L’éotilé ou bétiné est une langue kwa (J. Stewart 1989, K. Williamson et R. Blench 2000) de Côte d’Ivoire, pays de l’Afrique occidentale. A l’origine homogène, il s’est scindé (H. Dagri-Diabaté 1984) ...en deux variétés, l’adiaké et le vitré, autour du XVIIIe siècle ; induisant en synchronie des degrés de vitalité différents et une évolution dans des environnements sociolinguistiques distincts. Dans les faits, l’adiaké parlé dans la localité éponyme, avec six locuteurs, est moribond (A. F. Kakou 2014). Le vitré de mise à Grand- Bassam est dynamique avec environ 3500 locuteurs (T. L. Ahaté 2008, A. F. Kakou 2009). Les trajectoires opposées de ces dialectes du bétiné ont certainement eu comme conséquences des variations linguistiques. D’où la conduite de cette étude dont l’interrogation centrale est de savoir quelles sont les formes et la syntaxe des marques grammaticales de l’éotilé. L’objectif visé est de faire un inventaire comparé de ces morphèmes en question. Pour ce faire, les analyses ont porté sur un corpus constitué de 800 lexèmes et énoncés. De leurs examens, il ressort que les dialectes de l’éotilé possèdent en commun des morphèmes grammaticaux liés et libres. Toutefois, il existe également au niveau de ces unités grammaticales quelques différences de formes et de syntaxe.
A uniform nitrogen‐doped carbon coating layer is formed on Li4Ti5O12 particles by mixing porous Li4Ti5O12 powder with an ionic liquid and then treating the mixture at moderate temperature. Uniformly ...coated Li4Ti5O12 is shown to have significantly improved rate capability and cycling performance for Li‐ion batteries. This relatively simple approach is versatile and can be extended to modify other electrode materials for electrochemical devices.
Nanostructured carbides are refractory materials with high surface areas that could be used as alternatives to the oxide materials that are widely used as support materials for heterogeneous ...catalysts. Carbides are also catalytically active for a variety of reactions, offering additional opportunities to tune the overall performance of the catalyst. In this paper we describe the synthesis of molybdenum carbide supported platinum (Pt/Mo2C) catalysts and their rates for the water gas shift reaction. The synthesis method allowed interaction of the metal precursor with the native, unpassivated support. The resulting materials possessed very high WGS rates and atypical Pt particle morphologies. Under differential conditions, rates for these catalysts were higher than those for the most active oxide-supported Pt catalysts and a commercial Cu−Zn−Al catalyst. Experimental and computational results suggested that active sites on the Pt/Mo2C catalysts were located on the perimeter of the Pt particles and that strong interactions between Pt and the Mo2C surface gave rise to raft-like particles.
This article reviews the approaches developed to prepare and characterize porous structured materials by using the breath figures (BF) methodology. In particular, we have analyzed the topographical ...modifications of the surface that can be tuned with this approach, such as the control of the pore characteristics, changes in the pore morphology or use of non-planar substrates to create the porous materials among others. We have also given special attention to the functionality inside of the pores and how this can be created by using different kinds of polymers, from homopolymers to hybrid materials, as well as by changing the pore functionally after chemical modification. The approaches followed to obtain hierarchical structures, for example, by combination of the BF approach and nanostructure formation within the pores or by using soft-lithography have also been examined. In addition, we discuss the feasibility of obtaining stimuli-responsive honeycomb structured surfaces. The potential applications in different areas such as biomedicine, optics and so on, are also pointed out. Finally, we comment on some future perspectives of breath figures approach.
The effectiveness of side‐chain engineering is demonstrated to produce highly efficient all‐polymer solar cells (efficiency of 5.96%) using a series of naphthalene diimide‐based polymer acceptors ...with controlled side chains. The dramatic changes in the polymer packing, blend morphology, and electron mobility of all‐polymer solar cells elucidate clear trends in the photovoltaic performances.
The collapse potential, mineralogy, microstructure, and particle morphology of a loess from the Loess Plateau, China, were characterized by double oedometer testing, X-ray diffraction, scanning ...electron microscopy with energy-dispersive X-ray spectroscopy, and image analysis to elucidate the origin of its collapse behavior. Results show that the loess is highly collapsible with a maximum collapse index of 6.7% at a vertical stress of ∼200 kPa. The deposit contains both nonclay (i.e., quartz, albite, muscovite, and calcite) and clay (i.e., two chlorites) minerals. Microstructural, chemical, and image analyses indicate that interparticle calcite and clay cementation and silt particle morphology render the intact soil a metastable structure. Wetting-induced collapse is attributed to both primary and secondary microstructure features. The former is the abundance of weakly cemented, unsaturated, porous pure clay and clay–silt mixture aggregates whose slaking upon wetting initiates the overall structural collapse, while the latter consists of high porosity, unstable particle contacts, and clay coating on silt particles that act synergistically to augment the collapse. A conceptual microstructural model of a four-tiered hierarchy (i.e., primary clay and silt particles, clay aggregates and clay-coated silt particles, clay–silt mixture aggregates, and cemented aggregate matrix) is proposed to represent its structural characteristics and to account for its high collapsibility.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Perylene imides have been an object of research for 100 years and their derivatives are key n‐type semiconductors in the field of organic electronics. While perylene diimides have been applied in ...many electronic and photonic devices, their use can be traced back to the first efficient organic solar cell. By functionalizing different positions of the in total 12 positions (four peri, four bay, and four ortho‐positions) on the perylene core, perylene imides with significantly different optical, electronic and morphological properties may be prepared. Perylene imides and their derivatives have been used in several types of organic photovoltaics, including flat‐, and bulk‐heterojunction devices as well as dye‐sensitized solar cells. Additionally perylene imides‐based copolymers or oligomers play an important role in single junction devices. In this review, the relationship between the photovoltaic performance and the structure of perylene imides is discussed.
