersion system allows for the mass propagation of plant material in liquid culture. The present study aimed to identify morphological and molecular changes that occurred in variegated plants obtained during micropropagation in a temporary immersion system, the TIB®. To achieve this, the morphology of plants micropropagated in TIB® was assessed and analyzed at the molecular level using inter-simple sequence repeats. Molecular variation was analyzed over four subcultures, each lasting 45 days. Plants showed 100% uniformity (monomorphism) and morphological stability, which were confirmed by the heritability of leaf pigmentation (variegated individuals) in all micropropagated plants over all four subcultures. This study demonstrates that high genetic and morphological stability was achieved in variegated V. planifolia genotypes that were micropropagated in TIB®. This would allow for the establishment of a clonal line of variegated plants with ornamental applications. In addition, 100% survival of the plants was observed during acclimatization. The study forms part of a wider long-term effort to assess the potential of mass propagation of variegated vanilla for ornamental purposes.

Reshaping Dynamics of Gold Nanoparticles under H2 and O2 at Atmospheric Pressure.

Despite intensive research efforts, the nature of the active sites for O2 and H2 adsorption/dissociation by supported gold nanoparticles (NPs) is still an unresolved issue in heterogeneous catalysis. This stems from the absence of a clear picture of the structural evolution of Au NPs at near reaction conditions, i. e., at high pressures and high temperatures. We hereby report real-space observations of the equilibrium shapes of titania-supported Au NPs under O2 and H2 at atmospheric pressure using gas transmission electron microscopy. In situ TEM observations show instantaneous changes in the equilibrium shape of Au NPs during cooling under O2 from 400 °C to room temperature. In comparison, no instant change in equilibrium shape is observed under a H2 environment. To interpret these experimental observations, the equilibrium shape of Au NPs under O2, atomic oxygen, and H2 is predicted using a multiscale structure reconstruction model. Excellent agreement between TEM observations and theoretical modeling of Au NPs under O2 provides strong evidence for the molecular adsorption of oxygen on the Au NPs below 120 °C on specific Au facets, which are identified in this work. In the case of H2, theoretical modeling predicts no interaction with gold atoms that explain their high morphological stability under this gas. This work provides atomic structural information for the fundamental understanding of the O2 and H2 adsorption properties of Au NPs under real working conditions and shows a way to identify the active sites of heterogeneous nanocatalysts under reaction conditions by monitoring the structure reconstruction.

Design, synthesis, and photoelectric properties of V-shaped organic fluorescent compounds with a 1,3,4-oxadiazole moiety

A series of symmetric, silicon-linked organic fluorescent compounds with two electron-deficient 1,3,4-oxadiazole units were synthesized and characterized. The compounds possessed a V-shaped structure with a silicon atom, which weakened π–π stacking, promoting aggregation-induced emission. The compounds were fluorescent in both solution and solid-state thin films. The efficient fluorescent behavior of the materials was confirmed through optical and electrochemical measurements. The compounds displayed excellent thermal stability, with decomposition temperatures exceeding 400 °C. Amorphous films of the compounds possessed high morphological stability. These results indicate that the compounds may be promising emissive and electron-transporting materials.

Non-fullerene polymer acceptors based on perylene diimides in all-polymer solar cells

All-polymer solar cells (All-PSCs) have attracted a lot of attention in the recent years due to broad absorption spectra, adjustable chemical structures, high morphological stability, better donor-acceptor compatibility and better mechanical durability. This review summarizes the recent development of perylene diimides (PDI)-based electron acceptors used in all-PSCs because these polymers are promising candidates. The photovoltaic performances of non-fullerene polymer acceptors were compared, and the structure-performance relationship was discussed when the same donor material was used.

Lowering Molecular Symmetry To Improve the Morphological Properties of the Hole-Transport Layer for Stable Perovskite Solar Cells.

Inspired by the structural feature of the classical hole-transport material (HTM), Spiro-OMeTAD, many analogues based on a highly symmetrical spiro-core were reported for perovskite solar cells (PSCs). However, these HTMs were prone to crystallize because of the high molecular symmetry, forming non-uniform films, unfavorable for the device stability and large-area processing. By lowering the symmetry of spiro-core, we report herein a novel spirobisindane-based HTM, Spiro-I, which could form amorphous films with high uniformity and morphological stability. Compared to the Spiro-OMeTAD-based PSCs, those containing Spiro-I exhibit similar efficiencies for small area but higher ones for large area (1 cm2 ), and especially much higher air stability (retaining 80 % of initial PCE after 2400 h storage without encapsulation). Moreover, the Spiro-I can be synthesized from a cheap starting material bisphenol A and used with a small amount for the device fabrication.

Lowering Molecular Symmetry To Improve the Morphological Properties of the Hole‐Transport Layer for Stable Perovskite Solar Cells

AbstractInspired by the structural feature of the classical hole‐transport material (HTM), Spiro‐OMeTAD, many analogues based on a highly symmetrical spiro‐core were reported for perovskite solar cells (PSCs). However, these HTMs were prone to crystallize because of the high molecular symmetry, forming non‐uniform films, unfavorable for the device stability and large‐area processing. By lowering the symmetry of spiro‐core, we report herein a novel spirobisindane‐based HTM, Spiro‐I, which could form amorphous films with high uniformity and morphological stability. Compared to the Spiro‐OMeTAD‐based PSCs, those containing Spiro‐I exhibit similar efficiencies for small area but higher ones for large area (1 cm2), and especially much higher air stability (retaining 80 % of initial PCE after 2400 h storage without encapsulation). Moreover, the Spiro‐I can be synthesized from a cheap starting material bisphenol A and used with a small amount for the device fabrication.

Synthesis, aggregation-induced emission and electroluminescence of new luminogens based on thieno[3,2-b]thiophene S,S-dioxide

Organic luminescent materials with high fluorescence efficiencies in the solid state are highly desired in OLED devices. In this work, we report the synthesis and characterization of a series of novel dipolar luminogens based on thieno [3,2-b]thiophene S,S-dioxide (TTDO). The crystal structures, photophysical property, thermal stability, electronic structures and electrochemical behaviors of these TTDO-based luminogens are investigated. These luminogens have good aggregation-induced emission (AIE) property with high solid-state fluorescence quantum yields, and their emission wavelengths are tuned from green to red by different electron-donating substituents. They enjoy high thermal and morphological stabilities and have low LUMO energy levels. Nondoped OLEDs are fabricated with these new luminogens, providing orange to red electroluminescence (568–610 nm) with maximum external quantum efficiencies of up to 2.79%. These results demonstrate that these new AIE-active luminogens could be promising candidates for OLEDs.

High-Performance Polymer Solar Cell with Single Active Material of Fully Conjugated Block Copolymer Composed of Wide-Band gap Donor and Narrow-Band gap Acceptor Blocks.

We synthesized a novel fully conjugated block copolymer, P3, in which a wide-band gap donor block (P1) was connected to a narrow-band gap acceptor block (P2). As P3 contains P1 block with a wide bandgap and P2 block with a narrow bandgap, it exhibits a very wide complementary absorption. Transient photoluminescence measurement using P3 dilute solution demonstrated intramolecular charge transfer between the P1 block and the P2 block, which was not observed in a P1/P2 blend solution. A P3 thin film showed complete PL quenching because the photoinduced inter-/intramolecular charge transfer states were effectively formed. This phenomenon can play an important role in the photovoltaic properties of P3-based polymer solar cells. A single active material polymer solar cell (SAMPSC) fabricated from P3 alone exhibited a high power conversion efficiency (PCE) of 3.87% with a high open-circuit voltage of 0.93 V and a short-circuit current of 8.26 mA/cm2, demonstrating a much better performance than a binary P1-/P2-based polymer solar cell (PCE = 1.14%). This result facilitates the possible improvement of the photovoltaic performance of SAMPSCs by inducing favorable nanophase segregation between p- and n blocks. In addition, owing to the high morphological stability of the block copolymer, excellent shelf-life was observed in a P3-based SAMPSC compared with a P1/P2-based PSC.

A high T g small-molecule arylamine derivative as a doped hole-injection/transport material for stable organic light-emitting diodes

Abstract High performant hole-injection materials find important applications in organic electronics. In this contribution we report a simple small-molecule organic hole-injection/transport material N,N,N′,N′-tetra(4-methoxyphenyl)-[2,2′-binaphthalene]-6,6′-diamine for organic light-emitting diodes (OLEDs). It shows a high thermal and morphological stability with a Tg of 99 °C. The ultraviolet photoelectron spectroscopy measurements reveal a favorable HOMO level of −5.05 eV p-Doping with tetrafluorotetracyanoquinodimethane (F4-TCNQ) increases the hole conductivity up to 2.64 × 10−4 S m−1 vs. 1.68 × 10−4 S m−1 of the neat film. The characterization of the red and green phosphorescent OLEDs suggests that introducing this thick p-doped hole-injection layer may yield high electroluminescent efficiency and operational stability. Moreover the new compound shows enhanced thermal and conducting properties and thus better performances in contrast with a conventional hole-injection material N,N,N′,N′-tetra(4-methoxyphenyl)-[1,10-biphenyl]-4,4′- diamine (MeO-TPD) in the OLEDs.

Middle Triassic conodont assemblages from the Germanic Basin: implications for multi-element taxonomy and biogeography

Conodonts have been a key tool for biostratigraphical, evolutionary and palaeobiogeographical studies, and the Germanic Basin has been one of the most important regions for these studies. However, few modern studies provide systematic data on the mainly endemic conodonts of the Middle Triassic Germanic Basin. Here we document conodonts from two sections in Germany, one Bithynian in age and the other late Anisian to early Ladinian in age. The two sections captured two episodes of marine fauna invasion in the Germanic epicontinental basin during the Middle Triassic. The conodont Neogondolella mombergensis, elsewhere reported as appearing globally, is reviewed and revised, confirming previous suggestions that this species only occurs in the Germanic Basin. Apparatuses of Neogondolella haslachensis and Nicoraella germanica from the Germanic Basin are proposed. It was generally expected that S and M elements within clades have a very high morphological stability compared to P elements. However, the apparatus of Nicoraella germanica differs significantly from that of south China, indicating that the morphology of S elements within a genus can be unstable, and thus promotes our understanding of conodont evolution. The rarely documented genus Gondolatus, which was suggested as representing pathological specimens, is confirmed as a valid genus in the Germanic Basin. Our data suggest that endemic conodonts evolved twice, not only in the Upper Muschelkalk Subgroup, but also in the Lower Muschelkalk Subgroup.