1st (yesterday), 2nd (today) and 3rd (tomorrow) generation perylene imides, their designated material properties, and photovoltaic performance in organic solar cells are presented and discussed in this review. This class of chromophores has developed alongside photovoltaics and with the promises that the latest generation of perylene imides holds, they will continue to play a major role in the future.
The dependence of the thin film morphology and excited-state dynamics for the low-bandgap donor–acceptor copolymer ...poly2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta2,1-b;3,4-b′-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole) (PCPDTBT) in pristine films and in blends (1:2) with 6,6-phenyl-C61-butyric acid methyl ester (PCBM) on the use of the solvent additive 1,8-octanedithiol (ODT) is studied by solid-state nuclear magnetic resonance (NMR) spectroscopy and broadband visible and near-infrared pump–probe transient absorption spectroscopy (TAS) covering a spectral range from 500–2000 nm. The latter allows monitoring of the dynamics of excitons, bound interfacial charge-transfer (CT) states, and free charge carriers over a time range from femto- to microseconds. The broadband pump–probe experiments reveal that excitons are not only generated in the polymer but also in PCBM-rich domains. Depending on the morphology controlled by the use of solvent additives, polymer excitons undergo mainly ultrafast dissociation (<100 fs) in blends prepared without ODT or diffusion-limited dissociation in samples prepared with ODT. Excitons generated in PCBM diffuse slowly to the interface in both samples and undergo dissociation on a time scale of several tens of picoseconds up to hundreds of picoseconds. In both samples a significant fraction of the excitons creates strongly bound interfacial CT states, which exhibit subnanosecond geminate recombination. The total internal quantum efficiency loss due to geminate recombination is estimated to be 50% in samples prepared without ODT and is found to be reduced to 30% with ODT, indicating that more free charges are generated in samples prepared with solvent additives. In samples prepared with ODT, the free charges exhibit clear intensity-dependent recombination dynamics, which can be modeled by Langevin-type recombination with a bimolecular recombination coefficient of 6.3 × 10–11 cm3 s–1. In samples prepared without ODT, an additional nanosecond recombination of polaron pairs is observed in conjunction with an increased intensity-independent trap-assisted nongeminate recombination of charges. Furthermore, a comparison of the triplet-induced absorption spectra of PCPDTBT with the charge-induced absorption in PCPDTBT:PCBM blends reveals that triplets have a very similar excited-state absorption spectrum compared to the free charge carriers, however, in contrast have a distinct intensity-independent lifetime. Overall, our results suggest that whether free charges or strongly bound CT states are created upon dissociation of excitons at the PCPDTBT:PCBM interface is determined instantaneously upon exciton dissociation and that once formed strongly bound CT states rapidly recombine and thus are unlikely to dissociate into free charges. The observation of a significantly larger bimolecular recombination coefficient than previously determined for poly(3-hexylthiophen-2,5-diyl):PCBM (P3HT:PCBM) and PCDTBT:PCBM samples indicates that nongeminate recombination of free charges considerably competes with charge extraction in PCPDTBT:PCBM photovoltaic devices.
A significant enhancement of efficiency in thieno3,4‐b‐thiophene/benzodithiophene:6,6‐phenyl C71‐butyric acid methyl ester (PTB7:PC70BM) solar cells can be achieved by methanol treatment. The effects ...of methanol treatment are shown in an improvement of built‐in voltage, a decrease in series resistance, an enhanced charge‐transport property, an accelerated and enlarged charge extraction, and a reduced charge recombination, which induce a simultaneous enhancement in open‐circuit voltage (Voc), short‐circuit current (Jsc), and fill factor (FF) in the devices.
This article presents the recent developments of radical dispersion polymerizaton controlled by reversible addition fragmentation chain transfer (RAFT) for the production of block copolymer ...particles of various morphologies, such as core‐shell spheres, worms, or vesicles. It is not meant to be an exhaustive review but it rather provides guidelines for non‐specialists. The article is subdivided into eight sections. After a general introduction, the mechanism of polymerization‐induced self‐assembly (PISA) through RAFT‐mediated dispersion polymerization is presented and the different parameters that control the morphology produced are discussed. The next two sections are devoted to the choice of the monomer/solvent pair and the macroRAFT agent. Afterwards, post‐polymerization morphological order‐to‐order transitions (i.e. morphological transitions triggered by extrinsic stimuli) or order‐to‐disorder transitions (i.e. disassembly of chains) are discussed. Assemblies based on more complex polymer architectures, such as triblock copolymers, are presented next, and finally the possibility to stabilize these structures by crosslinking is reported. The manuscript ends with a short conclusion and an outlook.
RAFT dispersion polymerization is a versatile and efficient tool to prepare core‐shell particles of various morphologies by polymerization‐induced self‐assembly. This article reviews recent developments in this field, critically comments on them, and gives an outlook on further expected developments. It provides guidelines for non‐experts by highlighting important aspects that must carefully be considered when planning the preparation of core‐shell nanoobjects using this approach.