Influences of the Co content and of the level of high temperature on the microstructure and oxidation of cast {Ni, Co}-based Cr-rich TaC-containing cast alloys

A series of six alloys derived from a Ni-25Cr-0.4C-6Ta (wt.%) base one was developed by substituting nickel by cobalt. They were synthesized by casting and exposed to oxidative environment at two high temperatures. Their bulk microstructures were studied in as-cast condition and in two high temperature aged states. Their surfaces after oxidation during aging were characterized. The cobalt enrichment succeeded in avoiding chromium carbides formation and in stabilizing the TaC carbides at high temperature. As the high temperature morphologic stability of TaC was not perfect, it was much better than the one of the chromium carbides, but can be improved by the total removal of nickel. Unfortunately, at the same time, the oxidation behavior, initially good, shows increased rate of the oxides formation. The room temperature hardness was also significantly increased by the substitution of Ni by Co, and decreased after aging when carbides became rounder or fragmented.

D-A structured high efficiency solid luminogens with tunable emissions: Molecular design and photophysical properties

Fabrication of efficient solid luminogens with tunable emission is both fundamentally significant and technically important. Herein, based on our previous strategy for the construction of efficient and multifunctional solid luminogens through the combination of diverse aggregation-induced emission (AIE) units with other functional moieties, a group of luminophores with electron donor-acceptor (D-A) structure and typical intramolecular charge transfer (ICT) characteristics, namely CZ-DCDPP, DPA-DCDPP and DBPA-DCDPP were synthesized and investigated. The presence of twisting and AIE-active 2,3-dicyano-5,6-diphenylpyrazine (DCDPP) moiety endows them highly emissive in the solid states, whereas the introduction of arylamines with varied electron-donating capacity and different conjugation render them with tunable solid emissions from green to red. While CZ-DCDPP and DPA-DCDPP solids exhibit distinct mechanochromism, both DPA-DCDPP and DBPA-DCDPP solids can generate efficient red emission. Owing to their high efficiency, remarkable thermal and morphological stabilities and moreover red emission, they are promising for diverse optoelectronic and biological applications.

Highly Stable Silica-Coated Gold Nanoflowers Supported on Alumina.

Shape-controlled nanocrystals, such as nanowires and nanoflowers, are attractive because of their potential novel optical and catalytic properties. However, the dispersion and morphological stabilities of shape-controlled nanocrystals are easily destroyed by changing the dispersion solvent and temperature. Methods of support and the silica coating are known to improve the dispersion and morphological stabilities of metal nanocrystals. The silica-coating method often causes morphological changes in shape-controlled nanocrystals because the silica coating is formed in mixed solutions of water and organic solvents such as ethanol, and this results in aggregation due to changes in the dispersion solvent. Furthermore, ligand exchange, designed to improve the dispersion stability in the solvent, often causes morphological changes. This article introduces a method for the preparation of highly stable silica-coated Au nanoflowers (AuNFs) supported on Al2O3. The method of support prevents the aggregation and precipitation of AuNFs when the solvent is changed from water to water/ethanol. Through stability improvement, silica coating of AuNFs/Al2O3 was conducted in water/ethanol without ligand exchange that causes morphological changes. Furthermore, silica-coated AuNFs/Al2O3 exhibit high morphological stability under high-temperature conditions compared to uncoated AuNFs/Al2O3. These results are very useful when preparing highly morphologically stable, silica-coated, shape-controlled nanocrystals without ligand exchange.

(Invited) Contacts in Advanced CMOS: History and Emerging Challenges

With the continued evolution of CMOS technologies, which includes recent changes in both device geometries and contact schemes, contact lengths of advanced devices are now reaching below 20 nm. At these dimensions, material microstructure (grain size) becomes similar to contact size and interface quality becomes critical to device performance. The sustained reduction in contact size together with the complications associated with the introduction of non-planar devices have recently lead to drastic modifications in process flow for the contacts. These new process schemes have altered the materials requirements for the contacts to the point where two factors dominate material selection: a low intrinsic contact resistivity interface and a higher morphological stability. As a result, advanced CMOS development has unexpectedly made a return to contacts based on titanium. In this presentation, we will first describe the evolution of materials used for contacts through the scaling of CMOS technologies. We will discuss what is observed in the titanium thin films when annealed under various advanced treatments as the metal film thickness is reduced below 10 nm.